/* * Filesystem access notification for Linux * * Copyright (C) 2008 Red Hat, Inc., Eric Paris */ #ifndef __LINUX_FSNOTIFY_BACKEND_H #define __LINUX_FSNOTIFY_BACKEND_H #ifdef __KERNEL__ #include /* struct inode */ #include #include /* struct path */ #include #include #include /* * 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_IN_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 */ #define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\ FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\ FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\ FS_DELETE) /* listeners that hard code group numbers near the top */ #define DNOTIFY_GROUP_NUM UINT_MAX struct fsnotify_group; struct fsnotify_event; struct fsnotify_mark_entry; struct fsnotify_event_private_data; /* * Each group much define these ops. The fsnotify infrastructure will call * these operations for each relevant group. * * should_send_event - given a group, inode, and mask this function determines * if the group is interested in this event. * 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 - this means that a mark has been flagged to die when everything * finishes using it. The function is supplied with what must be a * valid group and inode to use to clean up. */ struct fsnotify_ops { bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask); int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event); void (*free_group_priv)(struct fsnotify_group *group); void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group); void (*free_event_priv)(struct fsnotify_event_private_data *priv); }; /* * 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 { /* * global list of all groups receiving events from fsnotify. * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex * or fsnotify_grp_srcu depending on write vs read. */ struct list_head group_list; /* * Defines all of the event types in which this group is interested. * This mask is a bitwise OR of the FS_* events from above. Each time * this mask changes for a group (if it changes) the correct functions * must be called to update the global structures which indicate global * interest in event types. */ __u32 mask; /* * 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 */ unsigned int group_num; /* simply prevents accidental group collision */ const struct fsnotify_ops *ops; /* how this group handles things */ /* needed to send notification to userspace */ struct mutex notification_mutex; /* 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 */ /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */ spinlock_t mark_lock; /* protect mark_entries list */ atomic_t num_marks; /* 1 for each mark entry and 1 for not being * past the point of no return when freeing * a group */ struct list_head mark_entries; /* all inode mark entries for this group */ /* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */ bool on_group_list; /* groups can define private fields here or use the void *private */ union { void *private; }; }; /* * A single event can be queued in multiple group->notification_lists. * * each group->notification_list will point to an event_holder which in turns points * to the actual event that needs to be sent to userspace. * * Seemed cheaper to create a refcnt'd event and a small holder for every group * than create a different event for every group * */ struct fsnotify_event_holder { struct fsnotify_event *event; struct list_head event_list; }; /* * Inotify needs to tack data onto an event. This struct lets us later find the * correct private data of the correct group. */ struct fsnotify_event_private_data { struct fsnotify_group *group; struct list_head event_list; }; /* * 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 { /* * If we create an event we are also likely going to need a holder * to link to a group. So embed one holder in the event. Means only * one allocation for the common case where we only have one group */ struct fsnotify_event_holder holder; spinlock_t lock; /* protection for the associated event_holder and private_list */ /* to_tell may ONLY be dereferenced during handle_event(). */ struct inode *to_tell; /* either the inode the event happened to or its parent */ /* * depending on the event type we should have either a path or inode * We hold a reference on path, but NOT on inode. Since we have the ref on * the path, it may be dereferenced at any point during this object's * lifetime. That reference is dropped when this object's refcnt hits * 0. If this event contains an inode instead of a path, the inode may * ONLY be used during handle_event(). */ union { struct path path; struct inode *inode; }; /* when calling fsnotify tell it if the data is a path or inode */ #define FSNOTIFY_EVENT_NONE 0 #define FSNOTIFY_EVENT_PATH 1 #define FSNOTIFY_EVENT_INODE 2 #define FSNOTIFY_EVENT_FILE 3 int data_type; /* which of the above union we have */ atomic_t refcnt; /* how many groups still are using/need to send this event */ __u32 mask; /* the type of access, bitwise OR for FS_* event types */ u32 sync_cookie; /* used to corrolate events, namely inotify mv events */ char *file_name; size_t name_len; struct list_head private_data_list; /* groups can store private data here */ }; /* * a mark is simply an entry 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. */ struct fsnotify_mark_entry { __u32 mask; /* mask this mark entry is for */ /* we hold ref for each i_list and g_list. also one ref for each 'thing' * in kernel that found and may be using this mark. */ atomic_t refcnt; /* active things looking at this mark */ struct inode *inode; /* inode this entry is associated with */ struct fsnotify_group *group; /* group this mark entry is for */ struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */ struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */ spinlock_t lock; /* protect group, inode, and killme */ struct list_head free_i_list; /* tmp list used when freeing this mark */ struct list_head free_g_list; /* tmp list used when freeing this mark */ void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */ }; #ifdef CONFIG_FSNOTIFY /* called from the vfs helpers */ /* main fsnotify call to send events */ extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, const char *name, u32 cookie); extern void __fsnotify_parent(struct dentry *dentry, __u32 mask); extern void __fsnotify_inode_delete(struct inode *inode); 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; } /* * 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_dcache_flags(struct dentry *dentry) { struct dentry *parent; assert_spin_locked(&dcache_lock); assert_spin_locked(&dentry->d_lock); parent = dentry->d_parent; if (fsnotify_inode_watches_children(parent->d_inode)) dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; else dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; } /* * fsnotify_d_instantiate - instantiate a dentry for inode * Called with dcache_lock held. */ static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode) { if (!inode) return; assert_spin_locked(&dcache_lock); spin_lock(&dentry->d_lock); __fsnotify_update_dcache_flags(dentry); spin_unlock(&dentry->d_lock); } /* called from fsnotify listeners, such as fanotify or dnotify */ /* must call when a group changes its ->mask */ extern void fsnotify_recalc_global_mask(void); /* get a reference to an existing or create a new group */ extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask, const struct fsnotify_ops *ops); /* run all marks associated with this group and update group->mask */ extern void fsnotify_recalc_group_mask(struct fsnotify_group *group); /* drop reference on a group from fsnotify_obtain_group */ extern void fsnotify_put_group(struct fsnotify_group *group); /* take a reference to an event */ extern void fsnotify_get_event(struct fsnotify_event *event); extern void fsnotify_put_event(struct fsnotify_event *event); /* find private data previously attached to an event and unlink it */ extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event); /* attach the event to the group notification queue */ extern int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event, struct fsnotify_event_private_data *priv); /* 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_notify_event(struct fsnotify_group *group); /* return AND dequeue the first event on the notification queue */ extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group); /* functions used to manipulate the marks attached to inodes */ /* run all marks associated with an inode and update inode->i_fsnotify_mask */ extern void fsnotify_recalc_inode_mask(struct inode *inode); extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry)); /* find (and take a reference) to a mark associated with group and inode */ extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode); /* attach the mark to both the group and the inode */ extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode); /* given a mark, flag it to be freed when all references are dropped */ extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry); /* run all the marks in a group, and flag them to be freed */ extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group); extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry); extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry); extern void fsnotify_unmount_inodes(struct list_head *list); /* put here because inotify does some weird stuff when destroying watches */ extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, int data_is, const char *name, u32 cookie); #else static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, const char *name, u32 cookie) {} static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask) {} static inline void __fsnotify_inode_delete(struct inode *inode) {} static inline void __fsnotify_update_dcache_flags(struct dentry *dentry) {} static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode) {} static inline u32 fsnotify_get_cookie(void) { return 0; } static inline void fsnotify_unmount_inodes(struct list_head *list) {} #endif /* CONFIG_FSNOTIFY */ #endif /* __KERNEL __ */ #endif /* __LINUX_FSNOTIFY_BACKEND_H */