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877 lines
26 KiB
877 lines
26 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <[email protected]> |
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*/ |
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|
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/* |
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* fsnotify inode mark locking/lifetime/and refcnting |
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* |
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* REFCNT: |
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* The group->recnt and mark->refcnt tell how many "things" in the kernel |
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* currently are referencing the objects. Both kind of objects typically will |
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* live inside the kernel with a refcnt of 2, one for its creation and one for |
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* the reference a group and a mark hold to each other. |
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* If you are holding the appropriate locks, you can take a reference and the |
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* object itself is guaranteed to survive until the reference is dropped. |
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* |
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* LOCKING: |
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* There are 3 locks involved with fsnotify inode marks and they MUST be taken |
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* in order as follows: |
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* |
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* group->mark_mutex |
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* mark->lock |
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* mark->connector->lock |
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* |
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* group->mark_mutex protects the marks_list anchored inside a given group and |
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* each mark is hooked via the g_list. It also protects the groups private |
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* data (i.e group limits). |
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|
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* mark->lock protects the marks attributes like its masks and flags. |
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* Furthermore it protects the access to a reference of the group that the mark |
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* is assigned to as well as the access to a reference of the inode/vfsmount |
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* that is being watched by the mark. |
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* |
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* mark->connector->lock protects the list of marks anchored inside an |
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* inode / vfsmount and each mark is hooked via the i_list. |
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* |
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* A list of notification marks relating to inode / mnt is contained in |
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* fsnotify_mark_connector. That structure is alive as long as there are any |
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* marks in the list and is also protected by fsnotify_mark_srcu. A mark gets |
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* detached from fsnotify_mark_connector when last reference to the mark is |
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* dropped. Thus having mark reference is enough to protect mark->connector |
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* pointer and to make sure fsnotify_mark_connector cannot disappear. Also |
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* because we remove mark from g_list before dropping mark reference associated |
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* with that, any mark found through g_list is guaranteed to have |
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* mark->connector set until we drop group->mark_mutex. |
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* |
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* LIFETIME: |
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* Inode marks survive between when they are added to an inode and when their |
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* refcnt==0. Marks are also protected by fsnotify_mark_srcu. |
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* |
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* The inode mark can be cleared for a number of different reasons including: |
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* - The inode is unlinked for the last time. (fsnotify_inode_remove) |
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* - The inode is being evicted from cache. (fsnotify_inode_delete) |
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* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes) |
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* - Something explicitly requests that it be removed. (fsnotify_destroy_mark) |
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* - The fsnotify_group associated with the mark is going away and all such marks |
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* need to be cleaned up. (fsnotify_clear_marks_by_group) |
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* |
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* This has the very interesting property of being able to run concurrently with |
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* any (or all) other directions. |
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*/ |
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|
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#include <linux/fs.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/kthread.h> |
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#include <linux/module.h> |
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#include <linux/mutex.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/srcu.h> |
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#include <linux/ratelimit.h> |
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#include <linux/atomic.h> |
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#include <linux/fsnotify_backend.h> |
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#include "fsnotify.h" |
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|
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#define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */ |
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struct srcu_struct fsnotify_mark_srcu; |
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struct kmem_cache *fsnotify_mark_connector_cachep; |
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|
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static DEFINE_SPINLOCK(destroy_lock); |
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static LIST_HEAD(destroy_list); |
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static struct fsnotify_mark_connector *connector_destroy_list; |
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|
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static void fsnotify_mark_destroy_workfn(struct work_struct *work); |
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static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn); |
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|
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static void fsnotify_connector_destroy_workfn(struct work_struct *work); |
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static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn); |
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|
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void fsnotify_get_mark(struct fsnotify_mark *mark) |
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{ |
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WARN_ON_ONCE(!refcount_read(&mark->refcnt)); |
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refcount_inc(&mark->refcnt); |
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} |
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|
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static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn) |
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{ |
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if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) |
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return &fsnotify_conn_inode(conn)->i_fsnotify_mask; |
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else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) |
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return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask; |
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else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) |
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return &fsnotify_conn_sb(conn)->s_fsnotify_mask; |
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return NULL; |
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} |
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|
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__u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn) |
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{ |
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if (WARN_ON(!fsnotify_valid_obj_type(conn->type))) |
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return 0; |
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|
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return *fsnotify_conn_mask_p(conn); |
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} |
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|
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static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) |
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{ |
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u32 new_mask = 0; |
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struct fsnotify_mark *mark; |
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assert_spin_locked(&conn->lock); |
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/* We can get detached connector here when inode is getting unlinked. */ |
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if (!fsnotify_valid_obj_type(conn->type)) |
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return; |
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hlist_for_each_entry(mark, &conn->list, obj_list) { |
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if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) |
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new_mask |= fsnotify_calc_mask(mark); |
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} |
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*fsnotify_conn_mask_p(conn) = new_mask; |
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} |
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|
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/* |
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* Calculate mask of events for a list of marks. The caller must make sure |
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* connector and connector->obj cannot disappear under us. Callers achieve |
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* this by holding a mark->lock or mark->group->mark_mutex for a mark on this |
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* list. |
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*/ |
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void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) |
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{ |
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if (!conn) |
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return; |
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spin_lock(&conn->lock); |
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__fsnotify_recalc_mask(conn); |
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spin_unlock(&conn->lock); |
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if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) |
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__fsnotify_update_child_dentry_flags( |
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fsnotify_conn_inode(conn)); |
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} |
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|
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/* Free all connectors queued for freeing once SRCU period ends */ |
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static void fsnotify_connector_destroy_workfn(struct work_struct *work) |
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{ |
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struct fsnotify_mark_connector *conn, *free; |
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spin_lock(&destroy_lock); |
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conn = connector_destroy_list; |
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connector_destroy_list = NULL; |
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spin_unlock(&destroy_lock); |
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synchronize_srcu(&fsnotify_mark_srcu); |
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while (conn) { |
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free = conn; |
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conn = conn->destroy_next; |
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kmem_cache_free(fsnotify_mark_connector_cachep, free); |
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} |
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} |
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static void fsnotify_get_inode_ref(struct inode *inode) |
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{ |
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ihold(inode); |
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atomic_long_inc(&inode->i_sb->s_fsnotify_connectors); |
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} |
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static void fsnotify_put_inode_ref(struct inode *inode) |
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{ |
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struct super_block *sb = inode->i_sb; |
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iput(inode); |
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if (atomic_long_dec_and_test(&sb->s_fsnotify_connectors)) |
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wake_up_var(&sb->s_fsnotify_connectors); |
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} |
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static void fsnotify_get_sb_connectors(struct fsnotify_mark_connector *conn) |
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{ |
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struct super_block *sb = fsnotify_connector_sb(conn); |
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if (sb) |
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atomic_long_inc(&sb->s_fsnotify_connectors); |
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} |
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static void fsnotify_put_sb_connectors(struct fsnotify_mark_connector *conn) |
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{ |
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struct super_block *sb = fsnotify_connector_sb(conn); |
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if (sb && atomic_long_dec_and_test(&sb->s_fsnotify_connectors)) |
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wake_up_var(&sb->s_fsnotify_connectors); |
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} |
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static void *fsnotify_detach_connector_from_object( |
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struct fsnotify_mark_connector *conn, |
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unsigned int *type) |
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{ |
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struct inode *inode = NULL; |
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*type = conn->type; |
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if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) |
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return NULL; |
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if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) { |
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inode = fsnotify_conn_inode(conn); |
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inode->i_fsnotify_mask = 0; |
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} else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) { |
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fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0; |
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} else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) { |
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fsnotify_conn_sb(conn)->s_fsnotify_mask = 0; |
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} |
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fsnotify_put_sb_connectors(conn); |
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rcu_assign_pointer(*(conn->obj), NULL); |
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conn->obj = NULL; |
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conn->type = FSNOTIFY_OBJ_TYPE_DETACHED; |
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return inode; |
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} |
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static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark) |
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{ |
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struct fsnotify_group *group = mark->group; |
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if (WARN_ON_ONCE(!group)) |
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return; |
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group->ops->free_mark(mark); |
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fsnotify_put_group(group); |
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} |
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/* Drop object reference originally held by a connector */ |
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static void fsnotify_drop_object(unsigned int type, void *objp) |
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{ |
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if (!objp) |
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return; |
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/* Currently only inode references are passed to be dropped */ |
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if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE)) |
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return; |
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fsnotify_put_inode_ref(objp); |
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} |
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void fsnotify_put_mark(struct fsnotify_mark *mark) |
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{ |
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struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector); |
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void *objp = NULL; |
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unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED; |
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bool free_conn = false; |
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/* Catch marks that were actually never attached to object */ |
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if (!conn) { |
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if (refcount_dec_and_test(&mark->refcnt)) |
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fsnotify_final_mark_destroy(mark); |
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return; |
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} |
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/* |
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* We have to be careful so that traversals of obj_list under lock can |
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* safely grab mark reference. |
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*/ |
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if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock)) |
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return; |
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hlist_del_init_rcu(&mark->obj_list); |
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if (hlist_empty(&conn->list)) { |
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objp = fsnotify_detach_connector_from_object(conn, &type); |
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free_conn = true; |
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} else { |
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__fsnotify_recalc_mask(conn); |
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} |
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WRITE_ONCE(mark->connector, NULL); |
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spin_unlock(&conn->lock); |
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fsnotify_drop_object(type, objp); |
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if (free_conn) { |
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spin_lock(&destroy_lock); |
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conn->destroy_next = connector_destroy_list; |
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connector_destroy_list = conn; |
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spin_unlock(&destroy_lock); |
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queue_work(system_unbound_wq, &connector_reaper_work); |
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} |
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/* |
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* Note that we didn't update flags telling whether inode cares about |
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* what's happening with children. We update these flags from |
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* __fsnotify_parent() lazily when next event happens on one of our |
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* children. |
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*/ |
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spin_lock(&destroy_lock); |
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list_add(&mark->g_list, &destroy_list); |
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spin_unlock(&destroy_lock); |
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queue_delayed_work(system_unbound_wq, &reaper_work, |
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FSNOTIFY_REAPER_DELAY); |
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} |
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EXPORT_SYMBOL_GPL(fsnotify_put_mark); |
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/* |
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* Get mark reference when we found the mark via lockless traversal of object |
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* list. Mark can be already removed from the list by now and on its way to be |
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* destroyed once SRCU period ends. |
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* |
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* Also pin the group so it doesn't disappear under us. |
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*/ |
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static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark) |
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{ |
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if (!mark) |
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return true; |
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if (refcount_inc_not_zero(&mark->refcnt)) { |
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spin_lock(&mark->lock); |
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if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) { |
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/* mark is attached, group is still alive then */ |
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atomic_inc(&mark->group->user_waits); |
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spin_unlock(&mark->lock); |
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return true; |
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} |
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spin_unlock(&mark->lock); |
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fsnotify_put_mark(mark); |
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} |
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return false; |
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} |
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/* |
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* Puts marks and wakes up group destruction if necessary. |
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* |
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* Pairs with fsnotify_get_mark_safe() |
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*/ |
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static void fsnotify_put_mark_wake(struct fsnotify_mark *mark) |
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{ |
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if (mark) { |
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struct fsnotify_group *group = mark->group; |
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fsnotify_put_mark(mark); |
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/* |
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* We abuse notification_waitq on group shutdown for waiting for |
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* all marks pinned when waiting for userspace. |
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*/ |
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if (atomic_dec_and_test(&group->user_waits) && group->shutdown) |
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wake_up(&group->notification_waitq); |
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} |
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} |
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bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info) |
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__releases(&fsnotify_mark_srcu) |
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{ |
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int type; |
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fsnotify_foreach_iter_type(type) { |
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/* This can fail if mark is being removed */ |
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if (!fsnotify_get_mark_safe(iter_info->marks[type])) { |
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__release(&fsnotify_mark_srcu); |
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goto fail; |
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} |
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} |
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/* |
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* Now that both marks are pinned by refcount in the inode / vfsmount |
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* lists, we can drop SRCU lock, and safely resume the list iteration |
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* once userspace returns. |
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*/ |
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srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx); |
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return true; |
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fail: |
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for (type--; type >= 0; type--) |
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fsnotify_put_mark_wake(iter_info->marks[type]); |
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return false; |
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} |
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void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info) |
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__acquires(&fsnotify_mark_srcu) |
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{ |
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int type; |
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iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); |
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fsnotify_foreach_iter_type(type) |
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fsnotify_put_mark_wake(iter_info->marks[type]); |
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} |
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|
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/* |
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* Mark mark as detached, remove it from group list. Mark still stays in object |
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* list until its last reference is dropped. Note that we rely on mark being |
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* removed from group list before corresponding reference to it is dropped. In |
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* particular we rely on mark->connector being valid while we hold |
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* group->mark_mutex if we found the mark through g_list. |
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* |
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* Must be called with group->mark_mutex held. The caller must either hold |
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* reference to the mark or be protected by fsnotify_mark_srcu. |
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*/ |
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void fsnotify_detach_mark(struct fsnotify_mark *mark) |
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{ |
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struct fsnotify_group *group = mark->group; |
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WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex)); |
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WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) && |
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refcount_read(&mark->refcnt) < 1 + |
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!!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)); |
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spin_lock(&mark->lock); |
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/* something else already called this function on this mark */ |
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if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) { |
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spin_unlock(&mark->lock); |
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return; |
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} |
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mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED; |
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list_del_init(&mark->g_list); |
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spin_unlock(&mark->lock); |
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/* Drop mark reference acquired in fsnotify_add_mark_locked() */ |
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fsnotify_put_mark(mark); |
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} |
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|
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/* |
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* Free fsnotify mark. The mark is actually only marked as being freed. The |
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* freeing is actually happening only once last reference to the mark is |
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* dropped from a workqueue which first waits for srcu period end. |
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* |
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* Caller must have a reference to the mark or be protected by |
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* fsnotify_mark_srcu. |
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*/ |
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void fsnotify_free_mark(struct fsnotify_mark *mark) |
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{ |
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struct fsnotify_group *group = mark->group; |
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spin_lock(&mark->lock); |
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/* something else already called this function on this mark */ |
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if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { |
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spin_unlock(&mark->lock); |
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return; |
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} |
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mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; |
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spin_unlock(&mark->lock); |
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|
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/* |
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* Some groups like to know that marks are being freed. This is a |
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* callback to the group function to let it know that this mark |
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* is being freed. |
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*/ |
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if (group->ops->freeing_mark) |
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group->ops->freeing_mark(mark, group); |
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} |
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void fsnotify_destroy_mark(struct fsnotify_mark *mark, |
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struct fsnotify_group *group) |
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{ |
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mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
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fsnotify_detach_mark(mark); |
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mutex_unlock(&group->mark_mutex); |
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fsnotify_free_mark(mark); |
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} |
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EXPORT_SYMBOL_GPL(fsnotify_destroy_mark); |
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|
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/* |
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* Sorting function for lists of fsnotify marks. |
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* |
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* Fanotify supports different notification classes (reflected as priority of |
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* notification group). Events shall be passed to notification groups in |
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* decreasing priority order. To achieve this marks in notification lists for |
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* inodes and vfsmounts are sorted so that priorities of corresponding groups |
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* are descending. |
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* |
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* Furthermore correct handling of the ignore mask requires processing inode |
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* and vfsmount marks of each group together. Using the group address as |
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* further sort criterion provides a unique sorting order and thus we can |
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* merge inode and vfsmount lists of marks in linear time and find groups |
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* present in both lists. |
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* |
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* A return value of 1 signifies that b has priority over a. |
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* A return value of 0 signifies that the two marks have to be handled together. |
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* A return value of -1 signifies that a has priority over b. |
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*/ |
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int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b) |
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{ |
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if (a == b) |
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return 0; |
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if (!a) |
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return 1; |
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if (!b) |
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return -1; |
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if (a->priority < b->priority) |
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return 1; |
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if (a->priority > b->priority) |
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return -1; |
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if (a < b) |
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return 1; |
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return -1; |
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} |
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|
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static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp, |
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unsigned int obj_type, |
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__kernel_fsid_t *fsid) |
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{ |
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struct inode *inode = NULL; |
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struct fsnotify_mark_connector *conn; |
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|
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conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL); |
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if (!conn) |
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return -ENOMEM; |
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spin_lock_init(&conn->lock); |
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INIT_HLIST_HEAD(&conn->list); |
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conn->type = obj_type; |
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conn->obj = connp; |
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/* Cache fsid of filesystem containing the object */ |
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if (fsid) { |
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conn->fsid = *fsid; |
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conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID; |
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} else { |
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conn->fsid.val[0] = conn->fsid.val[1] = 0; |
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conn->flags = 0; |
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} |
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if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) { |
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inode = fsnotify_conn_inode(conn); |
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fsnotify_get_inode_ref(inode); |
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} |
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fsnotify_get_sb_connectors(conn); |
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|
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/* |
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* cmpxchg() provides the barrier so that readers of *connp can see |
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* only initialized structure |
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*/ |
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if (cmpxchg(connp, NULL, conn)) { |
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/* Someone else created list structure for us */ |
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if (inode) |
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fsnotify_put_inode_ref(inode); |
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fsnotify_put_sb_connectors(conn); |
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kmem_cache_free(fsnotify_mark_connector_cachep, conn); |
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} |
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return 0; |
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} |
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|
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/* |
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* Get mark connector, make sure it is alive and return with its lock held. |
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* This is for users that get connector pointer from inode or mount. Users that |
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* hold reference to a mark on the list may directly lock connector->lock as |
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* they are sure list cannot go away under them. |
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*/ |
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static struct fsnotify_mark_connector *fsnotify_grab_connector( |
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fsnotify_connp_t *connp) |
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{ |
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struct fsnotify_mark_connector *conn; |
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int idx; |
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|
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idx = srcu_read_lock(&fsnotify_mark_srcu); |
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conn = srcu_dereference(*connp, &fsnotify_mark_srcu); |
|
if (!conn) |
|
goto out; |
|
spin_lock(&conn->lock); |
|
if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) { |
|
spin_unlock(&conn->lock); |
|
srcu_read_unlock(&fsnotify_mark_srcu, idx); |
|
return NULL; |
|
} |
|
out: |
|
srcu_read_unlock(&fsnotify_mark_srcu, idx); |
|
return conn; |
|
} |
|
|
|
/* |
|
* Add mark into proper place in given list of marks. These marks may be used |
|
* for the fsnotify backend to determine which event types should be delivered |
|
* to which group and for which inodes. These marks are ordered according to |
|
* priority, highest number first, and then by the group's location in memory. |
|
*/ |
|
static int fsnotify_add_mark_list(struct fsnotify_mark *mark, |
|
fsnotify_connp_t *connp, |
|
unsigned int obj_type, |
|
int allow_dups, __kernel_fsid_t *fsid) |
|
{ |
|
struct fsnotify_mark *lmark, *last = NULL; |
|
struct fsnotify_mark_connector *conn; |
|
int cmp; |
|
int err = 0; |
|
|
|
if (WARN_ON(!fsnotify_valid_obj_type(obj_type))) |
|
return -EINVAL; |
|
|
|
/* Backend is expected to check for zero fsid (e.g. tmpfs) */ |
|
if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1])) |
|
return -ENODEV; |
|
|
|
restart: |
|
spin_lock(&mark->lock); |
|
conn = fsnotify_grab_connector(connp); |
|
if (!conn) { |
|
spin_unlock(&mark->lock); |
|
err = fsnotify_attach_connector_to_object(connp, obj_type, |
|
fsid); |
|
if (err) |
|
return err; |
|
goto restart; |
|
} else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) { |
|
conn->fsid = *fsid; |
|
/* Pairs with smp_rmb() in fanotify_get_fsid() */ |
|
smp_wmb(); |
|
conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID; |
|
} else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) && |
|
(fsid->val[0] != conn->fsid.val[0] || |
|
fsid->val[1] != conn->fsid.val[1])) { |
|
/* |
|
* Backend is expected to check for non uniform fsid |
|
* (e.g. btrfs), but maybe we missed something? |
|
* Only allow setting conn->fsid once to non zero fsid. |
|
* inotify and non-fid fanotify groups do not set nor test |
|
* conn->fsid. |
|
*/ |
|
pr_warn_ratelimited("%s: fsid mismatch on object of type %u: " |
|
"%x.%x != %x.%x\n", __func__, conn->type, |
|
fsid->val[0], fsid->val[1], |
|
conn->fsid.val[0], conn->fsid.val[1]); |
|
err = -EXDEV; |
|
goto out_err; |
|
} |
|
|
|
/* is mark the first mark? */ |
|
if (hlist_empty(&conn->list)) { |
|
hlist_add_head_rcu(&mark->obj_list, &conn->list); |
|
goto added; |
|
} |
|
|
|
/* should mark be in the middle of the current list? */ |
|
hlist_for_each_entry(lmark, &conn->list, obj_list) { |
|
last = lmark; |
|
|
|
if ((lmark->group == mark->group) && |
|
(lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) && |
|
!allow_dups) { |
|
err = -EEXIST; |
|
goto out_err; |
|
} |
|
|
|
cmp = fsnotify_compare_groups(lmark->group, mark->group); |
|
if (cmp >= 0) { |
|
hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list); |
|
goto added; |
|
} |
|
} |
|
|
|
BUG_ON(last == NULL); |
|
/* mark should be the last entry. last is the current last entry */ |
|
hlist_add_behind_rcu(&mark->obj_list, &last->obj_list); |
|
added: |
|
/* |
|
* Since connector is attached to object using cmpxchg() we are |
|
* guaranteed that connector initialization is fully visible by anyone |
|
* seeing mark->connector set. |
|
*/ |
|
WRITE_ONCE(mark->connector, conn); |
|
out_err: |
|
spin_unlock(&conn->lock); |
|
spin_unlock(&mark->lock); |
|
return err; |
|
} |
|
|
|
/* |
|
* Attach an initialized mark to a given group and fs object. |
|
* These marks may be used for the fsnotify backend to determine which |
|
* event types should be delivered to which group. |
|
*/ |
|
int fsnotify_add_mark_locked(struct fsnotify_mark *mark, |
|
fsnotify_connp_t *connp, unsigned int obj_type, |
|
int allow_dups, __kernel_fsid_t *fsid) |
|
{ |
|
struct fsnotify_group *group = mark->group; |
|
int ret = 0; |
|
|
|
BUG_ON(!mutex_is_locked(&group->mark_mutex)); |
|
|
|
/* |
|
* LOCKING ORDER!!!! |
|
* group->mark_mutex |
|
* mark->lock |
|
* mark->connector->lock |
|
*/ |
|
spin_lock(&mark->lock); |
|
mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED; |
|
|
|
list_add(&mark->g_list, &group->marks_list); |
|
fsnotify_get_mark(mark); /* for g_list */ |
|
spin_unlock(&mark->lock); |
|
|
|
ret = fsnotify_add_mark_list(mark, connp, obj_type, allow_dups, fsid); |
|
if (ret) |
|
goto err; |
|
|
|
if (mark->mask || mark->ignored_mask) |
|
fsnotify_recalc_mask(mark->connector); |
|
|
|
return ret; |
|
err: |
|
spin_lock(&mark->lock); |
|
mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE | |
|
FSNOTIFY_MARK_FLAG_ATTACHED); |
|
list_del_init(&mark->g_list); |
|
spin_unlock(&mark->lock); |
|
|
|
fsnotify_put_mark(mark); |
|
return ret; |
|
} |
|
|
|
int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp, |
|
unsigned int obj_type, int allow_dups, |
|
__kernel_fsid_t *fsid) |
|
{ |
|
int ret; |
|
struct fsnotify_group *group = mark->group; |
|
|
|
mutex_lock(&group->mark_mutex); |
|
ret = fsnotify_add_mark_locked(mark, connp, obj_type, allow_dups, fsid); |
|
mutex_unlock(&group->mark_mutex); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(fsnotify_add_mark); |
|
|
|
/* |
|
* Given a list of marks, find the mark associated with given group. If found |
|
* take a reference to that mark and return it, else return NULL. |
|
*/ |
|
struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp, |
|
struct fsnotify_group *group) |
|
{ |
|
struct fsnotify_mark_connector *conn; |
|
struct fsnotify_mark *mark; |
|
|
|
conn = fsnotify_grab_connector(connp); |
|
if (!conn) |
|
return NULL; |
|
|
|
hlist_for_each_entry(mark, &conn->list, obj_list) { |
|
if (mark->group == group && |
|
(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) { |
|
fsnotify_get_mark(mark); |
|
spin_unlock(&conn->lock); |
|
return mark; |
|
} |
|
} |
|
spin_unlock(&conn->lock); |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(fsnotify_find_mark); |
|
|
|
/* Clear any marks in a group with given type mask */ |
|
void fsnotify_clear_marks_by_group(struct fsnotify_group *group, |
|
unsigned int obj_type) |
|
{ |
|
struct fsnotify_mark *lmark, *mark; |
|
LIST_HEAD(to_free); |
|
struct list_head *head = &to_free; |
|
|
|
/* Skip selection step if we want to clear all marks. */ |
|
if (obj_type == FSNOTIFY_OBJ_TYPE_ANY) { |
|
head = &group->marks_list; |
|
goto clear; |
|
} |
|
/* |
|
* We have to be really careful here. Anytime we drop mark_mutex, e.g. |
|
* fsnotify_clear_marks_by_inode() can come and free marks. Even in our |
|
* to_free list so we have to use mark_mutex even when accessing that |
|
* list. And freeing mark requires us to drop mark_mutex. So we can |
|
* reliably free only the first mark in the list. That's why we first |
|
* move marks to free to to_free list in one go and then free marks in |
|
* to_free list one by one. |
|
*/ |
|
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
|
list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) { |
|
if (mark->connector->type == obj_type) |
|
list_move(&mark->g_list, &to_free); |
|
} |
|
mutex_unlock(&group->mark_mutex); |
|
|
|
clear: |
|
while (1) { |
|
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING); |
|
if (list_empty(head)) { |
|
mutex_unlock(&group->mark_mutex); |
|
break; |
|
} |
|
mark = list_first_entry(head, struct fsnotify_mark, g_list); |
|
fsnotify_get_mark(mark); |
|
fsnotify_detach_mark(mark); |
|
mutex_unlock(&group->mark_mutex); |
|
fsnotify_free_mark(mark); |
|
fsnotify_put_mark(mark); |
|
} |
|
} |
|
|
|
/* Destroy all marks attached to an object via connector */ |
|
void fsnotify_destroy_marks(fsnotify_connp_t *connp) |
|
{ |
|
struct fsnotify_mark_connector *conn; |
|
struct fsnotify_mark *mark, *old_mark = NULL; |
|
void *objp; |
|
unsigned int type; |
|
|
|
conn = fsnotify_grab_connector(connp); |
|
if (!conn) |
|
return; |
|
/* |
|
* We have to be careful since we can race with e.g. |
|
* fsnotify_clear_marks_by_group() and once we drop the conn->lock, the |
|
* list can get modified. However we are holding mark reference and |
|
* thus our mark cannot be removed from obj_list so we can continue |
|
* iteration after regaining conn->lock. |
|
*/ |
|
hlist_for_each_entry(mark, &conn->list, obj_list) { |
|
fsnotify_get_mark(mark); |
|
spin_unlock(&conn->lock); |
|
if (old_mark) |
|
fsnotify_put_mark(old_mark); |
|
old_mark = mark; |
|
fsnotify_destroy_mark(mark, mark->group); |
|
spin_lock(&conn->lock); |
|
} |
|
/* |
|
* Detach list from object now so that we don't pin inode until all |
|
* mark references get dropped. It would lead to strange results such |
|
* as delaying inode deletion or blocking unmount. |
|
*/ |
|
objp = fsnotify_detach_connector_from_object(conn, &type); |
|
spin_unlock(&conn->lock); |
|
if (old_mark) |
|
fsnotify_put_mark(old_mark); |
|
fsnotify_drop_object(type, objp); |
|
} |
|
|
|
/* |
|
* Nothing fancy, just initialize lists and locks and counters. |
|
*/ |
|
void fsnotify_init_mark(struct fsnotify_mark *mark, |
|
struct fsnotify_group *group) |
|
{ |
|
memset(mark, 0, sizeof(*mark)); |
|
spin_lock_init(&mark->lock); |
|
refcount_set(&mark->refcnt, 1); |
|
fsnotify_get_group(group); |
|
mark->group = group; |
|
WRITE_ONCE(mark->connector, NULL); |
|
} |
|
EXPORT_SYMBOL_GPL(fsnotify_init_mark); |
|
|
|
/* |
|
* Destroy all marks in destroy_list, waits for SRCU period to finish before |
|
* actually freeing marks. |
|
*/ |
|
static void fsnotify_mark_destroy_workfn(struct work_struct *work) |
|
{ |
|
struct fsnotify_mark *mark, *next; |
|
struct list_head private_destroy_list; |
|
|
|
spin_lock(&destroy_lock); |
|
/* exchange the list head */ |
|
list_replace_init(&destroy_list, &private_destroy_list); |
|
spin_unlock(&destroy_lock); |
|
|
|
synchronize_srcu(&fsnotify_mark_srcu); |
|
|
|
list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) { |
|
list_del_init(&mark->g_list); |
|
fsnotify_final_mark_destroy(mark); |
|
} |
|
} |
|
|
|
/* Wait for all marks queued for destruction to be actually destroyed */ |
|
void fsnotify_wait_marks_destroyed(void) |
|
{ |
|
flush_delayed_work(&reaper_work); |
|
} |
|
EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);
|
|
|