From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40957) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dR34s-000817-7U for qemu-devel@nongnu.org; Fri, 30 Jun 2017 17:03:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dR34r-0008Mz-5s for qemu-devel@nongnu.org; Fri, 30 Jun 2017 17:03:46 -0400 Date: Fri, 30 Jun 2017 17:03:23 -0400 From: Jeff Cody Message-ID: <20170630210323.GJ4997@localhost.localdomain> References: <20170627192458.15519-1-eblake@redhat.com> <20170627192458.15519-11-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170627192458.15519-11-eblake@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3 10/20] mirror: Switch mirror_cow_align() to byte-based List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, kwolf@redhat.com, qemu-block@nongnu.org, jsnow@redhat.com, Max Reitz On Tue, Jun 27, 2017 at 02:24:48PM -0500, Eric Blake wrote: > We are gradually converting to byte-based interfaces, as they are > easier to reason about than sector-based. Convert another internal > function (no semantic change), and add mirror_clip_bytes() as a > counterpart to mirror_clip_sectors(). Some of the conversion is > a bit tricky, requiring temporaries to convert between units; it > will be cleared up in a following patch. > > Signed-off-by: Eric Blake > Reviewed-by: John Snow > Reviewed-by: Jeff Cody > --- > v2: tweak mirror_clip_bytes() signature to match previous patch > --- > block/mirror.c | 64 ++++++++++++++++++++++++++++++++++------------------------ > 1 file changed, 38 insertions(+), 26 deletions(-) > > diff --git a/block/mirror.c b/block/mirror.c > index 1a43304..1a4602a 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -176,6 +176,15 @@ static void mirror_read_complete(void *opaque, int ret) > aio_context_release(blk_get_aio_context(s->common.blk)); > } > > +/* Clip bytes relative to offset to not exceed end-of-file */ > +static inline int64_t mirror_clip_bytes(MirrorBlockJob *s, > + int64_t offset, > + int64_t bytes) > +{ > + return MIN(bytes, s->bdev_length - offset); > +} > + > +/* Clip nb_sectors relative to sector_num to not exceed end-of-file */ > static inline int mirror_clip_sectors(MirrorBlockJob *s, > int64_t sector_num, > int nb_sectors) > @@ -184,44 +193,39 @@ static inline int mirror_clip_sectors(MirrorBlockJob *s, > s->bdev_length / BDRV_SECTOR_SIZE - sector_num); > } > > -/* Round sector_num and/or nb_sectors to target cluster if COW is needed, and > - * return the offset of the adjusted tail sector against original. */ > -static int mirror_cow_align(MirrorBlockJob *s, > - int64_t *sector_num, > - int *nb_sectors) > +/* Round offset and/or bytes to target cluster if COW is needed, and > + * return the offset of the adjusted tail against original. */ > +static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset, > + unsigned int *bytes) > { > bool need_cow; > int ret = 0; > - int chunk_sectors = s->granularity >> BDRV_SECTOR_BITS; > - int64_t align_sector_num = *sector_num; > - int align_nb_sectors = *nb_sectors; > - int max_sectors = chunk_sectors * s->max_iov; > + int64_t align_offset = *offset; > + unsigned int align_bytes = *bytes; > + int max_bytes = s->granularity * s->max_iov; > > - need_cow = !test_bit(*sector_num / chunk_sectors, s->cow_bitmap); > - need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors, > + need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap); > + need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity, > s->cow_bitmap); > if (need_cow) { > - bdrv_round_sectors_to_clusters(blk_bs(s->target), *sector_num, > - *nb_sectors, &align_sector_num, > - &align_nb_sectors); > + bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes, > + &align_offset, &align_bytes); > } > > - if (align_nb_sectors > max_sectors) { > - align_nb_sectors = max_sectors; > + if (align_bytes > max_bytes) { > + align_bytes = max_bytes; > if (need_cow) { > - align_nb_sectors = QEMU_ALIGN_DOWN(align_nb_sectors, > - s->target_cluster_size >> > - BDRV_SECTOR_BITS); > + align_bytes = QEMU_ALIGN_DOWN(align_bytes, > + s->target_cluster_size); > } > } > - /* Clipping may result in align_nb_sectors unaligned to chunk boundary, but > + /* Clipping may result in align_bytes unaligned to chunk boundary, but > * that doesn't matter because it's already the end of source image. */ > - align_nb_sectors = mirror_clip_sectors(s, align_sector_num, > - align_nb_sectors); > + align_bytes = mirror_clip_bytes(s, align_offset, align_bytes); > > - ret = align_sector_num + align_nb_sectors - (*sector_num + *nb_sectors); > - *sector_num = align_sector_num; > - *nb_sectors = align_nb_sectors; > + ret = align_offset + align_bytes - (*offset + *bytes); > + *offset = align_offset; > + *bytes = align_bytes; > assert(ret >= 0); > return ret; > } > @@ -257,10 +261,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num, > nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors); > nb_sectors = MIN(max_sectors, nb_sectors); > assert(nb_sectors); > + assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS); > ret = nb_sectors; > > if (s->cow_bitmap) { > - ret += mirror_cow_align(s, §or_num, &nb_sectors); > + int64_t offset = sector_num * BDRV_SECTOR_SIZE; > + unsigned int bytes = nb_sectors * BDRV_SECTOR_SIZE; > + int gap; > + > + gap = mirror_cow_align(s, &offset, &bytes); > + sector_num = offset / BDRV_SECTOR_SIZE; > + nb_sectors = bytes / BDRV_SECTOR_SIZE; > + ret += gap / BDRV_SECTOR_SIZE; > } > assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size); > /* The sector range must meet granularity because: > -- > 2.9.4 >