393 lines
16 KiB
C
393 lines
16 KiB
C
/*
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* Filesystem access notification for Linux
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*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*/
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#ifndef __LINUX_FSNOTIFY_BACKEND_H
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#define __LINUX_FSNOTIFY_BACKEND_H
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#ifdef __KERNEL__
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#include <linux/idr.h> /* inotify uses this */
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#include <linux/fs.h> /* struct inode */
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#include <linux/list.h>
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#include <linux/path.h> /* struct path */
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include <asm/atomic.h>
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/*
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* IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
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* convert between them. dnotify only needs conversion at watch creation
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* so no perf loss there. fanotify isn't defined yet, so it can use the
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* wholes if it needs more events.
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*/
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#define FS_ACCESS 0x00000001 /* File was accessed */
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#define FS_MODIFY 0x00000002 /* File was modified */
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#define FS_ATTRIB 0x00000004 /* Metadata changed */
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#define FS_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
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#define FS_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
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#define FS_OPEN 0x00000020 /* File was opened */
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#define FS_MOVED_FROM 0x00000040 /* File was moved from X */
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#define FS_MOVED_TO 0x00000080 /* File was moved to Y */
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#define FS_CREATE 0x00000100 /* Subfile was created */
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#define FS_DELETE 0x00000200 /* Subfile was deleted */
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#define FS_DELETE_SELF 0x00000400 /* Self was deleted */
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#define FS_MOVE_SELF 0x00000800 /* Self was moved */
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#define FS_UNMOUNT 0x00002000 /* inode on umount fs */
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#define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
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#define FS_IN_IGNORED 0x00008000 /* last inotify event here */
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#define FS_IN_ISDIR 0x40000000 /* event occurred against dir */
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#define FS_IN_ONESHOT 0x80000000 /* only send event once */
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#define FS_DN_RENAME 0x10000000 /* file renamed */
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#define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
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/* This inode cares about things that happen to its children. Always set for
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* dnotify and inotify. */
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#define FS_EVENT_ON_CHILD 0x08000000
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/* This is a list of all events that may get sent to a parernt based on fs event
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* happening to inodes inside that directory */
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#define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
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FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
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FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
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FS_DELETE)
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#define FS_MOVE (FS_MOVED_FROM | FS_MOVED_TO)
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struct fsnotify_group;
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struct fsnotify_event;
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struct fsnotify_mark_entry;
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struct fsnotify_event_private_data;
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/*
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* Each group much define these ops. The fsnotify infrastructure will call
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* these operations for each relevant group.
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*
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* should_send_event - given a group, inode, and mask this function determines
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* if the group is interested in this event.
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* handle_event - main call for a group to handle an fs event
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* free_group_priv - called when a group refcnt hits 0 to clean up the private union
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* freeing-mark - this means that a mark has been flagged to die when everything
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* finishes using it. The function is supplied with what must be a
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* valid group and inode to use to clean up.
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*/
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struct fsnotify_ops {
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bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
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__u32 mask, void *data, int data_type);
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int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
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void (*free_group_priv)(struct fsnotify_group *group);
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void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
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void (*free_event_priv)(struct fsnotify_event_private_data *priv);
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};
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/*
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* A group is a "thing" that wants to receive notification about filesystem
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* events. The mask holds the subset of event types this group cares about.
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* refcnt on a group is up to the implementor and at any moment if it goes 0
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* everything will be cleaned up.
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*/
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struct fsnotify_group {
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/*
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* global list of all groups receiving events from fsnotify.
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* anchored by fsnotify_inode_groups and protected by either fsnotify_grp_mutex
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* or fsnotify_grp_srcu depending on write vs read.
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*/
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struct list_head inode_group_list;
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/*
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* Defines all of the event types in which this group is interested.
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* This mask is a bitwise OR of the FS_* events from above. Each time
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* this mask changes for a group (if it changes) the correct functions
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* must be called to update the global structures which indicate global
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* interest in event types.
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*/
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__u32 mask;
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/*
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* How the refcnt is used is up to each group. When the refcnt hits 0
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* fsnotify will clean up all of the resources associated with this group.
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* As an example, the dnotify group will always have a refcnt=1 and that
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* will never change. Inotify, on the other hand, has a group per
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* inotify_init() and the refcnt will hit 0 only when that fd has been
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* closed.
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*/
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atomic_t refcnt; /* things with interest in this group */
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const struct fsnotify_ops *ops; /* how this group handles things */
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/* needed to send notification to userspace */
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struct mutex notification_mutex; /* protect the notification_list */
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struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
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wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
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unsigned int q_len; /* events on the queue */
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unsigned int max_events; /* maximum events allowed on the list */
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/* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
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spinlock_t mark_lock; /* protect mark_entries list */
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atomic_t num_marks; /* 1 for each mark entry and 1 for not being
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* past the point of no return when freeing
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* a group */
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struct list_head mark_entries; /* all inode mark entries for this group */
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/* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
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bool on_inode_group_list;
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/* groups can define private fields here or use the void *private */
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union {
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void *private;
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#ifdef CONFIG_INOTIFY_USER
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struct inotify_group_private_data {
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spinlock_t idr_lock;
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struct idr idr;
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u32 last_wd;
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struct fasync_struct *fa; /* async notification */
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struct user_struct *user;
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} inotify_data;
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#endif
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};
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};
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/*
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* A single event can be queued in multiple group->notification_lists.
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*
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* each group->notification_list will point to an event_holder which in turns points
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* to the actual event that needs to be sent to userspace.
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*
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* Seemed cheaper to create a refcnt'd event and a small holder for every group
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* than create a different event for every group
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*
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*/
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struct fsnotify_event_holder {
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struct fsnotify_event *event;
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struct list_head event_list;
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};
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/*
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* Inotify needs to tack data onto an event. This struct lets us later find the
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* correct private data of the correct group.
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*/
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struct fsnotify_event_private_data {
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struct fsnotify_group *group;
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struct list_head event_list;
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};
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/*
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* all of the information about the original object we want to now send to
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* a group. If you want to carry more info from the accessing task to the
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* listener this structure is where you need to be adding fields.
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*/
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struct fsnotify_event {
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/*
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* If we create an event we are also likely going to need a holder
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* to link to a group. So embed one holder in the event. Means only
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* one allocation for the common case where we only have one group
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*/
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struct fsnotify_event_holder holder;
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spinlock_t lock; /* protection for the associated event_holder and private_list */
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/* to_tell may ONLY be dereferenced during handle_event(). */
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struct inode *to_tell; /* either the inode the event happened to or its parent */
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/*
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* depending on the event type we should have either a path or inode
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* We hold a reference on path, but NOT on inode. Since we have the ref on
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* the path, it may be dereferenced at any point during this object's
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* lifetime. That reference is dropped when this object's refcnt hits
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* 0. If this event contains an inode instead of a path, the inode may
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* ONLY be used during handle_event().
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*/
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union {
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struct path path;
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struct inode *inode;
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};
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/* when calling fsnotify tell it if the data is a path or inode */
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#define FSNOTIFY_EVENT_NONE 0
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#define FSNOTIFY_EVENT_PATH 1
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#define FSNOTIFY_EVENT_INODE 2
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#define FSNOTIFY_EVENT_FILE 3
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int data_type; /* which of the above union we have */
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atomic_t refcnt; /* how many groups still are using/need to send this event */
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__u32 mask; /* the type of access, bitwise OR for FS_* event types */
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u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
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char *file_name;
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size_t name_len;
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struct list_head private_data_list; /* groups can store private data here */
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};
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/*
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* a mark is simply an entry attached to an in core inode which allows an
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* fsnotify listener to indicate they are either no longer interested in events
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* of a type matching mask or only interested in those events.
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*
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* these are flushed when an inode is evicted from core and may be flushed
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* when the inode is modified (as seen by fsnotify_access). Some fsnotify users
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* (such as dnotify) will flush these when the open fd is closed and not at
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* inode eviction or modification.
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*/
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struct fsnotify_mark_entry {
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__u32 mask; /* mask this mark entry is for */
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/* we hold ref for each i_list and g_list. also one ref for each 'thing'
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* in kernel that found and may be using this mark. */
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atomic_t refcnt; /* active things looking at this mark */
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struct inode *inode; /* inode this entry is associated with */
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struct fsnotify_group *group; /* group this mark entry is for */
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struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */
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struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */
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spinlock_t lock; /* protect group, inode, and killme */
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struct list_head free_i_list; /* tmp list used when freeing this mark */
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struct list_head free_g_list; /* tmp list used when freeing this mark */
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void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
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};
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#ifdef CONFIG_FSNOTIFY
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/* called from the vfs helpers */
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/* main fsnotify call to send events */
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extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
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const char *name, u32 cookie);
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extern void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask);
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extern void __fsnotify_inode_delete(struct inode *inode);
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extern u32 fsnotify_get_cookie(void);
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static inline int fsnotify_inode_watches_children(struct inode *inode)
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{
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/* FS_EVENT_ON_CHILD is set if the inode may care */
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if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
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return 0;
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/* this inode might care about child events, does it care about the
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* specific set of events that can happen on a child? */
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return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
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}
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/*
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* Update the dentry with a flag indicating the interest of its parent to receive
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* filesystem events when those events happens to this dentry->d_inode.
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*/
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static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
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{
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struct dentry *parent;
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assert_spin_locked(&dcache_lock);
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assert_spin_locked(&dentry->d_lock);
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parent = dentry->d_parent;
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if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
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dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
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else
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dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
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}
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/*
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* fsnotify_d_instantiate - instantiate a dentry for inode
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* Called with dcache_lock held.
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*/
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static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
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{
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if (!inode)
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return;
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assert_spin_locked(&dcache_lock);
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spin_lock(&dentry->d_lock);
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__fsnotify_update_dcache_flags(dentry);
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spin_unlock(&dentry->d_lock);
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}
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/* called from fsnotify listeners, such as fanotify or dnotify */
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/* must call when a group changes its ->mask */
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extern void fsnotify_recalc_global_mask(void);
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/* get a reference to an existing or create a new group */
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extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
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/* run all marks associated with this group and update group->mask */
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extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
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/* drop reference on a group from fsnotify_alloc_group */
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extern void fsnotify_put_group(struct fsnotify_group *group);
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/* take a reference to an event */
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extern void fsnotify_get_event(struct fsnotify_event *event);
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extern void fsnotify_put_event(struct fsnotify_event *event);
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/* find private data previously attached to an event and unlink it */
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extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
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struct fsnotify_event *event);
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/* attach the event to the group notification queue */
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extern int fsnotify_add_notify_event(struct fsnotify_group *group,
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struct fsnotify_event *event,
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struct fsnotify_event_private_data *priv,
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int (*merge)(struct list_head *, struct fsnotify_event *));
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/* true if the group notification queue is empty */
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extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
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/* return, but do not dequeue the first event on the notification queue */
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extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
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/* return AND dequeue the first event on the notification queue */
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extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
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/* functions used to manipulate the marks attached to inodes */
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/* run all marks associated with an inode and update inode->i_fsnotify_mask */
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extern void fsnotify_recalc_inode_mask(struct inode *inode);
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extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
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/* find (and take a reference) to a mark associated with group and inode */
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extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
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/* copy the values from old into new */
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extern void fsnotify_duplicate_mark(struct fsnotify_mark_entry *new, struct fsnotify_mark_entry *old);
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/* attach the mark to both the group and the inode */
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extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode, int allow_dups);
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/* given a mark, flag it to be freed when all references are dropped */
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extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
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/* run all the marks in a group, and flag them to be freed */
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extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
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extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
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extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
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extern void fsnotify_unmount_inodes(struct list_head *list);
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/* put here because inotify does some weird stuff when destroying watches */
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extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
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void *data, int data_is, const char *name,
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u32 cookie, gfp_t gfp);
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/* fanotify likes to change events after they are on lists... */
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extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
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extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
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struct fsnotify_event *new_event);
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#else
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static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
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const char *name, u32 cookie)
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{}
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static inline void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask)
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{}
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static inline void __fsnotify_inode_delete(struct inode *inode)
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{}
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static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
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{}
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static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
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{}
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static inline u32 fsnotify_get_cookie(void)
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{
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return 0;
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}
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static inline void fsnotify_unmount_inodes(struct list_head *list)
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{}
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#endif /* CONFIG_FSNOTIFY */
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#endif /* __KERNEL __ */
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#endif /* __LINUX_FSNOTIFY_BACKEND_H */
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