From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53735) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dR3YX-0005Gm-Fu for qemu-devel@nongnu.org; Fri, 30 Jun 2017 17:34:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dR3YW-0005ie-Kk for qemu-devel@nongnu.org; Fri, 30 Jun 2017 17:34:25 -0400 Date: Fri, 30 Jun 2017 17:34:13 -0400 From: Jeff Cody Message-ID: <20170630213413.GB26034@localhost.localdomain> References: <20170627192458.15519-1-eblake@redhat.com> <20170627192458.15519-20-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170627192458.15519-20-eblake@redhat.com> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v3 19/20] block: Minimize raw use of bds->total_sectors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, kwolf@redhat.com, Fam Zheng , qemu-block@nongnu.org, Max Reitz , Stefan Hajnoczi On Tue, Jun 27, 2017 at 02:24:57PM -0500, Eric Blake wrote: > 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: Jeff Cody > --- > 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 0545180..5bbf153 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1924,6 +1924,7 @@ 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, > @@ -1941,13 +1942,14 @@ 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 > >