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Diffstat (limited to 'include/linux/fsnotify_backend.h')
| -rw-r--r-- | include/linux/fsnotify_backend.h | 387 |
1 files changed, 387 insertions, 0 deletions
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h new file mode 100644 index 000000000000..44848aa830dc --- /dev/null +++ b/include/linux/fsnotify_backend.h @@ -0,0 +1,387 @@ +/* + * Filesystem access notification for Linux + * + * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> + */ + +#ifndef __LINUX_FSNOTIFY_BACKEND_H +#define __LINUX_FSNOTIFY_BACKEND_H + +#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 <asm/atomic.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_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 +#define INOTIFY_GROUP_NUM (DNOTIFY_GROUP_NUM-1) + +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; +#ifdef CONFIG_INOTIFY_USER + struct inotify_group_private_data { + spinlock_t idr_lock; + struct idr idr; + u32 last_wd; + struct fasync_struct *fa; /* async notification */ + struct user_struct *user; + } inotify_data; +#endif + }; +}; + +/* + * 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 */ |