https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=248355
Description of problem:
Warnings in the kernel log (dmesg):
BUG: warning at fs/inotify.c:172/set_dentry_child_flags() (Not tainted)
[<c0497a37>] set_dentry_child_flags+0x67/0x13d
[<c0497c27>] remove_watch_no_event+0x2f/0x3b
[<c0497d15>] inotify_remove_watch_locked+0x12/0x3e
[<c0600c17>] mutex_lock+0x1a/0x29
[<c0497fdd>] inotify_rm_wd+0x6d/0x8a
[<c04983b1>] sys_inotify_rm_watch+0x38/0x4f
[<c0404f70>] syscall_call+0x7/0xb
Appears randomly, about every second/third day.
Still happening in kernel 2.6.22.
static void set_dentry_child_flags(struct inode *inode, int watched)
...
spin_lock(&dcache_lock);
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct dentry *child;
list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
if (!child->d_inode) {
WARN_ON(child->d_flags &
DCACHE_INOTIFY_PARENT_WATCHED);
continue;
}
But in dcache.c, the locks are dropped before this flag is cleared, leaving
a race window:
void d_delete(struct dentry * dentry)
...
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (atomic_read(&dentry->d_count) == 1) {
dentry_iput(dentry); <================ drops dcache_lock and
dentry->d_lock
fsnotify_nameremove(dentry, isdir);
/* remove this and other inotify debug checks after 2.6.18 */
dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
return;
}
(The comment is nice, it says the debug code should have been removed long ago.)
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