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1085 lines
27 KiB
1085 lines
27 KiB
// SPDX-License-Identifier: GPL-2.0-only |
|
/* |
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* fs/kernfs/file.c - kernfs file implementation |
|
* |
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* Copyright (c) 2001-3 Patrick Mochel |
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* Copyright (c) 2007 SUSE Linux Products GmbH |
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* Copyright (c) 2007, 2013 Tejun Heo <[email protected]> |
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*/ |
|
|
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#include <linux/fs.h> |
|
#include <linux/seq_file.h> |
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#include <linux/slab.h> |
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#include <linux/poll.h> |
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#include <linux/pagemap.h> |
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#include <linux/sched/mm.h> |
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#include <linux/fsnotify.h> |
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#include <linux/uio.h> |
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|
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#include "kernfs-internal.h" |
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|
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struct kernfs_open_node { |
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struct rcu_head rcu_head; |
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atomic_t event; |
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wait_queue_head_t poll; |
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struct list_head files; /* goes through kernfs_open_file.list */ |
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}; |
|
|
|
/* |
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* kernfs_notify() may be called from any context and bounces notifications |
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* through a work item. To minimize space overhead in kernfs_node, the |
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* pending queue is implemented as a singly linked list of kernfs_nodes. |
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* The list is terminated with the self pointer so that whether a |
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* kernfs_node is on the list or not can be determined by testing the next |
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* pointer for NULL. |
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*/ |
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#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list) |
|
|
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static DEFINE_SPINLOCK(kernfs_notify_lock); |
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static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL; |
|
|
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static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn) |
|
{ |
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int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS); |
|
|
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return &kernfs_locks->open_file_mutex[idx]; |
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} |
|
|
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static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn) |
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{ |
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struct mutex *lock; |
|
|
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lock = kernfs_open_file_mutex_ptr(kn); |
|
|
|
mutex_lock(lock); |
|
|
|
return lock; |
|
} |
|
|
|
/** |
|
* kernfs_deref_open_node - Get kernfs_open_node corresponding to @kn. |
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* |
|
* @of: associated kernfs_open_file instance. |
|
* @kn: target kernfs_node. |
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* |
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* Fetch and return ->attr.open of @kn if @of->list is non empty. |
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* If @of->list is not empty we can safely assume that @of is on |
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* @kn->attr.open->files list and this guarantees that @kn->attr.open |
|
* will not vanish i.e. dereferencing outside RCU read-side critical |
|
* section is safe here. |
|
* |
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* The caller needs to make sure that @of->list is not empty. |
|
*/ |
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static struct kernfs_open_node * |
|
kernfs_deref_open_node(struct kernfs_open_file *of, struct kernfs_node *kn) |
|
{ |
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struct kernfs_open_node *on; |
|
|
|
on = rcu_dereference_check(kn->attr.open, !list_empty(&of->list)); |
|
|
|
return on; |
|
} |
|
|
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/** |
|
* kernfs_deref_open_node_protected - Get kernfs_open_node corresponding to @kn |
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* |
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* @kn: target kernfs_node. |
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* |
|
* Fetch and return ->attr.open of @kn when caller holds the |
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* kernfs_open_file_mutex_ptr(kn). |
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* |
|
* Update of ->attr.open happens under kernfs_open_file_mutex_ptr(kn). So when |
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* the caller guarantees that this mutex is being held, other updaters can't |
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* change ->attr.open and this means that we can safely deref ->attr.open |
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* outside RCU read-side critical section. |
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* |
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* The caller needs to make sure that kernfs_open_file_mutex is held. |
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*/ |
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static struct kernfs_open_node * |
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kernfs_deref_open_node_protected(struct kernfs_node *kn) |
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{ |
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return rcu_dereference_protected(kn->attr.open, |
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lockdep_is_held(kernfs_open_file_mutex_ptr(kn))); |
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} |
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|
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static struct kernfs_open_file *kernfs_of(struct file *file) |
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{ |
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return ((struct seq_file *)file->private_data)->private; |
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} |
|
|
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/* |
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* Determine the kernfs_ops for the given kernfs_node. This function must |
|
* be called while holding an active reference. |
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*/ |
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static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn) |
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{ |
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if (kn->flags & KERNFS_LOCKDEP) |
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lockdep_assert_held(kn); |
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return kn->attr.ops; |
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} |
|
|
|
/* |
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* As kernfs_seq_stop() is also called after kernfs_seq_start() or |
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* kernfs_seq_next() failure, it needs to distinguish whether it's stopping |
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* a seq_file iteration which is fully initialized with an active reference |
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* or an aborted kernfs_seq_start() due to get_active failure. The |
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* position pointer is the only context for each seq_file iteration and |
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* thus the stop condition should be encoded in it. As the return value is |
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* directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable |
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* choice to indicate get_active failure. |
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* |
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* Unfortunately, this is complicated due to the optional custom seq_file |
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* operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop() |
|
* can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or |
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* custom seq_file operations and thus can't decide whether put_active |
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* should be performed or not only on ERR_PTR(-ENODEV). |
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* |
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* This is worked around by factoring out the custom seq_stop() and |
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* put_active part into kernfs_seq_stop_active(), skipping it from |
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* kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after |
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* custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures |
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* that kernfs_seq_stop_active() is skipped only after get_active failure. |
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*/ |
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static void kernfs_seq_stop_active(struct seq_file *sf, void *v) |
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{ |
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struct kernfs_open_file *of = sf->private; |
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const struct kernfs_ops *ops = kernfs_ops(of->kn); |
|
|
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if (ops->seq_stop) |
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ops->seq_stop(sf, v); |
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kernfs_put_active(of->kn); |
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} |
|
|
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static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) |
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{ |
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struct kernfs_open_file *of = sf->private; |
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const struct kernfs_ops *ops; |
|
|
|
/* |
|
* @of->mutex nests outside active ref and is primarily to ensure that |
|
* the ops aren't called concurrently for the same open file. |
|
*/ |
|
mutex_lock(&of->mutex); |
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if (!kernfs_get_active(of->kn)) |
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return ERR_PTR(-ENODEV); |
|
|
|
ops = kernfs_ops(of->kn); |
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if (ops->seq_start) { |
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void *next = ops->seq_start(sf, ppos); |
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/* see the comment above kernfs_seq_stop_active() */ |
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if (next == ERR_PTR(-ENODEV)) |
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kernfs_seq_stop_active(sf, next); |
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return next; |
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} |
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return single_start(sf, ppos); |
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} |
|
|
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static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos) |
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{ |
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struct kernfs_open_file *of = sf->private; |
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const struct kernfs_ops *ops = kernfs_ops(of->kn); |
|
|
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if (ops->seq_next) { |
|
void *next = ops->seq_next(sf, v, ppos); |
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/* see the comment above kernfs_seq_stop_active() */ |
|
if (next == ERR_PTR(-ENODEV)) |
|
kernfs_seq_stop_active(sf, next); |
|
return next; |
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} else { |
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/* |
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* The same behavior and code as single_open(), always |
|
* terminate after the initial read. |
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*/ |
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++*ppos; |
|
return NULL; |
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} |
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} |
|
|
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static void kernfs_seq_stop(struct seq_file *sf, void *v) |
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{ |
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struct kernfs_open_file *of = sf->private; |
|
|
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if (v != ERR_PTR(-ENODEV)) |
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kernfs_seq_stop_active(sf, v); |
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mutex_unlock(&of->mutex); |
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} |
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|
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static int kernfs_seq_show(struct seq_file *sf, void *v) |
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{ |
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struct kernfs_open_file *of = sf->private; |
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struct kernfs_open_node *on = kernfs_deref_open_node(of, of->kn); |
|
|
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if (!on) |
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return -EINVAL; |
|
|
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of->event = atomic_read(&on->event); |
|
|
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return of->kn->attr.ops->seq_show(sf, v); |
|
} |
|
|
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static const struct seq_operations kernfs_seq_ops = { |
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.start = kernfs_seq_start, |
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.next = kernfs_seq_next, |
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.stop = kernfs_seq_stop, |
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.show = kernfs_seq_show, |
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}; |
|
|
|
/* |
|
* As reading a bin file can have side-effects, the exact offset and bytes |
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* specified in read(2) call should be passed to the read callback making |
|
* it difficult to use seq_file. Implement simplistic custom buffering for |
|
* bin files. |
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*/ |
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static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
|
{ |
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struct kernfs_open_file *of = kernfs_of(iocb->ki_filp); |
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ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE); |
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const struct kernfs_ops *ops; |
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struct kernfs_open_node *on; |
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char *buf; |
|
|
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buf = of->prealloc_buf; |
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if (buf) |
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mutex_lock(&of->prealloc_mutex); |
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else |
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buf = kmalloc(len, GFP_KERNEL); |
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if (!buf) |
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return -ENOMEM; |
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|
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/* |
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* @of->mutex nests outside active ref and is used both to ensure that |
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* the ops aren't called concurrently for the same open file. |
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*/ |
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mutex_lock(&of->mutex); |
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if (!kernfs_get_active(of->kn)) { |
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len = -ENODEV; |
|
mutex_unlock(&of->mutex); |
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goto out_free; |
|
} |
|
|
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on = kernfs_deref_open_node(of, of->kn); |
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if (!on) { |
|
len = -EINVAL; |
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mutex_unlock(&of->mutex); |
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goto out_free; |
|
} |
|
|
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of->event = atomic_read(&on->event); |
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|
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ops = kernfs_ops(of->kn); |
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if (ops->read) |
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len = ops->read(of, buf, len, iocb->ki_pos); |
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else |
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len = -EINVAL; |
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|
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kernfs_put_active(of->kn); |
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mutex_unlock(&of->mutex); |
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|
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if (len < 0) |
|
goto out_free; |
|
|
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if (copy_to_iter(buf, len, iter) != len) { |
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len = -EFAULT; |
|
goto out_free; |
|
} |
|
|
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iocb->ki_pos += len; |
|
|
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out_free: |
|
if (buf == of->prealloc_buf) |
|
mutex_unlock(&of->prealloc_mutex); |
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else |
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kfree(buf); |
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return len; |
|
} |
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|
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static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
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{ |
|
if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW) |
|
return seq_read_iter(iocb, iter); |
|
return kernfs_file_read_iter(iocb, iter); |
|
} |
|
|
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/* |
|
* Copy data in from userland and pass it to the matching kernfs write |
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* operation. |
|
* |
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* There is no easy way for us to know if userspace is only doing a partial |
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* write, so we don't support them. We expect the entire buffer to come on |
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* the first write. Hint: if you're writing a value, first read the file, |
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* modify only the value you're changing, then write entire buffer |
|
* back. |
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*/ |
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static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter) |
|
{ |
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struct kernfs_open_file *of = kernfs_of(iocb->ki_filp); |
|
ssize_t len = iov_iter_count(iter); |
|
const struct kernfs_ops *ops; |
|
char *buf; |
|
|
|
if (of->atomic_write_len) { |
|
if (len > of->atomic_write_len) |
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return -E2BIG; |
|
} else { |
|
len = min_t(size_t, len, PAGE_SIZE); |
|
} |
|
|
|
buf = of->prealloc_buf; |
|
if (buf) |
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mutex_lock(&of->prealloc_mutex); |
|
else |
|
buf = kmalloc(len + 1, GFP_KERNEL); |
|
if (!buf) |
|
return -ENOMEM; |
|
|
|
if (copy_from_iter(buf, len, iter) != len) { |
|
len = -EFAULT; |
|
goto out_free; |
|
} |
|
buf[len] = '\0'; /* guarantee string termination */ |
|
|
|
/* |
|
* @of->mutex nests outside active ref and is used both to ensure that |
|
* the ops aren't called concurrently for the same open file. |
|
*/ |
|
mutex_lock(&of->mutex); |
|
if (!kernfs_get_active(of->kn)) { |
|
mutex_unlock(&of->mutex); |
|
len = -ENODEV; |
|
goto out_free; |
|
} |
|
|
|
ops = kernfs_ops(of->kn); |
|
if (ops->write) |
|
len = ops->write(of, buf, len, iocb->ki_pos); |
|
else |
|
len = -EINVAL; |
|
|
|
kernfs_put_active(of->kn); |
|
mutex_unlock(&of->mutex); |
|
|
|
if (len > 0) |
|
iocb->ki_pos += len; |
|
|
|
out_free: |
|
if (buf == of->prealloc_buf) |
|
mutex_unlock(&of->prealloc_mutex); |
|
else |
|
kfree(buf); |
|
return len; |
|
} |
|
|
|
static void kernfs_vma_open(struct vm_area_struct *vma) |
|
{ |
|
struct file *file = vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
|
|
if (!of->vm_ops) |
|
return; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return; |
|
|
|
if (of->vm_ops->open) |
|
of->vm_ops->open(vma); |
|
|
|
kernfs_put_active(of->kn); |
|
} |
|
|
|
static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf) |
|
{ |
|
struct file *file = vmf->vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
vm_fault_t ret; |
|
|
|
if (!of->vm_ops) |
|
return VM_FAULT_SIGBUS; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return VM_FAULT_SIGBUS; |
|
|
|
ret = VM_FAULT_SIGBUS; |
|
if (of->vm_ops->fault) |
|
ret = of->vm_ops->fault(vmf); |
|
|
|
kernfs_put_active(of->kn); |
|
return ret; |
|
} |
|
|
|
static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf) |
|
{ |
|
struct file *file = vmf->vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
vm_fault_t ret; |
|
|
|
if (!of->vm_ops) |
|
return VM_FAULT_SIGBUS; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return VM_FAULT_SIGBUS; |
|
|
|
ret = 0; |
|
if (of->vm_ops->page_mkwrite) |
|
ret = of->vm_ops->page_mkwrite(vmf); |
|
else |
|
file_update_time(file); |
|
|
|
kernfs_put_active(of->kn); |
|
return ret; |
|
} |
|
|
|
static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr, |
|
void *buf, int len, int write) |
|
{ |
|
struct file *file = vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
int ret; |
|
|
|
if (!of->vm_ops) |
|
return -EINVAL; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return -EINVAL; |
|
|
|
ret = -EINVAL; |
|
if (of->vm_ops->access) |
|
ret = of->vm_ops->access(vma, addr, buf, len, write); |
|
|
|
kernfs_put_active(of->kn); |
|
return ret; |
|
} |
|
|
|
#ifdef CONFIG_NUMA |
|
static int kernfs_vma_set_policy(struct vm_area_struct *vma, |
|
struct mempolicy *new) |
|
{ |
|
struct file *file = vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
int ret; |
|
|
|
if (!of->vm_ops) |
|
return 0; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return -EINVAL; |
|
|
|
ret = 0; |
|
if (of->vm_ops->set_policy) |
|
ret = of->vm_ops->set_policy(vma, new); |
|
|
|
kernfs_put_active(of->kn); |
|
return ret; |
|
} |
|
|
|
static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma, |
|
unsigned long addr) |
|
{ |
|
struct file *file = vma->vm_file; |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
struct mempolicy *pol; |
|
|
|
if (!of->vm_ops) |
|
return vma->vm_policy; |
|
|
|
if (!kernfs_get_active(of->kn)) |
|
return vma->vm_policy; |
|
|
|
pol = vma->vm_policy; |
|
if (of->vm_ops->get_policy) |
|
pol = of->vm_ops->get_policy(vma, addr); |
|
|
|
kernfs_put_active(of->kn); |
|
return pol; |
|
} |
|
|
|
#endif |
|
|
|
static const struct vm_operations_struct kernfs_vm_ops = { |
|
.open = kernfs_vma_open, |
|
.fault = kernfs_vma_fault, |
|
.page_mkwrite = kernfs_vma_page_mkwrite, |
|
.access = kernfs_vma_access, |
|
#ifdef CONFIG_NUMA |
|
.set_policy = kernfs_vma_set_policy, |
|
.get_policy = kernfs_vma_get_policy, |
|
#endif |
|
}; |
|
|
|
static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma) |
|
{ |
|
struct kernfs_open_file *of = kernfs_of(file); |
|
const struct kernfs_ops *ops; |
|
int rc; |
|
|
|
/* |
|
* mmap path and of->mutex are prone to triggering spurious lockdep |
|
* warnings and we don't want to add spurious locking dependency |
|
* between the two. Check whether mmap is actually implemented |
|
* without grabbing @of->mutex by testing HAS_MMAP flag. See the |
|
* comment in kernfs_file_open() for more details. |
|
*/ |
|
if (!(of->kn->flags & KERNFS_HAS_MMAP)) |
|
return -ENODEV; |
|
|
|
mutex_lock(&of->mutex); |
|
|
|
rc = -ENODEV; |
|
if (!kernfs_get_active(of->kn)) |
|
goto out_unlock; |
|
|
|
ops = kernfs_ops(of->kn); |
|
rc = ops->mmap(of, vma); |
|
if (rc) |
|
goto out_put; |
|
|
|
/* |
|
* PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup() |
|
* to satisfy versions of X which crash if the mmap fails: that |
|
* substitutes a new vm_file, and we don't then want bin_vm_ops. |
|
*/ |
|
if (vma->vm_file != file) |
|
goto out_put; |
|
|
|
rc = -EINVAL; |
|
if (of->mmapped && of->vm_ops != vma->vm_ops) |
|
goto out_put; |
|
|
|
/* |
|
* It is not possible to successfully wrap close. |
|
* So error if someone is trying to use close. |
|
*/ |
|
if (vma->vm_ops && vma->vm_ops->close) |
|
goto out_put; |
|
|
|
rc = 0; |
|
of->mmapped = true; |
|
of->vm_ops = vma->vm_ops; |
|
vma->vm_ops = &kernfs_vm_ops; |
|
out_put: |
|
kernfs_put_active(of->kn); |
|
out_unlock: |
|
mutex_unlock(&of->mutex); |
|
|
|
return rc; |
|
} |
|
|
|
/** |
|
* kernfs_get_open_node - get or create kernfs_open_node |
|
* @kn: target kernfs_node |
|
* @of: kernfs_open_file for this instance of open |
|
* |
|
* If @kn->attr.open exists, increment its reference count; otherwise, |
|
* create one. @of is chained to the files list. |
|
* |
|
* LOCKING: |
|
* Kernel thread context (may sleep). |
|
* |
|
* RETURNS: |
|
* 0 on success, -errno on failure. |
|
*/ |
|
static int kernfs_get_open_node(struct kernfs_node *kn, |
|
struct kernfs_open_file *of) |
|
{ |
|
struct kernfs_open_node *on, *new_on = NULL; |
|
struct mutex *mutex = NULL; |
|
|
|
mutex = kernfs_open_file_mutex_lock(kn); |
|
on = kernfs_deref_open_node_protected(kn); |
|
|
|
if (on) { |
|
list_add_tail(&of->list, &on->files); |
|
mutex_unlock(mutex); |
|
return 0; |
|
} else { |
|
/* not there, initialize a new one */ |
|
new_on = kmalloc(sizeof(*new_on), GFP_KERNEL); |
|
if (!new_on) { |
|
mutex_unlock(mutex); |
|
return -ENOMEM; |
|
} |
|
atomic_set(&new_on->event, 1); |
|
init_waitqueue_head(&new_on->poll); |
|
INIT_LIST_HEAD(&new_on->files); |
|
list_add_tail(&of->list, &new_on->files); |
|
rcu_assign_pointer(kn->attr.open, new_on); |
|
} |
|
mutex_unlock(mutex); |
|
|
|
return 0; |
|
} |
|
|
|
/** |
|
* kernfs_unlink_open_file - Unlink @of from @kn. |
|
* |
|
* @kn: target kernfs_node |
|
* @of: associated kernfs_open_file |
|
* |
|
* Unlink @of from list of @kn's associated open files. If list of |
|
* associated open files becomes empty, disassociate and free |
|
* kernfs_open_node. |
|
* |
|
* LOCKING: |
|
* None. |
|
*/ |
|
static void kernfs_unlink_open_file(struct kernfs_node *kn, |
|
struct kernfs_open_file *of) |
|
{ |
|
struct kernfs_open_node *on; |
|
struct mutex *mutex = NULL; |
|
|
|
mutex = kernfs_open_file_mutex_lock(kn); |
|
|
|
on = kernfs_deref_open_node_protected(kn); |
|
if (!on) { |
|
mutex_unlock(mutex); |
|
return; |
|
} |
|
|
|
if (of) |
|
list_del(&of->list); |
|
|
|
if (list_empty(&on->files)) { |
|
rcu_assign_pointer(kn->attr.open, NULL); |
|
kfree_rcu(on, rcu_head); |
|
} |
|
|
|
mutex_unlock(mutex); |
|
} |
|
|
|
static int kernfs_fop_open(struct inode *inode, struct file *file) |
|
{ |
|
struct kernfs_node *kn = inode->i_private; |
|
struct kernfs_root *root = kernfs_root(kn); |
|
const struct kernfs_ops *ops; |
|
struct kernfs_open_file *of; |
|
bool has_read, has_write, has_mmap; |
|
int error = -EACCES; |
|
|
|
if (!kernfs_get_active(kn)) |
|
return -ENODEV; |
|
|
|
ops = kernfs_ops(kn); |
|
|
|
has_read = ops->seq_show || ops->read || ops->mmap; |
|
has_write = ops->write || ops->mmap; |
|
has_mmap = ops->mmap; |
|
|
|
/* see the flag definition for details */ |
|
if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) { |
|
if ((file->f_mode & FMODE_WRITE) && |
|
(!(inode->i_mode & S_IWUGO) || !has_write)) |
|
goto err_out; |
|
|
|
if ((file->f_mode & FMODE_READ) && |
|
(!(inode->i_mode & S_IRUGO) || !has_read)) |
|
goto err_out; |
|
} |
|
|
|
/* allocate a kernfs_open_file for the file */ |
|
error = -ENOMEM; |
|
of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL); |
|
if (!of) |
|
goto err_out; |
|
|
|
/* |
|
* The following is done to give a different lockdep key to |
|
* @of->mutex for files which implement mmap. This is a rather |
|
* crude way to avoid false positive lockdep warning around |
|
* mm->mmap_lock - mmap nests @of->mutex under mm->mmap_lock and |
|
* reading /sys/block/sda/trace/act_mask grabs sr_mutex, under |
|
* which mm->mmap_lock nests, while holding @of->mutex. As each |
|
* open file has a separate mutex, it's okay as long as those don't |
|
* happen on the same file. At this point, we can't easily give |
|
* each file a separate locking class. Let's differentiate on |
|
* whether the file has mmap or not for now. |
|
* |
|
* Both paths of the branch look the same. They're supposed to |
|
* look that way and give @of->mutex different static lockdep keys. |
|
*/ |
|
if (has_mmap) |
|
mutex_init(&of->mutex); |
|
else |
|
mutex_init(&of->mutex); |
|
|
|
of->kn = kn; |
|
of->file = file; |
|
|
|
/* |
|
* Write path needs to atomic_write_len outside active reference. |
|
* Cache it in open_file. See kernfs_fop_write_iter() for details. |
|
*/ |
|
of->atomic_write_len = ops->atomic_write_len; |
|
|
|
error = -EINVAL; |
|
/* |
|
* ->seq_show is incompatible with ->prealloc, |
|
* as seq_read does its own allocation. |
|
* ->read must be used instead. |
|
*/ |
|
if (ops->prealloc && ops->seq_show) |
|
goto err_free; |
|
if (ops->prealloc) { |
|
int len = of->atomic_write_len ?: PAGE_SIZE; |
|
of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL); |
|
error = -ENOMEM; |
|
if (!of->prealloc_buf) |
|
goto err_free; |
|
mutex_init(&of->prealloc_mutex); |
|
} |
|
|
|
/* |
|
* Always instantiate seq_file even if read access doesn't use |
|
* seq_file or is not requested. This unifies private data access |
|
* and readable regular files are the vast majority anyway. |
|
*/ |
|
if (ops->seq_show) |
|
error = seq_open(file, &kernfs_seq_ops); |
|
else |
|
error = seq_open(file, NULL); |
|
if (error) |
|
goto err_free; |
|
|
|
of->seq_file = file->private_data; |
|
of->seq_file->private = of; |
|
|
|
/* seq_file clears PWRITE unconditionally, restore it if WRITE */ |
|
if (file->f_mode & FMODE_WRITE) |
|
file->f_mode |= FMODE_PWRITE; |
|
|
|
/* make sure we have open node struct */ |
|
error = kernfs_get_open_node(kn, of); |
|
if (error) |
|
goto err_seq_release; |
|
|
|
if (ops->open) { |
|
/* nobody has access to @of yet, skip @of->mutex */ |
|
error = ops->open(of); |
|
if (error) |
|
goto err_put_node; |
|
} |
|
|
|
/* open succeeded, put active references */ |
|
kernfs_put_active(kn); |
|
return 0; |
|
|
|
err_put_node: |
|
kernfs_unlink_open_file(kn, of); |
|
err_seq_release: |
|
seq_release(inode, file); |
|
err_free: |
|
kfree(of->prealloc_buf); |
|
kfree(of); |
|
err_out: |
|
kernfs_put_active(kn); |
|
return error; |
|
} |
|
|
|
/* used from release/drain to ensure that ->release() is called exactly once */ |
|
static void kernfs_release_file(struct kernfs_node *kn, |
|
struct kernfs_open_file *of) |
|
{ |
|
/* |
|
* @of is guaranteed to have no other file operations in flight and |
|
* we just want to synchronize release and drain paths. |
|
* @kernfs_open_file_mutex_ptr(kn) is enough. @of->mutex can't be used |
|
* here because drain path may be called from places which can |
|
* cause circular dependency. |
|
*/ |
|
lockdep_assert_held(kernfs_open_file_mutex_ptr(kn)); |
|
|
|
if (!of->released) { |
|
/* |
|
* A file is never detached without being released and we |
|
* need to be able to release files which are deactivated |
|
* and being drained. Don't use kernfs_ops(). |
|
*/ |
|
kn->attr.ops->release(of); |
|
of->released = true; |
|
} |
|
} |
|
|
|
static int kernfs_fop_release(struct inode *inode, struct file *filp) |
|
{ |
|
struct kernfs_node *kn = inode->i_private; |
|
struct kernfs_open_file *of = kernfs_of(filp); |
|
struct mutex *mutex = NULL; |
|
|
|
if (kn->flags & KERNFS_HAS_RELEASE) { |
|
mutex = kernfs_open_file_mutex_lock(kn); |
|
kernfs_release_file(kn, of); |
|
mutex_unlock(mutex); |
|
} |
|
|
|
kernfs_unlink_open_file(kn, of); |
|
seq_release(inode, filp); |
|
kfree(of->prealloc_buf); |
|
kfree(of); |
|
|
|
return 0; |
|
} |
|
|
|
void kernfs_drain_open_files(struct kernfs_node *kn) |
|
{ |
|
struct kernfs_open_node *on; |
|
struct kernfs_open_file *of; |
|
struct mutex *mutex = NULL; |
|
|
|
if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE))) |
|
return; |
|
|
|
/* |
|
* lockless opportunistic check is safe below because no one is adding to |
|
* ->attr.open at this point of time. This check allows early bail out |
|
* if ->attr.open is already NULL. kernfs_unlink_open_file makes |
|
* ->attr.open NULL only while holding kernfs_open_file_mutex so below |
|
* check under kernfs_open_file_mutex_ptr(kn) will ensure bailing out if |
|
* ->attr.open became NULL while waiting for the mutex. |
|
*/ |
|
if (!rcu_access_pointer(kn->attr.open)) |
|
return; |
|
|
|
mutex = kernfs_open_file_mutex_lock(kn); |
|
on = kernfs_deref_open_node_protected(kn); |
|
if (!on) { |
|
mutex_unlock(mutex); |
|
return; |
|
} |
|
|
|
list_for_each_entry(of, &on->files, list) { |
|
struct inode *inode = file_inode(of->file); |
|
|
|
if (kn->flags & KERNFS_HAS_MMAP) |
|
unmap_mapping_range(inode->i_mapping, 0, 0, 1); |
|
|
|
if (kn->flags & KERNFS_HAS_RELEASE) |
|
kernfs_release_file(kn, of); |
|
} |
|
|
|
mutex_unlock(mutex); |
|
} |
|
|
|
/* |
|
* Kernfs attribute files are pollable. The idea is that you read |
|
* the content and then you use 'poll' or 'select' to wait for |
|
* the content to change. When the content changes (assuming the |
|
* manager for the kobject supports notification), poll will |
|
* return EPOLLERR|EPOLLPRI, and select will return the fd whether |
|
* it is waiting for read, write, or exceptions. |
|
* Once poll/select indicates that the value has changed, you |
|
* need to close and re-open the file, or seek to 0 and read again. |
|
* Reminder: this only works for attributes which actively support |
|
* it, and it is not possible to test an attribute from userspace |
|
* to see if it supports poll (Neither 'poll' nor 'select' return |
|
* an appropriate error code). When in doubt, set a suitable timeout value. |
|
*/ |
|
__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait) |
|
{ |
|
struct kernfs_node *kn = kernfs_dentry_node(of->file->f_path.dentry); |
|
struct kernfs_open_node *on = kernfs_deref_open_node(of, kn); |
|
|
|
if (!on) |
|
return EPOLLERR; |
|
|
|
poll_wait(of->file, &on->poll, wait); |
|
|
|
if (of->event != atomic_read(&on->event)) |
|
return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI; |
|
|
|
return DEFAULT_POLLMASK; |
|
} |
|
|
|
static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait) |
|
{ |
|
struct kernfs_open_file *of = kernfs_of(filp); |
|
struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry); |
|
__poll_t ret; |
|
|
|
if (!kernfs_get_active(kn)) |
|
return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI; |
|
|
|
if (kn->attr.ops->poll) |
|
ret = kn->attr.ops->poll(of, wait); |
|
else |
|
ret = kernfs_generic_poll(of, wait); |
|
|
|
kernfs_put_active(kn); |
|
return ret; |
|
} |
|
|
|
static void kernfs_notify_workfn(struct work_struct *work) |
|
{ |
|
struct kernfs_node *kn; |
|
struct kernfs_super_info *info; |
|
struct kernfs_root *root; |
|
repeat: |
|
/* pop one off the notify_list */ |
|
spin_lock_irq(&kernfs_notify_lock); |
|
kn = kernfs_notify_list; |
|
if (kn == KERNFS_NOTIFY_EOL) { |
|
spin_unlock_irq(&kernfs_notify_lock); |
|
return; |
|
} |
|
kernfs_notify_list = kn->attr.notify_next; |
|
kn->attr.notify_next = NULL; |
|
spin_unlock_irq(&kernfs_notify_lock); |
|
|
|
root = kernfs_root(kn); |
|
/* kick fsnotify */ |
|
down_write(&root->kernfs_rwsem); |
|
|
|
list_for_each_entry(info, &kernfs_root(kn)->supers, node) { |
|
struct kernfs_node *parent; |
|
struct inode *p_inode = NULL; |
|
struct inode *inode; |
|
struct qstr name; |
|
|
|
/* |
|
* We want fsnotify_modify() on @kn but as the |
|
* modifications aren't originating from userland don't |
|
* have the matching @file available. Look up the inodes |
|
* and generate the events manually. |
|
*/ |
|
inode = ilookup(info->sb, kernfs_ino(kn)); |
|
if (!inode) |
|
continue; |
|
|
|
name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name)); |
|
parent = kernfs_get_parent(kn); |
|
if (parent) { |
|
p_inode = ilookup(info->sb, kernfs_ino(parent)); |
|
if (p_inode) { |
|
fsnotify(FS_MODIFY | FS_EVENT_ON_CHILD, |
|
inode, FSNOTIFY_EVENT_INODE, |
|
p_inode, &name, inode, 0); |
|
iput(p_inode); |
|
} |
|
|
|
kernfs_put(parent); |
|
} |
|
|
|
if (!p_inode) |
|
fsnotify_inode(inode, FS_MODIFY); |
|
|
|
iput(inode); |
|
} |
|
|
|
up_write(&root->kernfs_rwsem); |
|
kernfs_put(kn); |
|
goto repeat; |
|
} |
|
|
|
/** |
|
* kernfs_notify - notify a kernfs file |
|
* @kn: file to notify |
|
* |
|
* Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any |
|
* context. |
|
*/ |
|
void kernfs_notify(struct kernfs_node *kn) |
|
{ |
|
static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn); |
|
unsigned long flags; |
|
struct kernfs_open_node *on; |
|
|
|
if (WARN_ON(kernfs_type(kn) != KERNFS_FILE)) |
|
return; |
|
|
|
/* kick poll immediately */ |
|
rcu_read_lock(); |
|
on = rcu_dereference(kn->attr.open); |
|
if (on) { |
|
atomic_inc(&on->event); |
|
wake_up_interruptible(&on->poll); |
|
} |
|
rcu_read_unlock(); |
|
|
|
/* schedule work to kick fsnotify */ |
|
spin_lock_irqsave(&kernfs_notify_lock, flags); |
|
if (!kn->attr.notify_next) { |
|
kernfs_get(kn); |
|
kn->attr.notify_next = kernfs_notify_list; |
|
kernfs_notify_list = kn; |
|
schedule_work(&kernfs_notify_work); |
|
} |
|
spin_unlock_irqrestore(&kernfs_notify_lock, flags); |
|
} |
|
EXPORT_SYMBOL_GPL(kernfs_notify); |
|
|
|
const struct file_operations kernfs_file_fops = { |
|
.read_iter = kernfs_fop_read_iter, |
|
.write_iter = kernfs_fop_write_iter, |
|
.llseek = generic_file_llseek, |
|
.mmap = kernfs_fop_mmap, |
|
.open = kernfs_fop_open, |
|
.release = kernfs_fop_release, |
|
.poll = kernfs_fop_poll, |
|
.fsync = noop_fsync, |
|
.splice_read = generic_file_splice_read, |
|
.splice_write = iter_file_splice_write, |
|
}; |
|
|
|
/** |
|
* __kernfs_create_file - kernfs internal function to create a file |
|
* @parent: directory to create the file in |
|
* @name: name of the file |
|
* @mode: mode of the file |
|
* @uid: uid of the file |
|
* @gid: gid of the file |
|
* @size: size of the file |
|
* @ops: kernfs operations for the file |
|
* @priv: private data for the file |
|
* @ns: optional namespace tag of the file |
|
* @key: lockdep key for the file's active_ref, %NULL to disable lockdep |
|
* |
|
* Returns the created node on success, ERR_PTR() value on error. |
|
*/ |
|
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent, |
|
const char *name, |
|
umode_t mode, kuid_t uid, kgid_t gid, |
|
loff_t size, |
|
const struct kernfs_ops *ops, |
|
void *priv, const void *ns, |
|
struct lock_class_key *key) |
|
{ |
|
struct kernfs_node *kn; |
|
unsigned flags; |
|
int rc; |
|
|
|
flags = KERNFS_FILE; |
|
|
|
kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, |
|
uid, gid, flags); |
|
if (!kn) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
kn->attr.ops = ops; |
|
kn->attr.size = size; |
|
kn->ns = ns; |
|
kn->priv = priv; |
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC |
|
if (key) { |
|
lockdep_init_map(&kn->dep_map, "kn->active", key, 0); |
|
kn->flags |= KERNFS_LOCKDEP; |
|
} |
|
#endif |
|
|
|
/* |
|
* kn->attr.ops is accessible only while holding active ref. We |
|
* need to know whether some ops are implemented outside active |
|
* ref. Cache their existence in flags. |
|
*/ |
|
if (ops->seq_show) |
|
kn->flags |= KERNFS_HAS_SEQ_SHOW; |
|
if (ops->mmap) |
|
kn->flags |= KERNFS_HAS_MMAP; |
|
if (ops->release) |
|
kn->flags |= KERNFS_HAS_RELEASE; |
|
|
|
rc = kernfs_add_one(kn); |
|
if (rc) { |
|
kernfs_put(kn); |
|
return ERR_PTR(rc); |
|
} |
|
return kn; |
|
}
|
|
|