From patchwork Fri Nov 29 16:45:40 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 295469 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id A451E2C00DE for ; Sat, 30 Nov 2013 04:01:29 +1100 (EST) Received: from localhost ([::1]:48415 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VmRRX-0002M6-5b for incoming@patchwork.ozlabs.org; Fri, 29 Nov 2013 12:01:27 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54015) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VmRDb-0004Yq-Ki for qemu-devel@nongnu.org; Fri, 29 Nov 2013 11:47:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VmRDW-0002wV-AW for qemu-devel@nongnu.org; Fri, 29 Nov 2013 11:47:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:17229) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VmRDW-0002wI-1K for qemu-devel@nongnu.org; Fri, 29 Nov 2013 11:46:58 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rATGkufP000951 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 29 Nov 2013 11:46:56 -0500 Received: from dhcp-200-207.str.redhat.com (ovpn-116-75.ams2.redhat.com [10.36.116.75]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rATGkEqp019151; Fri, 29 Nov 2013 11:46:54 -0500 From: Kevin Wolf To: anthony@codemonkey.ws Date: Fri, 29 Nov 2013 17:45:40 +0100 Message-Id: <1385743555-27888-26-git-send-email-kwolf@redhat.com> In-Reply-To: <1385743555-27888-1-git-send-email-kwolf@redhat.com> References: <1385743555-27888-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [Qemu-devel] [PULL 25/41] COW: Extend checking allocated bits to beyond one sector X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Charlie Shepherd cow_co_is_allocated() only checks one sector's worth of allocated bits before returning. This is allowed but (slightly) inefficient, so extend it to check all of the file's metadata sectors. Signed-off-by: Charlie Shepherd Reviewed-by: Paolo Bonzini Signed-off-by: Stefan Hajnoczi [kwolf: silenced compiler warning (-Wmaybe-uninitialized for changed)] Signed-off-by: Kevin Wolf --- block/cow.c | 36 ++++++++++++++++++++++++++---------- 1 file changed, 26 insertions(+), 10 deletions(-) diff --git a/block/cow.c b/block/cow.c index f759496..dc15e46 100644 --- a/block/cow.c +++ b/block/cow.c @@ -152,18 +152,34 @@ static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs, { int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8; uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE; - uint8_t bitmap[BDRV_SECTOR_SIZE]; - int ret; - int changed; + bool first = true; + int changed = 0, same = 0; - ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap)); - if (ret < 0) { - return ret; - } + do { + int ret; + uint8_t bitmap[BDRV_SECTOR_SIZE]; + + bitnum &= BITS_PER_BITMAP_SECTOR - 1; + int sector_bits = MIN(nb_sectors, BITS_PER_BITMAP_SECTOR - bitnum); + + ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap)); + if (ret < 0) { + return ret; + } + + if (first) { + changed = cow_test_bit(bitnum, bitmap); + first = false; + } + + same += cow_find_streak(bitmap, changed, bitnum, nb_sectors); + + bitnum += sector_bits; + nb_sectors -= sector_bits; + offset += BDRV_SECTOR_SIZE; + } while (nb_sectors); - bitnum &= BITS_PER_BITMAP_SECTOR - 1; - changed = cow_test_bit(bitnum, bitmap); - *num_same = cow_find_streak(bitmap, changed, bitnum, nb_sectors); + *num_same = same; return changed; }