Re: [PATCH v3 4/5] btrfs: do not infinite loop in data reclaim if we aborted
From: Filipe Manana <hidden>
Date: 2021-09-28 10:23:06
On Mon, Sep 27, 2021 at 7:07 PM Josef Bacik [off-list ref] wrote:
Error injection stressing uncovered a busy loop in our data reclaim loop. There are two cases here, one where we loop creating block groups until space_info->full is set, or in the main loop we will skip erroring out any tickets if space_info->full == 0. Unfortunately if we aborted the transaction then we will never allocate chunks or reclaim any space and thus never get ->full, and you'll see stack traces like this watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [kworker/u4:4:139] CPU: 0 PID: 139 Comm: kworker/u4:4 Tainted: G W 5.13.0-rc1+ #328 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Workqueue: events_unbound btrfs_async_reclaim_data_space RIP: 0010:btrfs_join_transaction+0x12/0x20 RSP: 0018:ffffb2b780b77de0 EFLAGS: 00000246 RAX: ffffb2b781863d58 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000801 RSI: ffff987952b57400 RDI: ffff987940aa3000 RBP: ffff987954d55000 R08: 0000000000000001 R09: ffff98795539e8f0 R10: 000000000000000f R11: 000000000000000f R12: ffffffffffffffff R13: ffff987952b574c8 R14: ffff987952b57400 R15: 0000000000000008 FS: 0000000000000000(0000) GS:ffff9879bbc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0703da4000 CR3: 0000000113398004 CR4: 0000000000370ef0 Call Trace: flush_space+0x4a8/0x660 btrfs_async_reclaim_data_space+0x55/0x130 process_one_work+0x1e9/0x380 worker_thread+0x53/0x3e0 ? process_one_work+0x380/0x380 kthread+0x118/0x140 ? __kthread_bind_mask+0x60/0x60 ret_from_fork+0x1f/0x30 Fix this by checking to see if we have a btrfs fs error in either of the reclaim loops, and if so fail the tickets and bail. In addition to this, fix maybe_fail_all_tickets() to not try to grant tickets if we've aborted, simply fail everything. Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <redacted> Looks good, thanks.
quoted hunk ↗ jump to hunk
--- fs/btrfs/space-info.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c index aa5be0b24987..63423f9729c5 100644 --- a/fs/btrfs/space-info.c +++ b/fs/btrfs/space-info.c@@ -885,6 +885,7 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info, { struct reserve_ticket *ticket; u64 tickets_id = space_info->tickets_id; + const bool aborted = btrfs_has_fs_error(fs_info); trace_btrfs_fail_all_tickets(fs_info, space_info);@@ -898,16 +899,19 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info, ticket = list_first_entry(&space_info->tickets, struct reserve_ticket, list); - if (ticket->steal && + if (!aborted && ticket->steal && steal_from_global_rsv(fs_info, space_info, ticket)) return true; - if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) + if (!aborted && btrfs_test_opt(fs_info, ENOSPC_DEBUG)) btrfs_info(fs_info, "failing ticket with %llu bytes", ticket->bytes); remove_ticket(space_info, ticket); - ticket->error = -ENOSPC; + if (aborted) + ticket->error = -EIO; + else + ticket->error = -ENOSPC; wake_up(&ticket->wait); /*@@ -916,7 +920,8 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info, * here to see if we can make progress with the next ticket in * the list. */ - btrfs_try_granting_tickets(fs_info, space_info); + if (!aborted) + btrfs_try_granting_tickets(fs_info, space_info); } return (tickets_id != space_info->tickets_id); }@@ -1172,6 +1177,10 @@ static void btrfs_async_reclaim_data_space(struct work_struct *work) spin_unlock(&space_info->lock); return; } + + /* Something happened, fail everything and bail. */ + if (btrfs_has_fs_error(fs_info)) + goto aborted_fs; last_tickets_id = space_info->tickets_id; spin_unlock(&space_info->lock); }@@ -1202,9 +1211,19 @@ static void btrfs_async_reclaim_data_space(struct work_struct *work) } else { flush_state = 0; } + + /* Something happened, fail everything and bail. */ + if (btrfs_has_fs_error(fs_info)) + goto aborted_fs; + } spin_unlock(&space_info->lock); } + return; +aborted_fs: + maybe_fail_all_tickets(fs_info, space_info); + space_info->flush = 0; + spin_unlock(&space_info->lock); } void btrfs_init_async_reclaim_work(struct btrfs_fs_info *fs_info) --2.26.3
-- Filipe David Manana, “Whether you think you can, or you think you can't — you're right.”