linux-kernel - Re: [PATCH v2 1/4] fs: fix data invalidation in the cleancache during direct IO

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Date:   Tue, 25 Apr 2017 10:25:45 +0200
From:   Jan Kara <jack@...e.cz>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>, stable@...r.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>,
        Alexey Kuznetsov <kuznet@...tuozzo.com>,
        Christoph Hellwig <hch@....de>,
        Nikolay Borisov <n.borisov.lkml@...il.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v2 1/4] fs: fix data invalidation in the cleancache
 during direct IO

On Mon 24-04-17 19:41:32, Andrey Ryabinin wrote:
> Some direct IO write fs hooks call invalidate_inode_pages2[_range]()
> conditionally iff mapping->nrpages is not zero. This can't be right,
> because invalidate_inode_pages2[_ragne]() also invalidate data in
> the cleancache via cleancache_invalidate_inode() call.
> So if page cache is empty but there is some data in the cleancache,
> buffered read after direct IO write would get stale data from
> the cleancache.
> 
> Also it doesn't feel right to check only for ->nrpages because
> invalidate_inode_pages2[_range] invalidates exceptional entries as well.
> 
> Fix this by calling invalidate_inode_pages2[_range]() regardless of nrpages
> state.
> 
> Note: nfs,cifs,9p doesn't need similar fix because the never call
> cleancache_get_page() (nor directly, nor via mpage_readpage[s]()), so they
> are not affected by this bug.
> 
> Fixes: c515e1fd361c ("mm/fs: add hooks to support cleancache")
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: <stable@...r.kernel.org>

OK, looks good. You can add:

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

								Honza


> ---
>  fs/iomap.c   | 18 ++++++++----------
>  mm/filemap.c | 26 +++++++++++---------------
>  2 files changed, 19 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/iomap.c b/fs/iomap.c
> index cdeed39..f6a6013 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -881,16 +881,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  		flags |= IOMAP_WRITE;
>  	}
>  
> -	if (mapping->nrpages) {
> -		ret = filemap_write_and_wait_range(mapping, start, end);
> -		if (ret)
> -			goto out_free_dio;
> +	ret = filemap_write_and_wait_range(mapping, start, end);
> +	if (ret)
> +		goto out_free_dio;
>  
> -		ret = invalidate_inode_pages2_range(mapping,
> -				start >> PAGE_SHIFT, end >> PAGE_SHIFT);
> -		WARN_ON_ONCE(ret);
> -		ret = 0;
> -	}
> +	ret = invalidate_inode_pages2_range(mapping,
> +			start >> PAGE_SHIFT, end >> PAGE_SHIFT);
> +	WARN_ON_ONCE(ret);
> +	ret = 0;
>  
>  	inode_dio_begin(inode);
>  
> @@ -945,7 +943,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
>  	 * this invalidation fails, tough, the write still worked...
>  	 */
> -	if (iov_iter_rw(iter) == WRITE && mapping->nrpages) {
> +	if (iov_iter_rw(iter) == WRITE) {
>  		int err = invalidate_inode_pages2_range(mapping,
>  				start >> PAGE_SHIFT, end >> PAGE_SHIFT);
>  		WARN_ON_ONCE(err);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 9eab40e..b7b973b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2720,18 +2720,16 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
>  	 * about to write.  We do this *before* the write so that we can return
>  	 * without clobbering -EIOCBQUEUED from ->direct_IO().
>  	 */
> -	if (mapping->nrpages) {
> -		written = invalidate_inode_pages2_range(mapping,
> +	written = invalidate_inode_pages2_range(mapping,
>  					pos >> PAGE_SHIFT, end);
> -		/*
> -		 * If a page can not be invalidated, return 0 to fall back
> -		 * to buffered write.
> -		 */
> -		if (written) {
> -			if (written == -EBUSY)
> -				return 0;
> -			goto out;
> -		}
> +	/*
> +	 * If a page can not be invalidated, return 0 to fall back
> +	 * to buffered write.
> +	 */
> +	if (written) {
> +		if (written == -EBUSY)
> +			return 0;
> +		goto out;
>  	}
>  
>  	written = mapping->a_ops->direct_IO(iocb, from);
> @@ -2744,10 +2742,8 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
>  	 * so we don't support it 100%.  If this invalidation
>  	 * fails, tough, the write still worked...
>  	 */
> -	if (mapping->nrpages) {
> -		invalidate_inode_pages2_range(mapping,
> -					      pos >> PAGE_SHIFT, end);
> -	}
> +	invalidate_inode_pages2_range(mapping,
> +				pos >> PAGE_SHIFT, end);
>  
>  	if (written > 0) {
>  		pos += written;
> -- 
> 2.10.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR