From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46128) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hCXsL-0007kA-Q3 for qemu-devel@nongnu.org; Fri, 05 Apr 2019 19:03:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hCXf3-0007Kb-8m for qemu-devel@nongnu.org; Fri, 05 Apr 2019 18:50:14 -0400 References: <1554474244-553661-1-git-send-email-andrey.shinkevich@virtuozzo.com> From: John Snow Message-ID: Date: Fri, 5 Apr 2019 18:50:03 -0400 MIME-Version: 1.0 In-Reply-To: <1554474244-553661-1-git-send-email-andrey.shinkevich@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] block/io.c: fix for the allocation failure List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andrey Shinkevich , qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: fam@euphon.net, kwolf@redhat.com, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org On 4/5/19 10:24 AM, Andrey Shinkevich wrote: > On a file system used by the customer, fallocate() returns an error > if the block is not properly aligned. So, bdrv_co_pwrite_zeroes() > fails. We can handle that case the same way as it is done for the > unsupported cases, namely, call to bdrv_driver_pwritev() that writes > zeroes to an image for the unaligned chunk of the block. > > Suggested-by: Denis V. Lunev > Signed-off-by: Andrey Shinkevich > --- > block/io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/io.c b/block/io.c > index dfc153b..0412a51 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1516,7 +1516,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, > assert(!bs->supported_zero_flags); > } > > - if (ret == -ENOTSUP && !(flags & BDRV_REQ_NO_FALLBACK)) { > + if (ret < 0 && !(flags & BDRV_REQ_NO_FALLBACK)) { > /* Fall back to bounce buffer if write zeroes is unsupported */ > BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE; > > I suppose that if fallocate fails for any reason and we're allowing fallback, we're either going to succeed ... or fail again very soon thereafter. Are there any cases where it is vital to not ignore the first fallocate failure? I'm a little wary of ignoring the return code from bdrv_co_pwrite_zeroes, but I am assuming that if there is a "real" failure here that the following bounce writes will also fail "safely." I'm not completely confident, but I have no tangible objections: Reviewed-by: John Snow 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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A713C282CE for ; Fri, 5 Apr 2019 23:05:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5725D2175B for ; Fri, 5 Apr 2019 23:05:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5725D2175B Authentication-Results: mail.kernel.org; dmarc=fail (p=none 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qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fam@euphon.net, kwolf@redhat.com, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190405225003.HB_8th4Tgm_LVdeEciegzkQIr5h40io4SVjCvBqS0us@z> On 4/5/19 10:24 AM, Andrey Shinkevich wrote: > On a file system used by the customer, fallocate() returns an error > if the block is not properly aligned. So, bdrv_co_pwrite_zeroes() > fails. We can handle that case the same way as it is done for the > unsupported cases, namely, call to bdrv_driver_pwritev() that writes > zeroes to an image for the unaligned chunk of the block. > > Suggested-by: Denis V. Lunev > Signed-off-by: Andrey Shinkevich > --- > block/io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/io.c b/block/io.c > index dfc153b..0412a51 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1516,7 +1516,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, > assert(!bs->supported_zero_flags); > } > > - if (ret == -ENOTSUP && !(flags & BDRV_REQ_NO_FALLBACK)) { > + if (ret < 0 && !(flags & BDRV_REQ_NO_FALLBACK)) { > /* Fall back to bounce buffer if write zeroes is unsupported */ > BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE; > > I suppose that if fallocate fails for any reason and we're allowing fallback, we're either going to succeed ... or fail again very soon thereafter. Are there any cases where it is vital to not ignore the first fallocate failure? I'm a little wary of ignoring the return code from bdrv_co_pwrite_zeroes, but I am assuming that if there is a "real" failure here that the following bounce writes will also fail "safely." I'm not completely confident, but I have no tangible objections: Reviewed-by: John Snow