On 5/7/19 10:47 AM, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > It turns out that the log can consume nearly all the space in an AG, and > when this happens this it's possible that there will be less free space > in the AG than the reservation would try to hide. On a debug kernel > this can trigger an ASSERT in xfs/250: > > XFS: Assertion failed: xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved + xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved <= pag->pagf_freeblks + pag->pagf_flcount, file: fs/xfs/libxfs/xfs_ag_resv.c, line: 319 > > The log is permanently allocated, so we know we're never going to have > to expand the btrees to hold any records associated with the log space. > We therefore can treat the space as if it doesn't exist. Neato. > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > fs/xfs/libxfs/xfs_ialloc_btree.c | 9 +++++++++ > fs/xfs/libxfs/xfs_refcount_btree.c | 9 +++++++++ > fs/xfs/libxfs/xfs_rmap_btree.c | 9 +++++++++ > 3 files changed, 27 insertions(+) > > diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c > index 1080381ff243..bc2dfacd2f4a 100644 > --- a/fs/xfs/libxfs/xfs_ialloc_btree.c > +++ b/fs/xfs/libxfs/xfs_ialloc_btree.c > @@ -549,6 +549,15 @@ xfs_inobt_max_size( > if (mp->m_inobt_mxr[0] == 0) > return 0; > > + /* > + * The log is permanently allocated, so the space it occupies will > + * never be available for the kinds of things that would require btree > + * expansion. We therefore can pretend the space isn't there. > + */ > + if (mp->m_sb.sb_logstart && > + XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == agno) > + agblocks -= mp->m_sb.sb_logblocks; > + So we started agblocks at xfs_ag_block_count, and I wondered if we should roll this adjustment into that function, but no - most callers really want to know how many blocks are in it, not how many are available for use as we do here. This looks right to me, Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx> > return xfs_btree_calc_size(mp->m_inobt_mnr, > (uint64_t)agblocks * mp->m_sb.sb_inopblock / > XFS_INODES_PER_CHUNK); > diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c > index 6f47ab876d90..5d9de9b21726 100644 > --- a/fs/xfs/libxfs/xfs_refcount_btree.c > +++ b/fs/xfs/libxfs/xfs_refcount_btree.c > @@ -427,6 +427,15 @@ xfs_refcountbt_calc_reserves( > tree_len = be32_to_cpu(agf->agf_refcount_blocks); > xfs_trans_brelse(tp, agbp); > > + /* > + * The log is permanently allocated, so the space it occupies will > + * never be available for the kinds of things that would require btree > + * expansion. We therefore can pretend the space isn't there. > + */ > + if (mp->m_sb.sb_logstart && > + XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == agno) > + agblocks -= mp->m_sb.sb_logblocks; > + > *ask += xfs_refcountbt_max_size(mp, agblocks); > *used += tree_len; > > diff --git a/fs/xfs/libxfs/xfs_rmap_btree.c b/fs/xfs/libxfs/xfs_rmap_btree.c > index 5738e11055e6..5d1f8884c888 100644 > --- a/fs/xfs/libxfs/xfs_rmap_btree.c > +++ b/fs/xfs/libxfs/xfs_rmap_btree.c > @@ -578,6 +578,15 @@ xfs_rmapbt_calc_reserves( > tree_len = be32_to_cpu(agf->agf_rmap_blocks); > xfs_trans_brelse(tp, agbp); > > + /* > + * The log is permanently allocated, so the space it occupies will > + * never be available for the kinds of things that would require btree > + * expansion. We therefore can pretend the space isn't there. > + */ > + if (mp->m_sb.sb_logstart && > + XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == agno) > + agblocks -= mp->m_sb.sb_logblocks; > + > /* Reserve 1% of the AG or enough for 1 block per record. */ > *ask += max(agblocks / 100, xfs_rmapbt_max_size(mp, agblocks)); > *used += tree_len; >
