Messages in this thread | | | Date | Mon, 5 Jun 2006 22:06:52 +0200 | From | Jan Kara <> | Subject | Re: 2.6.17-rc5-mm3-lockdep - locking error in quotaon |
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> > > following confuses the code (and I agree that it's kind of ugly from > > quota code to do that): > > 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... > > can you point this out in a bit more detail, eg where exactly is this > happening? I think it is in this bit > /* As we bypass the pagecache we must now flush the inode so that > * we see all the changes from userspace... */ > write_inode_now(inode, 1); > /* And now flush the block cache so that kernel sees the changes > */ > invalidate_bdev(sb->s_bdev, 0); > mutex_lock(&inode->i_mutex); > mutex_lock(&dqopt->dqonoff_mutex); > if (sb_has_quota_enabled(sb, type)) { > error = -EBUSY; > goto out_lock; > > but that doesn't quite match your description... This piece of code is there just because we avoid page cache when doing quota writes. That is a different story and should cause problems with your lock checker. Standard way of running quota is: - get i_mutex for data_inode - write some data to data_inode - requires allocation -> calls DQUOT_ALLOC_SPACE - DQUOT_ALLOC_SPACE acquires some quota locks, decides it wants to write out quota structure (e.g. because we are journaling quota and must preserve quota integrity) - acquires dqio_sem, calls filesystem specific quota writing function - e.g. ext3_quota_write() - this function acquires i_mutex for quota file
I think this is the type of circle your checker has found.
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