fs/notify/fanotify/fanotify.c

   1 #include <linux/fdtable.h>
   2 #include <linux/fsnotify_backend.h>
   3 #include <linux/init.h>
   4 #include <linux/kernel.h> /* UINT_MAX */
   5 #include <linux/types.h>
   6
   7 #include "fanotify.h"
   8
   9 static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
  10 {
  11         pr_debug("%s: old=%p new=%p\n", __func__, old, new);
  12
  13         if ((old->to_tell == new->to_tell) &&
  14             (old->data_type == new->data_type)) {
  15                 switch (old->data_type) {
  16                 case (FSNOTIFY_EVENT_PATH):
  17                         if ((old->path.mnt == new->path.mnt) &&
  18                             (old->path.dentry == new->path.dentry))
  19                                 return true;
  20                 case (FSNOTIFY_EVENT_NONE):
  21                         return true;
  22                 default:
  23                         BUG();
  24                 };
  25         }
  26         return false;
  27 }
  28
  29 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
  30 {
  31         struct fsnotify_event_holder *test_holder;
  32         struct fsnotify_event *test_event;
  33         struct fsnotify_event *new_event;
  34         int ret = 0;
  35
  36         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
  37
  38         /* and the list better be locked by something too! */
  39
  40         list_for_each_entry_reverse(test_holder, list, event_list) {
  41                 test_event = test_holder->event;
  42                 if (should_merge(test_event, event)) {
  43                         ret = -EEXIST;
  44
  45                         /* if they are exactly the same we are done */
  46                         if (test_event->mask == event->mask)
  47                                 goto out;
  48
  49                         /*
  50                          * if the refcnt == 1 this is the only queue
  51                          * for this event and so we can update the mask
  52                          * in place.
  53                          */
  54                         if (atomic_read(&test_event->refcnt) == 1) {
  55                                 test_event->mask |= event->mask;
  56                                 goto out;
  57                         }
  58
  59                         /* can't allocate memory, merge was no possible */
  60                         new_event = fsnotify_clone_event(test_event);
  61                         if (unlikely(!new_event)) {
  62                                 ret = 0;
  63                                 goto out;
  64                         }
  65
  66                         /* build new event and replace it on the list */
  67                         new_event->mask = (test_event->mask | event->mask);
  68                         fsnotify_replace_event(test_holder, new_event);
  69                         /* match ref from fsnotify_clone_event() */
  70                         fsnotify_put_event(new_event);
  71
  72                         break;
  73                 }
  74         }
  75 out:
  76         return ret;
  77 }
  78
  79 static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
  80 {
  81         int ret;
  82
  83
  84         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
  85         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
  86         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
  87         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
  88         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
  89         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
  90         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
  91
  92         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  93
  94         ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
  95         /* -EEXIST means this event was merged with another, not that it was an error */
  96         if (ret == -EEXIST)
  97                 ret = 0;
  98         return ret;
  99 }
 100
 101 static bool fanotify_should_send_event(struct fsnotify_group *group, struct inode *inode,
 102                                        struct vfsmount *mnt, __u32 mask, void *data,
 103                                        int data_type)
 104 {
 105         struct fsnotify_mark *fsn_mark;
 106         bool send;
 107
 108         pr_debug("%s: group=%p inode=%p mask=%x data=%p data_type=%d\n",
 109                  __func__, group, inode, mask, data, data_type);
 110
 111         /* sorry, fanotify only gives a damn about files and dirs */
 112         if (!S_ISREG(inode->i_mode) &&
 113             !S_ISDIR(inode->i_mode))
 114                 return false;
 115
 116         /* if we don't have enough info to send an event to userspace say no */
 117         if (data_type != FSNOTIFY_EVENT_PATH)
 118                 return false;
 119
 120         fsn_mark = fsnotify_find_mark(group, inode);
 121         if (!fsn_mark)
 122                 return false;
 123
 124         /* if the event is for a child and this inode doesn't care about
 125          * events on the child, don't send it! */
 126         if ((mask & FS_EVENT_ON_CHILD) &&
 127             !(fsn_mark->mask & FS_EVENT_ON_CHILD)) {
 128                 send = false;
 129         } else {
 130                 /*
 131                  * We care about children, but do we care about this particular
 132                  * type of event?
 133                  */
 134                 mask = (mask & ~FS_EVENT_ON_CHILD);
 135                 send = (fsn_mark->mask & mask);
 136         }
 137
 138         /* find took a reference */
 139         fsnotify_put_mark(fsn_mark);
 140
 141         return send;
 142 }
 143
 144 const struct fsnotify_ops fanotify_fsnotify_ops = {
 145         .handle_event = fanotify_handle_event,
 146         .should_send_event = fanotify_should_send_event,
 147         .free_group_priv = NULL,
 148         .free_event_priv = NULL,
 149         .freeing_mark = NULL,
 150 };