From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
On filesystems that support them, bmap intent log items can be used to
change mappings in inode data or attr forks. However, if the bmbt must
expand, the enormous block reservations that we make for finishing
chains of deferred log items become a liability because the bmbt block
allocator sets minleft to the transaction reservation and there probably
aren't any AGs in the filesystem that have that much free space.
Whereas previously we would reserve 93% of the free blocks in the
filesystem, now we only want to reserve 7/8ths of the free space in the
least full AG, and no more than half of the usable blocks in an AG. In
theory we shouldn't run out of space because (prior to the unclean
shutdown) all of the in-progress transactions successfully reserved the
worst case number of disk blocks.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/xfs_log_recover.c | 55 ++++++++++++++++++++++++++++++++++++----------
1 file changed, 43 insertions(+), 12 deletions(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index e9b3e901d009..a416b028b320 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2669,6 +2669,44 @@ xlog_recover_process_data(
return 0;
}
+/*
+ * Estimate a block reservation for a log recovery transaction. Since we run
+ * separate transactions for each chain of deferred ops that get created as a
+ * result of recovering unfinished log intent items, we must be careful not to
+ * reserve so many blocks that block allocations fail because we can't satisfy
+ * the minleft requirements (e.g. for bmbt blocks).
+ */
+static int
+xlog_estimate_recovery_resblks(
+ struct xfs_mount *mp,
+ unsigned int *resblks)
+{
+ struct xfs_perag *pag;
+ xfs_agnumber_t agno;
+ unsigned int free = 0;
+ int error;
+
+ /* Don't use more than 7/8th of the free space in the least full AG. */
+ for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+ unsigned int ag_free;
+
+ error = xfs_alloc_pagf_init(mp, NULL, agno, 0);
+ if (error)
+ return error;
+ pag = xfs_perag_get(mp, agno);
+ ag_free = pag->pagf_freeblks + pag->pagf_flcount;
+ free = max(free, (ag_free * 7) / 8);
+ xfs_perag_put(pag);
+ }
+
+ /* Don't try to reserve more than half the usable AG blocks. */
+ *resblks = min(free, xfs_alloc_ag_max_usable(mp) / 2);
+ if (*resblks == 0)
+ return -ENOSPC;
+
+ return 0;
+}
+
/* Take all the collected deferred ops and finish them in order. */
static int
xlog_finish_defer_ops(
@@ -2677,27 +2715,20 @@ xlog_finish_defer_ops(
{
struct xfs_defer_freezer *dff, *next;
struct xfs_trans *tp;
- int64_t freeblks;
uint resblks;
int error = 0;
list_for_each_entry_safe(dff, next, dfops_freezers, dff_list) {
+ error = xlog_estimate_recovery_resblks(mp, &resblks);
+ if (error)
+ break;
+
/*
* We're finishing the defer_ops that accumulated as a result
* of recovering unfinished intent items during log recovery.
* We reserve an itruncate transaction because it is the
- * largest permanent transaction type. Since we're the only
- * user of the fs right now, take 93% (15/16) of the available
- * free blocks. Use weird math to avoid a 64-bit division.
+ * largest permanent transaction type.
*/
- freeblks = percpu_counter_sum(&mp->m_fdblocks);
- if (freeblks <= 0) {
- error = -ENOSPC;
- break;
- }
-
- resblks = min_t(int64_t, UINT_MAX, freeblks);
- resblks = (resblks * 15) >> 4;
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, resblks,
0, XFS_TRANS_RESERVE, &tp);
if (error)
