--On 10 October 2006 10:47:26 AM +1000 David Chinner <dgc@xxxxxxx> wrote:
On Mon, Oct 09, 2006 at 12:58:58PM -0500, Eric Sandeen wrote:
FC6 kernels are oopsing when lockdep & memory debugging are turned on,
looks like due to this code:
* Here we do a spurious inode lock in order to coordinate with
* xfs_sync(). This is because xfs_sync() references the inodes
* in the mount list without taking references on the
corresponding * vnodes. We make that OK here by ensuring that
we wait until * the inode is unlocked in xfs_sync() before we
go ahead and * free it. We get both the regular lock and the
io lock because * the xfs_sync() code may need to drop the
regular one but will * still hold the io lock.
xfs_ilock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
* Free all memory associated with the inode.
So, lock & free. This frees memory that lockdep is still pointing to,
and tries to use later.
Calling xfs_iunlock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL); just before
xfs_idestroy seems to solve it, but is this safe...?
It should be - we call xfs_iextract() before the xfs_ilock() call
shown above. That means the inode has been removed from the mount
list when we take the locks. Once the inode has been removed
from the mount list, the only possible current user is xfs_sync_inodes(),
and it will only be referencing the inode if it is currently working
on the inode. If it is working on the inode, then it will be holding
at least one of the inode locks.
Hence by the time we have the lock here in xfs_ireclaim we have guaranteed
that there are no other outstanding references and no new references
can occur. Therefore it should be safe to drop the lock before destroying
Yeah, there really seems like something would be wrong if you can't
unlock it before destroying it.
I would have thought you'd need to guarantee that you are the only
one with access to it before destroying it otherwise there'd be problems :)
(Which as you say we do)
This one rings a bell. I seem to recall multiple places where we destroy
without releasing the lock first.
And I vaguely remember Nathan mentioning that this was causing grief