linux-kernel - Re: [PATCH v2 6/9] mm: set mapping error when launder

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Date:   Wed, 8 Mar 2017 18:01:47 +0000
From:   Trond Myklebust <trondmy@...marydata.com>
To:     "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "jlayton@...hat.com" <jlayton@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:     "linux-nilfs@...r.kernel.org" <linux-nilfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "konishi.ryusuke@....ntt.co.jp" <konishi.ryusuke@....ntt.co.jp>,
        "neilb@...e.com" <neilb@...e.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "adilger@...ger.ca" <adilger@...ger.ca>,
        "James.Bottomley@...senPartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>,
        "openosd@...il.com" <openosd@...il.com>,
        "jack@...e.cz" <jack@...e.cz>
Subject: Re: [PATCH v2 6/9] mm: set mapping error when launder_pages fails

On Wed, 2017-03-08 at 11:29 -0500, Jeff Layton wrote:
> If launder_page fails, then we hit a problem writing back some inode
> data. Ensure that we communicate that fact in a subsequent fsync
> since
> another task could still have it open for write.
> 
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  mm/truncate.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 6263affdef88..29ae420a5bf9 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -594,11 +594,15 @@ invalidate_complete_page2(struct address_space
> *mapping, struct page *page)
>  
>  static int do_launder_page(struct address_space *mapping, struct
> page *page)
>  {
> +	int ret;
> +
>  	if (!PageDirty(page))
>  		return 0;
>  	if (page->mapping != mapping || mapping->a_ops->launder_page 
> == NULL)
>  		return 0;
> -	return mapping->a_ops->launder_page(page);
> +	ret = mapping->a_ops->launder_page(page);
> +	mapping_set_error(mapping, ret);
> +	return ret;
>  }
>  
>  /**

No. At that layer, you don't know that this is a page error. In the NFS
case, it could, for instance, just as well be a fatal signal.

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@...marydata.com