linux-ext4 - Re: [PATCH v4 21/27] mm: clean up error handling in write_one

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Date:   Mon, 15 May 2017 14:01:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-cifs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, jfs-discussion@...ts.sourceforge.net,
        linux-xfs@...r.kernel.org, cluster-devel@...hat.com,
        linux-f2fs-devel@...ts.sourceforge.net,
        v9fs-developer@...ts.sourceforge.net, linux-nilfs@...r.kernel.org,
        linux-block@...r.kernel.org, dhowells@...hat.com,
        akpm@...ux-foundation.org, hch@...radead.org,
        ross.zwisler@...ux.intel.com, mawilcox@...rosoft.com,
        jack@...e.com, viro@...iv.linux.org.uk, corbet@....net,
        neilb@...e.de, clm@...com, tytso@....edu, axboe@...nel.dk,
        josef@...icpanda.com, hubcap@...ibond.com, rpeterso@...hat.com,
        bo.li.liu@...cle.com
Subject: Re: [PATCH v4 21/27] mm: clean up error handling in write_one_page

On Tue 09-05-17 11:49:24, Jeff Layton wrote:
> Don't try to check PageError since that's potentially racy and not
> necessarily going to be set after writepage errors out.
> 
> Instead, sample the mapping error early on, and use that value to tell
> us whether we got a writeback error since then.
> 
> Signed-off-by: Jeff Layton <jlayton@...hat.com>

Looks good to me. You can add:

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

								Honza

> ---
>  mm/page-writeback.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index de0dbf12e2c1..1643456881b4 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2373,11 +2373,12 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  int write_one_page(struct page *page)
>  {
>  	struct address_space *mapping = page->mapping;
> -	int ret = 0;
> +	int ret = 0, ret2;
>  	struct writeback_control wbc = {
>  		.sync_mode = WB_SYNC_ALL,
>  		.nr_to_write = 1,
>  	};
> +	errseq_t since = filemap_sample_wb_error(mapping);
>  
>  	BUG_ON(!PageLocked(page));
>  
> @@ -2386,16 +2387,14 @@ int write_one_page(struct page *page)
>  	if (clear_page_dirty_for_io(page)) {
>  		get_page(page);
>  		ret = mapping->a_ops->writepage(page, &wbc);
> -		if (ret == 0) {
> +		if (ret == 0)
>  			wait_on_page_writeback(page);
> -			if (PageError(page))
> -				ret = -EIO;
> -		}
>  		put_page(page);
>  	} else {
>  		unlock_page(page);
>  	}
> -	return ret;
> +	ret2 = filemap_check_wb_error(mapping, since);
> +	return ret ? : ret2;
>  }
>  EXPORT_SYMBOL(write_one_page);
>  
> -- 
> 2.9.3
> 
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR