Every time we allocate or free a data extent, we might need to split the refcount btree. Reserve some blocks in the transaction to handle this possibility. Even though the deferred refcount code can roll a transaction to avoid overloading the transaction, we can still exceed the reservation. Certain pathological workloads (1k blocks, no cowextsize hint, random directio writes), cause a perfect storm wherein a refcount adjustment of a large range of blocks causes full tree splits in two separate extents in two separate refcount tree blocks; allocating new refcount tree blocks causes rmap btree splits; and all the allocation activity causes the freespace btrees to split, blowing the reservation. (Reproduced by generic/167 over NFS atop XFS) Signed-off-by: Christoph Hellwig <hch@xxxxxx> [darrick.wong@xxxxxxxxxx: add commit message] Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- fs/xfs/libxfs/xfs_trans_resv.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c index 7c840e1..a59838f 100644 --- a/fs/xfs/libxfs/xfs_trans_resv.c +++ b/fs/xfs/libxfs/xfs_trans_resv.c @@ -67,7 +67,8 @@ xfs_calc_buf_res( * Per-extent log reservation for the btree changes involved in freeing or * allocating an extent. In classic XFS there were two trees that will be * modified (bnobt + cntbt). With rmap enabled, there are three trees - * (rmapbt). The number of blocks reserved is based on the formula: + * (rmapbt). With reflink, there are four trees (refcountbt). The number of + * blocks reserved is based on the formula: * * num trees * ((2 blocks/level * max depth) - 1) * @@ -83,6 +84,8 @@ xfs_allocfree_log_count( blocks = num_ops * 2 * (2 * mp->m_ag_maxlevels - 1); if (xfs_sb_version_hasrmapbt(&mp->m_sb)) blocks += num_ops * (2 * mp->m_rmap_maxlevels - 1); + if (xfs_sb_version_hasreflink(&mp->m_sb)) + blocks += num_ops * (2 * mp->m_refc_maxlevels - 1); return blocks; } -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
