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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 08B1BC282E1 for ; Fri, 24 May 2019 23:38:48 +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 BD6722184E for ; Fri, 24 May 2019 23:38:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD6722184E 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]:33200 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hUJlu-0002ii-KV for qemu-devel@archiver.kernel.org; Fri, 24 May 2019 19:38:46 -0400 Received: from eggs.gnu.org ([209.51.188.92]:57618) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hUJkz-0002Na-8a for qemu-devel@nongnu.org; Fri, 24 May 2019 19:37:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hUJkw-0001s1-4n for qemu-devel@nongnu.org; Fri, 24 May 2019 19:37:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46242) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hUJkq-0001nD-V6; Fri, 24 May 2019 19:37:41 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E3209368E3; Fri, 24 May 2019 23:37:39 +0000 (UTC) Received: from [10.10.123.140] (ovpn-123-140.rdu2.redhat.com [10.10.123.140]) by smtp.corp.redhat.com (Postfix) with ESMTP id DD4D219069; Fri, 24 May 2019 23:37:37 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org References: <20190523154733.54944-1-vsementsov@virtuozzo.com> <20190523154733.54944-3-vsementsov@virtuozzo.com> From: John Snow Openpgp: preference=signencrypt Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef rj8u5BN93s5uCVTus0oiVA6W+iXYzTvVDStMFVqnTxSxlpZoH5RGKvmoWV3uutByQyBPHW2U 1Y6n6iEZ9MlP3hcDqlo0S8jeP03HaD4gOqCuqLceWF5+2WyHzNfylpNMFVi+Hp0H/nSDtCvQ 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i0HjnLoJP5jDcoMTabZTIazXmJz3pKM11HYJ5/ZsTIf3ZRJJKIvXJpbmcAPVwTZII6XxiJdh RSSX4Mvd5pL/+5WI6NTdW6DMfigTtdd85fe6PwBNVJL2ZvBfsBJZ5rxg1TOH3KLsYBqBTgW2 glQofxhkJhDEcvjLhe3Y2BlbCWKOmvM8XS9TRt0OwUs= Message-ID: <2a5e3401-34fe-c0ba-7f73-5a05add965e9@redhat.com> Date: Fri, 24 May 2019 19:37:36 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190523154733.54944-3-vsementsov@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 24 May 2019 23:37:39 +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] [PATCH 2/3] block/qcow2-bitmap: get rid of bdrv_has_changed_persistent_bitmaps 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, kwolf@redhat.com, den@openvz.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/23/19 11:47 AM, Vladimir Sementsov-Ogievskiy wrote: > Firstly, no reason to optimize failure path. Then, function name is > ambiguous: it checks for readonly and similar things, but someone may > think that it will ignore normal bitmaps which was just unchanged, and > this is in bad relation with the fact that we should drop IN_USE flag > for unchanged bitmaps in the image. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > include/block/dirty-bitmap.h | 1 - > block/dirty-bitmap.c | 12 ------------ > block/qcow2-bitmap.c | 23 +++++++++++++---------- > 3 files changed, 13 insertions(+), 23 deletions(-) > > diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h > index 8044ace63e..816022972b 100644 > --- a/include/block/dirty-bitmap.h > +++ b/include/block/dirty-bitmap.h > @@ -105,7 +105,6 @@ bool bdrv_has_readonly_bitmaps(BlockDriverState *bs); > bool bdrv_dirty_bitmap_get_autoload(const BdrvDirtyBitmap *bitmap); > bool bdrv_dirty_bitmap_get_persistence(BdrvDirtyBitmap *bitmap); > bool bdrv_dirty_bitmap_inconsistent(const BdrvDirtyBitmap *bitmap); > -bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs); > BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs, > BdrvDirtyBitmap *bitmap); > char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp); > diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c > index 59e6ebb861..eca2eed0bf 100644 > --- a/block/dirty-bitmap.c > +++ b/block/dirty-bitmap.c > @@ -775,18 +775,6 @@ bool bdrv_dirty_bitmap_inconsistent(const BdrvDirtyBitmap *bitmap) > return bitmap->inconsistent; > } > > -bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs) > -{ > - BdrvDirtyBitmap *bm; > - QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) { > - if (bm->persistent && !bm->readonly && !bm->migration) { The loop down below has these conditionals for skipping bitmaps: if (!bdrv_dirty_bitmap_get_persistence(bitmap) || bdrv_dirty_bitmap_readonly(bitmap) || bdrv_dirty_bitmap_inconsistent(bitmap)) { continue; } It looks like a semantic change, but hiding inside of get_persistence is this: bitmap->persistent && !bitmap->migration; So this is equivalent, actually. It's not readily apparent at a glance. > - return true; > - } > - } > - > - return false; > -} > - > BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs, > BdrvDirtyBitmap *bitmap) > { > diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c > index 8a75366c92..2b84bfa007 100644 > --- a/block/qcow2-bitmap.c > +++ b/block/qcow2-bitmap.c > @@ -1457,16 +1457,7 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp) > Qcow2Bitmap *bm; > QSIMPLEQ_HEAD(, Qcow2BitmapTable) drop_tables; > Qcow2BitmapTable *tb, *tb_next; > - > - if (!bdrv_has_changed_persistent_bitmaps(bs)) { > - /* nothing to do */ > - return; > - } > - > - if (!can_write(bs)) { > - error_setg(errp, "No write access"); > - return; > - } > + bool need_write = false; > > QSIMPLEQ_INIT(&drop_tables); > > @@ -1494,6 +1485,8 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp) > continue; > } > > + need_write = true; > + > if (check_constraints_on_bitmap(bs, name, granularity, errp) < 0) { > error_prepend(errp, "Bitmap '%s' doesn't satisfy the constraints: ", > name); > @@ -1532,6 +1525,15 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp) > bm->dirty_bitmap = bitmap; > } > > + if (!need_write) { > + goto success; > + } > + > + if (!can_write(bs)) { > + error_setg(errp, "No write access"); > + goto fail; > + } > + > /* allocate clusters and store bitmaps */ > QSIMPLEQ_FOREACH(bm, bm_list, entry) { > if (bm->dirty_bitmap == NULL) { > @@ -1573,6 +1575,7 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp) > bdrv_release_dirty_bitmap(bs, bm->dirty_bitmap); > } > > +success: > bitmap_list_free(bm_list); > return; > > Alright, interesting. You're right that the function you're removing is pretty badly named for what it actually does. I got confused by that not too long ago. The rationale against optimizing the error path works for me, too. Seems like it's equivalent before and after, so: Reviewed-by: John Snow