fsnotify: call iput on inodes when no longer marked

fsnotify takes an igrab on an inode when it adds a mark.  The code was
supposed to drop the reference when the mark was removed but didn't.
This caused problems when an fs was unmounted because those inodes would
clearly not be gone.  Thus resulting in the most devistating of messages:

VFS: Busy inodes after unmount of loop0. Self-destruct in 5 seconds.
>>> Have a nice day...

Jiri Slaby bisected the problem to a patch in the fsnotify tree.  The
code snippets below show my stupidity quite clearly.

void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
	...
	mark->inode = NULL;
	...
}

void fsnotify_destroy_mark(struct fsnotify_mark *mark)
{
	struct inode *inode = NULL;
	...
	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
		fsnotify_destroy_inode_mark(mark);
		inode = mark->i.inode;
	}
	...
	if (inode)
		iput(inode);
	...
}

Obviously the intent was to capture the inode before it was set to NULL in
fsnotify_destory_inode_mark() so we wouldn't be leaking inodes forever.
Instead we leaked them (and exploded on umount)

Reported-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 1e824e64441d101d71916c52a26c6f355aacf4ca..8f3b0e7a543dec3b547453ca9b8591bb4db2c174 100644 (file)
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -133,8 +133,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
        spin_lock(&group->mark_lock);
 
        if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
-               fsnotify_destroy_inode_mark(mark);
                inode = mark->i.inode;
+               fsnotify_destroy_inode_mark(mark);
        } else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
                fsnotify_destroy_vfsmount_mark(mark);
        else