From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:52796) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hDRFt-0002sV-9G for qemu-devel@nongnu.org; Mon, 08 Apr 2019 06:11:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hDRFr-0005LD-Tv for qemu-devel@nongnu.org; Mon, 08 Apr 2019 06:11:57 -0400 Date: Mon, 8 Apr 2019 12:04:42 +0200 From: Kevin Wolf Message-ID: <20190408100442.GA11997@linux.fritz.box> References: <1554474244-553661-1-git-send-email-andrey.shinkevich@virtuozzo.com> <468cc6c9-c338-a4fe-57b1-b4df5b2b24c0@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <468cc6c9-c338-a4fe-57b1-b4df5b2b24c0@virtuozzo.com> 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 Cc: John Snow , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" , "fam@euphon.net" , Vladimir Sementsov-Ogievskiy , "mreitz@redhat.com" , "stefanha@redhat.com" , Denis Lunev Am 08.04.2019 um 11:44 hat Andrey Shinkevich geschrieben: > > > On 06/04/2019 01:50, John Snow wrote: > > > > > > 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 > > > > Thank you for your review, John! > > Let me clarify the circumstances and quote the bug report: > "Customer had Win-2012 VM with 50GB system disk which was later resized > to 256GB without resizing the partition inside VM. > Now, while trying to resize to 50G, the following error will appear > 'Failed to reduce the number of L2 tables: Invalid argument' > It was found that it is possible to shrink the disk to 128G and any size > above that number, but size below 128G will bring the mentioned error." > > The fallocate() returns no error on that file system if the offset and > the (offset + bytes) parameters of the bdrv_co_do_pwrite_zeroes() both > are aligned to 4K. What is the return value you get from this file system? Maybe turning that into ENOTSUP in file-posix would be less invasive. Just falling back for any error gives me the vague feeling that it could cause problems sooner or later. Kevin 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=-8.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 9CB93C10F14 for ; Mon, 8 Apr 2019 10:12:50 +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 716342148D for ; Mon, 8 Apr 2019 10:12:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 716342148D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:50539 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hDRGj-0003DX-Hl for qemu-devel@archiver.kernel.org; Mon, 08 Apr 2019 06:12:49 -0400 Received: from eggs.gnu.org ([209.51.188.92]:52796) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hDRFt-0002sV-9G for qemu-devel@nongnu.org; Mon, 08 Apr 2019 06:11:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hDRFr-0005LD-Tv for qemu-devel@nongnu.org; Mon, 08 Apr 2019 06:11:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46502) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hDRFn-0005Hk-RU; Mon, 08 Apr 2019 06:11:52 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6B54081243; Mon, 8 Apr 2019 10:04:48 +0000 (UTC) Received: from linux.fritz.box (ovpn-117-165.ams2.redhat.com [10.36.117.165]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2ACE75D719; Mon, 8 Apr 2019 10:04:43 +0000 (UTC) Date: Mon, 8 Apr 2019 12:04:42 +0200 From: Kevin Wolf To: Andrey Shinkevich Message-ID: <20190408100442.GA11997@linux.fritz.box> References: <1554474244-553661-1-git-send-email-andrey.shinkevich@virtuozzo.com> <468cc6c9-c338-a4fe-57b1-b4df5b2b24c0@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <468cc6c9-c338-a4fe-57b1-b4df5b2b24c0@virtuozzo.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 08 Apr 2019 10:04:48 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] block/io.c: fix for the allocation failure X-BeenThere: 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" , Vladimir Sementsov-Ogievskiy , Denis Lunev , "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" , "mreitz@redhat.com" , "stefanha@redhat.com" , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190408100442.rzSKMqL3bcpumUB2fTe9iYXyekiC_5ncHq4U3YjiDcI@z> Am 08.04.2019 um 11:44 hat Andrey Shinkevich geschrieben: > > > On 06/04/2019 01:50, John Snow wrote: > > > > > > 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 > > > > Thank you for your review, John! > > Let me clarify the circumstances and quote the bug report: > "Customer had Win-2012 VM with 50GB system disk which was later resized > to 256GB without resizing the partition inside VM. > Now, while trying to resize to 50G, the following error will appear > 'Failed to reduce the number of L2 tables: Invalid argument' > It was found that it is possible to shrink the disk to 128G and any size > above that number, but size below 128G will bring the mentioned error." > > The fallocate() returns no error on that file system if the offset and > the (offset + bytes) parameters of the bdrv_co_do_pwrite_zeroes() both > are aligned to 4K. What is the return value you get from this file system? Maybe turning that into ENOTSUP in file-posix would be less invasive. Just falling back for any error gives me the vague feeling that it could cause problems sooner or later. Kevin