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3272 lines
85 KiB
3272 lines
85 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* fs/dcache.c |
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* |
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* Complete reimplementation |
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* (C) 1997 Thomas Schoebel-Theuer, |
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* with heavy changes by Linus Torvalds |
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*/ |
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|
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/* |
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* Notes on the allocation strategy: |
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* |
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* The dcache is a master of the icache - whenever a dcache entry |
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* exists, the inode will always exist. "iput()" is done either when |
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* the dcache entry is deleted or garbage collected. |
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*/ |
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|
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#include <linux/ratelimit.h> |
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#include <linux/string.h> |
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#include <linux/mm.h> |
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#include <linux/fs.h> |
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#include <linux/fscrypt.h> |
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#include <linux/fsnotify.h> |
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#include <linux/slab.h> |
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#include <linux/init.h> |
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#include <linux/hash.h> |
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#include <linux/cache.h> |
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#include <linux/export.h> |
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#include <linux/security.h> |
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#include <linux/seqlock.h> |
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#include <linux/memblock.h> |
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#include <linux/bit_spinlock.h> |
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#include <linux/rculist_bl.h> |
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#include <linux/list_lru.h> |
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#include "internal.h" |
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#include "mount.h" |
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|
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/* |
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* Usage: |
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* dcache->d_inode->i_lock protects: |
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* - i_dentry, d_u.d_alias, d_inode of aliases |
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* dcache_hash_bucket lock protects: |
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* - the dcache hash table |
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* s_roots bl list spinlock protects: |
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* - the s_roots list (see __d_drop) |
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* dentry->d_sb->s_dentry_lru_lock protects: |
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* - the dcache lru lists and counters |
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* d_lock protects: |
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* - d_flags |
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* - d_name |
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* - d_lru |
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* - d_count |
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* - d_unhashed() |
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* - d_parent and d_subdirs |
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* - childrens' d_child and d_parent |
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* - d_u.d_alias, d_inode |
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* |
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* Ordering: |
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* dentry->d_inode->i_lock |
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* dentry->d_lock |
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* dentry->d_sb->s_dentry_lru_lock |
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* dcache_hash_bucket lock |
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* s_roots lock |
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* |
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* If there is an ancestor relationship: |
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* dentry->d_parent->...->d_parent->d_lock |
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* ... |
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* dentry->d_parent->d_lock |
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* dentry->d_lock |
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* |
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* If no ancestor relationship: |
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* arbitrary, since it's serialized on rename_lock |
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*/ |
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int sysctl_vfs_cache_pressure __read_mostly = 100; |
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); |
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); |
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|
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EXPORT_SYMBOL(rename_lock); |
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|
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static struct kmem_cache *dentry_cache __read_mostly; |
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|
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const struct qstr empty_name = QSTR_INIT("", 0); |
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EXPORT_SYMBOL(empty_name); |
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const struct qstr slash_name = QSTR_INIT("/", 1); |
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EXPORT_SYMBOL(slash_name); |
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const struct qstr dotdot_name = QSTR_INIT("..", 2); |
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EXPORT_SYMBOL(dotdot_name); |
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|
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/* |
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* This is the single most critical data structure when it comes |
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* to the dcache: the hashtable for lookups. Somebody should try |
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* to make this good - I've just made it work. |
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* |
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* This hash-function tries to avoid losing too many bits of hash |
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* information, yet avoid using a prime hash-size or similar. |
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*/ |
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|
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static unsigned int d_hash_shift __read_mostly; |
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|
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static struct hlist_bl_head *dentry_hashtable __read_mostly; |
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|
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static inline struct hlist_bl_head *d_hash(unsigned int hash) |
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{ |
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return dentry_hashtable + (hash >> d_hash_shift); |
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} |
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#define IN_LOOKUP_SHIFT 10 |
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static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT]; |
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|
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static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent, |
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unsigned int hash) |
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{ |
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hash += (unsigned long) parent / L1_CACHE_BYTES; |
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return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT); |
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} |
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|
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/* Statistics gathering. */ |
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struct dentry_stat_t dentry_stat = { |
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.age_limit = 45, |
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}; |
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|
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static DEFINE_PER_CPU(long, nr_dentry); |
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static DEFINE_PER_CPU(long, nr_dentry_unused); |
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static DEFINE_PER_CPU(long, nr_dentry_negative); |
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|
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) |
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|
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/* |
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* Here we resort to our own counters instead of using generic per-cpu counters |
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* for consistency with what the vfs inode code does. We are expected to harvest |
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* better code and performance by having our own specialized counters. |
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* |
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* Please note that the loop is done over all possible CPUs, not over all online |
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* CPUs. The reason for this is that we don't want to play games with CPUs going |
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* on and off. If one of them goes off, we will just keep their counters. |
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* |
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* glommer: See cffbc8a for details, and if you ever intend to change this, |
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* please update all vfs counters to match. |
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*/ |
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static long get_nr_dentry(void) |
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{ |
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int i; |
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long sum = 0; |
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for_each_possible_cpu(i) |
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sum += per_cpu(nr_dentry, i); |
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return sum < 0 ? 0 : sum; |
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} |
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|
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static long get_nr_dentry_unused(void) |
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{ |
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int i; |
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long sum = 0; |
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for_each_possible_cpu(i) |
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sum += per_cpu(nr_dentry_unused, i); |
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return sum < 0 ? 0 : sum; |
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} |
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|
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static long get_nr_dentry_negative(void) |
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{ |
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int i; |
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long sum = 0; |
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|
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for_each_possible_cpu(i) |
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sum += per_cpu(nr_dentry_negative, i); |
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return sum < 0 ? 0 : sum; |
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} |
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|
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int proc_nr_dentry(struct ctl_table *table, int write, void *buffer, |
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size_t *lenp, loff_t *ppos) |
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{ |
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dentry_stat.nr_dentry = get_nr_dentry(); |
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dentry_stat.nr_unused = get_nr_dentry_unused(); |
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dentry_stat.nr_negative = get_nr_dentry_negative(); |
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return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
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} |
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#endif |
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/* |
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* Compare 2 name strings, return 0 if they match, otherwise non-zero. |
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* The strings are both count bytes long, and count is non-zero. |
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*/ |
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#ifdef CONFIG_DCACHE_WORD_ACCESS |
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|
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#include <asm/word-at-a-time.h> |
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/* |
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* NOTE! 'cs' and 'scount' come from a dentry, so it has a |
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* aligned allocation for this particular component. We don't |
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* strictly need the load_unaligned_zeropad() safety, but it |
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* doesn't hurt either. |
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* |
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* In contrast, 'ct' and 'tcount' can be from a pathname, and do |
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* need the careful unaligned handling. |
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*/ |
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
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{ |
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unsigned long a,b,mask; |
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|
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for (;;) { |
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a = read_word_at_a_time(cs); |
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b = load_unaligned_zeropad(ct); |
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if (tcount < sizeof(unsigned long)) |
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break; |
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if (unlikely(a != b)) |
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return 1; |
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cs += sizeof(unsigned long); |
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ct += sizeof(unsigned long); |
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tcount -= sizeof(unsigned long); |
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if (!tcount) |
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return 0; |
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} |
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mask = bytemask_from_count(tcount); |
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return unlikely(!!((a ^ b) & mask)); |
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} |
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#else |
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
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{ |
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do { |
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if (*cs != *ct) |
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return 1; |
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cs++; |
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ct++; |
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tcount--; |
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} while (tcount); |
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return 0; |
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} |
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#endif |
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static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount) |
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{ |
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/* |
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* Be careful about RCU walk racing with rename: |
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* use 'READ_ONCE' to fetch the name pointer. |
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* |
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* NOTE! Even if a rename will mean that the length |
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* was not loaded atomically, we don't care. The |
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* RCU walk will check the sequence count eventually, |
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* and catch it. And we won't overrun the buffer, |
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* because we're reading the name pointer atomically, |
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* and a dentry name is guaranteed to be properly |
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* terminated with a NUL byte. |
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* |
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* End result: even if 'len' is wrong, we'll exit |
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* early because the data cannot match (there can |
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* be no NUL in the ct/tcount data) |
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*/ |
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const unsigned char *cs = READ_ONCE(dentry->d_name.name); |
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|
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return dentry_string_cmp(cs, ct, tcount); |
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} |
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|
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struct external_name { |
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union { |
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atomic_t count; |
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struct rcu_head head; |
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} u; |
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unsigned char name[]; |
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}; |
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static inline struct external_name *external_name(struct dentry *dentry) |
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{ |
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return container_of(dentry->d_name.name, struct external_name, name[0]); |
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} |
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static void __d_free(struct rcu_head *head) |
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{ |
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struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
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|
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kmem_cache_free(dentry_cache, dentry); |
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} |
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|
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static void __d_free_external(struct rcu_head *head) |
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{ |
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struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
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kfree(external_name(dentry)); |
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kmem_cache_free(dentry_cache, dentry); |
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} |
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|
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static inline int dname_external(const struct dentry *dentry) |
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{ |
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return dentry->d_name.name != dentry->d_iname; |
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} |
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|
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void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry) |
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{ |
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spin_lock(&dentry->d_lock); |
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name->name = dentry->d_name; |
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if (unlikely(dname_external(dentry))) { |
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atomic_inc(&external_name(dentry)->u.count); |
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} else { |
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memcpy(name->inline_name, dentry->d_iname, |
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dentry->d_name.len + 1); |
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name->name.name = name->inline_name; |
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} |
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spin_unlock(&dentry->d_lock); |
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} |
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EXPORT_SYMBOL(take_dentry_name_snapshot); |
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|
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void release_dentry_name_snapshot(struct name_snapshot *name) |
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{ |
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if (unlikely(name->name.name != name->inline_name)) { |
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struct external_name *p; |
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p = container_of(name->name.name, struct external_name, name[0]); |
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if (unlikely(atomic_dec_and_test(&p->u.count))) |
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kfree_rcu(p, u.head); |
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} |
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} |
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EXPORT_SYMBOL(release_dentry_name_snapshot); |
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|
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static inline void __d_set_inode_and_type(struct dentry *dentry, |
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struct inode *inode, |
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unsigned type_flags) |
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{ |
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unsigned flags; |
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dentry->d_inode = inode; |
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flags = READ_ONCE(dentry->d_flags); |
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flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU); |
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flags |= type_flags; |
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smp_store_release(&dentry->d_flags, flags); |
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} |
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|
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static inline void __d_clear_type_and_inode(struct dentry *dentry) |
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{ |
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unsigned flags = READ_ONCE(dentry->d_flags); |
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flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU); |
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WRITE_ONCE(dentry->d_flags, flags); |
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dentry->d_inode = NULL; |
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if (dentry->d_flags & DCACHE_LRU_LIST) |
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this_cpu_inc(nr_dentry_negative); |
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} |
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|
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static void dentry_free(struct dentry *dentry) |
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{ |
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WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias)); |
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if (unlikely(dname_external(dentry))) { |
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struct external_name *p = external_name(dentry); |
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if (likely(atomic_dec_and_test(&p->u.count))) { |
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call_rcu(&dentry->d_u.d_rcu, __d_free_external); |
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return; |
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} |
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} |
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/* if dentry was never visible to RCU, immediate free is OK */ |
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if (dentry->d_flags & DCACHE_NORCU) |
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__d_free(&dentry->d_u.d_rcu); |
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else |
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call_rcu(&dentry->d_u.d_rcu, __d_free); |
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} |
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|
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/* |
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* Release the dentry's inode, using the filesystem |
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* d_iput() operation if defined. |
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*/ |
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static void dentry_unlink_inode(struct dentry * dentry) |
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__releases(dentry->d_lock) |
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__releases(dentry->d_inode->i_lock) |
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{ |
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struct inode *inode = dentry->d_inode; |
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|
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raw_write_seqcount_begin(&dentry->d_seq); |
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__d_clear_type_and_inode(dentry); |
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hlist_del_init(&dentry->d_u.d_alias); |
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raw_write_seqcount_end(&dentry->d_seq); |
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spin_unlock(&dentry->d_lock); |
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spin_unlock(&inode->i_lock); |
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if (!inode->i_nlink) |
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fsnotify_inoderemove(inode); |
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if (dentry->d_op && dentry->d_op->d_iput) |
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dentry->d_op->d_iput(dentry, inode); |
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else |
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iput(inode); |
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} |
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|
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/* |
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* The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry |
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* is in use - which includes both the "real" per-superblock |
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* LRU list _and_ the DCACHE_SHRINK_LIST use. |
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* |
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* The DCACHE_SHRINK_LIST bit is set whenever the dentry is |
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* on the shrink list (ie not on the superblock LRU list). |
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* |
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* The per-cpu "nr_dentry_unused" counters are updated with |
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* the DCACHE_LRU_LIST bit. |
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* |
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* The per-cpu "nr_dentry_negative" counters are only updated |
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* when deleted from or added to the per-superblock LRU list, not |
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* from/to the shrink list. That is to avoid an unneeded dec/inc |
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* pair when moving from LRU to shrink list in select_collect(). |
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* |
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* These helper functions make sure we always follow the |
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* rules. d_lock must be held by the caller. |
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*/ |
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#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x)) |
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static void d_lru_add(struct dentry *dentry) |
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{ |
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D_FLAG_VERIFY(dentry, 0); |
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dentry->d_flags |= DCACHE_LRU_LIST; |
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this_cpu_inc(nr_dentry_unused); |
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if (d_is_negative(dentry)) |
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this_cpu_inc(nr_dentry_negative); |
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WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
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} |
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|
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static void d_lru_del(struct dentry *dentry) |
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{ |
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D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
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dentry->d_flags &= ~DCACHE_LRU_LIST; |
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this_cpu_dec(nr_dentry_unused); |
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if (d_is_negative(dentry)) |
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this_cpu_dec(nr_dentry_negative); |
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WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
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} |
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|
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static void d_shrink_del(struct dentry *dentry) |
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{ |
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D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
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list_del_init(&dentry->d_lru); |
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dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
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this_cpu_dec(nr_dentry_unused); |
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} |
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|
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static void d_shrink_add(struct dentry *dentry, struct list_head *list) |
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{ |
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D_FLAG_VERIFY(dentry, 0); |
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list_add(&dentry->d_lru, list); |
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dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST; |
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this_cpu_inc(nr_dentry_unused); |
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} |
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|
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/* |
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* These can only be called under the global LRU lock, ie during the |
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* callback for freeing the LRU list. "isolate" removes it from the |
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* LRU lists entirely, while shrink_move moves it to the indicated |
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* private list. |
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*/ |
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static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry) |
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{ |
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D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
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dentry->d_flags &= ~DCACHE_LRU_LIST; |
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this_cpu_dec(nr_dentry_unused); |
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if (d_is_negative(dentry)) |
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this_cpu_dec(nr_dentry_negative); |
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list_lru_isolate(lru, &dentry->d_lru); |
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} |
|
|
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static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry, |
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struct list_head *list) |
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{ |
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D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
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dentry->d_flags |= DCACHE_SHRINK_LIST; |
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if (d_is_negative(dentry)) |
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this_cpu_dec(nr_dentry_negative); |
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list_lru_isolate_move(lru, &dentry->d_lru, list); |
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} |
|
|
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static void ___d_drop(struct dentry *dentry) |
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{ |
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struct hlist_bl_head *b; |
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/* |
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* Hashed dentries are normally on the dentry hashtable, |
|
* with the exception of those newly allocated by |
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* d_obtain_root, which are always IS_ROOT: |
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*/ |
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if (unlikely(IS_ROOT(dentry))) |
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b = &dentry->d_sb->s_roots; |
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else |
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b = d_hash(dentry->d_name.hash); |
|
|
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hlist_bl_lock(b); |
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__hlist_bl_del(&dentry->d_hash); |
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hlist_bl_unlock(b); |
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} |
|
|
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void __d_drop(struct dentry *dentry) |
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{ |
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if (!d_unhashed(dentry)) { |
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___d_drop(dentry); |
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dentry->d_hash.pprev = NULL; |
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write_seqcount_invalidate(&dentry->d_seq); |
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} |
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} |
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EXPORT_SYMBOL(__d_drop); |
|
|
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/** |
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* d_drop - drop a dentry |
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* @dentry: dentry to drop |
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* |
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* d_drop() unhashes the entry from the parent dentry hashes, so that it won't |
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* be found through a VFS lookup any more. Note that this is different from |
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* deleting the dentry - d_delete will try to mark the dentry negative if |
|
* possible, giving a successful _negative_ lookup, while d_drop will |
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* just make the cache lookup fail. |
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* |
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* d_drop() is used mainly for stuff that wants to invalidate a dentry for some |
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* reason (NFS timeouts or autofs deletes). |
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* |
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* __d_drop requires dentry->d_lock |
|
* |
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* ___d_drop doesn't mark dentry as "unhashed" |
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* (dentry->d_hash.pprev will be LIST_POISON2, not NULL). |
|
*/ |
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void d_drop(struct dentry *dentry) |
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{ |
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spin_lock(&dentry->d_lock); |
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__d_drop(dentry); |
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spin_unlock(&dentry->d_lock); |
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} |
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EXPORT_SYMBOL(d_drop); |
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|
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static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent) |
|
{ |
|
struct dentry *next; |
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/* |
|
* Inform d_walk() and shrink_dentry_list() that we are no longer |
|
* attached to the dentry tree |
|
*/ |
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dentry->d_flags |= DCACHE_DENTRY_KILLED; |
|
if (unlikely(list_empty(&dentry->d_child))) |
|
return; |
|
__list_del_entry(&dentry->d_child); |
|
/* |
|
* Cursors can move around the list of children. While we'd been |
|
* a normal list member, it didn't matter - ->d_child.next would've |
|
* been updated. However, from now on it won't be and for the |
|
* things like d_walk() it might end up with a nasty surprise. |
|
* Normally d_walk() doesn't care about cursors moving around - |
|
* ->d_lock on parent prevents that and since a cursor has no children |
|
* of its own, we get through it without ever unlocking the parent. |
|
* There is one exception, though - if we ascend from a child that |
|
* gets killed as soon as we unlock it, the next sibling is found |
|
* using the value left in its ->d_child.next. And if _that_ |
|
* pointed to a cursor, and cursor got moved (e.g. by lseek()) |
|
* before d_walk() regains parent->d_lock, we'll end up skipping |
|
* everything the cursor had been moved past. |
|
* |
|
* Solution: make sure that the pointer left behind in ->d_child.next |
|
* points to something that won't be moving around. I.e. skip the |
|
* cursors. |
|
*/ |
|
while (dentry->d_child.next != &parent->d_subdirs) { |
|
next = list_entry(dentry->d_child.next, struct dentry, d_child); |
|
if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR))) |
|
break; |
|
dentry->d_child.next = next->d_child.next; |
|
} |
|
} |
|
|
|
static void __dentry_kill(struct dentry *dentry) |
|
{ |
|
struct dentry *parent = NULL; |
|
bool can_free = true; |
|
if (!IS_ROOT(dentry)) |
|
parent = dentry->d_parent; |
|
|
|
/* |
|
* The dentry is now unrecoverably dead to the world. |
|
*/ |
|
lockref_mark_dead(&dentry->d_lockref); |
|
|
|
/* |
|
* inform the fs via d_prune that this dentry is about to be |
|
* unhashed and destroyed. |
|
*/ |
|
if (dentry->d_flags & DCACHE_OP_PRUNE) |
|
dentry->d_op->d_prune(dentry); |
|
|
|
if (dentry->d_flags & DCACHE_LRU_LIST) { |
|
if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) |
|
d_lru_del(dentry); |
|
} |
|
/* if it was on the hash then remove it */ |
|
__d_drop(dentry); |
|
dentry_unlist(dentry, parent); |
|
if (parent) |
|
spin_unlock(&parent->d_lock); |
|
if (dentry->d_inode) |
|
dentry_unlink_inode(dentry); |
|
else |
|
spin_unlock(&dentry->d_lock); |
|
this_cpu_dec(nr_dentry); |
|
if (dentry->d_op && dentry->d_op->d_release) |
|
dentry->d_op->d_release(dentry); |
|
|
|
spin_lock(&dentry->d_lock); |
|
if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
|
dentry->d_flags |= DCACHE_MAY_FREE; |
|
can_free = false; |
|
} |
|
spin_unlock(&dentry->d_lock); |
|
if (likely(can_free)) |
|
dentry_free(dentry); |
|
cond_resched(); |
|
} |
|
|
|
static struct dentry *__lock_parent(struct dentry *dentry) |
|
{ |
|
struct dentry *parent; |
|
rcu_read_lock(); |
|
spin_unlock(&dentry->d_lock); |
|
again: |
|
parent = READ_ONCE(dentry->d_parent); |
|
spin_lock(&parent->d_lock); |
|
/* |
|
* We can't blindly lock dentry until we are sure |
|
* that we won't violate the locking order. |
|
* Any changes of dentry->d_parent must have |
|
* been done with parent->d_lock held, so |
|
* spin_lock() above is enough of a barrier |
|
* for checking if it's still our child. |
|
*/ |
|
if (unlikely(parent != dentry->d_parent)) { |
|
spin_unlock(&parent->d_lock); |
|
goto again; |
|
} |
|
rcu_read_unlock(); |
|
if (parent != dentry) |
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
|
else |
|
parent = NULL; |
|
return parent; |
|
} |
|
|
|
static inline struct dentry *lock_parent(struct dentry *dentry) |
|
{ |
|
struct dentry *parent = dentry->d_parent; |
|
if (IS_ROOT(dentry)) |
|
return NULL; |
|
if (likely(spin_trylock(&parent->d_lock))) |
|
return parent; |
|
return __lock_parent(dentry); |
|
} |
|
|
|
static inline bool retain_dentry(struct dentry *dentry) |
|
{ |
|
WARN_ON(d_in_lookup(dentry)); |
|
|
|
/* Unreachable? Get rid of it */ |
|
if (unlikely(d_unhashed(dentry))) |
|
return false; |
|
|
|
if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) |
|
return false; |
|
|
|
if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) { |
|
if (dentry->d_op->d_delete(dentry)) |
|
return false; |
|
} |
|
|
|
if (unlikely(dentry->d_flags & DCACHE_DONTCACHE)) |
|
return false; |
|
|
|
/* retain; LRU fodder */ |
|
dentry->d_lockref.count--; |
|
if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) |
|
d_lru_add(dentry); |
|
else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED))) |
|
dentry->d_flags |= DCACHE_REFERENCED; |
|
return true; |
|
} |
|
|
|
void d_mark_dontcache(struct inode *inode) |
|
{ |
|
struct dentry *de; |
|
|
|
spin_lock(&inode->i_lock); |
|
hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) { |
|
spin_lock(&de->d_lock); |
|
de->d_flags |= DCACHE_DONTCACHE; |
|
spin_unlock(&de->d_lock); |
|
} |
|
inode->i_state |= I_DONTCACHE; |
|
spin_unlock(&inode->i_lock); |
|
} |
|
EXPORT_SYMBOL(d_mark_dontcache); |
|
|
|
/* |
|
* Finish off a dentry we've decided to kill. |
|
* dentry->d_lock must be held, returns with it unlocked. |
|
* Returns dentry requiring refcount drop, or NULL if we're done. |
|
*/ |
|
static struct dentry *dentry_kill(struct dentry *dentry) |
|
__releases(dentry->d_lock) |
|
{ |
|
struct inode *inode = dentry->d_inode; |
|
struct dentry *parent = NULL; |
|
|
|
if (inode && unlikely(!spin_trylock(&inode->i_lock))) |
|
goto slow_positive; |
|
|
|
if (!IS_ROOT(dentry)) { |
|
parent = dentry->d_parent; |
|
if (unlikely(!spin_trylock(&parent->d_lock))) { |
|
parent = __lock_parent(dentry); |
|
if (likely(inode || !dentry->d_inode)) |
|
goto got_locks; |
|
/* negative that became positive */ |
|
if (parent) |
|
spin_unlock(&parent->d_lock); |
|
inode = dentry->d_inode; |
|
goto slow_positive; |
|
} |
|
} |
|
__dentry_kill(dentry); |
|
return parent; |
|
|
|
slow_positive: |
|
spin_unlock(&dentry->d_lock); |
|
spin_lock(&inode->i_lock); |
|
spin_lock(&dentry->d_lock); |
|
parent = lock_parent(dentry); |
|
got_locks: |
|
if (unlikely(dentry->d_lockref.count != 1)) { |
|
dentry->d_lockref.count--; |
|
} else if (likely(!retain_dentry(dentry))) { |
|
__dentry_kill(dentry); |
|
return parent; |
|
} |
|
/* we are keeping it, after all */ |
|
if (inode) |
|
spin_unlock(&inode->i_lock); |
|
if (parent) |
|
spin_unlock(&parent->d_lock); |
|
spin_unlock(&dentry->d_lock); |
|
return NULL; |
|
} |
|
|
|
/* |
|
* Try to do a lockless dput(), and return whether that was successful. |
|
* |
|
* If unsuccessful, we return false, having already taken the dentry lock. |
|
* |
|
* The caller needs to hold the RCU read lock, so that the dentry is |
|
* guaranteed to stay around even if the refcount goes down to zero! |
|
*/ |
|
static inline bool fast_dput(struct dentry *dentry) |
|
{ |
|
int ret; |
|
unsigned int d_flags; |
|
|
|
/* |
|
* If we have a d_op->d_delete() operation, we sould not |
|
* let the dentry count go to zero, so use "put_or_lock". |
|
*/ |
|
if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) |
|
return lockref_put_or_lock(&dentry->d_lockref); |
|
|
|
/* |
|
* .. otherwise, we can try to just decrement the |
|
* lockref optimistically. |
|
*/ |
|
ret = lockref_put_return(&dentry->d_lockref); |
|
|
|
/* |
|
* If the lockref_put_return() failed due to the lock being held |
|
* by somebody else, the fast path has failed. We will need to |
|
* get the lock, and then check the count again. |
|
*/ |
|
if (unlikely(ret < 0)) { |
|
spin_lock(&dentry->d_lock); |
|
if (dentry->d_lockref.count > 1) { |
|
dentry->d_lockref.count--; |
|
spin_unlock(&dentry->d_lock); |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
/* |
|
* If we weren't the last ref, we're done. |
|
*/ |
|
if (ret) |
|
return true; |
|
|
|
/* |
|
* Careful, careful. The reference count went down |
|
* to zero, but we don't hold the dentry lock, so |
|
* somebody else could get it again, and do another |
|
* dput(), and we need to not race with that. |
|
* |
|
* However, there is a very special and common case |
|
* where we don't care, because there is nothing to |
|
* do: the dentry is still hashed, it does not have |
|
* a 'delete' op, and it's referenced and already on |
|
* the LRU list. |
|
* |
|
* NOTE! Since we aren't locked, these values are |
|
* not "stable". However, it is sufficient that at |
|
* some point after we dropped the reference the |
|
* dentry was hashed and the flags had the proper |
|
* value. Other dentry users may have re-gotten |
|
* a reference to the dentry and change that, but |
|
* our work is done - we can leave the dentry |
|
* around with a zero refcount. |
|
* |
|
* Nevertheless, there are two cases that we should kill |
|
* the dentry anyway. |
|
* 1. free disconnected dentries as soon as their refcount |
|
* reached zero. |
|
* 2. free dentries if they should not be cached. |
|
*/ |
|
smp_rmb(); |
|
d_flags = READ_ONCE(dentry->d_flags); |
|
d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | |
|
DCACHE_DISCONNECTED | DCACHE_DONTCACHE; |
|
|
|
/* Nothing to do? Dropping the reference was all we needed? */ |
|
if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry)) |
|
return true; |
|
|
|
/* |
|
* Not the fast normal case? Get the lock. We've already decremented |
|
* the refcount, but we'll need to re-check the situation after |
|
* getting the lock. |
|
*/ |
|
spin_lock(&dentry->d_lock); |
|
|
|
/* |
|
* Did somebody else grab a reference to it in the meantime, and |
|
* we're no longer the last user after all? Alternatively, somebody |
|
* else could have killed it and marked it dead. Either way, we |
|
* don't need to do anything else. |
|
*/ |
|
if (dentry->d_lockref.count) { |
|
spin_unlock(&dentry->d_lock); |
|
return true; |
|
} |
|
|
|
/* |
|
* Re-get the reference we optimistically dropped. We hold the |
|
* lock, and we just tested that it was zero, so we can just |
|
* set it to 1. |
|
*/ |
|
dentry->d_lockref.count = 1; |
|
return false; |
|
} |
|
|
|
|
|
/* |
|
* This is dput |
|
* |
|
* This is complicated by the fact that we do not want to put |
|
* dentries that are no longer on any hash chain on the unused |
|
* list: we'd much rather just get rid of them immediately. |
|
* |
|
* However, that implies that we have to traverse the dentry |
|
* tree upwards to the parents which might _also_ now be |
|
* scheduled for deletion (it may have been only waiting for |
|
* its last child to go away). |
|
* |
|
* This tail recursion is done by hand as we don't want to depend |
|
* on the compiler to always get this right (gcc generally doesn't). |
|
* Real recursion would eat up our stack space. |
|
*/ |
|
|
|
/* |
|
* dput - release a dentry |
|
* @dentry: dentry to release |
|
* |
|
* Release a dentry. This will drop the usage count and if appropriate |
|
* call the dentry unlink method as well as removing it from the queues and |
|
* releasing its resources. If the parent dentries were scheduled for release |
|
* they too may now get deleted. |
|
*/ |
|
void dput(struct dentry *dentry) |
|
{ |
|
while (dentry) { |
|
might_sleep(); |
|
|
|
rcu_read_lock(); |
|
if (likely(fast_dput(dentry))) { |
|
rcu_read_unlock(); |
|
return; |
|
} |
|
|
|
/* Slow case: now with the dentry lock held */ |
|
rcu_read_unlock(); |
|
|
|
if (likely(retain_dentry(dentry))) { |
|
spin_unlock(&dentry->d_lock); |
|
return; |
|
} |
|
|
|
dentry = dentry_kill(dentry); |
|
} |
|
} |
|
EXPORT_SYMBOL(dput); |
|
|
|
static void __dput_to_list(struct dentry *dentry, struct list_head *list) |
|
__must_hold(&dentry->d_lock) |
|
{ |
|
if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
|
/* let the owner of the list it's on deal with it */ |
|
--dentry->d_lockref.count; |
|
} else { |
|
if (dentry->d_flags & DCACHE_LRU_LIST) |
|
d_lru_del(dentry); |
|
if (!--dentry->d_lockref.count) |
|
d_shrink_add(dentry, list); |
|
} |
|
} |
|
|
|
void dput_to_list(struct dentry *dentry, struct list_head *list) |
|
{ |
|
rcu_read_lock(); |
|
if (likely(fast_dput(dentry))) { |
|
rcu_read_unlock(); |
|
return; |
|
} |
|
rcu_read_unlock(); |
|
if (!retain_dentry(dentry)) |
|
__dput_to_list(dentry, list); |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
|
|
/* This must be called with d_lock held */ |
|
static inline void __dget_dlock(struct dentry *dentry) |
|
{ |
|
dentry->d_lockref.count++; |
|
} |
|
|
|
static inline void __dget(struct dentry *dentry) |
|
{ |
|
lockref_get(&dentry->d_lockref); |
|
} |
|
|
|
struct dentry *dget_parent(struct dentry *dentry) |
|
{ |
|
int gotref; |
|
struct dentry *ret; |
|
unsigned seq; |
|
|
|
/* |
|
* Do optimistic parent lookup without any |
|
* locking. |
|
*/ |
|
rcu_read_lock(); |
|
seq = raw_seqcount_begin(&dentry->d_seq); |
|
ret = READ_ONCE(dentry->d_parent); |
|
gotref = lockref_get_not_zero(&ret->d_lockref); |
|
rcu_read_unlock(); |
|
if (likely(gotref)) { |
|
if (!read_seqcount_retry(&dentry->d_seq, seq)) |
|
return ret; |
|
dput(ret); |
|
} |
|
|
|
repeat: |
|
/* |
|
* Don't need rcu_dereference because we re-check it was correct under |
|
* the lock. |
|
*/ |
|
rcu_read_lock(); |
|
ret = dentry->d_parent; |
|
spin_lock(&ret->d_lock); |
|
if (unlikely(ret != dentry->d_parent)) { |
|
spin_unlock(&ret->d_lock); |
|
rcu_read_unlock(); |
|
goto repeat; |
|
} |
|
rcu_read_unlock(); |
|
BUG_ON(!ret->d_lockref.count); |
|
ret->d_lockref.count++; |
|
spin_unlock(&ret->d_lock); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(dget_parent); |
|
|
|
static struct dentry * __d_find_any_alias(struct inode *inode) |
|
{ |
|
struct dentry *alias; |
|
|
|
if (hlist_empty(&inode->i_dentry)) |
|
return NULL; |
|
alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias); |
|
__dget(alias); |
|
return alias; |
|
} |
|
|
|
/** |
|
* d_find_any_alias - find any alias for a given inode |
|
* @inode: inode to find an alias for |
|
* |
|
* If any aliases exist for the given inode, take and return a |
|
* reference for one of them. If no aliases exist, return %NULL. |
|
*/ |
|
struct dentry *d_find_any_alias(struct inode *inode) |
|
{ |
|
struct dentry *de; |
|
|
|
spin_lock(&inode->i_lock); |
|
de = __d_find_any_alias(inode); |
|
spin_unlock(&inode->i_lock); |
|
return de; |
|
} |
|
EXPORT_SYMBOL(d_find_any_alias); |
|
|
|
static struct dentry *__d_find_alias(struct inode *inode) |
|
{ |
|
struct dentry *alias; |
|
|
|
if (S_ISDIR(inode->i_mode)) |
|
return __d_find_any_alias(inode); |
|
|
|
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { |
|
spin_lock(&alias->d_lock); |
|
if (!d_unhashed(alias)) { |
|
__dget_dlock(alias); |
|
spin_unlock(&alias->d_lock); |
|
return alias; |
|
} |
|
spin_unlock(&alias->d_lock); |
|
} |
|
return NULL; |
|
} |
|
|
|
/** |
|
* d_find_alias - grab a hashed alias of inode |
|
* @inode: inode in question |
|
* |
|
* If inode has a hashed alias, or is a directory and has any alias, |
|
* acquire the reference to alias and return it. Otherwise return NULL. |
|
* Notice that if inode is a directory there can be only one alias and |
|
* it can be unhashed only if it has no children, or if it is the root |
|
* of a filesystem, or if the directory was renamed and d_revalidate |
|
* was the first vfs operation to notice. |
|
* |
|
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer |
|
* any other hashed alias over that one. |
|
*/ |
|
struct dentry *d_find_alias(struct inode *inode) |
|
{ |
|
struct dentry *de = NULL; |
|
|
|
if (!hlist_empty(&inode->i_dentry)) { |
|
spin_lock(&inode->i_lock); |
|
de = __d_find_alias(inode); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
return de; |
|
} |
|
EXPORT_SYMBOL(d_find_alias); |
|
|
|
/* |
|
* Caller MUST be holding rcu_read_lock() and be guaranteed |
|
* that inode won't get freed until rcu_read_unlock(). |
|
*/ |
|
struct dentry *d_find_alias_rcu(struct inode *inode) |
|
{ |
|
struct hlist_head *l = &inode->i_dentry; |
|
struct dentry *de = NULL; |
|
|
|
spin_lock(&inode->i_lock); |
|
// ->i_dentry and ->i_rcu are colocated, but the latter won't be |
|
// used without having I_FREEING set, which means no aliases left |
|
if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) { |
|
if (S_ISDIR(inode->i_mode)) { |
|
de = hlist_entry(l->first, struct dentry, d_u.d_alias); |
|
} else { |
|
hlist_for_each_entry(de, l, d_u.d_alias) |
|
if (!d_unhashed(de)) |
|
break; |
|
} |
|
} |
|
spin_unlock(&inode->i_lock); |
|
return de; |
|
} |
|
|
|
/* |
|
* Try to kill dentries associated with this inode. |
|
* WARNING: you must own a reference to inode. |
|
*/ |
|
void d_prune_aliases(struct inode *inode) |
|
{ |
|
struct dentry *dentry; |
|
restart: |
|
spin_lock(&inode->i_lock); |
|
hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) { |
|
spin_lock(&dentry->d_lock); |
|
if (!dentry->d_lockref.count) { |
|
struct dentry *parent = lock_parent(dentry); |
|
if (likely(!dentry->d_lockref.count)) { |
|
__dentry_kill(dentry); |
|
dput(parent); |
|
goto restart; |
|
} |
|
if (parent) |
|
spin_unlock(&parent->d_lock); |
|
} |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
spin_unlock(&inode->i_lock); |
|
} |
|
EXPORT_SYMBOL(d_prune_aliases); |
|
|
|
/* |
|
* Lock a dentry from shrink list. |
|
* Called under rcu_read_lock() and dentry->d_lock; the former |
|
* guarantees that nothing we access will be freed under us. |
|
* Note that dentry is *not* protected from concurrent dentry_kill(), |
|
* d_delete(), etc. |
|
* |
|
* Return false if dentry has been disrupted or grabbed, leaving |
|
* the caller to kick it off-list. Otherwise, return true and have |
|
* that dentry's inode and parent both locked. |
|
*/ |
|
static bool shrink_lock_dentry(struct dentry *dentry) |
|
{ |
|
struct inode *inode; |
|
struct dentry *parent; |
|
|
|
if (dentry->d_lockref.count) |
|
return false; |
|
|
|
inode = dentry->d_inode; |
|
if (inode && unlikely(!spin_trylock(&inode->i_lock))) { |
|
spin_unlock(&dentry->d_lock); |
|
spin_lock(&inode->i_lock); |
|
spin_lock(&dentry->d_lock); |
|
if (unlikely(dentry->d_lockref.count)) |
|
goto out; |
|
/* changed inode means that somebody had grabbed it */ |
|
if (unlikely(inode != dentry->d_inode)) |
|
goto out; |
|
} |
|
|
|
parent = dentry->d_parent; |
|
if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock))) |
|
return true; |
|
|
|
spin_unlock(&dentry->d_lock); |
|
spin_lock(&parent->d_lock); |
|
if (unlikely(parent != dentry->d_parent)) { |
|
spin_unlock(&parent->d_lock); |
|
spin_lock(&dentry->d_lock); |
|
goto out; |
|
} |
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
|
if (likely(!dentry->d_lockref.count)) |
|
return true; |
|
spin_unlock(&parent->d_lock); |
|
out: |
|
if (inode) |
|
spin_unlock(&inode->i_lock); |
|
return false; |
|
} |
|
|
|
void shrink_dentry_list(struct list_head *list) |
|
{ |
|
while (!list_empty(list)) { |
|
struct dentry *dentry, *parent; |
|
|
|
dentry = list_entry(list->prev, struct dentry, d_lru); |
|
spin_lock(&dentry->d_lock); |
|
rcu_read_lock(); |
|
if (!shrink_lock_dentry(dentry)) { |
|
bool can_free = false; |
|
rcu_read_unlock(); |
|
d_shrink_del(dentry); |
|
if (dentry->d_lockref.count < 0) |
|
can_free = dentry->d_flags & DCACHE_MAY_FREE; |
|
spin_unlock(&dentry->d_lock); |
|
if (can_free) |
|
dentry_free(dentry); |
|
continue; |
|
} |
|
rcu_read_unlock(); |
|
d_shrink_del(dentry); |
|
parent = dentry->d_parent; |
|
if (parent != dentry) |
|
__dput_to_list(parent, list); |
|
__dentry_kill(dentry); |
|
} |
|
} |
|
|
|
static enum lru_status dentry_lru_isolate(struct list_head *item, |
|
struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) |
|
{ |
|
struct list_head *freeable = arg; |
|
struct dentry *dentry = container_of(item, struct dentry, d_lru); |
|
|
|
|
|
/* |
|
* we are inverting the lru lock/dentry->d_lock here, |
|
* so use a trylock. If we fail to get the lock, just skip |
|
* it |
|
*/ |
|
if (!spin_trylock(&dentry->d_lock)) |
|
return LRU_SKIP; |
|
|
|
/* |
|
* Referenced dentries are still in use. If they have active |
|
* counts, just remove them from the LRU. Otherwise give them |
|
* another pass through the LRU. |
|
*/ |
|
if (dentry->d_lockref.count) { |
|
d_lru_isolate(lru, dentry); |
|
spin_unlock(&dentry->d_lock); |
|
return LRU_REMOVED; |
|
} |
|
|
|
if (dentry->d_flags & DCACHE_REFERENCED) { |
|
dentry->d_flags &= ~DCACHE_REFERENCED; |
|
spin_unlock(&dentry->d_lock); |
|
|
|
/* |
|
* The list move itself will be made by the common LRU code. At |
|
* this point, we've dropped the dentry->d_lock but keep the |
|
* lru lock. This is safe to do, since every list movement is |
|
* protected by the lru lock even if both locks are held. |
|
* |
|
* This is guaranteed by the fact that all LRU management |
|
* functions are intermediated by the LRU API calls like |
|
* list_lru_add and list_lru_del. List movement in this file |
|
* only ever occur through this functions or through callbacks |
|
* like this one, that are called from the LRU API. |
|
* |
|
* The only exceptions to this are functions like |
|
* shrink_dentry_list, and code that first checks for the |
|
* DCACHE_SHRINK_LIST flag. Those are guaranteed to be |
|
* operating only with stack provided lists after they are |
|
* properly isolated from the main list. It is thus, always a |
|
* local access. |
|
*/ |
|
return LRU_ROTATE; |
|
} |
|
|
|
d_lru_shrink_move(lru, dentry, freeable); |
|
spin_unlock(&dentry->d_lock); |
|
|
|
return LRU_REMOVED; |
|
} |
|
|
|
/** |
|
* prune_dcache_sb - shrink the dcache |
|
* @sb: superblock |
|
* @sc: shrink control, passed to list_lru_shrink_walk() |
|
* |
|
* Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This |
|
* is done when we need more memory and called from the superblock shrinker |
|
* function. |
|
* |
|
* This function may fail to free any resources if all the dentries are in |
|
* use. |
|
*/ |
|
long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc) |
|
{ |
|
LIST_HEAD(dispose); |
|
long freed; |
|
|
|
freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc, |
|
dentry_lru_isolate, &dispose); |
|
shrink_dentry_list(&dispose); |
|
return freed; |
|
} |
|
|
|
static enum lru_status dentry_lru_isolate_shrink(struct list_head *item, |
|
struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) |
|
{ |
|
struct list_head *freeable = arg; |
|
struct dentry *dentry = container_of(item, struct dentry, d_lru); |
|
|
|
/* |
|
* we are inverting the lru lock/dentry->d_lock here, |
|
* so use a trylock. If we fail to get the lock, just skip |
|
* it |
|
*/ |
|
if (!spin_trylock(&dentry->d_lock)) |
|
return LRU_SKIP; |
|
|
|
d_lru_shrink_move(lru, dentry, freeable); |
|
spin_unlock(&dentry->d_lock); |
|
|
|
return LRU_REMOVED; |
|
} |
|
|
|
|
|
/** |
|
* shrink_dcache_sb - shrink dcache for a superblock |
|
* @sb: superblock |
|
* |
|
* Shrink the dcache for the specified super block. This is used to free |
|
* the dcache before unmounting a file system. |
|
*/ |
|
void shrink_dcache_sb(struct super_block *sb) |
|
{ |
|
do { |
|
LIST_HEAD(dispose); |
|
|
|
list_lru_walk(&sb->s_dentry_lru, |
|
dentry_lru_isolate_shrink, &dispose, 1024); |
|
shrink_dentry_list(&dispose); |
|
} while (list_lru_count(&sb->s_dentry_lru) > 0); |
|
} |
|
EXPORT_SYMBOL(shrink_dcache_sb); |
|
|
|
/** |
|
* enum d_walk_ret - action to talke during tree walk |
|
* @D_WALK_CONTINUE: contrinue walk |
|
* @D_WALK_QUIT: quit walk |
|
* @D_WALK_NORETRY: quit when retry is needed |
|
* @D_WALK_SKIP: skip this dentry and its children |
|
*/ |
|
enum d_walk_ret { |
|
D_WALK_CONTINUE, |
|
D_WALK_QUIT, |
|
D_WALK_NORETRY, |
|
D_WALK_SKIP, |
|
}; |
|
|
|
/** |
|
* d_walk - walk the dentry tree |
|
* @parent: start of walk |
|
* @data: data passed to @enter() and @finish() |
|
* @enter: callback when first entering the dentry |
|
* |
|
* The @enter() callbacks are called with d_lock held. |
|
*/ |
|
static void d_walk(struct dentry *parent, void *data, |
|
enum d_walk_ret (*enter)(void *, struct dentry *)) |
|
{ |
|
struct dentry *this_parent; |
|
struct list_head *next; |
|
unsigned seq = 0; |
|
enum d_walk_ret ret; |
|
bool retry = true; |
|
|
|
again: |
|
read_seqbegin_or_lock(&rename_lock, &seq); |
|
this_parent = parent; |
|
spin_lock(&this_parent->d_lock); |
|
|
|
ret = enter(data, this_parent); |
|
switch (ret) { |
|
case D_WALK_CONTINUE: |
|
break; |
|
case D_WALK_QUIT: |
|
case D_WALK_SKIP: |
|
goto out_unlock; |
|
case D_WALK_NORETRY: |
|
retry = false; |
|
break; |
|
} |
|
repeat: |
|
next = this_parent->d_subdirs.next; |
|
resume: |
|
while (next != &this_parent->d_subdirs) { |
|
struct list_head *tmp = next; |
|
struct dentry *dentry = list_entry(tmp, struct dentry, d_child); |
|
next = tmp->next; |
|
|
|
if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR)) |
|
continue; |
|
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
|
|
|
ret = enter(data, dentry); |
|
switch (ret) { |
|
case D_WALK_CONTINUE: |
|
break; |
|
case D_WALK_QUIT: |
|
spin_unlock(&dentry->d_lock); |
|
goto out_unlock; |
|
case D_WALK_NORETRY: |
|
retry = false; |
|
break; |
|
case D_WALK_SKIP: |
|
spin_unlock(&dentry->d_lock); |
|
continue; |
|
} |
|
|
|
if (!list_empty(&dentry->d_subdirs)) { |
|
spin_unlock(&this_parent->d_lock); |
|
spin_release(&dentry->d_lock.dep_map, _RET_IP_); |
|
this_parent = dentry; |
|
spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
|
goto repeat; |
|
} |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
/* |
|
* All done at this level ... ascend and resume the search. |
|
*/ |
|
rcu_read_lock(); |
|
ascend: |
|
if (this_parent != parent) { |
|
struct dentry *child = this_parent; |
|
this_parent = child->d_parent; |
|
|
|
spin_unlock(&child->d_lock); |
|
spin_lock(&this_parent->d_lock); |
|
|
|
/* might go back up the wrong parent if we have had a rename. */ |
|
if (need_seqretry(&rename_lock, seq)) |
|
goto rename_retry; |
|
/* go into the first sibling still alive */ |
|
do { |
|
next = child->d_child.next; |
|
if (next == &this_parent->d_subdirs) |
|
goto ascend; |
|
child = list_entry(next, struct dentry, d_child); |
|
} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)); |
|
rcu_read_unlock(); |
|
goto resume; |
|
} |
|
if (need_seqretry(&rename_lock, seq)) |
|
goto rename_retry; |
|
rcu_read_unlock(); |
|
|
|
out_unlock: |
|
spin_unlock(&this_parent->d_lock); |
|
done_seqretry(&rename_lock, seq); |
|
return; |
|
|
|
rename_retry: |
|
spin_unlock(&this_parent->d_lock); |
|
rcu_read_unlock(); |
|
BUG_ON(seq & 1); |
|
if (!retry) |
|
return; |
|
seq = 1; |
|
goto again; |
|
} |
|
|
|
struct check_mount { |
|
struct vfsmount *mnt; |
|
unsigned int mounted; |
|
}; |
|
|
|
static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry) |
|
{ |
|
struct check_mount *info = data; |
|
struct path path = { .mnt = info->mnt, .dentry = dentry }; |
|
|
|
if (likely(!d_mountpoint(dentry))) |
|
return D_WALK_CONTINUE; |
|
if (__path_is_mountpoint(&path)) { |
|
info->mounted = 1; |
|
return D_WALK_QUIT; |
|
} |
|
return D_WALK_CONTINUE; |
|
} |
|
|
|
/** |
|
* path_has_submounts - check for mounts over a dentry in the |
|
* current namespace. |
|
* @parent: path to check. |
|
* |
|
* Return true if the parent or its subdirectories contain |
|
* a mount point in the current namespace. |
|
*/ |
|
int path_has_submounts(const struct path *parent) |
|
{ |
|
struct check_mount data = { .mnt = parent->mnt, .mounted = 0 }; |
|
|
|
read_seqlock_excl(&mount_lock); |
|
d_walk(parent->dentry, &data, path_check_mount); |
|
read_sequnlock_excl(&mount_lock); |
|
|
|
return data.mounted; |
|
} |
|
EXPORT_SYMBOL(path_has_submounts); |
|
|
|
/* |
|
* Called by mount code to set a mountpoint and check if the mountpoint is |
|
* reachable (e.g. NFS can unhash a directory dentry and then the complete |
|
* subtree can become unreachable). |
|
* |
|
* Only one of d_invalidate() and d_set_mounted() must succeed. For |
|
* this reason take rename_lock and d_lock on dentry and ancestors. |
|
*/ |
|
int d_set_mounted(struct dentry *dentry) |
|
{ |
|
struct dentry *p; |
|
int ret = -ENOENT; |
|
write_seqlock(&rename_lock); |
|
for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) { |
|
/* Need exclusion wrt. d_invalidate() */ |
|
spin_lock(&p->d_lock); |
|
if (unlikely(d_unhashed(p))) { |
|
spin_unlock(&p->d_lock); |
|
goto out; |
|
} |
|
spin_unlock(&p->d_lock); |
|
} |
|
spin_lock(&dentry->d_lock); |
|
if (!d_unlinked(dentry)) { |
|
ret = -EBUSY; |
|
if (!d_mountpoint(dentry)) { |
|
dentry->d_flags |= DCACHE_MOUNTED; |
|
ret = 0; |
|
} |
|
} |
|
spin_unlock(&dentry->d_lock); |
|
out: |
|
write_sequnlock(&rename_lock); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Search the dentry child list of the specified parent, |
|
* and move any unused dentries to the end of the unused |
|
* list for prune_dcache(). We descend to the next level |
|
* whenever the d_subdirs list is non-empty and continue |
|
* searching. |
|
* |
|
* It returns zero iff there are no unused children, |
|
* otherwise it returns the number of children moved to |
|
* the end of the unused list. This may not be the total |
|
* number of unused children, because select_parent can |
|
* drop the lock and return early due to latency |
|
* constraints. |
|
*/ |
|
|
|
struct select_data { |
|
struct dentry *start; |
|
union { |
|
long found; |
|
struct dentry *victim; |
|
}; |
|
struct list_head dispose; |
|
}; |
|
|
|
static enum d_walk_ret select_collect(void *_data, struct dentry *dentry) |
|
{ |
|
struct select_data *data = _data; |
|
enum d_walk_ret ret = D_WALK_CONTINUE; |
|
|
|
if (data->start == dentry) |
|
goto out; |
|
|
|
if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
|
data->found++; |
|
} else { |
|
if (dentry->d_flags & DCACHE_LRU_LIST) |
|
d_lru_del(dentry); |
|
if (!dentry->d_lockref.count) { |
|
d_shrink_add(dentry, &data->dispose); |
|
data->found++; |
|
} |
|
} |
|
/* |
|
* We can return to the caller if we have found some (this |
|
* ensures forward progress). We'll be coming back to find |
|
* the rest. |
|
*/ |
|
if (!list_empty(&data->dispose)) |
|
ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY; |
|
out: |
|
return ret; |
|
} |
|
|
|
static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry) |
|
{ |
|
struct select_data *data = _data; |
|
enum d_walk_ret ret = D_WALK_CONTINUE; |
|
|
|
if (data->start == dentry) |
|
goto out; |
|
|
|
if (dentry->d_flags & DCACHE_SHRINK_LIST) { |
|
if (!dentry->d_lockref.count) { |
|
rcu_read_lock(); |
|
data->victim = dentry; |
|
return D_WALK_QUIT; |
|
} |
|
} else { |
|
if (dentry->d_flags & DCACHE_LRU_LIST) |
|
d_lru_del(dentry); |
|
if (!dentry->d_lockref.count) |
|
d_shrink_add(dentry, &data->dispose); |
|
} |
|
/* |
|
* We can return to the caller if we have found some (this |
|
* ensures forward progress). We'll be coming back to find |
|
* the rest. |
|
*/ |
|
if (!list_empty(&data->dispose)) |
|
ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY; |
|
out: |
|
return ret; |
|
} |
|
|
|
/** |
|
* shrink_dcache_parent - prune dcache |
|
* @parent: parent of entries to prune |
|
* |
|
* Prune the dcache to remove unused children of the parent dentry. |
|
*/ |
|
void shrink_dcache_parent(struct dentry *parent) |
|
{ |
|
for (;;) { |
|
struct select_data data = {.start = parent}; |
|
|
|
INIT_LIST_HEAD(&data.dispose); |
|
d_walk(parent, &data, select_collect); |
|
|
|
if (!list_empty(&data.dispose)) { |
|
shrink_dentry_list(&data.dispose); |
|
continue; |
|
} |
|
|
|
cond_resched(); |
|
if (!data.found) |
|
break; |
|
data.victim = NULL; |
|
d_walk(parent, &data, select_collect2); |
|
if (data.victim) { |
|
struct dentry *parent; |
|
spin_lock(&data.victim->d_lock); |
|
if (!shrink_lock_dentry(data.victim)) { |
|
spin_unlock(&data.victim->d_lock); |
|
rcu_read_unlock(); |
|
} else { |
|
rcu_read_unlock(); |
|
parent = data.victim->d_parent; |
|
if (parent != data.victim) |
|
__dput_to_list(parent, &data.dispose); |
|
__dentry_kill(data.victim); |
|
} |
|
} |
|
if (!list_empty(&data.dispose)) |
|
shrink_dentry_list(&data.dispose); |
|
} |
|
} |
|
EXPORT_SYMBOL(shrink_dcache_parent); |
|
|
|
static enum d_walk_ret umount_check(void *_data, struct dentry *dentry) |
|
{ |
|
/* it has busy descendents; complain about those instead */ |
|
if (!list_empty(&dentry->d_subdirs)) |
|
return D_WALK_CONTINUE; |
|
|
|
/* root with refcount 1 is fine */ |
|
if (dentry == _data && dentry->d_lockref.count == 1) |
|
return D_WALK_CONTINUE; |
|
|
|
printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} " |
|
" still in use (%d) [unmount of %s %s]\n", |
|
dentry, |
|
dentry->d_inode ? |
|
dentry->d_inode->i_ino : 0UL, |
|
dentry, |
|
dentry->d_lockref.count, |
|
dentry->d_sb->s_type->name, |
|
dentry->d_sb->s_id); |
|
WARN_ON(1); |
|
return D_WALK_CONTINUE; |
|
} |
|
|
|
static void do_one_tree(struct dentry *dentry) |
|
{ |
|
shrink_dcache_parent(dentry); |
|
d_walk(dentry, dentry, umount_check); |
|
d_drop(dentry); |
|
dput(dentry); |
|
} |
|
|
|
/* |
|
* destroy the dentries attached to a superblock on unmounting |
|
*/ |
|
void shrink_dcache_for_umount(struct super_block *sb) |
|
{ |
|
struct dentry *dentry; |
|
|
|
WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked"); |
|
|
|
dentry = sb->s_root; |
|
sb->s_root = NULL; |
|
do_one_tree(dentry); |
|
|
|
while (!hlist_bl_empty(&sb->s_roots)) { |
|
dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash)); |
|
do_one_tree(dentry); |
|
} |
|
} |
|
|
|
static enum d_walk_ret find_submount(void *_data, struct dentry *dentry) |
|
{ |
|
struct dentry **victim = _data; |
|
if (d_mountpoint(dentry)) { |
|
__dget_dlock(dentry); |
|
*victim = dentry; |
|
return D_WALK_QUIT; |
|
} |
|
return D_WALK_CONTINUE; |
|
} |
|
|
|
/** |
|
* d_invalidate - detach submounts, prune dcache, and drop |
|
* @dentry: dentry to invalidate (aka detach, prune and drop) |
|
*/ |
|
void d_invalidate(struct dentry *dentry) |
|
{ |
|
bool had_submounts = false; |
|
spin_lock(&dentry->d_lock); |
|
if (d_unhashed(dentry)) { |
|
spin_unlock(&dentry->d_lock); |
|
return; |
|
} |
|
__d_drop(dentry); |
|
spin_unlock(&dentry->d_lock); |
|
|
|
/* Negative dentries can be dropped without further checks */ |
|
if (!dentry->d_inode) |
|
return; |
|
|
|
shrink_dcache_parent(dentry); |
|
for (;;) { |
|
struct dentry *victim = NULL; |
|
d_walk(dentry, &victim, find_submount); |
|
if (!victim) { |
|
if (had_submounts) |
|
shrink_dcache_parent(dentry); |
|
return; |
|
} |
|
had_submounts = true; |
|
detach_mounts(victim); |
|
dput(victim); |
|
} |
|
} |
|
EXPORT_SYMBOL(d_invalidate); |
|
|
|
/** |
|
* __d_alloc - allocate a dcache entry |
|
* @sb: filesystem it will belong to |
|
* @name: qstr of the name |
|
* |
|
* Allocates a dentry. It returns %NULL if there is insufficient memory |
|
* available. On a success the dentry is returned. The name passed in is |
|
* copied and the copy passed in may be reused after this call. |
|
*/ |
|
|
|
static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) |
|
{ |
|
struct dentry *dentry; |
|
char *dname; |
|
int err; |
|
|
|
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); |
|
if (!dentry) |
|
return NULL; |
|
|
|
/* |
|
* We guarantee that the inline name is always NUL-terminated. |
|
* This way the memcpy() done by the name switching in rename |
|
* will still always have a NUL at the end, even if we might |
|
* be overwriting an internal NUL character |
|
*/ |
|
dentry->d_iname[DNAME_INLINE_LEN-1] = 0; |
|
if (unlikely(!name)) { |
|
name = &slash_name; |
|
dname = dentry->d_iname; |
|
} else if (name->len > DNAME_INLINE_LEN-1) { |
|
size_t size = offsetof(struct external_name, name[1]); |
|
struct external_name *p = kmalloc(size + name->len, |
|
GFP_KERNEL_ACCOUNT | |
|
__GFP_RECLAIMABLE); |
|
if (!p) { |
|
kmem_cache_free(dentry_cache, dentry); |
|
return NULL; |
|
} |
|
atomic_set(&p->u.count, 1); |
|
dname = p->name; |
|
} else { |
|
dname = dentry->d_iname; |
|
} |
|
|
|
dentry->d_name.len = name->len; |
|
dentry->d_name.hash = name->hash; |
|
memcpy(dname, name->name, name->len); |
|
dname[name->len] = 0; |
|
|
|
/* Make sure we always see the terminating NUL character */ |
|
smp_store_release(&dentry->d_name.name, dname); /* ^^^ */ |
|
|
|
dentry->d_lockref.count = 1; |
|
dentry->d_flags = 0; |
|
spin_lock_init(&dentry->d_lock); |
|
seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock); |
|
dentry->d_inode = NULL; |
|
dentry->d_parent = dentry; |
|
dentry->d_sb = sb; |
|
dentry->d_op = NULL; |
|
dentry->d_fsdata = NULL; |
|
INIT_HLIST_BL_NODE(&dentry->d_hash); |
|
INIT_LIST_HEAD(&dentry->d_lru); |
|
INIT_LIST_HEAD(&dentry->d_subdirs); |
|
INIT_HLIST_NODE(&dentry->d_u.d_alias); |
|
INIT_LIST_HEAD(&dentry->d_child); |
|
d_set_d_op(dentry, dentry->d_sb->s_d_op); |
|
|
|
if (dentry->d_op && dentry->d_op->d_init) { |
|
err = dentry->d_op->d_init(dentry); |
|
if (err) { |
|
if (dname_external(dentry)) |
|
kfree(external_name(dentry)); |
|
kmem_cache_free(dentry_cache, dentry); |
|
return NULL; |
|
} |
|
} |
|
|
|
this_cpu_inc(nr_dentry); |
|
|
|
return dentry; |
|
} |
|
|
|
/** |
|
* d_alloc - allocate a dcache entry |
|
* @parent: parent of entry to allocate |
|
* @name: qstr of the name |
|
* |
|
* Allocates a dentry. It returns %NULL if there is insufficient memory |
|
* available. On a success the dentry is returned. The name passed in is |
|
* copied and the copy passed in may be reused after this call. |
|
*/ |
|
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) |
|
{ |
|
struct dentry *dentry = __d_alloc(parent->d_sb, name); |
|
if (!dentry) |
|
return NULL; |
|
spin_lock(&parent->d_lock); |
|
/* |
|
* don't need child lock because it is not subject |
|
* to concurrency here |
|
*/ |
|
__dget_dlock(parent); |
|
dentry->d_parent = parent; |
|
list_add(&dentry->d_child, &parent->d_subdirs); |
|
spin_unlock(&parent->d_lock); |
|
|
|
return dentry; |
|
} |
|
EXPORT_SYMBOL(d_alloc); |
|
|
|
struct dentry *d_alloc_anon(struct super_block *sb) |
|
{ |
|
return __d_alloc(sb, NULL); |
|
} |
|
EXPORT_SYMBOL(d_alloc_anon); |
|
|
|
struct dentry *d_alloc_cursor(struct dentry * parent) |
|
{ |
|
struct dentry *dentry = d_alloc_anon(parent->d_sb); |
|
if (dentry) { |
|
dentry->d_flags |= DCACHE_DENTRY_CURSOR; |
|
dentry->d_parent = dget(parent); |
|
} |
|
return dentry; |
|
} |
|
|
|
/** |
|
* d_alloc_pseudo - allocate a dentry (for lookup-less filesystems) |
|
* @sb: the superblock |
|
* @name: qstr of the name |
|
* |
|
* For a filesystem that just pins its dentries in memory and never |
|
* performs lookups at all, return an unhashed IS_ROOT dentry. |
|
* This is used for pipes, sockets et.al. - the stuff that should |
|
* never be anyone's children or parents. Unlike all other |
|
* dentries, these will not have RCU delay between dropping the |
|
* last reference and freeing them. |
|
* |
|
* The only user is alloc_file_pseudo() and that's what should |
|
* be considered a public interface. Don't use directly. |
|
*/ |
|
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) |
|
{ |
|
struct dentry *dentry = __d_alloc(sb, name); |
|
if (likely(dentry)) |
|
dentry->d_flags |= DCACHE_NORCU; |
|
return dentry; |
|
} |
|
|
|
struct dentry *d_alloc_name(struct dentry *parent, const char *name) |
|
{ |
|
struct qstr q; |
|
|
|
q.name = name; |
|
q.hash_len = hashlen_string(parent, name); |
|
return d_alloc(parent, &q); |
|
} |
|
EXPORT_SYMBOL(d_alloc_name); |
|
|
|
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) |
|
{ |
|
WARN_ON_ONCE(dentry->d_op); |
|
WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | |
|
DCACHE_OP_COMPARE | |
|
DCACHE_OP_REVALIDATE | |
|
DCACHE_OP_WEAK_REVALIDATE | |
|
DCACHE_OP_DELETE | |
|
DCACHE_OP_REAL)); |
|
dentry->d_op = op; |
|
if (!op) |
|
return; |
|
if (op->d_hash) |
|
dentry->d_flags |= DCACHE_OP_HASH; |
|
if (op->d_compare) |
|
dentry->d_flags |= DCACHE_OP_COMPARE; |
|
if (op->d_revalidate) |
|
dentry->d_flags |= DCACHE_OP_REVALIDATE; |
|
if (op->d_weak_revalidate) |
|
dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE; |
|
if (op->d_delete) |
|
dentry->d_flags |= DCACHE_OP_DELETE; |
|
if (op->d_prune) |
|
dentry->d_flags |= DCACHE_OP_PRUNE; |
|
if (op->d_real) |
|
dentry->d_flags |= DCACHE_OP_REAL; |
|
|
|
} |
|
EXPORT_SYMBOL(d_set_d_op); |
|
|
|
|
|
/* |
|
* d_set_fallthru - Mark a dentry as falling through to a lower layer |
|
* @dentry - The dentry to mark |
|
* |
|
* Mark a dentry as falling through to the lower layer (as set with |
|
* d_pin_lower()). This flag may be recorded on the medium. |
|
*/ |
|
void d_set_fallthru(struct dentry *dentry) |
|
{ |
|
spin_lock(&dentry->d_lock); |
|
dentry->d_flags |= DCACHE_FALLTHRU; |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
EXPORT_SYMBOL(d_set_fallthru); |
|
|
|
static unsigned d_flags_for_inode(struct inode *inode) |
|
{ |
|
unsigned add_flags = DCACHE_REGULAR_TYPE; |
|
|
|
if (!inode) |
|
return DCACHE_MISS_TYPE; |
|
|
|
if (S_ISDIR(inode->i_mode)) { |
|
add_flags = DCACHE_DIRECTORY_TYPE; |
|
if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) { |
|
if (unlikely(!inode->i_op->lookup)) |
|
add_flags = DCACHE_AUTODIR_TYPE; |
|
else |
|
inode->i_opflags |= IOP_LOOKUP; |
|
} |
|
goto type_determined; |
|
} |
|
|
|
if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { |
|
if (unlikely(inode->i_op->get_link)) { |
|
add_flags = DCACHE_SYMLINK_TYPE; |
|
goto type_determined; |
|
} |
|
inode->i_opflags |= IOP_NOFOLLOW; |
|
} |
|
|
|
if (unlikely(!S_ISREG(inode->i_mode))) |
|
add_flags = DCACHE_SPECIAL_TYPE; |
|
|
|
type_determined: |
|
if (unlikely(IS_AUTOMOUNT(inode))) |
|
add_flags |= DCACHE_NEED_AUTOMOUNT; |
|
return add_flags; |
|
} |
|
|
|
static void __d_instantiate(struct dentry *dentry, struct inode *inode) |
|
{ |
|
unsigned add_flags = d_flags_for_inode(inode); |
|
WARN_ON(d_in_lookup(dentry)); |
|
|
|
spin_lock(&dentry->d_lock); |
|
/* |
|
* Decrement negative dentry count if it was in the LRU list. |
|
*/ |
|
if (dentry->d_flags & DCACHE_LRU_LIST) |
|
this_cpu_dec(nr_dentry_negative); |
|
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
|
raw_write_seqcount_begin(&dentry->d_seq); |
|
__d_set_inode_and_type(dentry, inode, add_flags); |
|
raw_write_seqcount_end(&dentry->d_seq); |
|
fsnotify_update_flags(dentry); |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
|
|
/** |
|
* d_instantiate - fill in inode information for a dentry |
|
* @entry: dentry to complete |
|
* @inode: inode to attach to this dentry |
|
* |
|
* Fill in inode information in the entry. |
|
* |
|
* This turns negative dentries into productive full members |
|
* of society. |
|
* |
|
* NOTE! This assumes that the inode count has been incremented |
|
* (or otherwise set) by the caller to indicate that it is now |
|
* in use by the dcache. |
|
*/ |
|
|
|
void d_instantiate(struct dentry *entry, struct inode * inode) |
|
{ |
|
BUG_ON(!hlist_unhashed(&entry->d_u.d_alias)); |
|
if (inode) { |
|
security_d_instantiate(entry, inode); |
|
spin_lock(&inode->i_lock); |
|
__d_instantiate(entry, inode); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
} |
|
EXPORT_SYMBOL(d_instantiate); |
|
|
|
/* |
|
* This should be equivalent to d_instantiate() + unlock_new_inode(), |
|
* with lockdep-related part of unlock_new_inode() done before |
|
* anything else. Use that instead of open-coding d_instantiate()/ |
|
* unlock_new_inode() combinations. |
|
*/ |
|
void d_instantiate_new(struct dentry *entry, struct inode *inode) |
|
{ |
|
BUG_ON(!hlist_unhashed(&entry->d_u.d_alias)); |
|
BUG_ON(!inode); |
|
lockdep_annotate_inode_mutex_key(inode); |
|
security_d_instantiate(entry, inode); |
|
spin_lock(&inode->i_lock); |
|
__d_instantiate(entry, inode); |
|
WARN_ON(!(inode->i_state & I_NEW)); |
|
inode->i_state &= ~I_NEW & ~I_CREATING; |
|
smp_mb(); |
|
wake_up_bit(&inode->i_state, __I_NEW); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
EXPORT_SYMBOL(d_instantiate_new); |
|
|
|
struct dentry *d_make_root(struct inode *root_inode) |
|
{ |
|
struct dentry *res = NULL; |
|
|
|
if (root_inode) { |
|
res = d_alloc_anon(root_inode->i_sb); |
|
if (res) |
|
d_instantiate(res, root_inode); |
|
else |
|
iput(root_inode); |
|
} |
|
return res; |
|
} |
|
EXPORT_SYMBOL(d_make_root); |
|
|
|
static struct dentry *__d_instantiate_anon(struct dentry *dentry, |
|
struct inode *inode, |
|
bool disconnected) |
|
{ |
|
struct dentry *res; |
|
unsigned add_flags; |
|
|
|
security_d_instantiate(dentry, inode); |
|
spin_lock(&inode->i_lock); |
|
res = __d_find_any_alias(inode); |
|
if (res) { |
|
spin_unlock(&inode->i_lock); |
|
dput(dentry); |
|
goto out_iput; |
|
} |
|
|
|
/* attach a disconnected dentry */ |
|
add_flags = d_flags_for_inode(inode); |
|
|
|
if (disconnected) |
|
add_flags |= DCACHE_DISCONNECTED; |
|
|
|
spin_lock(&dentry->d_lock); |
|
__d_set_inode_and_type(dentry, inode, add_flags); |
|
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
|
if (!disconnected) { |
|
hlist_bl_lock(&dentry->d_sb->s_roots); |
|
hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots); |
|
hlist_bl_unlock(&dentry->d_sb->s_roots); |
|
} |
|
spin_unlock(&dentry->d_lock); |
|
spin_unlock(&inode->i_lock); |
|
|
|
return dentry; |
|
|
|
out_iput: |
|
iput(inode); |
|
return res; |
|
} |
|
|
|
struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode) |
|
{ |
|
return __d_instantiate_anon(dentry, inode, true); |
|
} |
|
EXPORT_SYMBOL(d_instantiate_anon); |
|
|
|
static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected) |
|
{ |
|
struct dentry *tmp; |
|
struct dentry *res; |
|
|
|
if (!inode) |
|
return ERR_PTR(-ESTALE); |
|
if (IS_ERR(inode)) |
|
return ERR_CAST(inode); |
|
|
|
res = d_find_any_alias(inode); |
|
if (res) |
|
goto out_iput; |
|
|
|
tmp = d_alloc_anon(inode->i_sb); |
|
if (!tmp) { |
|
res = ERR_PTR(-ENOMEM); |
|
goto out_iput; |
|
} |
|
|
|
return __d_instantiate_anon(tmp, inode, disconnected); |
|
|
|
out_iput: |
|
iput(inode); |
|
return res; |
|
} |
|
|
|
/** |
|
* d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode |
|
* @inode: inode to allocate the dentry for |
|
* |
|
* Obtain a dentry for an inode resulting from NFS filehandle conversion or |
|
* similar open by handle operations. The returned dentry may be anonymous, |
|
* or may have a full name (if the inode was already in the cache). |
|
* |
|
* When called on a directory inode, we must ensure that the inode only ever |
|
* has one dentry. If a dentry is found, that is returned instead of |
|
* allocating a new one. |
|
* |
|
* On successful return, the reference to the inode has been transferred |
|
* to the dentry. In case of an error the reference on the inode is released. |
|
* To make it easier to use in export operations a %NULL or IS_ERR inode may |
|
* be passed in and the error will be propagated to the return value, |
|
* with a %NULL @inode replaced by ERR_PTR(-ESTALE). |
|
*/ |
|
struct dentry *d_obtain_alias(struct inode *inode) |
|
{ |
|
return __d_obtain_alias(inode, true); |
|
} |
|
EXPORT_SYMBOL(d_obtain_alias); |
|
|
|
/** |
|
* d_obtain_root - find or allocate a dentry for a given inode |
|
* @inode: inode to allocate the dentry for |
|
* |
|
* Obtain an IS_ROOT dentry for the root of a filesystem. |
|
* |
|
* We must ensure that directory inodes only ever have one dentry. If a |
|
* dentry is found, that is returned instead of allocating a new one. |
|
* |
|
* On successful return, the reference to the inode has been transferred |
|
* to the dentry. In case of an error the reference on the inode is |
|
* released. A %NULL or IS_ERR inode may be passed in and will be the |
|
* error will be propagate to the return value, with a %NULL @inode |
|
* replaced by ERR_PTR(-ESTALE). |
|
*/ |
|
struct dentry *d_obtain_root(struct inode *inode) |
|
{ |
|
return __d_obtain_alias(inode, false); |
|
} |
|
EXPORT_SYMBOL(d_obtain_root); |
|
|
|
/** |
|
* d_add_ci - lookup or allocate new dentry with case-exact name |
|
* @inode: the inode case-insensitive lookup has found |
|
* @dentry: the negative dentry that was passed to the parent's lookup func |
|
* @name: the case-exact name to be associated with the returned dentry |
|
* |
|
* This is to avoid filling the dcache with case-insensitive names to the |
|
* same inode, only the actual correct case is stored in the dcache for |
|
* case-insensitive filesystems. |
|
* |
|
* For a case-insensitive lookup match and if the case-exact dentry |
|
* already exists in the dcache, use it and return it. |
|
* |
|
* If no entry exists with the exact case name, allocate new dentry with |
|
* the exact case, and return the spliced entry. |
|
*/ |
|
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, |
|
struct qstr *name) |
|
{ |
|
struct dentry *found, *res; |
|
|
|
/* |
|
* First check if a dentry matching the name already exists, |
|
* if not go ahead and create it now. |
|
*/ |
|
found = d_hash_and_lookup(dentry->d_parent, name); |
|
if (found) { |
|
iput(inode); |
|
return found; |
|
} |
|
if (d_in_lookup(dentry)) { |
|
found = d_alloc_parallel(dentry->d_parent, name, |
|
dentry->d_wait); |
|
if (IS_ERR(found) || !d_in_lookup(found)) { |
|
iput(inode); |
|
return found; |
|
} |
|
} else { |
|
found = d_alloc(dentry->d_parent, name); |
|
if (!found) { |
|
iput(inode); |
|
return ERR_PTR(-ENOMEM); |
|
} |
|
} |
|
res = d_splice_alias(inode, found); |
|
if (res) { |
|
dput(found); |
|
return res; |
|
} |
|
return found; |
|
} |
|
EXPORT_SYMBOL(d_add_ci); |
|
|
|
|
|
static inline bool d_same_name(const struct dentry *dentry, |
|
const struct dentry *parent, |
|
const struct qstr *name) |
|
{ |
|
if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) { |
|
if (dentry->d_name.len != name->len) |
|
return false; |
|
return dentry_cmp(dentry, name->name, name->len) == 0; |
|
} |
|
return parent->d_op->d_compare(dentry, |
|
dentry->d_name.len, dentry->d_name.name, |
|
name) == 0; |
|
} |
|
|
|
/** |
|
* __d_lookup_rcu - search for a dentry (racy, store-free) |
|
* @parent: parent dentry |
|
* @name: qstr of name we wish to find |
|
* @seqp: returns d_seq value at the point where the dentry was found |
|
* Returns: dentry, or NULL |
|
* |
|
* __d_lookup_rcu is the dcache lookup function for rcu-walk name |
|
* resolution (store-free path walking) design described in |
|
* Documentation/filesystems/path-lookup.txt. |
|
* |
|
* This is not to be used outside core vfs. |
|
* |
|
* __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock |
|
* held, and rcu_read_lock held. The returned dentry must not be stored into |
|
* without taking d_lock and checking d_seq sequence count against @seq |
|
* returned here. |
|
* |
|
* A refcount may be taken on the found dentry with the d_rcu_to_refcount |
|
* function. |
|
* |
|
* Alternatively, __d_lookup_rcu may be called again to look up the child of |
|
* the returned dentry, so long as its parent's seqlock is checked after the |
|
* child is looked up. Thus, an interlocking stepping of sequence lock checks |
|
* is formed, giving integrity down the path walk. |
|
* |
|
* NOTE! The caller *has* to check the resulting dentry against the sequence |
|
* number we've returned before using any of the resulting dentry state! |
|
*/ |
|
struct dentry *__d_lookup_rcu(const struct dentry *parent, |
|
const struct qstr *name, |
|
unsigned *seqp) |
|
{ |
|
u64 hashlen = name->hash_len; |
|
const unsigned char *str = name->name; |
|
struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen)); |
|
struct hlist_bl_node *node; |
|
struct dentry *dentry; |
|
|
|
/* |
|
* Note: There is significant duplication with __d_lookup_rcu which is |
|
* required to prevent single threaded performance regressions |
|
* especially on architectures where smp_rmb (in seqcounts) are costly. |
|
* Keep the two functions in sync. |
|
*/ |
|
|
|
/* |
|
* The hash list is protected using RCU. |
|
* |
|
* Carefully use d_seq when comparing a candidate dentry, to avoid |
|
* races with d_move(). |
|
* |
|
* It is possible that concurrent renames can mess up our list |
|
* walk here and result in missing our dentry, resulting in the |
|
* false-negative result. d_lookup() protects against concurrent |
|
* renames using rename_lock seqlock. |
|
* |
|
* See Documentation/filesystems/path-lookup.txt for more details. |
|
*/ |
|
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
|
unsigned seq; |
|
|
|
seqretry: |
|
/* |
|
* The dentry sequence count protects us from concurrent |
|
* renames, and thus protects parent and name fields. |
|
* |
|
* The caller must perform a seqcount check in order |
|
* to do anything useful with the returned dentry. |
|
* |
|
* NOTE! We do a "raw" seqcount_begin here. That means that |
|
* we don't wait for the sequence count to stabilize if it |
|
* is in the middle of a sequence change. If we do the slow |
|
* dentry compare, we will do seqretries until it is stable, |
|
* and if we end up with a successful lookup, we actually |
|
* want to exit RCU lookup anyway. |
|
* |
|
* Note that raw_seqcount_begin still *does* smp_rmb(), so |
|
* we are still guaranteed NUL-termination of ->d_name.name. |
|
*/ |
|
seq = raw_seqcount_begin(&dentry->d_seq); |
|
if (dentry->d_parent != parent) |
|
continue; |
|
if (d_unhashed(dentry)) |
|
continue; |
|
|
|
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { |
|
int tlen; |
|
const char *tname; |
|
if (dentry->d_name.hash != hashlen_hash(hashlen)) |
|
continue; |
|
tlen = dentry->d_name.len; |
|
tname = dentry->d_name.name; |
|
/* we want a consistent (name,len) pair */ |
|
if (read_seqcount_retry(&dentry->d_seq, seq)) { |
|
cpu_relax(); |
|
goto seqretry; |
|
} |
|
if (parent->d_op->d_compare(dentry, |
|
tlen, tname, name) != 0) |
|
continue; |
|
} else { |
|
if (dentry->d_name.hash_len != hashlen) |
|
continue; |
|
if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0) |
|
continue; |
|
} |
|
*seqp = seq; |
|
return dentry; |
|
} |
|
return NULL; |
|
} |
|
|
|
/** |
|
* d_lookup - search for a dentry |
|
* @parent: parent dentry |
|
* @name: qstr of name we wish to find |
|
* Returns: dentry, or NULL |
|
* |
|
* d_lookup searches the children of the parent dentry for the name in |
|
* question. If the dentry is found its reference count is incremented and the |
|
* dentry is returned. The caller must use dput to free the entry when it has |
|
* finished using it. %NULL is returned if the dentry does not exist. |
|
*/ |
|
struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name) |
|
{ |
|
struct dentry *dentry; |
|
unsigned seq; |
|
|
|
do { |
|
seq = read_seqbegin(&rename_lock); |
|
dentry = __d_lookup(parent, name); |
|
if (dentry) |
|
break; |
|
} while (read_seqretry(&rename_lock, seq)); |
|
return dentry; |
|
} |
|
EXPORT_SYMBOL(d_lookup); |
|
|
|
/** |
|
* __d_lookup - search for a dentry (racy) |
|
* @parent: parent dentry |
|
* @name: qstr of name we wish to find |
|
* Returns: dentry, or NULL |
|
* |
|
* __d_lookup is like d_lookup, however it may (rarely) return a |
|
* false-negative result due to unrelated rename activity. |
|
* |
|
* __d_lookup is slightly faster by avoiding rename_lock read seqlock, |
|
* however it must be used carefully, eg. with a following d_lookup in |
|
* the case of failure. |
|
* |
|
* __d_lookup callers must be commented. |
|
*/ |
|
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) |
|
{ |
|
unsigned int hash = name->hash; |
|
struct hlist_bl_head *b = d_hash(hash); |
|
struct hlist_bl_node *node; |
|
struct dentry *found = NULL; |
|
struct dentry *dentry; |
|
|
|
/* |
|
* Note: There is significant duplication with __d_lookup_rcu which is |
|
* required to prevent single threaded performance regressions |
|
* especially on architectures where smp_rmb (in seqcounts) are costly. |
|
* Keep the two functions in sync. |
|
*/ |
|
|
|
/* |
|
* The hash list is protected using RCU. |
|
* |
|
* Take d_lock when comparing a candidate dentry, to avoid races |
|
* with d_move(). |
|
* |
|
* It is possible that concurrent renames can mess up our list |
|
* walk here and result in missing our dentry, resulting in the |
|
* false-negative result. d_lookup() protects against concurrent |
|
* renames using rename_lock seqlock. |
|
* |
|
* See Documentation/filesystems/path-lookup.txt for more details. |
|
*/ |
|
rcu_read_lock(); |
|
|
|
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
|
|
|
if (dentry->d_name.hash != hash) |
|
continue; |
|
|
|
spin_lock(&dentry->d_lock); |
|
if (dentry->d_parent != parent) |
|
goto next; |
|
if (d_unhashed(dentry)) |
|
goto next; |
|
|
|
if (!d_same_name(dentry, parent, name)) |
|
goto next; |
|
|
|
dentry->d_lockref.count++; |
|
found = dentry; |
|
spin_unlock(&dentry->d_lock); |
|
break; |
|
next: |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
rcu_read_unlock(); |
|
|
|
return found; |
|
} |
|
|
|
/** |
|
* d_hash_and_lookup - hash the qstr then search for a dentry |
|
* @dir: Directory to search in |
|
* @name: qstr of name we wish to find |
|
* |
|
* On lookup failure NULL is returned; on bad name - ERR_PTR(-error) |
|
*/ |
|
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) |
|
{ |
|
/* |
|
* Check for a fs-specific hash function. Note that we must |
|
* calculate the standard hash first, as the d_op->d_hash() |
|
* routine may choose to leave the hash value unchanged. |
|
*/ |
|
name->hash = full_name_hash(dir, name->name, name->len); |
|
if (dir->d_flags & DCACHE_OP_HASH) { |
|
int err = dir->d_op->d_hash(dir, name); |
|
if (unlikely(err < 0)) |
|
return ERR_PTR(err); |
|
} |
|
return d_lookup(dir, name); |
|
} |
|
EXPORT_SYMBOL(d_hash_and_lookup); |
|
|
|
/* |
|
* When a file is deleted, we have two options: |
|
* - turn this dentry into a negative dentry |
|
* - unhash this dentry and free it. |
|
* |
|
* Usually, we want to just turn this into |
|
* a negative dentry, but if anybody else is |
|
* currently using the dentry or the inode |
|
* we can't do that and we fall back on removing |
|
* it from the hash queues and waiting for |
|
* it to be deleted later when it has no users |
|
*/ |
|
|
|
/** |
|
* d_delete - delete a dentry |
|
* @dentry: The dentry to delete |
|
* |
|
* Turn the dentry into a negative dentry if possible, otherwise |
|
* remove it from the hash queues so it can be deleted later |
|
*/ |
|
|
|
void d_delete(struct dentry * dentry) |
|
{ |
|
struct inode *inode = dentry->d_inode; |
|
|
|
spin_lock(&inode->i_lock); |
|
spin_lock(&dentry->d_lock); |
|
/* |
|
* Are we the only user? |
|
*/ |
|
if (dentry->d_lockref.count == 1) { |
|
dentry->d_flags &= ~DCACHE_CANT_MOUNT; |
|
dentry_unlink_inode(dentry); |
|
} else { |
|
__d_drop(dentry); |
|
spin_unlock(&dentry->d_lock); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
} |
|
EXPORT_SYMBOL(d_delete); |
|
|
|
static void __d_rehash(struct dentry *entry) |
|
{ |
|
struct hlist_bl_head *b = d_hash(entry->d_name.hash); |
|
|
|
hlist_bl_lock(b); |
|
hlist_bl_add_head_rcu(&entry->d_hash, b); |
|
hlist_bl_unlock(b); |
|
} |
|
|
|
/** |
|
* d_rehash - add an entry back to the hash |
|
* @entry: dentry to add to the hash |
|
* |
|
* Adds a dentry to the hash according to its name. |
|
*/ |
|
|
|
void d_rehash(struct dentry * entry) |
|
{ |
|
spin_lock(&entry->d_lock); |
|
__d_rehash(entry); |
|
spin_unlock(&entry->d_lock); |
|
} |
|
EXPORT_SYMBOL(d_rehash); |
|
|
|
static inline unsigned start_dir_add(struct inode *dir) |
|
{ |
|
|
|
for (;;) { |
|
unsigned n = dir->i_dir_seq; |
|
if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n) |
|
return n; |
|
cpu_relax(); |
|
} |
|
} |
|
|
|
static inline void end_dir_add(struct inode *dir, unsigned n) |
|
{ |
|
smp_store_release(&dir->i_dir_seq, n + 2); |
|
} |
|
|
|
static void d_wait_lookup(struct dentry *dentry) |
|
{ |
|
if (d_in_lookup(dentry)) { |
|
DECLARE_WAITQUEUE(wait, current); |
|
add_wait_queue(dentry->d_wait, &wait); |
|
do { |
|
set_current_state(TASK_UNINTERRUPTIBLE); |
|
spin_unlock(&dentry->d_lock); |
|
schedule(); |
|
spin_lock(&dentry->d_lock); |
|
} while (d_in_lookup(dentry)); |
|
} |
|
} |
|
|
|
struct dentry *d_alloc_parallel(struct dentry *parent, |
|
const struct qstr *name, |
|
wait_queue_head_t *wq) |
|
{ |
|
unsigned int hash = name->hash; |
|
struct hlist_bl_head *b = in_lookup_hash(parent, hash); |
|
struct hlist_bl_node *node; |
|
struct dentry *new = d_alloc(parent, name); |
|
struct dentry *dentry; |
|
unsigned seq, r_seq, d_seq; |
|
|
|
if (unlikely(!new)) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
retry: |
|
rcu_read_lock(); |
|
seq = smp_load_acquire(&parent->d_inode->i_dir_seq); |
|
r_seq = read_seqbegin(&rename_lock); |
|
dentry = __d_lookup_rcu(parent, name, &d_seq); |
|
if (unlikely(dentry)) { |
|
if (!lockref_get_not_dead(&dentry->d_lockref)) { |
|
rcu_read_unlock(); |
|
goto retry; |
|
} |
|
if (read_seqcount_retry(&dentry->d_seq, d_seq)) { |
|
rcu_read_unlock(); |
|
dput(dentry); |
|
goto retry; |
|
} |
|
rcu_read_unlock(); |
|
dput(new); |
|
return dentry; |
|
} |
|
if (unlikely(read_seqretry(&rename_lock, r_seq))) { |
|
rcu_read_unlock(); |
|
goto retry; |
|
} |
|
|
|
if (unlikely(seq & 1)) { |
|
rcu_read_unlock(); |
|
goto retry; |
|
} |
|
|
|
hlist_bl_lock(b); |
|
if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) { |
|
hlist_bl_unlock(b); |
|
rcu_read_unlock(); |
|
goto retry; |
|
} |
|
/* |
|
* No changes for the parent since the beginning of d_lookup(). |
|
* Since all removals from the chain happen with hlist_bl_lock(), |
|
* any potential in-lookup matches are going to stay here until |
|
* we unlock the chain. All fields are stable in everything |
|
* we encounter. |
|
*/ |
|
hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) { |
|
if (dentry->d_name.hash != hash) |
|
continue; |
|
if (dentry->d_parent != parent) |
|
continue; |
|
if (!d_same_name(dentry, parent, name)) |
|
continue; |
|
hlist_bl_unlock(b); |
|
/* now we can try to grab a reference */ |
|
if (!lockref_get_not_dead(&dentry->d_lockref)) { |
|
rcu_read_unlock(); |
|
goto retry; |
|
} |
|
|
|
rcu_read_unlock(); |
|
/* |
|
* somebody is likely to be still doing lookup for it; |
|
* wait for them to finish |
|
*/ |
|
spin_lock(&dentry->d_lock); |
|
d_wait_lookup(dentry); |
|
/* |
|
* it's not in-lookup anymore; in principle we should repeat |
|
* everything from dcache lookup, but it's likely to be what |
|
* d_lookup() would've found anyway. If it is, just return it; |
|
* otherwise we really have to repeat the whole thing. |
|
*/ |
|
if (unlikely(dentry->d_name.hash != hash)) |
|
goto mismatch; |
|
if (unlikely(dentry->d_parent != parent)) |
|
goto mismatch; |
|
if (unlikely(d_unhashed(dentry))) |
|
goto mismatch; |
|
if (unlikely(!d_same_name(dentry, parent, name))) |
|
goto mismatch; |
|
/* OK, it *is* a hashed match; return it */ |
|
spin_unlock(&dentry->d_lock); |
|
dput(new); |
|
return dentry; |
|
} |
|
rcu_read_unlock(); |
|
/* we can't take ->d_lock here; it's OK, though. */ |
|
new->d_flags |= DCACHE_PAR_LOOKUP; |
|
new->d_wait = wq; |
|
hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b); |
|
hlist_bl_unlock(b); |
|
return new; |
|
mismatch: |
|
spin_unlock(&dentry->d_lock); |
|
dput(dentry); |
|
goto retry; |
|
} |
|
EXPORT_SYMBOL(d_alloc_parallel); |
|
|
|
void __d_lookup_done(struct dentry *dentry) |
|
{ |
|
struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent, |
|
dentry->d_name.hash); |
|
hlist_bl_lock(b); |
|
dentry->d_flags &= ~DCACHE_PAR_LOOKUP; |
|
__hlist_bl_del(&dentry->d_u.d_in_lookup_hash); |
|
wake_up_all(dentry->d_wait); |
|
dentry->d_wait = NULL; |
|
hlist_bl_unlock(b); |
|
INIT_HLIST_NODE(&dentry->d_u.d_alias); |
|
INIT_LIST_HEAD(&dentry->d_lru); |
|
} |
|
EXPORT_SYMBOL(__d_lookup_done); |
|
|
|
/* inode->i_lock held if inode is non-NULL */ |
|
|
|
static inline void __d_add(struct dentry *dentry, struct inode *inode) |
|
{ |
|
struct inode *dir = NULL; |
|
unsigned n; |
|
spin_lock(&dentry->d_lock); |
|
if (unlikely(d_in_lookup(dentry))) { |
|
dir = dentry->d_parent->d_inode; |
|
n = start_dir_add(dir); |
|
__d_lookup_done(dentry); |
|
} |
|
if (inode) { |
|
unsigned add_flags = d_flags_for_inode(inode); |
|
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry); |
|
raw_write_seqcount_begin(&dentry->d_seq); |
|
__d_set_inode_and_type(dentry, inode, add_flags); |
|
raw_write_seqcount_end(&dentry->d_seq); |
|
fsnotify_update_flags(dentry); |
|
} |
|
__d_rehash(dentry); |
|
if (dir) |
|
end_dir_add(dir, n); |
|
spin_unlock(&dentry->d_lock); |
|
if (inode) |
|
spin_unlock(&inode->i_lock); |
|
} |
|
|
|
/** |
|
* d_add - add dentry to hash queues |
|
* @entry: dentry to add |
|
* @inode: The inode to attach to this dentry |
|
* |
|
* This adds the entry to the hash queues and initializes @inode. |
|
* The entry was actually filled in earlier during d_alloc(). |
|
*/ |
|
|
|
void d_add(struct dentry *entry, struct inode *inode) |
|
{ |
|
if (inode) { |
|
security_d_instantiate(entry, inode); |
|
spin_lock(&inode->i_lock); |
|
} |
|
__d_add(entry, inode); |
|
} |
|
EXPORT_SYMBOL(d_add); |
|
|
|
/** |
|
* d_exact_alias - find and hash an exact unhashed alias |
|
* @entry: dentry to add |
|
* @inode: The inode to go with this dentry |
|
* |
|
* If an unhashed dentry with the same name/parent and desired |
|
* inode already exists, hash and return it. Otherwise, return |
|
* NULL. |
|
* |
|
* Parent directory should be locked. |
|
*/ |
|
struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode) |
|
{ |
|
struct dentry *alias; |
|
unsigned int hash = entry->d_name.hash; |
|
|
|
spin_lock(&inode->i_lock); |
|
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { |
|
/* |
|
* Don't need alias->d_lock here, because aliases with |
|
* d_parent == entry->d_parent are not subject to name or |
|
* parent changes, because the parent inode i_mutex is held. |
|
*/ |
|
if (alias->d_name.hash != hash) |
|
continue; |
|
if (alias->d_parent != entry->d_parent) |
|
continue; |
|
if (!d_same_name(alias, entry->d_parent, &entry->d_name)) |
|
continue; |
|
spin_lock(&alias->d_lock); |
|
if (!d_unhashed(alias)) { |
|
spin_unlock(&alias->d_lock); |
|
alias = NULL; |
|
} else { |
|
__dget_dlock(alias); |
|
__d_rehash(alias); |
|
spin_unlock(&alias->d_lock); |
|
} |
|
spin_unlock(&inode->i_lock); |
|
return alias; |
|
} |
|
spin_unlock(&inode->i_lock); |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL(d_exact_alias); |
|
|
|
static void swap_names(struct dentry *dentry, struct dentry *target) |
|
{ |
|
if (unlikely(dname_external(target))) { |
|
if (unlikely(dname_external(dentry))) { |
|
/* |
|
* Both external: swap the pointers |
|
*/ |
|
swap(target->d_name.name, dentry->d_name.name); |
|
} else { |
|
/* |
|
* dentry:internal, target:external. Steal target's |
|
* storage and make target internal. |
|
*/ |
|
memcpy(target->d_iname, dentry->d_name.name, |
|
dentry->d_name.len + 1); |
|
dentry->d_name.name = target->d_name.name; |
|
target->d_name.name = target->d_iname; |
|
} |
|
} else { |
|
if (unlikely(dname_external(dentry))) { |
|
/* |
|
* dentry:external, target:internal. Give dentry's |
|
* storage to target and make dentry internal |
|
*/ |
|
memcpy(dentry->d_iname, target->d_name.name, |
|
target->d_name.len + 1); |
|
target->d_name.name = dentry->d_name.name; |
|
dentry->d_name.name = dentry->d_iname; |
|
} else { |
|
/* |
|
* Both are internal. |
|
*/ |
|
unsigned int i; |
|
BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long))); |
|
for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) { |
|
swap(((long *) &dentry->d_iname)[i], |
|
((long *) &target->d_iname)[i]); |
|
} |
|
} |
|
} |
|
swap(dentry->d_name.hash_len, target->d_name.hash_len); |
|
} |
|
|
|
static void copy_name(struct dentry *dentry, struct dentry *target) |
|
{ |
|
struct external_name *old_name = NULL; |
|
if (unlikely(dname_external(dentry))) |
|
old_name = external_name(dentry); |
|
if (unlikely(dname_external(target))) { |
|
atomic_inc(&external_name(target)->u.count); |
|
dentry->d_name = target->d_name; |
|
} else { |
|
memcpy(dentry->d_iname, target->d_name.name, |
|
target->d_name.len + 1); |
|
dentry->d_name.name = dentry->d_iname; |
|
dentry->d_name.hash_len = target->d_name.hash_len; |
|
} |
|
if (old_name && likely(atomic_dec_and_test(&old_name->u.count))) |
|
kfree_rcu(old_name, u.head); |
|
} |
|
|
|
/* |
|
* __d_move - move a dentry |
|
* @dentry: entry to move |
|
* @target: new dentry |
|
* @exchange: exchange the two dentries |
|
* |
|
* Update the dcache to reflect the move of a file name. Negative |
|
* dcache entries should not be moved in this way. Caller must hold |
|
* rename_lock, the i_mutex of the source and target directories, |
|
* and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). |
|
*/ |
|
static void __d_move(struct dentry *dentry, struct dentry *target, |
|
bool exchange) |
|
{ |
|
struct dentry *old_parent, *p; |
|
struct inode *dir = NULL; |
|
unsigned n; |
|
|
|
WARN_ON(!dentry->d_inode); |
|
if (WARN_ON(dentry == target)) |
|
return; |
|
|
|
BUG_ON(d_ancestor(target, dentry)); |
|
old_parent = dentry->d_parent; |
|
p = d_ancestor(old_parent, target); |
|
if (IS_ROOT(dentry)) { |
|
BUG_ON(p); |
|
spin_lock(&target->d_parent->d_lock); |
|
} else if (!p) { |
|
/* target is not a descendent of dentry->d_parent */ |
|
spin_lock(&target->d_parent->d_lock); |
|
spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED); |
|
} else { |
|
BUG_ON(p == dentry); |
|
spin_lock(&old_parent->d_lock); |
|
if (p != target) |
|
spin_lock_nested(&target->d_parent->d_lock, |
|
DENTRY_D_LOCK_NESTED); |
|
} |
|
spin_lock_nested(&dentry->d_lock, 2); |
|
spin_lock_nested(&target->d_lock, 3); |
|
|
|
if (unlikely(d_in_lookup(target))) { |
|
dir = target->d_parent->d_inode; |
|
n = start_dir_add(dir); |
|
__d_lookup_done(target); |
|
} |
|
|
|
write_seqcount_begin(&dentry->d_seq); |
|
write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED); |
|
|
|
/* unhash both */ |
|
if (!d_unhashed(dentry)) |
|
___d_drop(dentry); |
|
if (!d_unhashed(target)) |
|
___d_drop(target); |
|
|
|
/* ... and switch them in the tree */ |
|
dentry->d_parent = target->d_parent; |
|
if (!exchange) { |
|
copy_name(dentry, target); |
|
target->d_hash.pprev = NULL; |
|
dentry->d_parent->d_lockref.count++; |
|
if (dentry != old_parent) /* wasn't IS_ROOT */ |
|
WARN_ON(!--old_parent->d_lockref.count); |
|
} else { |
|
target->d_parent = old_parent; |
|
swap_names(dentry, target); |
|
list_move(&target->d_child, &target->d_parent->d_subdirs); |
|
__d_rehash(target); |
|
fsnotify_update_flags(target); |
|
} |
|
list_move(&dentry->d_child, &dentry->d_parent->d_subdirs); |
|
__d_rehash(dentry); |
|
fsnotify_update_flags(dentry); |
|
fscrypt_handle_d_move(dentry); |
|
|
|
write_seqcount_end(&target->d_seq); |
|
write_seqcount_end(&dentry->d_seq); |
|
|
|
if (dir) |
|
end_dir_add(dir, n); |
|
|
|
if (dentry->d_parent != old_parent) |
|
spin_unlock(&dentry->d_parent->d_lock); |
|
if (dentry != old_parent) |
|
spin_unlock(&old_parent->d_lock); |
|
spin_unlock(&target->d_lock); |
|
spin_unlock(&dentry->d_lock); |
|
} |
|
|
|
/* |
|
* d_move - move a dentry |
|
* @dentry: entry to move |
|
* @target: new dentry |
|
* |
|
* Update the dcache to reflect the move of a file name. Negative |
|
* dcache entries should not be moved in this way. See the locking |
|
* requirements for __d_move. |
|
*/ |
|
void d_move(struct dentry *dentry, struct dentry *target) |
|
{ |
|
write_seqlock(&rename_lock); |
|
__d_move(dentry, target, false); |
|
write_sequnlock(&rename_lock); |
|
} |
|
EXPORT_SYMBOL(d_move); |
|
|
|
/* |
|
* d_exchange - exchange two dentries |
|
* @dentry1: first dentry |
|
* @dentry2: second dentry |
|
*/ |
|
void d_exchange(struct dentry *dentry1, struct dentry *dentry2) |
|
{ |
|
write_seqlock(&rename_lock); |
|
|
|
WARN_ON(!dentry1->d_inode); |
|
WARN_ON(!dentry2->d_inode); |
|
WARN_ON(IS_ROOT(dentry1)); |
|
WARN_ON(IS_ROOT(dentry2)); |
|
|
|
__d_move(dentry1, dentry2, true); |
|
|
|
write_sequnlock(&rename_lock); |
|
} |
|
|
|
/** |
|
* d_ancestor - search for an ancestor |
|
* @p1: ancestor dentry |
|
* @p2: child dentry |
|
* |
|
* Returns the ancestor dentry of p2 which is a child of p1, if p1 is |
|
* an ancestor of p2, else NULL. |
|
*/ |
|
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) |
|
{ |
|
struct dentry *p; |
|
|
|
for (p = p2; !IS_ROOT(p); p = p->d_parent) { |
|
if (p->d_parent == p1) |
|
return p; |
|
} |
|
return NULL; |
|
} |
|
|
|
/* |
|
* This helper attempts to cope with remotely renamed directories |
|
* |
|
* It assumes that the caller is already holding |
|
* dentry->d_parent->d_inode->i_mutex, and rename_lock |
|
* |
|
* Note: If ever the locking in lock_rename() changes, then please |
|
* remember to update this too... |
|
*/ |
|
static int __d_unalias(struct inode *inode, |
|
struct dentry *dentry, struct dentry *alias) |
|
{ |
|
struct mutex *m1 = NULL; |
|
struct rw_semaphore *m2 = NULL; |
|
int ret = -ESTALE; |
|
|
|
/* If alias and dentry share a parent, then no extra locks required */ |
|
if (alias->d_parent == dentry->d_parent) |
|
goto out_unalias; |
|
|
|
/* See lock_rename() */ |
|
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) |
|
goto out_err; |
|
m1 = &dentry->d_sb->s_vfs_rename_mutex; |
|
if (!inode_trylock_shared(alias->d_parent->d_inode)) |
|
goto out_err; |
|
m2 = &alias->d_parent->d_inode->i_rwsem; |
|
out_unalias: |
|
__d_move(alias, dentry, false); |
|
ret = 0; |
|
out_err: |
|
if (m2) |
|
up_read(m2); |
|
if (m1) |
|
mutex_unlock(m1); |
|
return ret; |
|
} |
|
|
|
/** |
|
* d_splice_alias - splice a disconnected dentry into the tree if one exists |
|
* @inode: the inode which may have a disconnected dentry |
|
* @dentry: a negative dentry which we want to point to the inode. |
|
* |
|
* If inode is a directory and has an IS_ROOT alias, then d_move that in |
|
* place of the given dentry and return it, else simply d_add the inode |
|
* to the dentry and return NULL. |
|
* |
|
* If a non-IS_ROOT directory is found, the filesystem is corrupt, and |
|
* we should error out: directories can't have multiple aliases. |
|
* |
|
* This is needed in the lookup routine of any filesystem that is exportable |
|
* (via knfsd) so that we can build dcache paths to directories effectively. |
|
* |
|
* If a dentry was found and moved, then it is returned. Otherwise NULL |
|
* is returned. This matches the expected return value of ->lookup. |
|
* |
|
* Cluster filesystems may call this function with a negative, hashed dentry. |
|
* In that case, we know that the inode will be a regular file, and also this |
|
* will only occur during atomic_open. So we need to check for the dentry |
|
* being already hashed only in the final case. |
|
*/ |
|
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) |
|
{ |
|
if (IS_ERR(inode)) |
|
return ERR_CAST(inode); |
|
|
|
BUG_ON(!d_unhashed(dentry)); |
|
|
|
if (!inode) |
|
goto out; |
|
|
|
security_d_instantiate(dentry, inode); |
|
spin_lock(&inode->i_lock); |
|
if (S_ISDIR(inode->i_mode)) { |
|
struct dentry *new = __d_find_any_alias(inode); |
|
if (unlikely(new)) { |
|
/* The reference to new ensures it remains an alias */ |
|
spin_unlock(&inode->i_lock); |
|
write_seqlock(&rename_lock); |
|
if (unlikely(d_ancestor(new, dentry))) { |
|
write_sequnlock(&rename_lock); |
|
dput(new); |
|
new = ERR_PTR(-ELOOP); |
|
pr_warn_ratelimited( |
|
"VFS: Lookup of '%s' in %s %s" |
|
" would have caused loop\n", |
|
dentry->d_name.name, |
|
inode->i_sb->s_type->name, |
|
inode->i_sb->s_id); |
|
} else if (!IS_ROOT(new)) { |
|
struct dentry *old_parent = dget(new->d_parent); |
|
int err = __d_unalias(inode, dentry, new); |
|
write_sequnlock(&rename_lock); |
|
if (err) { |
|
dput(new); |
|
new = ERR_PTR(err); |
|
} |
|
dput(old_parent); |
|
} else { |
|
__d_move(new, dentry, false); |
|
write_sequnlock(&rename_lock); |
|
} |
|
iput(inode); |
|
return new; |
|
} |
|
} |
|
out: |
|
__d_add(dentry, inode); |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL(d_splice_alias); |
|
|
|
/* |
|
* Test whether new_dentry is a subdirectory of old_dentry. |
|
* |
|
* Trivially implemented using the dcache structure |
|
*/ |
|
|
|
/** |
|
* is_subdir - is new dentry a subdirectory of old_dentry |
|
* @new_dentry: new dentry |
|
* @old_dentry: old dentry |
|
* |
|
* Returns true if new_dentry is a subdirectory of the parent (at any depth). |
|
* Returns false otherwise. |
|
* Caller must ensure that "new_dentry" is pinned before calling is_subdir() |
|
*/ |
|
|
|
bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) |
|
{ |
|
bool result; |
|
unsigned seq; |
|
|
|
if (new_dentry == old_dentry) |
|
return true; |
|
|
|
do { |
|
/* for restarting inner loop in case of seq retry */ |
|
seq = read_seqbegin(&rename_lock); |
|
/* |
|
* Need rcu_readlock to protect against the d_parent trashing |
|
* due to d_move |
|
*/ |
|
rcu_read_lock(); |
|
if (d_ancestor(old_dentry, new_dentry)) |
|
result = true; |
|
else |
|
result = false; |
|
rcu_read_unlock(); |
|
} while (read_seqretry(&rename_lock, seq)); |
|
|
|
return result; |
|
} |
|
EXPORT_SYMBOL(is_subdir); |
|
|
|
static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry) |
|
{ |
|
struct dentry *root = data; |
|
if (dentry != root) { |
|
if (d_unhashed(dentry) || !dentry->d_inode) |
|
return D_WALK_SKIP; |
|
|
|
if (!(dentry->d_flags & DCACHE_GENOCIDE)) { |
|
dentry->d_flags |= DCACHE_GENOCIDE; |
|
dentry->d_lockref.count--; |
|
} |
|
} |
|
return D_WALK_CONTINUE; |
|
} |
|
|
|
void d_genocide(struct dentry *parent) |
|
{ |
|
d_walk(parent, parent, d_genocide_kill); |
|
} |
|
|
|
EXPORT_SYMBOL(d_genocide); |
|
|
|
void d_tmpfile(struct dentry *dentry, struct inode *inode) |
|
{ |
|
inode_dec_link_count(inode); |
|
BUG_ON(dentry->d_name.name != dentry->d_iname || |
|
!hlist_unhashed(&dentry->d_u.d_alias) || |
|
!d_unlinked(dentry)); |
|
spin_lock(&dentry->d_parent->d_lock); |
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
|
dentry->d_name.len = sprintf(dentry->d_iname, "#%llu", |
|
(unsigned long long)inode->i_ino); |
|
spin_unlock(&dentry->d_lock); |
|
spin_unlock(&dentry->d_parent->d_lock); |
|
d_instantiate(dentry, inode); |
|
} |
|
EXPORT_SYMBOL(d_tmpfile); |
|
|
|
static __initdata unsigned long dhash_entries; |
|
static int __init set_dhash_entries(char *str) |
|
{ |
|
if (!str) |
|
return 0; |
|
dhash_entries = simple_strtoul(str, &str, 0); |
|
return 1; |
|
} |
|
__setup("dhash_entries=", set_dhash_entries); |
|
|
|
static void __init dcache_init_early(void) |
|
{ |
|
/* If hashes are distributed across NUMA nodes, defer |
|
* hash allocation until vmalloc space is available. |
|
*/ |
|
if (hashdist) |
|
return; |
|
|
|
dentry_hashtable = |
|
alloc_large_system_hash("Dentry cache", |
|
sizeof(struct hlist_bl_head), |
|
dhash_entries, |
|
13, |
|
HASH_EARLY | HASH_ZERO, |
|
&d_hash_shift, |
|
NULL, |
|
0, |
|
0); |
|
d_hash_shift = 32 - d_hash_shift; |
|
} |
|
|
|
static void __init dcache_init(void) |
|
{ |
|
/* |
|
* A constructor could be added for stable state like the lists, |
|
* but it is probably not worth it because of the cache nature |
|
* of the dcache. |
|
*/ |
|
dentry_cache = KMEM_CACHE_USERCOPY(dentry, |
|
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT, |
|
d_iname); |
|
|
|
/* Hash may have been set up in dcache_init_early */ |
|
if (!hashdist) |
|
return; |
|
|
|
dentry_hashtable = |
|
alloc_large_system_hash("Dentry cache", |
|
sizeof(struct hlist_bl_head), |
|
dhash_entries, |
|
13, |
|
HASH_ZERO, |
|
&d_hash_shift, |
|
NULL, |
|
0, |
|
0); |
|
d_hash_shift = 32 - d_hash_shift; |
|
} |
|
|
|
/* SLAB cache for __getname() consumers */ |
|
struct kmem_cache *names_cachep __read_mostly; |
|
EXPORT_SYMBOL(names_cachep); |
|
|
|
void __init vfs_caches_init_early(void) |
|
{ |
|
int i; |
|
|
|
for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++) |
|
INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]); |
|
|
|
dcache_init_early(); |
|
inode_init_early(); |
|
} |
|
|
|
void __init vfs_caches_init(void) |
|
{ |
|
names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0, |
|
SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL); |
|
|
|
dcache_init(); |
|
inode_init(); |
|
files_init(); |
|
files_maxfiles_init(); |
|
mnt_init(); |
|
bdev_cache_init(); |
|
chrdev_init(); |
|
}
|
|
|