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Release 4.12 include/linux/fsnotify_backend.h

Directory: include/linux
 * Filesystem access notification for Linux
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <>



#ifdef __KERNEL__

#include <linux/idr.h> /* inotify uses this */
#include <linux/fs.h> /* struct inode */
#include <linux/list.h>
#include <linux/path.h> /* struct path */
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/user_namespace.h>

 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
 * convert between them.  dnotify only needs conversion at watch creation
 * so no perf loss there.  fanotify isn't defined yet, so it can use the
 * wholes if it needs more events.

#define FS_ACCESS		0x00000001	
/* File was accessed */

#define FS_MODIFY		0x00000002	
/* File was modified */

#define FS_ATTRIB		0x00000004	
/* Metadata changed */

#define FS_CLOSE_WRITE		0x00000008	
/* Writtable file was closed */

#define FS_CLOSE_NOWRITE	0x00000010	
/* Unwrittable file closed */

#define FS_OPEN			0x00000020	
/* File was opened */

#define FS_MOVED_FROM		0x00000040	
/* File was moved from X */

#define FS_MOVED_TO		0x00000080	
/* File was moved to Y */

#define FS_CREATE		0x00000100	
/* Subfile was created */

#define FS_DELETE		0x00000200	
/* Subfile was deleted */

#define FS_DELETE_SELF		0x00000400	
/* Self was deleted */

#define FS_MOVE_SELF		0x00000800	
/* Self was moved */

#define FS_UNMOUNT		0x00002000	
/* inode on umount fs */

#define FS_Q_OVERFLOW		0x00004000	
/* Event queued overflowed */

#define FS_IN_IGNORED		0x00008000	
/* last inotify event here */

#define FS_OPEN_PERM		0x00010000	
/* open event in an permission hook */

#define FS_ACCESS_PERM		0x00020000	
/* access event in a permissions hook */

#define FS_EXCL_UNLINK		0x04000000	
/* do not send events if object is unlinked */

#define FS_ISDIR		0x40000000	
/* event occurred against dir */

#define FS_IN_ONESHOT		0x80000000	
/* only send event once */

#define FS_DN_RENAME		0x10000000	
/* file renamed */

#define FS_DN_MULTISHOT		0x20000000	
/* dnotify multishot */

/* This inode cares about things that happen to its children.  Always set for
 * dnotify and inotify. */

#define FS_EVENT_ON_CHILD	0x08000000

/* This is a list of all events that may get sent to a parernt based on fs event
 * happening to inodes inside that directory */

                                   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
                                   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
                                   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)



                             FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
                             FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
                             FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
                             FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
                             FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
                             FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
                             FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)

struct fsnotify_group;
struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
struct fsnotify_iter_info;

 * Each group much define these ops.  The fsnotify infrastructure will call
 * these operations for each relevant group.
 * handle_event - main call for a group to handle an fs event
 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
 * freeing_mark - called when a mark is being destroyed for some reason.  The group
 *              MUST be holding a reference on each mark and that reference must be
 *              dropped in this function.  inotify uses this function to send
 *              userspace messages that marks have been removed.

struct fsnotify_ops {
int (*handle_event)(struct fsnotify_group *group,
			    struct inode *inode,
			    struct fsnotify_mark *inode_mark,
			    struct fsnotify_mark *vfsmount_mark,
			    u32 mask, const void *data, int data_type,
			    const unsigned char *file_name, u32 cookie,
			    struct fsnotify_iter_info *iter_info);
void (*free_group_priv)(struct fsnotify_group *group);
void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
void (*free_event)(struct fsnotify_event *event);
	/* called on final put+free to free memory */
void (*free_mark)(struct fsnotify_mark *mark);

 * all of the information about the original object we want to now send to
 * a group.  If you want to carry more info from the accessing task to the
 * listener this structure is where you need to be adding fields.

struct fsnotify_event {
struct list_head list;
	/* inode may ONLY be dereferenced during handle_event(). */
struct inode *inode;	/* either the inode the event happened to or its parent */
u32 mask;		/* the type of access, bitwise OR for FS_* event types */

 * A group is a "thing" that wants to receive notification about filesystem
 * events.  The mask holds the subset of event types this group cares about.
 * refcnt on a group is up to the implementor and at any moment if it goes 0
 * everything will be cleaned up.

struct fsnotify_group {
         * How the refcnt is used is up to each group.  When the refcnt hits 0
         * fsnotify will clean up all of the resources associated with this group.
         * As an example, the dnotify group will always have a refcnt=1 and that
         * will never change.  Inotify, on the other hand, has a group per
         * inotify_init() and the refcnt will hit 0 only when that fd has been
         * closed.
atomic_t refcnt;		/* things with interest in this group */

const struct fsnotify_ops *ops;	/* how this group handles things */

	/* needed to send notification to userspace */
spinlock_t notification_lock;		/* protect the notification_list */
struct list_head notification_list;	/* list of event_holder this group needs to send to userspace */
wait_queue_head_t notification_waitq;	/* read() on the notification file blocks on this waitq */
unsigned int q_len;			/* events on the queue */
unsigned int max_events;		/* maximum events allowed on the list */
         * Valid fsnotify group priorities.  Events are send in order from highest
         * priority to lowest priority.  We default to the lowest priority.
#define FS_PRIO_0	0 /* normal notifiers, no permissions */
#define FS_PRIO_1	1 /* fanotify content based access control */
#define FS_PRIO_2	2 /* fanotify pre-content access */
unsigned int priority;
bool shutdown;		/* group is being shut down, don't queue more events */

	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
struct mutex mark_mutex;	/* protect marks_list */
atomic_t num_marks;		/* 1 for each mark and 1 for not being
                                         * past the point of no return when freeing
                                         * a group */
struct list_head marks_list;	/* all inode marks for this group */

struct fasync_struct *fsn_fa;    /* async notification */

struct fsnotify_event *overflow_event;	/* Event we queue when the
                                                 * notification list is too
                                                 * full */
atomic_t user_waits;		/* Number of tasks waiting for user
                                         * response */

	/* groups can define private fields here or use the void *private */
	union {
void *private;
struct inotify_group_private_data {
spinlock_t	idr_lock;
struct idr      idr;
struct ucounts *ucounts;
} inotify_data;
struct fanotify_group_private_data {
			/* allows a group to block waiting for a userspace response */
struct list_head access_list;
wait_queue_head_t access_waitq;
int f_flags;
unsigned int max_marks;
struct user_struct *user;
} fanotify_data;
#endif /* CONFIG_FANOTIFY */

/* when calling fsnotify tell it if the data is a path or inode */




 * Inode / vfsmount point to this structure which tracks all marks attached to
 * the inode / vfsmount. The reference to inode / vfsmount is held by this
 * structure. We destroy this structure when there are no more marks attached
 * to it. The structure is protected by fsnotify_mark_srcu.

struct fsnotify_mark_connector {
spinlock_t lock;



unsigned int flags;	/* Type of object [lock] */
	union {	/* Object pointer [lock] */
struct inode *inode;
struct vfsmount *mnt;
	union {
struct hlist_head list;
		/* Used listing heads to free after srcu period expires */
struct fsnotify_mark_connector *destroy_next;

 * A mark is simply an object attached to an in core inode which allows an
 * fsnotify listener to indicate they are either no longer interested in events
 * of a type matching mask or only interested in those events.
 * These are flushed when an inode is evicted from core and may be flushed
 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 * users (such as dnotify) will flush these when the open fd is closed and not
 * at inode eviction or modification.
 * Text in brackets is showing the lock(s) protecting modifications of a
 * particular entry. obj_lock means either inode->i_lock or
 * mnt->mnt_root->d_lock depending on the mark type.

struct fsnotify_mark {
	/* Mask this mark is for [mark->lock, group->mark_mutex] */
__u32 mask;
	/* We hold one for presence in g_list. Also one ref for each 'thing'
         * in kernel that found and may be using this mark. */
atomic_t refcnt;
	/* Group this mark is for. Set on mark creation, stable until last ref
         * is dropped */
struct fsnotify_group *group;
	/* List of marks by group->i_fsnotify_marks. Also reused for queueing
         * mark into destroy_list when it's waiting for the end of SRCU period
         * before it can be freed. [group->mark_mutex] */
struct list_head g_list;
	/* Protects inode / mnt pointers, flags, masks */
spinlock_t lock;
	/* List of marks for inode / vfsmount [connector->lock, mark ref] */
struct hlist_node obj_list;
	/* Head of list of marks for an object [mark ref] */
struct fsnotify_mark_connector *connector;
	/* Events types to ignore [mark->lock, group->mark_mutex] */
__u32 ignored_mask;



unsigned int flags;		/* flags [mark->lock] */


/* called from the vfs helpers */

/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
		    const unsigned char *name, u32 cookie);
extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern u32 fsnotify_get_cookie(void);

static inline int fsnotify_inode_watches_children(struct inode *inode) { /* FS_EVENT_ON_CHILD is set if the inode may care */ if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD)) return 0; /* this inode might care about child events, does it care about the * specific set of events that can happen on a child? */ return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD; }


Eric Paris35100.00%1100.00%

/* * Update the dentry with a flag indicating the interest of its parent to receive * filesystem events when those events happens to this dentry->d_inode. */
static inline void fsnotify_update_flags(struct dentry *dentry) { assert_spin_locked(&dentry->d_lock); /* * Serialisation of setting PARENT_WATCHED on the dentries is provided * by d_lock. If inotify_inode_watched changes after we have taken * d_lock, the following __fsnotify_update_child_dentry_flags call will * find our entry, so it will spin until we complete here, and update * us with the new state. */ if (fsnotify_inode_watches_children(dentry->d_parent->d_inode)) dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; else dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; }


Eric Paris4189.13%133.33%
Al Viro48.70%133.33%
Nicholas Piggin12.17%133.33%

/* called from fsnotify listeners, such as fanotify or dnotify */ /* create a new group */ extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops); /* get reference to a group */ extern void fsnotify_get_group(struct fsnotify_group *group); /* drop reference on a group from fsnotify_alloc_group */ extern void fsnotify_put_group(struct fsnotify_group *group); /* group destruction begins, stop queuing new events */ extern void fsnotify_group_stop_queueing(struct fsnotify_group *group); /* destroy group */ extern void fsnotify_destroy_group(struct fsnotify_group *group); /* fasync handler function */ extern int fsnotify_fasync(int fd, struct file *file, int on); /* Free event from memory */ extern void fsnotify_destroy_event(struct fsnotify_group *group, struct fsnotify_event *event); /* attach the event to the group notification queue */ extern int fsnotify_add_event(struct fsnotify_group *group, struct fsnotify_event *event, int (*merge)(struct list_head *, struct fsnotify_event *)); /* true if the group notification queue is empty */ extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group); /* return, but do not dequeue the first event on the notification queue */ extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group); /* return AND dequeue the first event on the notification queue */ extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group); /* functions used to manipulate the marks attached to inodes */ /* Calculate mask of events for a list of marks */ extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn); extern void fsnotify_init_mark(struct fsnotify_mark *mark, struct fsnotify_group *group); /* Find mark belonging to given group in the list of marks */ extern struct fsnotify_mark *fsnotify_find_mark( struct fsnotify_mark_connector __rcu **connp, struct fsnotify_group *group); /* attach the mark to the inode or vfsmount */ extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode, struct vfsmount *mnt, int allow_dups); extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct inode *inode, struct vfsmount *mnt, int allow_dups); /* given a group and a mark, flag mark to be freed when all references are dropped */ extern void fsnotify_destroy_mark(struct fsnotify_mark *mark, struct fsnotify_group *group); /* detach mark from inode / mount list, group list, drop inode reference */ extern void fsnotify_detach_mark(struct fsnotify_mark *mark); /* free mark */ extern void fsnotify_free_mark(struct fsnotify_mark *mark); /* run all the marks in a group, and clear all of the marks attached to given object type */ extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type); /* run all the marks in a group, and clear all of the vfsmount marks */
static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group) { fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT); }


Jan Kara1263.16%266.67%
Eric Paris736.84%133.33%

/* run all the marks in a group, and clear all of the inode marks */
static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group) { fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE); }


Jan Kara1263.16%266.67%
Eric Paris736.84%133.33%

extern void fsnotify_get_mark(struct fsnotify_mark *mark); extern void fsnotify_put_mark(struct fsnotify_mark *mark); extern void fsnotify_unmount_inodes(struct super_block *sb); extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info); extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info); /* put here because inotify does some weird stuff when destroying watches */ extern void fsnotify_init_event(struct fsnotify_event *event, struct inode *to_tell, u32 mask); #else
static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, const unsigned char *name, u32 cookie) { return 0; }


Eric Paris3497.14%583.33%
Al Viro12.86%116.67%

static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) { return 0; }


Eric Paris2187.50%360.00%
Linus Torvalds28.33%120.00%
Al Viro14.17%120.00%

static inline void __fsnotify_inode_delete(struct inode *inode) {}


Eric Paris11100.00%1100.00%

static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt) {}


Andreas Gruenbacher11100.00%1100.00%

static inline void fsnotify_update_flags(struct dentry *dentry) {}


Eric Paris1090.91%150.00%
Al Viro19.09%150.00%

static inline u32 fsnotify_get_cookie(void) { return 0; }


Eric Paris12100.00%1100.00%

static inline void fsnotify_unmount_inodes(struct super_block *sb) {}


Eric Paris981.82%150.00%
Dave Chinner218.18%150.00%

#endif /* CONFIG_FSNOTIFY */ #endif /* __KERNEL __ */ #endif /* __LINUX_FSNOTIFY_BACKEND_H */

Overall Contributors

Eric Paris91268.99%4148.81%
Jan Kara29222.09%2529.76%
Lino Sanfilippo664.99%55.95%
Andreas Gruenbacher211.59%11.19%
Al Viro100.76%44.76%
Nikolay Borisov60.45%22.38%
Linus Torvalds50.38%11.19%
Dave Chinner40.30%11.19%
Richard Kennedy30.23%11.19%
Nicholas Piggin10.08%11.19%
Arun Sharma10.08%11.19%
Naohiro Aota10.08%11.19%
Directory: include/linux
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