linux-kernel - Re: [PATCH v4 RESEND 2/2] buffer: record blockdev write errors in super

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Message-ID: <20200414162639.GK28226@quack2.suse.cz>
Date:   Tue, 14 Apr 2020 18:26:39 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        andres@...razel.de, willy@...radead.org, dhowells@...hat.com,
        hch@...radead.org, jack@...e.cz, akpm@...ux-foundation.org,
        david@...morbit.com
Subject: Re: [PATCH v4 RESEND 2/2] buffer: record blockdev write errors in
 super_block that it backs

On Tue 14-04-20 08:04:09, Jeff Layton wrote:
> From: Jeff Layton <jlayton@...hat.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@...nel.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@...e.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@...e.com>
SUSE Labs, CR