@@ -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 void mirror_clip_bytes(MirrorBlockJob *s,
+ int64_t offset,
+ unsigned int *bytes)
+{
+ *bytes = MIN(*bytes, s->bdev_length - offset);
+}
+
+/* Clip nb_sectors relative to sector_num to not exceed end-of-file */
static inline void mirror_clip_sectors(MirrorBlockJob *s,
int64_t sector_num,
int *nb_sectors)
@@ -184,43 +193,39 @@ static inline void 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. */
- mirror_clip_sectors(s, align_sector_num, &align_nb_sectors);
+ 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;
}
@@ -256,10 +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:
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> --- block/mirror.c | 63 +++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 38 insertions(+), 25 deletions(-)