Re: [PATCH v3 0/2] btrfs: zoned: mark relocation as writing

[David Sterba <dsterba@suse.cz>]

On Fri, Feb 18, 2022 at 01:14:17PM +0900, Naohiro Aota wrote:
> 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 extent 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().
> 
> The first patch is a preparation patch to add asserting functions to
> check if sb_start_{write,pagefault,intwrite} is called.
> 
> The second patch adds sb_{start,end}_write and the assert function at
> proper places.
> 
> Changelog:
> v3:
>   - Return bool instead of asserting and let caller decide what to do
>     (suggested by Dave Chinner)
> v2:
>   - Implement asserting functions not to directly touch the internal
>     implementation
> 
> Naohiro Aota (2):
>   fs: add asserting functions for sb_start_{write,pagefault,intwrite}
>   btrfs: zoned: mark relocation as writing

Topic branch updated, thanks.