At IO time, make sure an EFI contains only one extent. Transaction rolling in
xfs_defer_finish() would commit the busy blocks for previous EFIs. By that we
avoid holding busy extents (for previously extents in the same EFI) in current
transaction when allocating blocks for AGFL where we could be otherwise stuck
waiting the busy extents held by current transaction to be flushed (thus a
deadlock).
The log changes
1) before change:
358 rbbn 13 rec_lsn: 1,12 Oper 5: tid: ee327fd2 len: 48 flags: None
359 EFI nextents:2 id:ffff9fef708ba940
360 EFI id=ffff9fef708ba940 (0x21, 7)
361 EFI id=ffff9fef708ba940 (0x18, 8)
362 -----------------------------------------------------------------
363 rbbn 13 rec_lsn: 1,12 Oper 6: tid: ee327fd2 len: 48 flags: None
364 EFD nextents:2 id:ffff9fef708ba940
365 EFD id=ffff9fef708ba940 (0x21, 7)
366 EFD id=ffff9fef708ba940 (0x18, 8)
2) after change:
830 rbbn 31 rec_lsn: 1,30 Oper 5: tid: 319f015f len: 32 flags: None
831 EFI nextents:1 id:ffff9fef708b9b80
832 EFI id=ffff9fef708b9b80 (0x21, 7)
833 -----------------------------------------------------------------
834 rbbn 31 rec_lsn: 1,30 Oper 6: tid: 319f015f len: 32 flags: None
835 EFI nextents:1 id:ffff9fef708b9d38
836 EFI id=ffff9fef708b9d38 (0x18, 8)
837 -----------------------------------------------------------------
838 rbbn 31 rec_lsn: 1,30 Oper 7: tid: 319f015f len: 32 flags: None
839 EFD nextents:1 id:ffff9fef708b9b80
840 EFD id=ffff9fef708b9b80 (0x21, 7)
841 -----------------------------------------------------------------
842 rbbn 31 rec_lsn: 1,30 Oper 8: tid: 319f015f len: 32 flags: None
843 EFD nextents:1 id:ffff9fef708b9d38
844 EFD id=ffff9fef708b9d38 (0x18, 8)
Signed-off-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx>
---
fs/xfs/xfs_extfree_item.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h
index da6a5afa607c..ae84d77eaf30 100644
--- a/fs/xfs/xfs_extfree_item.h
+++ b/fs/xfs/xfs_extfree_item.h
@@ -13,8 +13,15 @@ struct kmem_cache;
/*
* Max number of extents in fast allocation path.
+ *
+ * At IO time, make sure an EFI contains only one extent. Transaction rolling
+ * in xfs_defer_finish() would commit the busy blocks for previous EFIs. By
+ * that we avoid holding busy extents (for previously extents in the same EFI)
+ * in current transaction when allocating blocks for AGFL where we could be
+ * otherwise stuck waiting the busy extents held by current transaction to be
+ * flushed (thus a deadlock).
*/
-#define XFS_EFI_MAX_FAST_EXTENTS 16
+#define XFS_EFI_MAX_FAST_EXTENTS 1
/*
* This is the "extent free intention" log item. It is used to log the fact
--
2.21.0 (Apple Git-122.2)
