linux-kernel - Re: [PATCH v3 10/20] fuse: set mapping error in writepage

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Date:   Mon, 24 Apr 2017 13:14:36 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-cifs@...r.kernel.org, linux-mm@...ck.org,
        jfs-discussion@...ts.sourceforge.net, linux-xfs@...r.kernel.org,
        cluster-devel@...hat.com, linux-f2fs-devel@...ts.sourceforge.net,
        v9fs-developer@...ts.sourceforge.net, osd-dev@...n-osd.org,
        linux-nilfs@...r.kernel.org, linux-block@...r.kernel.org,
        dhowells@...hat.com, akpm@...ux-foundation.org, hch@...radead.org,
        ross.zwisler@...ux.intel.com, mawilcox@...rosoft.com,
        jack@...e.com, viro@...iv.linux.org.uk, corbet@....net,
        neilb@...e.de, clm@...com, tytso@....edu, axboe@...nel.dk
Subject: Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked
 when it fails

On Mon, 2017-04-24 at 18:04 +0200, Jan Kara wrote:
> On Mon 24-04-17 09:22:49, Jeff Layton wrote:
> > This ensures that we see errors on fsync when writeback fails.
> > 
> > Signed-off-by: Jeff Layton <jlayton@...hat.com>
> 
> Hum, but do we really want to clobber mapping errors with temporary stuff
> like ENOMEM? Or do you want to handle that in mapping_set_error?
> 

Right now we don't really have such a thing as temporary errors in the
writeback codepath. If you return an error here, the data doesn't stay
dirty or anything, and I think we want to ensure that that gets reported
via fsync.

I'd like to see us add better handling for retryable errors for stuff
like ENOMEM or EAGAIN. I think this is the first step toward that
though. Once we have more consistent handling of writeback errors in
general, then we can start doing more interesting things with retryable
errors.

So yeah, I this is the right thing to do for now.

> 
> > ---
> >  fs/fuse/file.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > index ec238fb5a584..07d0efcb050c 100644
> > --- a/fs/fuse/file.c
> > +++ b/fs/fuse/file.c
> > @@ -1669,6 +1669,7 @@ static int fuse_writepage_locked(struct page *page)
> >  err_free:
> >  	fuse_request_free(req);
> >  err:
> > +	mapping_set_error(page->mapping, error);
> >  	end_page_writeback(page);
> >  	return error;
> >  }
> > -- 
> > 2.9.3
> > 
> > 

-- 
Jeff Layton <jlayton@...hat.com>