On Thu, 2010-11-25 at 14:48 +1100, Nick Piggin wrote:
> On Wed, Nov 24, 2010 at 03:03:41PM -0500, Christoph Hellwig wrote:
> > On Wed, Nov 24, 2010 at 08:12:58AM +1100, Dave Chinner wrote:
> > > It is supposed to be handled by the re-initialisation of the
> > > ip->i_iolock in ->evict_inode (xfs_fs_evict_inode). An inode found
> > > in the reclaim state must have passed through this reinitialisation,
> > > so from a lockdep perspective the iolock in the vfs path is a
> > > different context to the iolock in the reclaim path. That fixed all
> > > the non-reclaim state related lockdep false positives, so Perhaps
> > > there is an issue with the lockdep reclaim state checking that does
> > > not interact well with re-initialised lock contexts?
> > I've been looking through this again, and I think it's indeed not
> > enough. We don't just need to re-initialize it, but also set a
> > different lockclass for it.
> Doesn't init_rwsem give it a new class?
Per call-site, yes it should.
> Guys, can you take a quick look at the code Dave is referring to
> (xfs_fs_evict_inode), and check that it actually does what he
Right, so this is trying to set a different class from the regular init
site, which (/me applies grep) lives in xfs_inode_alloc(), right?
Ought to work.. assuming the inode will be fully destroyed and new
inodes are always obtained through xfs_inode_alloc() and not reused.
> We're getting what seems to be false positives in reclaim inversion
> of lockings. Backtraces here
Right, so there its holding the inode in the read path while taking a
page-fault which does an allocation.
acquiring the inode in the xfs_reclaim_node_shrink() path.
Presumably the whole xfs_fs_evict_inode() stuff will happen _after_ its
possible to end up in that read path?
Something like the below would give the lock-class an explicit name,
because both sites now use the exact same init thing they're called:
Which is hard to tell apart, but I suspect #2 is the dead one, since
they get numbered in order of appearance and its hard to have a dead
inode before having a life one ;-)
In that case though, it would suggest the inode got re-used instead of
destroyed and re-created using xfs_alloc_inode(), is that at all
fs/xfs/linux-2.6/xfs_super.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 064f964..721c1c5 100644
@@ -1091,6 +1091,8 @@ xfs_fs_write_inode(
+static struct lock_class_key xfs_dead_inode;
struct inode *inode)
@@ -1118,6 +1120,8 @@ xfs_fs_evict_inode(
mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
+ lockdep_set_class_and_name(&ip->i_iolock->mr_lock, &xfs_dead_inode,