From: Qu Wenruo wqu@suse.com
[ Upstream commit 43794446548730ac8461be30bbe47d5d027d1d16 ]
[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 gets 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 gets removed, the above warning gets triggered.
[FIX] Just let btrfs_delete_unused_bgs() skip block group which still has pinned bytes.
However there is a minor side effect: 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 gets 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 Signed-off-by: Sasha Levin alexander.levin@microsoft.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 f7a96f7871b7..95c9ad49a3d5 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -10687,7 +10687,7 @@ 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)) {