From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 448DEC43334 for ; Mon, 6 Jun 2022 19:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229928AbiFFTS3 (ORCPT ); Mon, 6 Jun 2022 15:18:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230475AbiFFTS2 (ORCPT ); Mon, 6 Jun 2022 15:18:28 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69939AFAF8; Mon, 6 Jun 2022 12:18:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Y8ptkrk4XEC5HIV2odtW0wPcnRHidH2SG3SnYcDw0Hs=; b=QdoGU4CiwUKCth0VhVwplDeCdu zCK2eocNCW437F9lFD8iWu41aTBLdaa/9qKsfP3RNJlu+lSUBroQLT2R4wXUa6NQbqfkM2BfyxPzY A4VQmBpcUqeHsBjgTmjFxC/BcjGBUsUk2L86FhL5RYTRCtGaSElPT5ho/T5aHRPH1A3yt3q0LaVcV xXENhNaFeSjubGSi2fyCfbeDEGDUmcnx+aU6eR+F22y0v7wNxXip7aqyeDCH1cY949dfZsLTHHcGm AOruk84wSlZ3VlWQdZXM5Q4PHoxwVM9UTzNOgQ87q6fTDJdgmUUCH4xTsmzYTf6SJ7HGDd4EmLtSw EEGh+4LQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nyIEw-00AwKS-7d; Mon, 06 Jun 2022 19:18:14 +0000 Date: Mon, 6 Jun 2022 20:18:14 +0100 From: Matthew Wilcox To: Stefan Roesch Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, david@fromorbit.com, jack@suse.cz, hch@infradead.org, axboe@kernel.dk Subject: Re: [PATCH v7 06/15] iomap: Return error code from iomap_write_iter() Message-ID: References: <20220601210141.3773402-1-shr@fb.com> <20220601210141.3773402-7-shr@fb.com> <0f83316c-3aa2-3cb6-ede1-c2dd2dd3ab31@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0f83316c-3aa2-3cb6-ede1-c2dd2dd3ab31@fb.com> Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Mon, Jun 06, 2022 at 09:39:03AM -0700, Stefan Roesch wrote: > > > On 6/2/22 5:38 AM, Matthew Wilcox wrote: > > On Wed, Jun 01, 2022 at 02:01:32PM -0700, Stefan Roesch wrote: > >> Change the signature of iomap_write_iter() to return an error code. In > >> case we cannot allocate a page in iomap_write_begin(), we will not retry > >> the memory alloction in iomap_write_begin(). > > > > loff_t can already represent an error code. And it's already used like > > that. > > > >> @@ -829,7 +830,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) > >> length -= status; > >> } while (iov_iter_count(i) && length); > >> > >> - return written ? written : status; > >> + *processed = written ? written : error; > >> + return error; > > > > I think the change you really want is: > > > > if (status == -EAGAIN) > > return -EAGAIN; > > if (written) > > return written; > > return status; > > > > I think the change needs to be: > > - return written ? written : status; > + if (status == -EAGAIN) { > + iov_iter_revert(i, written); > + return -EAGAIN; > + } > + if (written) > + return written; > + return status; Ah yes, I think you're right. Does it work to leave everything the way it is, call back into the iomap_write_iter() after having done a short write, get the -EAGAIN at that point and pass the already-advanced iterator to the worker thread? I haven't looked into the details of how that works, so maybe you just can't do that.