There is deadlock with calltrace on process 10133:
PID 10133 not sceduled for 4403385ms (was on CPU[10])
#0 context_switch() kernel/sched/core.c:3881
#1 __schedule() kernel/sched/core.c:5111
#2 schedule() kernel/sched/core.c:5186
#3 xfs_extent_busy_flush() fs/xfs/xfs_extent_busy.c:598
#4 xfs_alloc_ag_vextent_size() fs/xfs/libxfs/xfs_alloc.c:1641
#5 xfs_alloc_ag_vextent() fs/xfs/libxfs/xfs_alloc.c:828
#6 xfs_alloc_fix_freelist() fs/xfs/libxfs/xfs_alloc.c:2362
#7 xfs_free_extent_fix_freelist() fs/xfs/libxfs/xfs_alloc.c:3029
#8 __xfs_free_extent() fs/xfs/libxfs/xfs_alloc.c:3067
#9 xfs_trans_free_extent() fs/xfs/xfs_extfree_item.c:370
#10 xfs_efi_recover() fs/xfs/xfs_extfree_item.c:626
#11 xlog_recover_process_efi() fs/xfs/xfs_log_recover.c:4605
#12 xlog_recover_process_intents() fs/xfs/xfs_log_recover.c:4893
#13 xlog_recover_finish() fs/xfs/xfs_log_recover.c:5824
#14 xfs_log_mount_finish() fs/xfs/xfs_log.c:764
#15 xfs_mountfs() fs/xfs/xfs_mount.c:978
#16 xfs_fs_fill_super() fs/xfs/xfs_super.c:1908
#17 mount_bdev() fs/super.c:1417
#18 xfs_fs_mount() fs/xfs/xfs_super.c:1985
#19 legacy_get_tree() fs/fs_context.c:647
#20 vfs_get_tree() fs/super.c:1547
#21 do_new_mount() fs/namespace.c:2843
#22 do_mount() fs/namespace.c:3163
#23 ksys_mount() fs/namespace.c:3372
#24 __do_sys_mount() fs/namespace.c:3386
#25 __se_sys_mount() fs/namespace.c:3383
#26 __x64_sys_mount() fs/namespace.c:3383
#27 do_syscall_64() arch/x86/entry/common.c:296
#28 entry_SYSCALL_64() arch/x86/entry/entry_64.S:180
It's waiting xfs_perag.pagb_gen to increase (busy extent clearing happen).
>From the vmcore, it's waiting on AG 1. And the ONLY busy extent for AG 1 is
with the transaction (in xfs_trans.t_busy) for process 10133. That busy extent
is created in a previous EFI with the same transaction. Process 10133 is
waiting, it has no change to commit that that transaction. So busy extent
clearing can't happen and pagb_gen remain unchanged. So dead lock formed.
commit 06058bc40534530e617e5623775c53bb24f032cb disallowed using busy extents
for any path that calls xfs_extent_busy_trim(). That looks over-killing.
For AGFL block allocation, it just use the first extent that satisfies, it won't
try another extent for choose a "better" one. So it's safe to reuse busy extent
for AGFL.
To fix above dead lock, this patch allows reusing busy extent for AGFL.
Signed-off-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx>
---
fs/xfs/xfs_extent_busy.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/xfs/xfs_extent_busy.c b/fs/xfs/xfs_extent_busy.c
index ef17c1f6db32..f857a5759506 100644
--- a/fs/xfs/xfs_extent_busy.c
+++ b/fs/xfs/xfs_extent_busy.c
@@ -344,6 +344,7 @@ xfs_extent_busy_trim(
ASSERT(*len > 0);
spin_lock(&args->pag->pagb_lock);
+restart:
fbno = *bno;
flen = *len;
rbp = args->pag->pagb_tree.rb_node;
@@ -362,6 +363,20 @@ xfs_extent_busy_trim(
continue;
}
+ /*
+ * AGFL reserving (metadata) is just using the first-
+ * fit extent, there is no optimization that tries further
+ * extents. So it's safe to reuse the busy extent and safe
+ * to update the busy extent.
+ * Reuse for AGFL even busy extent being discarded.
+ */
+ if (args->resv == XFS_AG_RESV_AGFL) {
+ if (!xfs_extent_busy_update_extent(args->mp, args->pag,
+ busyp, fbno, flen, false))
+ goto restart;
+ continue;
+ }
+
if (bbno <= fbno) {
/* start overlap */
--
2.21.0 (Apple Git-122.2)
