From: Naohiro Aota naohiro.aota@wdc.com
commit ca5e4ea0beaec8bc674121838bf8614c089effb9 upstream.
There is a hung_task issue with running generic/068 on an SMR device. The hang occurs while a process is trying to thaw the filesystem. The process is trying to take sb->s_umount to thaw the FS. The lock is held by fsstress, which calls btrfs_sync_fs() and is waiting for an ordered extent to finish. However, as the FS is frozen, the ordered extents never finish.
Having an ordered extent while the FS is frozen is the root cause of the hang. The ordered extent is initiated from btrfs_relocate_chunk() which is called from btrfs_reclaim_bgs_work().
This commit adds sb_*_write() around btrfs_relocate_chunk() call site. For the usual "btrfs balance" command, we already call it with mnt_want_file() in btrfs_ioctl_balance().
Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones") CC: stable@vger.kernel.org # 5.13+ Link: https://github.com/naota/linux/issues/56 Reviewed-by: Johannes Thumshirn johannes.thumshirn@wdc.com Signed-off-by: Naohiro Aota naohiro.aota@wdc.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/block-group.c | 8 +++++++- fs/btrfs/volumes.c | 3 +++ 2 files changed, 10 insertions(+), 1 deletion(-)
--- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1521,8 +1521,12 @@ void btrfs_reclaim_bgs_work(struct work_ if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags)) return;
- if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) + sb_start_write(fs_info->sb); + + if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) { + sb_end_write(fs_info->sb); return; + }
/* * Long running balances can keep us blocked here for eternity, so @@ -1530,6 +1534,7 @@ void btrfs_reclaim_bgs_work(struct work_ */ if (!mutex_trylock(&fs_info->reclaim_bgs_lock)) { btrfs_exclop_finish(fs_info); + sb_end_write(fs_info->sb); return; }
@@ -1604,6 +1609,7 @@ next: spin_unlock(&fs_info->unused_bgs_lock); mutex_unlock(&fs_info->reclaim_bgs_lock); btrfs_exclop_finish(fs_info); + sb_end_write(fs_info->sb); }
void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info) --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -8263,10 +8263,12 @@ static int relocating_repair_kthread(voi target = cache->start; btrfs_put_block_group(cache);
+ sb_start_write(fs_info->sb); if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) { btrfs_info(fs_info, "zoned: skip relocating block group %llu to repair: EBUSY", target); + sb_end_write(fs_info->sb); return -EBUSY; }
@@ -8294,6 +8296,7 @@ out: btrfs_put_block_group(cache); mutex_unlock(&fs_info->reclaim_bgs_lock); btrfs_exclop_finish(fs_info); + sb_end_write(fs_info->sb);
return ret; }