From: John McCutchan <ttb@tentacle.dhs.org>
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>
---
fs/inotify.c | 9 ++++++++-
include/linux/inotify.h | 1 +
2 files changed, 9 insertions(+), 1 deletion(-)
diff -puN fs/inotify.c~inotify-fix-event-loss-on-hardlinked-files fs/inotify.c
--- 25/fs/inotify.c~inotify-fix-event-loss-on-hardlinked-files Wed Aug 31 13:14:45 2005
+++ 25-akpm/fs/inotify.c Wed Aug 31 13:14:45 2005
@@ -925,6 +925,7 @@ asmlinkage long sys_inotify_add_watch(in
struct nameidata nd;
struct file *filp;
int ret, fput_needed;
+ int mask_add = 0;
filp = fget_light(fd, &fput_needed);
if (unlikely(!filp))
@@ -947,6 +948,9 @@ asmlinkage long sys_inotify_add_watch(in
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)) {
@@ -960,7 +964,10 @@ asmlinkage long sys_inotify_add_watch(in
*/
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 -puN include/linux/inotify.h~inotify-fix-event-loss-on-hardlinked-files include/linux/inotify.h
--- 25/include/linux/inotify.h~inotify-fix-event-loss-on-hardlinked-files Wed Aug 31 13:14:45 2005
+++ 25-akpm/include/linux/inotify.h Wed Aug 31 13:14:45 2005
@@ -47,6 +47,7 @@ struct inotify_event {
#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 */
_