linux-kernel - Re: [PATCH v2 06/17] mm: doc comment for scary spot in write_one

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Message-ID: <1492002094.2937.4.camel@redhat.com>
Date:   Wed, 12 Apr 2017 09:01:34 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        tytso@....edu, jack@...e.cz, willy@...radead.org, neilb@...e.com,
        viro@...iv.linux.org.uk
Subject: Re: [PATCH v2 06/17] mm: doc comment for scary spot in
 write_one_page

On Wed, 2017-04-12 at 08:06 -0400, Jeff Layton wrote:
> Not sure what to do here just yet.
> 
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  mm/page-writeback.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index de0dbf12e2c1..3ac8399dc984 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2388,6 +2388,12 @@ int write_one_page(struct page *page)
>  		ret = mapping->a_ops->writepage(page, &wbc);
>  		if (ret == 0) {
>  			wait_on_page_writeback(page);
> +			/*
> +			 * FIXME: is this racy? What guarantees that PG_error
> +			 * will still be set once we get around to checking it?
> +			 * What if writeback fails, but then a read is issued
> +			 * before we check this, and that calls ClearPageError?
> +			 */
>  			if (PageError(page))
>  				ret = -EIO;
>  		}

Ahh, we are always under the page lock here, and this is generally used
for writing out directory pages anyway. I'm fine with dropping this
patch unless someone else sees a problem here.
-- 
Jeff Layton <jlayton@...hat.com>