On Wed, Apr 17, 2019 at 07:37:59AM -0700, Darrick J. Wong wrote: > On Wed, Apr 17, 2019 at 05:36:08AM -0400, Brian Foster wrote: > > 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. > > > > Reported-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> > > --- > > > > This is motivated by Darrick's recent xfs/104 failure report[1]. Note > > that I made the assert a bit more explicit than originally suggested > > because I think any transaction that performs block allocation should be > > expected to be able to handle arbitrary AGFL fixups. This survives an > > fstests auto run without any regressions[2] or assert failures. > > > > Brian > > > > [1] https://marc.info/?l=linux-xfs&m=155537961822223&w=2 > > [2] Note that I was never able to reproduce the original xfs/104 > > failure. > > > > fs/xfs/libxfs/xfs_alloc.c | 2 ++ > > fs/xfs/libxfs/xfs_trans_resv.c | 6 +++++- > > 2 files changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > > index bc3367b8b7bb..e4df1866f949 100644 > > --- a/fs/xfs/libxfs/xfs_alloc.c > > +++ b/fs/xfs/libxfs/xfs_alloc.c > > @@ -2237,6 +2237,8 @@ xfs_alloc_fix_freelist( > > xfs_extlen_t need; /* total blocks needed in freelist */ > > int error = 0; > > > > + ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES); > > /me wonders if we ought to have a comment here about why we're asserting > on this? i.e. > Yep. > /* > * This function can shrink the AGFL, which uses a deferred op to avoid > * exceeding transaction reservation (or whatever the original reason > * was). Deferred ops require a transaction with a permanent > * reservation, so check that here. > */ > ASSERT(...); > > Send me back a finished comment and I'll add it on its way in; the rest > of the patch looks ok to me. > Though to me a one-liner seems sufficient since this is just an assert. E.g., /* deferred ops (AGFL block frees) require permanent transactions */ ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES); ... seems enough to document the intent. Hm? Brian > --D > > > + > > if (!pag->pagf_init) { > > error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp); > > if (error) > > 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); > > -- > > 2.17.2 > >
