include/linux/fsnotify_backend.h

   1 /*
   2  * Filesystem access notification for Linux
   3  *
   4  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
   5  */
   6
   7 #ifndef __LINUX_FSNOTIFY_BACKEND_H
   8 #define __LINUX_FSNOTIFY_BACKEND_H
   9
  10 #ifdef __KERNEL__
  11
  12 #include <linux/fs.h> /* struct inode */
  13 #include <linux/list.h>
  14 #include <linux/path.h> /* struct path */
  15 #include <linux/spinlock.h>
  16 #include <linux/types.h>
  17
  18 #include <asm/atomic.h>
  19
  20 /*
  21  * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
  22  * convert between them.  dnotify only needs conversion at watch creation
  23  * so no perf loss there.  fanotify isn't defined yet, so it can use the
  24  * wholes if it needs more events.
  25  */
  26 #define FS_ACCESS               0x00000001      /* File was accessed */
  27 #define FS_MODIFY               0x00000002      /* File was modified */
  28 #define FS_ATTRIB               0x00000004      /* Metadata changed */
  29 #define FS_CLOSE_WRITE          0x00000008      /* Writtable file was closed */
  30 #define FS_CLOSE_NOWRITE        0x00000010      /* Unwrittable file closed */
  31 #define FS_OPEN                 0x00000020      /* File was opened */
  32 #define FS_MOVED_FROM           0x00000040      /* File was moved from X */
  33 #define FS_MOVED_TO             0x00000080      /* File was moved to Y */
  34 #define FS_CREATE               0x00000100      /* Subfile was created */
  35 #define FS_DELETE               0x00000200      /* Subfile was deleted */
  36 #define FS_DELETE_SELF          0x00000400      /* Self was deleted */
  37 #define FS_MOVE_SELF            0x00000800      /* Self was moved */
  38
  39 #define FS_UNMOUNT              0x00002000      /* inode on umount fs */
  40 #define FS_Q_OVERFLOW           0x00004000      /* Event queued overflowed */
  41 #define FS_IN_IGNORED           0x00008000      /* last inotify event here */
  42
  43 #define FS_IN_ISDIR             0x40000000      /* event occurred against dir */
  44 #define FS_IN_ONESHOT           0x80000000      /* only send event once */
  45
  46 #define FS_DN_RENAME            0x10000000      /* file renamed */
  47 #define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
  48
  49 /* This inode cares about things that happen to its children.  Always set for
  50  * dnotify and inotify. */
  51 #define FS_EVENT_ON_CHILD       0x08000000
  52
  53 /* This is a list of all events that may get sent to a parernt based on fs event
  54  * happening to inodes inside that directory */
  55 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
  56                                    FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
  57                                    FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
  58                                    FS_DELETE)
  59
  60 /* listeners that hard code group numbers near the top */
  61 #define DNOTIFY_GROUP_NUM       UINT_MAX
  62
  63 struct fsnotify_group;
  64 struct fsnotify_event;
  65 struct fsnotify_mark_entry;
  66
  67 /*
  68  * Each group much define these ops.  The fsnotify infrastructure will call
  69  * these operations for each relevant group.
  70  *
  71  * should_send_event - given a group, inode, and mask this function determines
  72  *              if the group is interested in this event.
  73  * handle_event - main call for a group to handle an fs event
  74  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
  75  * freeing-mark - this means that a mark has been flagged to die when everything
  76  *              finishes using it.  The function is supplied with what must be a
  77  *              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         int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
  82         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  * A group is a "thing" that wants to receive notification about filesystem
  88  * events.  The mask holds the subset of event types this group cares about.
  89  * refcnt on a group is up to the implementor and at any moment if it goes 0
  90  * everything will be cleaned up.
  91  */
  92 struct fsnotify_group {
  93         /*
  94          * global list of all groups receiving events from fsnotify.
  95          * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
  96          * or fsnotify_grp_srcu depending on write vs read.
  97          */
  98         struct list_head group_list;
  99
 100         /*
 101          * Defines all of the event types in which this group is interested.
 102          * This mask is a bitwise OR of the FS_* events from above.  Each time
 103          * this mask changes for a group (if it changes) the correct functions
 104          * must be called to update the global structures which indicate global
 105          * interest in event types.
 106          */
 107         __u32 mask;
 108
 109         /*
 110          * How the refcnt is used is up to each group.  When the refcnt hits 0
 111          * fsnotify will clean up all of the resources associated with this group.
 112          * As an example, the dnotify group will always have a refcnt=1 and that
 113          * will never change.  Inotify, on the other hand, has a group per
 114          * inotify_init() and the refcnt will hit 0 only when that fd has been
 115          * closed.
 116          */
 117         atomic_t refcnt;                /* things with interest in this group */
 118         unsigned int group_num;         /* simply prevents accidental group collision */
 119
 120         const struct fsnotify_ops *ops; /* how this group handles things */
 121
 122         /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
 123         spinlock_t mark_lock;           /* protect mark_entries list */
 124         atomic_t num_marks;             /* 1 for each mark entry and 1 for not being
 125                                          * past the point of no return when freeing
 126                                          * a group */
 127         struct list_head mark_entries;  /* all inode mark entries for this group */
 128
 129         /* prevents double list_del of group_list.  protected by global fsnotify_grp_mutex */
 130         bool on_group_list;
 131
 132         /* groups can define private fields here or use the void *private */
 133         union {
 134                 void *private;
 135         };
 136 };
 137
 138 /*
 139  * all of the information about the original object we want to now send to
 140  * a group.  If you want to carry more info from the accessing task to the
 141  * listener this structure is where you need to be adding fields.
 142  */
 143 struct fsnotify_event {
 144         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 145         /* to_tell may ONLY be dereferenced during handle_event(). */
 146         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 147         /*
 148          * depending on the event type we should have either a path or inode
 149          * We hold a reference on path, but NOT on inode.  Since we have the ref on
 150          * the path, it may be dereferenced at any point during this object's
 151          * lifetime.  That reference is dropped when this object's refcnt hits
 152          * 0.  If this event contains an inode instead of a path, the inode may
 153          * ONLY be used during handle_event().
 154          */
 155         union {
 156                 struct path path;
 157                 struct inode *inode;
 158         };
 159 /* when calling fsnotify tell it if the data is a path or inode */
 160 #define FSNOTIFY_EVENT_NONE     0
 161 #define FSNOTIFY_EVENT_PATH     1
 162 #define FSNOTIFY_EVENT_INODE    2
 163 #define FSNOTIFY_EVENT_FILE     3
 164         int data_type;          /* which of the above union we have */
 165         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 166         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 167 };
 168
 169 /*
 170  * a mark is simply an entry attached to an in core inode which allows an
 171  * fsnotify listener to indicate they are either no longer interested in events
 172  * of a type matching mask or only interested in those events.
 173  *
 174  * these are flushed when an inode is evicted from core and may be flushed
 175  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 176  * (such as dnotify) will flush these when the open fd is closed and not at
 177  * inode eviction or modification.
 178  */
 179 struct fsnotify_mark_entry {
 180         __u32 mask;                     /* mask this mark entry is for */
 181         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 182          * in kernel that found and may be using this mark. */
 183         atomic_t refcnt;                /* active things looking at this mark */
 184         struct inode *inode;            /* inode this entry is associated with */
 185         struct fsnotify_group *group;   /* group this mark entry is for */
 186         struct hlist_node i_list;       /* list of mark_entries by inode->i_fsnotify_mark_entries */
 187         struct list_head g_list;        /* list of mark_entries by group->i_fsnotify_mark_entries */
 188         spinlock_t lock;                /* protect group, inode, and killme */
 189         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 190         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 191         void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
 192 };
 193
 194 #ifdef CONFIG_FSNOTIFY
 195
 196 /* called from the vfs helpers */
 197
 198 /* main fsnotify call to send events */
 199 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
 200 extern void __fsnotify_parent(struct dentry *dentry, __u32 mask);
 201 extern void __fsnotify_inode_delete(struct inode *inode);
 202
 203 static inline int fsnotify_inode_watches_children(struct inode *inode)
 204 {
 205         /* FS_EVENT_ON_CHILD is set if the inode may care */
 206         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 207                 return 0;
 208         /* this inode might care about child events, does it care about the
 209          * specific set of events that can happen on a child? */
 210         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 211 }
 212
 213 /*
 214  * Update the dentry with a flag indicating the interest of its parent to receive
 215  * filesystem events when those events happens to this dentry->d_inode.
 216  */
 217 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 218 {
 219         struct dentry *parent;
 220
 221         assert_spin_locked(&dcache_lock);
 222         assert_spin_locked(&dentry->d_lock);
 223
 224         parent = dentry->d_parent;
 225         if (fsnotify_inode_watches_children(parent->d_inode))
 226                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 227         else
 228                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 229 }
 230
 231 /*
 232  * fsnotify_d_instantiate - instantiate a dentry for inode
 233  * Called with dcache_lock held.
 234  */
 235 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 236 {
 237         if (!inode)
 238                 return;
 239
 240         assert_spin_locked(&dcache_lock);
 241
 242         spin_lock(&dentry->d_lock);
 243         __fsnotify_update_dcache_flags(dentry);
 244         spin_unlock(&dentry->d_lock);
 245 }
 246
 247 /* called from fsnotify listeners, such as fanotify or dnotify */
 248
 249 /* must call when a group changes its ->mask */
 250 extern void fsnotify_recalc_global_mask(void);
 251 /* get a reference to an existing or create a new group */
 252 extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
 253                                                     __u32 mask,
 254                                                     const struct fsnotify_ops *ops);
 255 /* run all marks associated with this group and update group->mask */
 256 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
 257 /* drop reference on a group from fsnotify_obtain_group */
 258 extern void fsnotify_put_group(struct fsnotify_group *group);
 259
 260 /* take a reference to an event */
 261 extern void fsnotify_get_event(struct fsnotify_event *event);
 262 extern void fsnotify_put_event(struct fsnotify_event *event);
 263 /* find private data previously attached to an event */
 264 extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
 265                                                                         struct fsnotify_event *event);
 266
 267 /* functions used to manipulate the marks attached to inodes */
 268
 269 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 270 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 271 extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
 272 /* find (and take a reference) to a mark associated with group and inode */
 273 extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
 274 /* attach the mark to both the group and the inode */
 275 extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
 276 /* given a mark, flag it to be freed when all references are dropped */
 277 extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
 278 /* run all the marks in a group, and flag them to be freed */
 279 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 280 extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
 281 extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
 282
 283 /* put here because inotify does some weird stuff when destroying watches */
 284 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 285                                                     void *data, int data_is);
 286 #else
 287
 288 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
 289 {}
 290
 291 static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask)
 292 {}
 293
 294 static inline void __fsnotify_inode_delete(struct inode *inode)
 295 {}
 296
 297 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 298 {}
 299
 300 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 301 {}
 302
 303 #endif  /* CONFIG_FSNOTIFY */
 304
 305 #endif  /* __KERNEL __ */
 306
 307 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */