Re: [PATCH v4 RESEND 2/2] buffer: record blockdev write errors in super_block that it backs

Jan Kara
2020-04-14T16:26:47Z

On Tue 14-04-20 08:04:09, Jeff Layton wrote:
> From: Jeff Layton <jlayton@redhat.com>
>
> When syncing out a block device (a'la __sync_blockdev), any error
> encountered will only be recorded in the bd_inode's mapping. When the
> blockdev contains a filesystem however, we'd like to also record the
> error in the super_block that's stored there.
>
> Make mark_buffer_write_io_error also record the error in the
> corresponding super_block when a writeback error occurs and the block
> device contains a mounted superblock.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

The patch looks good to me. I'd just note that bh->b_bdev->bd_super
dereference is safe only because we will flush all dirty data when
unmounting a filesystem which is somewhat tricky. Maybe that warrants a
comment? Otherwise feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/buffer.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index f73276d746bb..a9d986d27fa1 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1160,6 +1160,8 @@ void mark_buffer_write_io_error(struct buffer_head *bh)
> mapping_set_error(bh->b_page->mapping, -EIO);
> if (bh->b_assoc_map)
> mapping_set_error(bh->b_assoc_map, -EIO);
> + if (bh->b_bdev->bd_super)
> + errseq_set(&bh->b_bdev->bd_super->s_wb_err, -EIO);
> }
> EXPORT_SYMBOL(mark_buffer_write_io_error);
>
> --
> 2.25.2
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR