From:   "Benjamin Coddington" <bcodding@redhat.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH v2] NFS: Don't use page_file_mapping after removing the
 page
Date:   Tue, 12 Feb 2019 13:52:36 -0500
Message-ID: <D1443158-8840-4D21-8215-68B96138F45C@redhat.com>
In-Reply-To: <5eb439e690e72e3a69ad0a5bb48827c7e5ce32a8.1549451324.git.bcodding@redhat.com>
References: <5eb439e690e72e3a69ad0a5bb48827c7e5ce32a8.1549451324.git.bcodding@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; format=flowed
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

Hi Trond and Anna,

I want to bump this.  The problem we created is easier to hit now than 
the problem we were fixing, so something should be done for 5.0 if 
possible.

Ben

On 6 Feb 2019, at 6:09, Benjamin Coddington wrote:

> If nfs_page_async_flush() removes the page from the mapping, then we 
> can't
> use page_file_mapping() on it as nfs_updatepate() is wont to do when
> receiving an error.  Instead, push the mapping to the stack before the 
> page
> is possibly truncated.
>
> Fixes: 8fc75bed96bb ("NFS: Fix up return value on fatal errors in 
> nfs_page_async_flush()")
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---
>  fs/nfs/write.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index f12cb31a41e5..d09c9f878141 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -238,9 +238,9 @@ static void nfs_grow_file(struct page *page, 
> unsigned int offset, unsigned int c
>  }
>
>  /* A writeback failed: mark the page as bad, and invalidate the page 
> cache */
> -static void nfs_set_pageerror(struct page *page)
> +static void nfs_set_pageerror(struct address_space *mapping)
>  {
> -	nfs_zap_mapping(page_file_mapping(page)->host, 
> page_file_mapping(page));
> +	nfs_zap_mapping(mapping->host, mapping);
>  }
>
>  /*
> @@ -994,7 +994,7 @@ static void nfs_write_completion(struct 
> nfs_pgio_header *hdr)
>  		nfs_list_remove_request(req);
>  		if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) &&
>  		    (hdr->good_bytes < bytes)) {
> -			nfs_set_pageerror(req->wb_page);
> +			nfs_set_pageerror(page_file_mapping(req->wb_page));
>  			nfs_context_set_write_error(req->wb_context, hdr->error);
>  			goto remove_req;
>  		}
> @@ -1348,7 +1348,8 @@ int nfs_updatepage(struct file *file, struct 
> page *page,
>  		unsigned int offset, unsigned int count)
>  {
>  	struct nfs_open_context *ctx = nfs_file_open_context(file);
> -	struct inode	*inode = page_file_mapping(page)->host;
> +	struct address_space *mapping = page_file_mapping(page);
> +	struct inode	*inode = mapping->host;
>  	int		status = 0;
>
>  	nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
> @@ -1366,7 +1367,7 @@ int nfs_updatepage(struct file *file, struct 
> page *page,
>
>  	status = nfs_writepage_setup(ctx, page, offset, count);
>  	if (status < 0)
> -		nfs_set_pageerror(page);
> +		nfs_set_pageerror(mapping);
>  	else
>  		__set_page_dirty_nobuffers(page);
>  out:
> -- 
> 2.14.3