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 struct fsnotify_group;
  50 struct fsnotify_event;
  51 struct fsnotify_mark_entry;
  52
  53 /*
  54  * Each group much define these ops.  The fsnotify infrastructure will call
  55  * these operations for each relevant group.
  56  *
  57  * should_send_event - given a group, inode, and mask this function determines
  58  *              if the group is interested in this event.
  59  * handle_event - main call for a group to handle an fs event
  60  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
  61  * freeing-mark - this means that a mark has been flagged to die when everything
  62  *              finishes using it.  The function is supplied with what must be a
  63  *              valid group and inode to use to clean up.
  64  */
  65 struct fsnotify_ops {
  66         bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
  67         int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
  68         void (*free_group_priv)(struct fsnotify_group *group);
  69         void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
  70 };
  71
  72 /*
  73  * A group is a "thing" that wants to receive notification about filesystem
  74  * events.  The mask holds the subset of event types this group cares about.
  75  * refcnt on a group is up to the implementor and at any moment if it goes 0
  76  * everything will be cleaned up.
  77  */
  78 struct fsnotify_group {
  79         /*
  80          * global list of all groups receiving events from fsnotify.
  81          * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
  82          * or fsnotify_grp_srcu depending on write vs read.
  83          */
  84         struct list_head group_list;
  85
  86         /*
  87          * Defines all of the event types in which this group is interested.
  88          * This mask is a bitwise OR of the FS_* events from above.  Each time
  89          * this mask changes for a group (if it changes) the correct functions
  90          * must be called to update the global structures which indicate global
  91          * interest in event types.
  92          */
  93         __u32 mask;
  94
  95         /*
  96          * How the refcnt is used is up to each group.  When the refcnt hits 0
  97          * fsnotify will clean up all of the resources associated with this group.
  98          * As an example, the dnotify group will always have a refcnt=1 and that
  99          * will never change.  Inotify, on the other hand, has a group per
 100          * inotify_init() and the refcnt will hit 0 only when that fd has been
 101          * closed.
 102          */
 103         atomic_t refcnt;                /* things with interest in this group */
 104         unsigned int group_num;         /* simply prevents accidental group collision */
 105
 106         const struct fsnotify_ops *ops; /* how this group handles things */
 107
 108         /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
 109         spinlock_t mark_lock;           /* protect mark_entries list */
 110         atomic_t num_marks;             /* 1 for each mark entry and 1 for not being
 111                                          * past the point of no return when freeing
 112                                          * a group */
 113         struct list_head mark_entries;  /* all inode mark entries for this group */
 114
 115         /* prevents double list_del of group_list.  protected by global fsnotify_grp_mutex */
 116         bool on_group_list;
 117
 118         /* groups can define private fields here or use the void *private */
 119         union {
 120                 void *private;
 121         };
 122 };
 123
 124 /*
 125  * all of the information about the original object we want to now send to
 126  * a group.  If you want to carry more info from the accessing task to the
 127  * listener this structure is where you need to be adding fields.
 128  */
 129 struct fsnotify_event {
 130         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 131         /* to_tell may ONLY be dereferenced during handle_event(). */
 132         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 133         /*
 134          * depending on the event type we should have either a path or inode
 135          * We hold a reference on path, but NOT on inode.  Since we have the ref on
 136          * the path, it may be dereferenced at any point during this object's
 137          * lifetime.  That reference is dropped when this object's refcnt hits
 138          * 0.  If this event contains an inode instead of a path, the inode may
 139          * ONLY be used during handle_event().
 140          */
 141         union {
 142                 struct path path;
 143                 struct inode *inode;
 144         };
 145 /* when calling fsnotify tell it if the data is a path or inode */
 146 #define FSNOTIFY_EVENT_NONE     0
 147 #define FSNOTIFY_EVENT_PATH     1
 148 #define FSNOTIFY_EVENT_INODE    2
 149 #define FSNOTIFY_EVENT_FILE     3
 150         int data_type;          /* which of the above union we have */
 151         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 152         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 153 };
 154
 155 /*
 156  * a mark is simply an entry attached to an in core inode which allows an
 157  * fsnotify listener to indicate they are either no longer interested in events
 158  * of a type matching mask or only interested in those events.
 159  *
 160  * these are flushed when an inode is evicted from core and may be flushed
 161  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 162  * (such as dnotify) will flush these when the open fd is closed and not at
 163  * inode eviction or modification.
 164  */
 165 struct fsnotify_mark_entry {
 166         __u32 mask;                     /* mask this mark entry is for */
 167         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 168          * in kernel that found and may be using this mark. */
 169         atomic_t refcnt;                /* active things looking at this mark */
 170         struct inode *inode;            /* inode this entry is associated with */
 171         struct fsnotify_group *group;   /* group this mark entry is for */
 172         struct hlist_node i_list;       /* list of mark_entries by inode->i_fsnotify_mark_entries */
 173         struct list_head g_list;        /* list of mark_entries by group->i_fsnotify_mark_entries */
 174         spinlock_t lock;                /* protect group, inode, and killme */
 175         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 176         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 177         void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
 178 };
 179
 180 #ifdef CONFIG_FSNOTIFY
 181
 182 /* called from the vfs helpers */
 183
 184 /* main fsnotify call to send events */
 185 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
 186 extern void __fsnotify_inode_delete(struct inode *inode);
 187
 188
 189 /* called from fsnotify listeners, such as fanotify or dnotify */
 190
 191 /* must call when a group changes its ->mask */
 192 extern void fsnotify_recalc_global_mask(void);
 193 /* get a reference to an existing or create a new group */
 194 extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
 195                                                     __u32 mask,
 196                                                     const struct fsnotify_ops *ops);
 197 /* run all marks associated with this group and update group->mask */
 198 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
 199 /* drop reference on a group from fsnotify_obtain_group */
 200 extern void fsnotify_put_group(struct fsnotify_group *group);
 201
 202 /* take a reference to an event */
 203 extern void fsnotify_get_event(struct fsnotify_event *event);
 204 extern void fsnotify_put_event(struct fsnotify_event *event);
 205 /* find private data previously attached to an event */
 206 extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
 207                                                                         struct fsnotify_event *event);
 208
 209 /* functions used to manipulate the marks attached to inodes */
 210
 211 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 212 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 213 extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
 214 /* find (and take a reference) to a mark associated with group and inode */
 215 extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
 216 /* attach the mark to both the group and the inode */
 217 extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
 218 /* given a mark, flag it to be freed when all references are dropped */
 219 extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
 220 /* run all the marks in a group, and flag them to be freed */
 221 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 222 extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
 223 extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
 224
 225 /* put here because inotify does some weird stuff when destroying watches */
 226 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 227                                                     void *data, int data_is);
 228 #else
 229
 230 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
 231 {}
 232
 233 static inline void __fsnotify_inode_delete(struct inode *inode)
 234 {}
 235
 236 #endif  /* CONFIG_FSNOTIFY */
 237
 238 #endif  /* __KERNEL __ */
 239
 240 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */