linux-ext4 - Re: [PATCH] mm: have filemap_check_and_advance_wb_err clear AS_EIO/AS

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Date:   Mon, 25 Sep 2017 15:53:12 -0400
From:   Jeff Layton <jlayton@...chiereds.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Eryu Guan <eguan@...hat.com>, Jan Kara <jack@...e.cz>,
        linux-ext4@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] mm: have filemap_check_and_advance_wb_err clear
 AS_EIO/AS_ENOSPC

On Fri, 2017-09-22 at 09:33 -0400, Jeff Layton wrote:
> From: Jeff Layton <jlayton@...hat.com>
> 
> Eryu noticed that he could sometimes get a leftover error reported when
> it shouldn't be on fsync with ext2 and non-journalled ext4. The problem
> is that writeback_single_inode still uses filemap_fdatawait. That picks
> up a previously set AS_EIO flag, which would ordinarily have been
> cleared before.
> 
> Since we're mostly using this function as a replacement for
> filemap_check_errors, have filemap_check_and_advance_wb_err clear AS_EIO
> and AS_ENOSPC when reporting an error. That should allow the new
> function to better emulate the behavior of the old with respect to these
> flags.
> 
> Reported-by: Eryu Guan <eguan@...hat.com>
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  mm/filemap.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 870971e20967..404722ea0fdd 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -620,6 +620,14 @@ int file_check_and_advance_wb_err(struct file *file)
>  		trace_file_check_and_advance_wb_err(file, old);
>  		spin_unlock(&file->f_lock);
>  	}
> +
> +	/*
> +	 * We're mostly using this function as a drop in replacement for
> +	 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
> +	 * that the legacy code would have had on these flags.
> +	 */
> +	clear_bit(AS_EIO, &mapping->flags);
> +	clear_bit(AS_ENOSPC, &mapping->flags);
>  	return err;
>  }
>  EXPORT_SYMBOL(file_check_and_advance_wb_err);

Andrew, would you mind picking this patch up? It seems to work fine for
me, but it wouldn't hurt to let it stew in linux-next for a bit.

Thanks,
-- 
Jeff Layton <jlayton@...chiereds.net>