On Mon, Oct 24, 2011 at 04:22:19AM -0400, Christoph Hellwig wrote:
> On Fri, Oct 21, 2011 at 01:28:57PM -0700, Simon Kirby wrote:
> > > So we're waiting for the inode to be flushed, aka I/O again.
> >
> > But I don't seem to see any queued I/O, hmm.
>
> Well, as far as XFS is concerned the inode is beeing flushed and
> the buffer is locked. It could be stuck in the XFS internal delwri
> list because a buffer for example is pinned.
>
> If that is the case the big hammer patch I attached below - probably
> not the final issue, but it should fix the hang if that is the case.
>
> > > If this doesn't help I'll probably need to come up with some tracing
> > > patches for you.
> >
> > It seemes 3.0.7+gregkh's stable-queue queue-3.0 patches seems to be
> > running fine without blocking at all on this SSD box, so that should
> > narrow it down significantly.
> >
> > Hmm, looking at git diff --stat v3.0.7..v3.1-rc10 fs/xfs , maybe not.. :)
> >
> > Maybe 3.1 fs/xfs would transplant into 3.0 or vice-versa?
>
> If the patch above doesn't work I'll prepare a backport for you.
>
> Index: linux-2.6/fs/xfs/xfs_sync.c
> ===================================================================
> --- linux-2.6.orig/fs/xfs/xfs_sync.c 2011-10-24 10:02:27.361971264 +0200
> +++ linux-2.6/fs/xfs/xfs_sync.c 2011-10-24 10:11:03.301036954 +0200
> @@ -764,7 +764,8 @@ xfs_reclaim_inode(
> struct xfs_perag *pag,
> int sync_mode)
> {
> - int error;
> + struct xfs_mount *mp = ip->i_mount;
> + int error;
>
> restart:
> error = 0;
> @@ -772,6 +773,18 @@ restart:
> if (!xfs_iflock_nowait(ip)) {
> if (!(sync_mode & SYNC_WAIT))
> goto out;
> +
> + /*
> + * If the inode is flush locked we probably had someone else
> + * push it to the buffer and the buffer is now sitting in
> + * the delwri list.
> + *
> + * Use the big hammer to force it.
> + */
> + xfs_log_force(mp, XFS_LOG_SYNC);
> + set_bit(XBT_FORCE_FLUSH, &mp->m_ddev_targp->bt_flags);
> + wake_up_process(mp->m_ddev_targp->bt_task);
> +
> xfs_iflock(ip);
> }
>
This patch seems to work, at least on an SSD box. No more hung task
warnings, and everything appears normal.
Do we know what caused this regression and/or how to fix it without the
big hammer, or do we need to break it down further?
Thanks!
Simon-
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