Re: [RFC PATCH 08/11] xfs: have sync_fs op report writeback errors when passed a since pointer

From: Jeff Layton
Date: Mon May 21 2018 - 18:28:46 EST


On Tue, 2018-05-22 at 09:01 +1000, Dave Chinner wrote:
> On Fri, May 18, 2018 at 08:34:12AM -0400, Jeff Layton wrote:
> > From: Jeff Layton <jlayton@xxxxxxxxxx>
> >
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/xfs/xfs_super.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> > index 9255de2767b4..7dc847f48f9f 100644
> > --- a/fs/xfs/xfs_super.c
> > +++ b/fs/xfs/xfs_super.c
> > @@ -1092,6 +1092,7 @@ xfs_fs_sync_fs(
> > int wait,
> > errseq_t *since)
> > {
> > + int ret;
> > struct xfs_mount *mp = XFS_M(sb);
> >
> > /*
> > @@ -1110,7 +1111,13 @@ xfs_fs_sync_fs(
> > flush_delayed_work(&mp->m_log->l_work);
> > }
> > out:
> > - return __sync_blockdev(sb->s_bdev, wait);
>
> Where did this come from? XFS doesn't use the underlying blockdev
> address space, so this does nothing at all and should not be here.
>

An earlier patch that pushed this down into the sync_fs routines. We
call this today for all filesystems, and I wasn't sure about xfs.

Christoph already pointed out that it's not needed so it's removed from
my current branch.

> > + ret = __sync_blockdev(sb->s_bdev, wait);
> > + if (since) {
> > + int ret2 = errseq_check_and_advance(&sb->s_wb_err, since);
> > + if (ret == 0)
> > + ret = ret2;
> > + }
> > + return ret;
> > }
>
> So to return errors correctly, xfs_fs_sync_fs() needs to capture
> errors from the log force (i.e. metadata errors such as filesystem
> shutdowns, journal IO errors, etc), then check for pending data IO
> errors. i.e:
>
>
> STATIC int
> xfs_fs_sync_fs(
> struct super_block *sb,
> int wait)
> {
> struct xfs_mount *mp = XFS_M(sb);
> + int err;
>
> /*
> * Doing anything during the async pass would be counterproductive.
> */
> if (!wait)
> return 0;
>
> - xfs_log_force(mp, XFS_LOG_SYNC);
> + err = xfs_log_force(mp, XFS_LOG_SYNC);
> + if (err)
> + return err;
> +
> if (laptop_mode) {
> /*
> * The disk must be active because we're syncing.
> * We schedule log work now (now that the disk is
> * active) instead of later (when it might not be).
> */
> flush_delayed_work(&mp->m_log->l_work);
> }
>
> - return 0
> + return errseq_check_and_advance(&sb->s_wb_err, since);
> }
>

Ok, sounds good. I'll fix that too.

FWIW, we'll actually want to advance the cursor even if xfs_log_force
returns an error to ensure that we don't end up reporting errors twice,
but that's simple enough to do.

Thanks!
--
Jeff Layton <jlayton@xxxxxxxxxx>