mirror: Switch mirror_cow_align() to byte-based
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 <eblake@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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@ -176,6 +176,15 @@ static void mirror_read_complete(void *opaque, int ret)
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aio_context_release(blk_get_aio_context(s->common.blk));
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aio_context_release(blk_get_aio_context(s->common.blk));
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}
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}
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/* Clip bytes relative to offset to not exceed end-of-file */
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static inline int64_t mirror_clip_bytes(MirrorBlockJob *s,
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int64_t offset,
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int64_t bytes)
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{
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return MIN(bytes, s->bdev_length - offset);
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}
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/* Clip nb_sectors relative to sector_num to not exceed end-of-file */
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static inline int mirror_clip_sectors(MirrorBlockJob *s,
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static inline int mirror_clip_sectors(MirrorBlockJob *s,
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int64_t sector_num,
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int64_t sector_num,
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int nb_sectors)
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int nb_sectors)
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@ -184,44 +193,38 @@ static inline int mirror_clip_sectors(MirrorBlockJob *s,
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s->bdev_length / BDRV_SECTOR_SIZE - sector_num);
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s->bdev_length / BDRV_SECTOR_SIZE - sector_num);
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}
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}
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/* Round sector_num and/or nb_sectors to target cluster if COW is needed, and
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/* Round offset and/or bytes to target cluster if COW is needed, and
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* return the offset of the adjusted tail sector against original. */
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* return the offset of the adjusted tail against original. */
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static int mirror_cow_align(MirrorBlockJob *s,
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static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
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int64_t *sector_num,
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unsigned int *bytes)
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int *nb_sectors)
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{
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{
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bool need_cow;
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bool need_cow;
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int ret = 0;
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int ret = 0;
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int chunk_sectors = s->granularity >> BDRV_SECTOR_BITS;
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int64_t align_offset = *offset;
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int64_t align_sector_num = *sector_num;
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unsigned int align_bytes = *bytes;
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int align_nb_sectors = *nb_sectors;
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int max_bytes = s->granularity * s->max_iov;
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int max_sectors = chunk_sectors * s->max_iov;
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need_cow = !test_bit(*sector_num / chunk_sectors, s->cow_bitmap);
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need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
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need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors,
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need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
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s->cow_bitmap);
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s->cow_bitmap);
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if (need_cow) {
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if (need_cow) {
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bdrv_round_sectors_to_clusters(blk_bs(s->target), *sector_num,
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bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes,
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*nb_sectors, &align_sector_num,
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&align_offset, &align_bytes);
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&align_nb_sectors);
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}
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}
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if (align_nb_sectors > max_sectors) {
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if (align_bytes > max_bytes) {
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align_nb_sectors = max_sectors;
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align_bytes = max_bytes;
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if (need_cow) {
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if (need_cow) {
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align_nb_sectors = QEMU_ALIGN_DOWN(align_nb_sectors,
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align_bytes = QEMU_ALIGN_DOWN(align_bytes, s->target_cluster_size);
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s->target_cluster_size >>
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BDRV_SECTOR_BITS);
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}
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}
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}
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}
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/* Clipping may result in align_nb_sectors unaligned to chunk boundary, but
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/* Clipping may result in align_bytes unaligned to chunk boundary, but
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* that doesn't matter because it's already the end of source image. */
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* that doesn't matter because it's already the end of source image. */
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align_nb_sectors = mirror_clip_sectors(s, align_sector_num,
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align_bytes = mirror_clip_bytes(s, align_offset, align_bytes);
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align_nb_sectors);
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ret = align_sector_num + align_nb_sectors - (*sector_num + *nb_sectors);
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ret = align_offset + align_bytes - (*offset + *bytes);
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*sector_num = align_sector_num;
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*offset = align_offset;
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*nb_sectors = align_nb_sectors;
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*bytes = align_bytes;
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assert(ret >= 0);
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assert(ret >= 0);
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return ret;
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return ret;
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}
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}
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@ -257,10 +260,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
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nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
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nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
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nb_sectors = MIN(max_sectors, nb_sectors);
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nb_sectors = MIN(max_sectors, nb_sectors);
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assert(nb_sectors);
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assert(nb_sectors);
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assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS);
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ret = nb_sectors;
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ret = nb_sectors;
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if (s->cow_bitmap) {
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if (s->cow_bitmap) {
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ret += mirror_cow_align(s, §or_num, &nb_sectors);
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int64_t offset = sector_num * BDRV_SECTOR_SIZE;
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unsigned int bytes = nb_sectors * BDRV_SECTOR_SIZE;
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int gap;
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gap = mirror_cow_align(s, &offset, &bytes);
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sector_num = offset / BDRV_SECTOR_SIZE;
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nb_sectors = bytes / BDRV_SECTOR_SIZE;
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ret += gap / BDRV_SECTOR_SIZE;
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}
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}
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assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size);
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assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size);
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/* The sector range must meet granularity because:
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/* The sector range must meet granularity because:
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