[Ocfs2-devel] [PATCH] quota: Fix deadlock during path resolution

[Christoph Hellwig]

On Wed, Sep 15, 2010 at 11:39:51PM +0200, Jan Kara wrote:
> As Al Viro pointed out path resolution during Q_QUOTAON calls to quotactl
> is prone to deadlocks. We hold s_umount semaphore for reading during the
> path resolution and resolution itself may need to acquire the semaphore
> for writing when e. g. autofs mountpoint is passed.
> 
> Solve the problem by performing the resolution before we get hold of the
> superblock (and thus s_umount semaphore). The whole thing is complicated
> by the fact that some filesystems (OCFS2) ignore the path argument. So to
> distinguish between filesystem which want the path and which do not we
> introduce new .quota_on_meta callback which does not get the path. OCFS2
> then uses this callback instead of old .quota_on.

FYI I have a patch that switches ocfs to share the quota_on method with
XFS which behaves the same, and consolidate the quota_off method for all
filesystems.  I think that's better than adding yet another method.

I'll rebase it and send it out soon.