linux-kernel - Re: [PATCH v2 3/3] fs: warn if stale pagecache is left after direct write

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Date:   Thu, 21 Nov 2019 17:23:58 +0100
From:   Jan Kara <jack@...e.cz>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 3/3] fs: warn if stale pagecache is left after direct
 write

On Sat 02-11-19 16:13:03, Konstantin Khlebnikov wrote:
> Function generic_file_direct_write() tries to invalidate pagecache after
> O_DIRECT write. Unlike to similar code in dio_complete() this silently
> ignores error returned from invalidate_inode_pages2_range().
> 
> According to comment this code here because not all filesystems call
> dio_complete() to do proper invalidation after O_DIRECT write.
> Noticeable example is a blkdev_direct_IO().
> 
> This patch calls dio_warn_stale_pagecache() if invalidation fails.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

Looks good to me. You can add:

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

								Honza

> ---
>  mm/filemap.c |    8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 189b8f318da2..dc3b78db079b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3241,11 +3241,13 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
>  	 * do not end up with dio_complete() being called, so let's not break
>  	 * them by removing it completely.
>  	 *
> +	 * Noticeable example is a blkdev_direct_IO().
> +	 *
>  	 * Skip invalidation for async writes or if mapping has no pages.
>  	 */
> -	if (written > 0 && mapping->nrpages)
> -		invalidate_inode_pages2_range(mapping,
> -					pos >> PAGE_SHIFT, end);
> +	if (written > 0 && mapping->nrpages &&
> +	    invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
> +		dio_warn_stale_pagecache(file);
>  
>  	if (written > 0) {
>  		pos += written;
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR