On Mon, Mar 30, 2020 at 08:15:44AM -0400, Brian Foster wrote: > On Mon, Mar 30, 2020 at 09:46:02AM +1100, Dave Chinner wrote: > > On Thu, Mar 26, 2020 at 09:17:02AM -0400, Brian Foster wrote: > > > A dquot flush currently blocks on the buffer lock for the underlying > > > dquot buffer. In turn, this causes xfsaild to block rather than > > > continue processing other items in the meantime. Update > > > xfs_qm_dqflush() to trylock the buffer, similar to how inode buffers > > > are handled, and return -EAGAIN if the lock fails. Fix up any > > > callers that don't currently handle the error properly. > > > > > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> > > > --- > > > fs/xfs/xfs_dquot.c | 6 +++--- > > > fs/xfs/xfs_dquot_item.c | 3 ++- > > > fs/xfs/xfs_qm.c | 14 +++++++++----- > > > 3 files changed, 14 insertions(+), 9 deletions(-) > > > > > > diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c > > > index 711376ca269f..af2c8e5ceea0 100644 > > > --- a/fs/xfs/xfs_dquot.c > > > +++ b/fs/xfs/xfs_dquot.c > > > @@ -1105,8 +1105,8 @@ xfs_qm_dqflush( > > > * Get the buffer containing the on-disk dquot > > > */ > > > error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp, dqp->q_blkno, > > > - mp->m_quotainfo->qi_dqchunklen, 0, &bp, > > > - &xfs_dquot_buf_ops); > > > + mp->m_quotainfo->qi_dqchunklen, XBF_TRYLOCK, > > > + &bp, &xfs_dquot_buf_ops); > > > if (error) > > > goto out_unlock; > > > > > > @@ -1177,7 +1177,7 @@ xfs_qm_dqflush( > > > > > > out_unlock: > > > xfs_dqfunlock(dqp); > > > - return -EIO; > > > + return error; > > > } > > > > > > /* > > > diff --git a/fs/xfs/xfs_dquot_item.c b/fs/xfs/xfs_dquot_item.c > > > index cf65e2e43c6e..baad1748d0d1 100644 > > > --- a/fs/xfs/xfs_dquot_item.c > > > +++ b/fs/xfs/xfs_dquot_item.c > > > @@ -189,7 +189,8 @@ xfs_qm_dquot_logitem_push( > > > if (!xfs_buf_delwri_queue(bp, buffer_list)) > > > rval = XFS_ITEM_FLUSHING; > > > xfs_buf_relse(bp); > > > - } > > > + } else if (error == -EAGAIN) > > > + rval = XFS_ITEM_LOCKED; > > > > Doesn't xfs_inode_item_push() also have this problem in that it > > doesn't handle -EAGAIN properly? > > > > Also, we can get -EIO, -EFSCORRUPTED, etc here. They probably > > shouldn't return XFS_ITEM_SUCCESS, either.... > > > > Good point. I'm actually not sure what we should return in that case > given the item return codes all seem to assume a valid state. We could > define an XFS_ITEM_ERROR return, but I'm not sure it's worth it for what > is currently stat/tracepoint logic in the caller. Perhaps a broader > rework of error handling in this context is in order that would lift > generic (fatal) error handling into xfsaild. Yeah, that's where my thoughts were heading as well. > E.g., I see that > xfs_qm_dqflush() is inconsistent by itself in that the item is removed > from the AIL if we're already shut down, but not if that function > invokes the shutdown; we shutdown if the direct xfs_dqblk_verify() call > fails but not if the read verifier (which also looks like it calls > xfs_dqblk_verify() on every on-disk dquot) returns -EFSCORRUPTED, etc. > It might make some sense to let iop_push() return negative error codes > if that facilitates consistent error handling... Yes, it's a bit of a mess. I suspect that what we should be doing here is pulling the failed buffer write retry code up into the main push loop. That is, we can set LI_FAILED on log items that fail to flush, either directly at submit time, or at IO completion for write errors. Then we can have the main AIL loop set LI_FAILED on push failures, and also the main loop detect LI_FAILED directly and call a new ->iop_resubmit() function rather than having to handle that the resubmit cases as special cases in every ->iop_push() path. That seems like a much cleaner way of handling submission failure and retries for all log item types that need it compared to the way we currently handle it for buffers... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
