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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>
This commit is contained in:
Eric Blake 2017-07-07 07:44:49 -05:00 committed by Kevin Wolf
parent 931e52607f
commit 782d97efec
1 changed files with 37 additions and 26 deletions
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63
block/mirror.c
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@ -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 +193,38 @@ 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 +260,18 @@ 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, &sector_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: