[PATCH] inotify: fix event loss on hardlinked files
People have run into a problem when they do this:
watch (file1, all_events);
watch (file2, some_events);
if file2 is a hard link to file1, some events will be missed because by
default we replace the mask. The patch below adds a flag IN_MASK_ADD which
will cause inotify to add to the existing mask if present.
Signed-off-by: John McCutchan <ttb@tentacle.dhs.org>
Signed-off-by: Robert Love <rml@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/inotify.c b/fs/inotify.c
index 2fd97ef..a37e9fb 100644
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -931,6 +931,7 @@
struct nameidata nd;
struct file *filp;
int ret, fput_needed;
+ int mask_add = 0;
filp = fget_light(fd, &fput_needed);
if (unlikely(!filp))
@@ -953,6 +954,9 @@
down(&inode->inotify_sem);
down(&dev->sem);
+ if (mask & IN_MASK_ADD)
+ mask_add = 1;
+
/* don't let user-space set invalid bits: we don't want flags set */
mask &= IN_ALL_EVENTS;
if (unlikely(!mask)) {
@@ -966,7 +970,10 @@
*/
old = inode_find_dev(inode, dev);
if (unlikely(old)) {
- old->mask = mask;
+ if (mask_add)
+ old->mask |= mask;
+ else
+ old->mask = mask;
ret = old->wd;
goto out;
}
diff --git a/include/linux/inotify.h b/include/linux/inotify.h
index 93bb3af..ee5b239 100644
--- a/include/linux/inotify.h
+++ b/include/linux/inotify.h
@@ -47,6 +47,7 @@
#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* moves */
/* special flags */
+#define IN_MASK_ADD 0x20000000 /* add to the mask of an already existing watch */
#define IN_ISDIR 0x40000000 /* event occurred against dir */
#define IN_ONESHOT 0x80000000 /* only send event once */