Commit 0e24f6d8 authored Oct 05, 2021 by Josef Bacik Committed by David Sterba Oct 26, 2021

btrfs: do not infinite loop in data reclaim if we aborted



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.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 84961539

fs/btrfs/space-info.c

+24 −4

Original line number	Diff line number	Diff line
		@@ -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_FS_ERROR(fs_info);

		trace_btrfs_fail_all_tickets(fs_info, space_info);

		@@ -898,15 +899,18 @@ 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);
		if (aborted)
		ticket->error = -EIO;
		else
		ticket->error = -ENOSPC;
		wake_up(&ticket->wait);

		@@ -916,6 +920,7 @@ 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.
		*/
		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_FS_ERROR(fs_info))
		goto aborted_fs;
		last_tickets_id = space_info->tickets_id;
		spin_unlock(&space_info->lock);
		}
		@@ -1202,9 +1211,20 @@ static void btrfs_async_reclaim_data_space(struct work_struct *work)
		} else {
		flush_state = 0;
		}

		/* Something happened, fail everything and bail. */
		if (BTRFS_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)