linux-kernel - Re: [PATCH v2 16/16] iomap: Make readpage synchronous

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Message-ID: <20201016063546.GA4808@infradead.org>
Date:   Fri, 16 Oct 2020 07:35:46 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        linux-afs@...ts.infradead.org, ceph-devel@...r.kernel.org,
        linux-cifs@...r.kernel.org, ecryptfs@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-mtd@...ts.infradead.org,
        Richard Weinberger <richard@....at>, linux-xfs@...r.kernel.org
Subject: Re: [PATCH v2 16/16] iomap: Make readpage synchronous

On Thu, Oct 15, 2020 at 08:03:12PM +0100, Matthew Wilcox wrote:
> I honestly don't see the problem.  We have to assign the status
> conditionally anyway so we don't overwrite an error with a subsequent
> success.

Yes, but having a potential NULL pointer to a common structure is just
waiting for trouble.

> 
> > True.  I'd still prefer the AOP_UPDATED_PAGE as the fallthrough case
> > and an explicit goto out_unlock, though.
> 
> So this?
> 
>         if (ctx.bio) {
>                 submit_bio(ctx.bio);
>                 wait_for_completion(&ctx.done);
>                 if (ret < 0)
>                         goto err;
>                 ret = blk_status_to_errno(ctx.status);
>         }
> 
>         if (ret < 0)
>                 goto err;
>         return AOP_UPDATED_PAGE;
> err:
>         unlock_page(page);
>         return ret;
> 

Looks good.