fsnotify_backend.h 12.2 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
/*
 * 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/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 */

E
Eric Paris 已提交
49 50 51 52 53 54 55 56 57 58 59
/* 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)

60 61 62
/* listeners that hard code group numbers near the top */
#define DNOTIFY_GROUP_NUM	UINT_MAX

63 64
struct fsnotify_group;
struct fsnotify_event;
65
struct fsnotify_mark_entry;
66 67 68 69 70

/*
 * Each group much define these ops.  The fsnotify infrastructure will call
 * these operations for each relevant group.
 *
71 72
 * should_send_event - given a group, inode, and mask this function determines
 *		if the group is interested in this event.
73 74
 * 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
75 76 77
 * 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.
78 79
 */
struct fsnotify_ops {
80
	bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
81 82
	int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
	void (*free_group_priv)(struct fsnotify_group *group);
83
	void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
};

/*
 * 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 */

122 123 124 125 126 127 128 129
	/* 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 */
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
	bool on_group_list;

	/* groups can define private fields here or use the void *private */
	union {
		void *private;
	};
};

/*
 * 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 {
	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 */
};

169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193
/*
 * 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 */
};

194 195 196 197 198 199
#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);
E
Eric Paris 已提交
200
extern void __fsnotify_parent(struct dentry *dentry, __u32 mask);
201
extern void __fsnotify_inode_delete(struct inode *inode);
202

E
Eric Paris 已提交
203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245
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);
}
246 247 248 249 250 251 252 253 254

/* 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);
255 256
/* run all marks associated with this group and update group->mask */
extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
257 258 259 260 261 262 263 264 265 266
/* 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 */
extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
									struct fsnotify_event *event);

267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282
/* 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);

283 284 285 286 287 288 289
/* 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);
#else

static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
{}
290

E
Eric Paris 已提交
291 292 293
static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask)
{}

294 295 296
static inline void __fsnotify_inode_delete(struct inode *inode)
{}

E
Eric Paris 已提交
297 298 299 300 301 302
static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
{}

static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
{}

303 304 305 306 307
#endif	/* CONFIG_FSNOTIFY */

#endif	/* __KERNEL __ */

#endif	/* __LINUX_FSNOTIFY_BACKEND_H */