From ebbf58173eb6b4ce30baa8a686a9b83cb91e80f6 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Fri, 22 Jun 2018 12:35:00 +0800
Subject: [PATCH] btrfs: Don't remove block group still has pinned down bytes
Patch-mainline: v4.19-rc1
Git-commit: 43794446548730ac8461be30bbe47d5d027d1d16
References: bsc#1086457
[BUG]
Under certain KVM load and LTP tests, it is possible to hit the
following calltrace if quota is enabled:
BTRFS critical (device vda2): unable to find logical 8820195328 length 4096
BTRFS critical (device vda2): unable to find logical 8820195328 length 4096
WARNING: CPU: 0 PID: 49 at ../block/blk-core.c:172 blk_status_to_errno+0x1a/0x30
CPU: 0 PID: 49 Comm: kworker/u2:1 Not tainted 4.12.14-15-default #1 SLE15 (unreleased)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
task: ffff9f827b340bc0 task.stack: ffffb4f8c0304000
RIP: 0010:blk_status_to_errno+0x1a/0x30
Call Trace:
submit_extent_page+0x191/0x270 [btrfs]
? btrfs_create_repair_bio+0x130/0x130 [btrfs]
__do_readpage+0x2d2/0x810 [btrfs]
? btrfs_create_repair_bio+0x130/0x130 [btrfs]
? run_one_async_done+0xc0/0xc0 [btrfs]
__extent_read_full_page+0xe7/0x100 [btrfs]
? run_one_async_done+0xc0/0xc0 [btrfs]
read_extent_buffer_pages+0x1ab/0x2d0 [btrfs]
? run_one_async_done+0xc0/0xc0 [btrfs]
btree_read_extent_buffer_pages+0x94/0xf0 [btrfs]
read_tree_block+0x31/0x60 [btrfs]
read_block_for_search.isra.35+0xf0/0x2e0 [btrfs]
btrfs_search_slot+0x46b/0xa00 [btrfs]
? kmem_cache_alloc+0x1a8/0x510
? btrfs_get_token_32+0x5b/0x120 [btrfs]
find_parent_nodes+0x11d/0xeb0 [btrfs]
? leaf_space_used+0xb8/0xd0 [btrfs]
? btrfs_leaf_free_space+0x49/0x90 [btrfs]
? btrfs_find_all_roots_safe+0x93/0x100 [btrfs]
btrfs_find_all_roots_safe+0x93/0x100 [btrfs]
btrfs_find_all_roots+0x45/0x60 [btrfs]
btrfs_qgroup_trace_extent_post+0x20/0x40 [btrfs]
btrfs_add_delayed_data_ref+0x1a3/0x1d0 [btrfs]
btrfs_alloc_reserved_file_extent+0x38/0x40 [btrfs]
insert_reserved_file_extent.constprop.71+0x289/0x2e0 [btrfs]
btrfs_finish_ordered_io+0x2f4/0x7f0 [btrfs]
? pick_next_task_fair+0x2cd/0x530
? __switch_to+0x92/0x4b0
btrfs_worker_helper+0x81/0x300 [btrfs]
process_one_work+0x1da/0x3f0
worker_thread+0x2b/0x3f0
? process_one_work+0x3f0/0x3f0
kthread+0x11a/0x130
? kthread_create_on_node+0x40/0x40
ret_from_fork+0x35/0x40
BTRFS critical (device vda2): unable to find logical 8820195328 length 16384
BTRFS: error (device vda2) in btrfs_finish_ordered_io:3023: errno=-5 IO failure
BTRFS info (device vda2): forced readonly
BTRFS error (device vda2): pending csums is 2887680
[CAUSE]
It's caused by race with block group auto removal:
- There is a meta block group X, which has only one tree block
The tree block belongs to fs tree 257.
- In current transaction, some operation modified fs tree 257
The tree block get COWed, so the block group X is empty, and marked as
unused, queued to be deleted.
- Some workload (like fsync) wakes up cleaner_kthread()
Which will call btrfs_delete_unused_bgs() to remove unused block
groups.
So block group X along its chunk map get removed.
- Some delalloc work finished for fs tree 257
Quota needs to get the original reference of the extent, which will
read tree blocks of commit root of 257.
Then since the chunk map get removed, the above warning gets triggered.
[FIX]
Just let btrfs_delete_unused_bgs() to skip block group which still has
pinned bytes.
However there is a minor side effect, since currently we only queue
empty blocks at update_block_group(), and such empty block group with
pinned bytes won't go through update_block_group() again, such block
group won't be removed, until it get new extent allocated and removed.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/extent-tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0ca3999356c7..37d8927015d9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10702,7 +10702,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
/* Don't want to race with allocators so take the groups_sem */
down_write(&space_info->groups_sem);
spin_lock(&block_group->lock);
- if (block_group->reserved ||
+ if (block_group->reserved || block_group->pinned ||
btrfs_block_group_used(&block_group->item) ||
block_group->ro ||
list_is_singular(&block_group->list)) {
--
2.18.0