>From c7a79bccca1aac70f5e50fb145942b932eca79ba Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Sat, 6 Sep 2014 08:35:24 +0400 Subject: [PATCH] fs: don't remove inotify watchers from alive inode-s (v2) Currently watchers are removed in dentry_iput(), if n_link is zero. But other detries can be linked with this inode. For example if we create two hard links, open the first one and set an inotify watcher on one of them. Then if we remove the opened file and then another file, the inotify watcher will be removed. But we will have the alive file descriptor, which allows us to generate more events. And here is another behaviour, if files are removed in another order. The watcher will not be removed and we will keep getting inotify events for that inode. This patch removes difference of behaviours for these cases. Watchers are removed, only if nlink is zero and i_dentry list is empty. The resulting behaviour is the same with what has been described in the second case. Look at a following example: fd = inotify_init1(IN_NONBLOCK); deleted = open(path, O_CREAT | O_TRUNC | O_WRONLY, 0666); link(path, path_link); wd_deleted = inotify_add_watch(fd, path_link, IN_ALL_EVENTS); unlink(path); unlink(path_link); printf(" --- unlink path, path_link\n"); read_evetns(fd); close(deleted); printf(" --- close\n"); read_evetns(fd); printf(" --- end\n"); We expect to get the same set of events for this case and for the case, when files are deleted in another order. But now we get the different set of events. Without this patch: The first case, when "path" is deleted before "path_link" --- unlink path, path_link 4 (IN_ATTRIB) 400 (IN_DELETE_SELF) 8000 (IN_IGNORED) --- close --- end and for the case, when "path_link" is deleted before "path" --- unlink path_link, path 4 (IN_ATTRIB) --- close 8 (IN_CLOSE_WRITE) 400 (IN_DELETE_SELF) 8000 (IN_IGNORED) --- end With this patch we have the same output for both cases: --- unlink 4 (IN_ATTRIB) --- close 8 (IN_CLOSE_WRITE) 400 (IN_DELETE_SELF) 8000 (IN_IGNORED) --- end PASS v2: generate IN_DELETE_SELF when the last link to the file is removed Cc: Jan Kara Cc: Heinrich Schuchardt Cc: Alexander Viro Cc: John McCutchan Cc: Robert Love Cc: Eric Paris Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Signed-off-by: Andrey Vagin --- fs/dcache.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 7a5b514..3a0e3bc 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -278,12 +278,15 @@ static void dentry_iput(struct dentry * dentry) __releases(dentry->d_inode->i_lock) { struct inode *inode = dentry->d_inode; + bool last_dentry; + if (inode) { dentry->d_inode = NULL; hlist_del_init(&dentry->d_alias); + last_dentry = hlist_empty(&inode->i_dentry); spin_unlock(&dentry->d_lock); spin_unlock(&inode->i_lock); - if (!inode->i_nlink) + if (!inode->i_nlink && last_dentry) fsnotify_inoderemove(inode); if (dentry->d_op && dentry->d_op->d_iput) dentry->d_op->d_iput(dentry, inode); @@ -303,13 +306,16 @@ static void dentry_unlink_inode(struct dentry * dentry) __releases(dentry->d_inode->i_lock) { struct inode *inode = dentry->d_inode; + bool last_dentry; + __d_clear_type(dentry); dentry->d_inode = NULL; hlist_del_init(&dentry->d_alias); dentry_rcuwalk_barrier(dentry); + last_dentry = hlist_empty(&inode->i_dentry); spin_unlock(&dentry->d_lock); spin_unlock(&inode->i_lock); - if (!inode->i_nlink) + if (!inode->i_nlink && last_dentry) fsnotify_inoderemove(inode); if (dentry->d_op && dentry->d_op->d_iput) dentry->d_op->d_iput(dentry, inode); -- 1.9.3