From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38234) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dSrYF-0005HN-Gq for qemu-devel@nongnu.org; Wed, 05 Jul 2017 17:09:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dSrYE-0002sj-II for qemu-devel@nongnu.org; Wed, 05 Jul 2017 17:09:35 -0400 From: Eric Blake Date: Wed, 5 Jul 2017 16:08:41 -0500 Message-Id: <20170705210842.960-21-eblake@redhat.com> In-Reply-To: <20170705210842.960-1-eblake@redhat.com> References: <20170705210842.960-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH v4 20/21] block: Minimize raw use of bds->total_sectors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, jsnow@redhat.com, jcody@redhat.com, qemu-block@nongnu.org, Stefan Hajnoczi , Fam Zheng , Max Reitz bdrv_is_allocated_above() was relying on intermediate->total_sectors, which is a field that can have stale contents depending on the value of intermediate->has_variable_length. An audit shows that we are safe (we were first calling through bdrv_co_get_block_status() which in turn calls bdrv_nb_sectors() and therefore just refreshed the current length), but it's nicer to favor our accessor functions to avoid having to repeat such an audit, even if it means refresh_total_sectors() is called more frequently. Suggested-by: John Snow Signed-off-by: Eric Blake Reviewed-by: Manos Pitsidianakis Reviewed-by: Jeff Cody --- v3-v4: no change v2: new patch --- block/io.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/block/io.c b/block/io.c index cb40069..fb8d1c7 100644 --- a/block/io.c +++ b/block/io.c @@ -1952,6 +1952,7 @@ int bdrv_is_allocated_above(BlockDriverState *top, intermediate = top; while (intermediate && intermediate != base) { int64_t pnum_inter; + int64_t size_inter; int psectors_inter; ret = bdrv_is_allocated(intermediate, sector_num * BDRV_SECTOR_SIZE, @@ -1969,13 +1970,14 @@ int bdrv_is_allocated_above(BlockDriverState *top, /* * [sector_num, nb_sectors] is unallocated on top but intermediate - * might have - * - * [sector_num+x, nr_sectors] allocated. + * might have [sector_num+x, nb_sectors-x] allocated. */ + size_inter = bdrv_nb_sectors(intermediate); + if (size_inter < 0) { + return size_inter; + } if (n > psectors_inter && - (intermediate == top || - sector_num + psectors_inter < intermediate->total_sectors)) { + (intermediate == top || sector_num + psectors_inter < size_inter)) { n = psectors_inter; } -- 2.9.4