Re: [PATCH] xfs: make tr_growdata a permanent transaction

Darrick J. Wong
2019-04-23T15:49:59Z

On Tue, Apr 23, 2019 at 11:28:27AM -0400, Brian Foster wrote:
> On Tue, Apr 23, 2019 at 08:07:09AM -0700, Darrick J. Wong wrote:
> > From: Brian Foster <bfoster@redhat.com>
> >
> > The growdata transaction is used by growfs operations to increase
> > the data size of the filesystem. Part of this sequence involves
> > extending the size of the last preexisting AG in the fs, if
> > necessary. This is implemented by freeing the newly available
> > physical range to the AG.
> >
> > tr_growdata is not a permanent transaction, however, and block
> > allocation transactions must be permanent to handle deferred frees
> > of AGFL blocks. If the grow operation extends an existing AG that
> > requires AGFL fixing, assert failures occur due to a populated dfops
> > list on a non-permanent transaction and the AGFL free does not
> > occur. This is reproduced (rarely) by xfs/104.
> >
> > Change tr_growdata to a permanent transaction with a default log
> > count. This increases initial transaction reservation size, but
> > growfs is an infrequent and non-performance critical operation and
> > so should have minimal impact. Also add an assert in the block
> > allocation path to make this transaction requirement explicit and
> > obvious to future callers.
> >
>
> We should drop the last sentence from this commit log too if we push the
> assert to its own patch.

Ok, will do.

--D

>
> Brian
>
> > Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > [darrick: add a comment to the assert]
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> > fs/xfs/libxfs/xfs_trans_resv.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
> > index f99a7aefe418..83f4ee2afc49 100644
> > --- a/fs/xfs/libxfs/xfs_trans_resv.c
> > +++ b/fs/xfs/libxfs/xfs_trans_resv.c
> > @@ -876,9 +876,13 @@ xfs_trans_resv_calc(
> > resp->tr_sb.tr_logres = xfs_calc_sb_reservation(mp);
> > resp->tr_sb.tr_logcount = XFS_DEFAULT_LOG_COUNT;
> >
> > + /* growdata requires permanent res; it can free space to the last AG */
> > + resp->tr_growdata.tr_logres = xfs_calc_growdata_reservation(mp);
> > + resp->tr_growdata.tr_logcount = XFS_DEFAULT_PERM_LOG_COUNT;
> > + resp->tr_growdata.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
> > +
> > /* The following transaction are logged in logical format */
> > resp->tr_ichange.tr_logres = xfs_calc_ichange_reservation(mp);
> > - resp->tr_growdata.tr_logres = xfs_calc_growdata_reservation(mp);
> > resp->tr_fsyncts.tr_logres = xfs_calc_swrite_reservation(mp);
> > resp->tr_writeid.tr_logres = xfs_calc_writeid_reservation(mp);
> > resp->tr_attrsetrt.tr_logres = xfs_calc_attrsetrt_reservation(mp);