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From: Kevin Wolf <kwolf@redhat.com>
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Subject: [Qemu-devel] [PULL 030/100] mirror: Switch mirror_cow_align() to
byte-based
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From: Eric Blake <eblake@redhat.com>
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>
---
block/mirror.c | 63 ++++++++++++++++++++++++++++++++++--------------------=
----
1 file changed, 37 insertions(+), 26 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index a41ef25..0378bd2 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));
}
=20
+/* 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);
}
=20
-/* 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 =3D 0;
- int chunk_sectors =3D s->granularity >> BDRV_SECTOR_BITS;
- int64_t align_sector_num =3D *sector_num;
- int align_nb_sectors =3D *nb_sectors;
- int max_sectors =3D chunk_sectors * s->max_iov;
+ int64_t align_offset =3D *offset;
+ unsigned int align_bytes =3D *bytes;
+ int max_bytes =3D s->granularity * s->max_iov;
=20
- need_cow =3D !test_bit(*sector_num / chunk_sectors, s->cow_bitmap);
- need_cow |=3D !test_bit((*sector_num + *nb_sectors - 1) / chunk_sector=
s,
+ need_cow =3D !test_bit(*offset / s->granularity, s->cow_bitmap);
+ need_cow |=3D !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);
}
=20
- if (align_nb_sectors > max_sectors) {
- align_nb_sectors =3D max_sectors;
+ if (align_bytes > max_bytes) {
+ align_bytes =3D max_bytes;
if (need_cow) {
- align_nb_sectors =3D QEMU_ALIGN_DOWN(align_nb_sectors,
- s->target_cluster_size >>
- BDRV_SECTOR_BITS);
+ align_bytes =3D 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 =3D mirror_clip_sectors(s, align_sector_num,
- align_nb_sectors);
+ align_bytes =3D mirror_clip_bytes(s, align_offset, align_bytes);
=20
- ret =3D align_sector_num + align_nb_sectors - (*sector_num + *nb_secto=
rs);
- *sector_num =3D align_sector_num;
- *nb_sectors =3D align_nb_sectors;
+ ret =3D align_offset + align_bytes - (*offset + *bytes);
+ *offset =3D align_offset;
+ *bytes =3D align_bytes;
assert(ret >=3D 0);
return ret;
}
@@ -257,10 +260,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t =
sector_num,
nb_sectors =3D MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
nb_sectors =3D MIN(max_sectors, nb_sectors);
assert(nb_sectors);
+ assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS);
ret =3D nb_sectors;
=20
if (s->cow_bitmap) {
- ret +=3D mirror_cow_align(s, §or_num, &nb_sectors);
+ int64_t offset =3D sector_num * BDRV_SECTOR_SIZE;
+ unsigned int bytes =3D nb_sectors * BDRV_SECTOR_SIZE;
+ int gap;
+
+ gap =3D mirror_cow_align(s, &offset, &bytes);
+ sector_num =3D offset / BDRV_SECTOR_SIZE;
+ nb_sectors =3D bytes / BDRV_SECTOR_SIZE;
+ ret +=3D gap / BDRV_SECTOR_SIZE;
}
assert(nb_sectors << BDRV_SECTOR_BITS <=3D s->buf_size);
/* The sector range must meet granularity because:
--=20
1.8.3.1