From 5c81a4197de38411fe3e27f8593fff73a5d6b868 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Mon, 3 Jul 2006 00:25:20 -0700 Subject: [PATCH] lockdep: annotate the quota code The quota code plays interesting games with the lock ordering; to quote Jan: | i_mutex of inode containing quota file is acquired after all other | quota locks. i_mutex of all other inodes is acquired before quota | locks. Quota code makes sure (by resetting inode operations and | setting special flag on inode) that noone tries to enter quota code | while holding i_mutex on a quota file... The good news is that all of this special case i_mutex grabbing happens in the (per filesystem) low level quota write function. For this special case we need a new I_MUTEX_* nesting level, since this just entirely outside any of the regular VFS locking rules for i_mutex. I trust Jan on his blue eyes that this is not ever going to deadlock; and based on that the patch below is what it takes to inform lockdep of these very interesting new locking rules. The new locking rule for the I_MUTEX_QUOTA nesting level is that this is the deepest possible level of nesting for i_mutex, and that this only should be used in quota write (and possibly read) function of filesystems. This makes the lock ordering of the I_MUTEX_* levels: I_MUTEX_PARENT -> I_MUTEX_CHILD -> I_MUTEX_NORMAL -> I_MUTEX_QUOTA Has no effect on non-lockdep kernels. Signed-off-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ext2/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/ext2') diff --git a/fs/ext2/super.c b/fs/ext2/super.c index 9f43879d6d68..f2702cda9779 100644 --- a/fs/ext2/super.c +++ b/fs/ext2/super.c @@ -1157,7 +1157,7 @@ static ssize_t ext2_quota_write(struct super_block *sb, int type, struct buffer_head tmp_bh; struct buffer_head *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; -- cgit v1.2.3