We are gradually moving away from sector-based interfaces, towards
byte-based. The qcow driver is now ready to fully utilize the
byte-based callback interface, as long as we override the default
alignment to still be 512 (needed at least for encryption, but
easier to do everywhere than to audit which sub-sector requests
are handled correctly).
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
block/qcow.c | 35 ++++++++++++++++++++---------------
1 file changed, 20 insertions(+), 15 deletions(-)
diff --git a/block/qcow.c b/block/qcow.c
index ea81a3bf87d..75fd75cf976 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -69,7 +69,6 @@ typedef struct QCowHeader {
typedef struct BDRVQcowState {
int cluster_bits;
int cluster_size;
- int cluster_sectors;
int l2_bits;
int l2_size;
unsigned int l1_size;
@@ -235,7 +234,6 @@ static int qcow_open(BlockDriverState *bs, QDict *options,
int flags,
}
s->cluster_bits = header.cluster_bits;
s->cluster_size = 1 << s->cluster_bits;
- s->cluster_sectors = 1 << (s->cluster_bits - 9);
s->l2_bits = header.l2_bits;
s->l2_size = 1 << s->l2_bits;
bs->total_sectors = header.size / 512;
@@ -612,8 +610,18 @@ static int decompress_cluster(BlockDriverState *bs,
uint64_t cluster_offset)
return 0;
}
-static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
- int nb_sectors, QEMUIOVector *qiov)
+static void qcow_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+ /* At least encrypted images require 512-byte alignment. Apply the
+ * limit universally, rather than just on encrypted images, as
+ * it's easier to let the block layer handle rounding than to
+ * audit this code further. */
+ bs->bl.request_alignment = BDRV_SECTOR_SIZE;
+}
+
+static coroutine_fn int qcow_co_preadv(BlockDriverState *bs, uint64_t offset,
+ uint64_t bytes, QEMUIOVector *qiov,
+ int flags)
{
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
@@ -623,9 +631,8 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs,
int64_t sector_num,
QEMUIOVector hd_qiov;
uint8_t *buf;
void *orig_buf;
- int64_t offset = sector_num << BDRV_SECTOR_BITS;
- int64_t bytes = nb_sectors << BDRV_SECTOR_BITS;
+ assert(!flags);
if (qiov->niov > 1) {
buf = orig_buf = qemu_try_blockalign(bs, qiov->size);
if (buf == NULL) {
@@ -718,9 +725,9 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs,
int64_t sector_num,
return ret;
}
-static coroutine_fn int qcow_co_writev(BlockDriverState *bs, int64_t
sector_num,
- int nb_sectors, QEMUIOVector *qiov,
- int flags)
+static coroutine_fn int qcow_co_pwritev(BlockDriverState *bs, uint64_t offset,
+ uint64_t bytes, QEMUIOVector *qiov,
+ int flags)
{
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
@@ -730,8 +737,6 @@ static coroutine_fn int qcow_co_writev(BlockDriverState
*bs, int64_t sector_num,
QEMUIOVector hd_qiov;
uint8_t *buf;
void *orig_buf;
- int64_t offset = sector_num << BDRV_SECTOR_BITS;
- int64_t bytes = nb_sectors << BDRV_SECTOR_BITS;
assert(!flags);
s->cluster_cache_offset = -1; /* disable compressed cache */
@@ -1108,8 +1113,7 @@ qcow_co_pwritev_compressed(BlockDriverState *bs, uint64_t
offset,
if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
/* could not compress: write normal cluster */
- ret = qcow_co_writev(bs, offset >> BDRV_SECTOR_BITS,
- bytes >> BDRV_SECTOR_BITS, qiov, 0);
+ ret = qcow_co_pwritev(bs, offset, bytes, qiov, 0);
if (ret < 0) {
goto fail;
}
@@ -1194,9 +1198,10 @@ static BlockDriver bdrv_qcow = {
.bdrv_co_create_opts = qcow_co_create_opts,
.bdrv_has_zero_init = bdrv_has_zero_init_1,
.supports_backing = true,
+ .bdrv_refresh_limits = qcow_refresh_limits,
- .bdrv_co_readv = qcow_co_readv,
- .bdrv_co_writev = qcow_co_writev,
+ .bdrv_co_preadv = qcow_co_preadv,
+ .bdrv_co_pwritev = qcow_co_pwritev,
.bdrv_co_block_status = qcow_co_block_status,
.bdrv_make_empty = qcow_make_empty,
--
2.14.3
