The other four drivers that support backing files (qcow, qcow2,
parallels, vmdk) all rely on the block layer to populate zeroes when
reading beyond EOF of a short backing file. We can simplify the qed
code by doing likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
---
I noticed this during my audit that v1 of Vladimir's series was correct.
No change in iotests results (test 274 is currently failing for qed,
but for other reasons:
+Traceback (most recent call last):
+ File "274", line 24, in <module>
+ iotests.verify_image_format(supported_fmts=['qcow2'])
+AttributeError: module 'iotests' has no attribute 'verify_image_format'
)
block/qed.h | 1 -
block/qed.c | 64 +++++------------------------------------------------
2 files changed, 6 insertions(+), 59 deletions(-)
diff --git a/block/qed.h b/block/qed.h
index 42c115d8220c..3d12bf78d412 100644
--- a/block/qed.h
+++ b/block/qed.h
@@ -140,7 +140,6 @@ typedef struct QEDAIOCB {
/* Current cluster scatter-gather list */
QEMUIOVector cur_qiov;
- QEMUIOVector *backing_qiov;
uint64_t cur_pos; /* position on block device, in bytes */
uint64_t cur_cluster; /* cluster offset in image file */
unsigned int cur_nclusters; /* number of clusters being accessed */
diff --git a/block/qed.c b/block/qed.c
index 927382995a0c..bea4b9f6cc97 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -849,56 +849,18 @@ static BDRVQEDState *acb_to_s(QEDAIOCB *acb)
* @s: QED state
* @pos: Byte position in device
* @qiov: Destination I/O vector
- * @backing_qiov: Possibly shortened copy of qiov, to be allocated here
- * @cb: Completion function
- * @opaque: User data for completion function
*
* This function reads qiov->size bytes starting at pos from the backing file.
* If there is no backing file then zeroes are read.
*/
static int coroutine_fn qed_read_backing_file(BDRVQEDState *s, uint64_t pos,
- QEMUIOVector *qiov,
- QEMUIOVector **backing_qiov)
+ QEMUIOVector *qiov)
{
- uint64_t backing_length = 0;
- size_t size;
- int ret;
-
- /* If there is a backing file, get its length. Treat the absence of a
- * backing file like a zero length backing file.
- */
if (s->bs->backing) {
- int64_t l = bdrv_getlength(s->bs->backing->bs);
- if (l < 0) {
- return l;
- }
- backing_length = l;
- }
-
- /* Zero all sectors if reading beyond the end of the backing file */
- if (pos >= backing_length ||
- pos + qiov->size > backing_length) {
- qemu_iovec_memset(qiov, 0, 0, qiov->size);
- }
-
- /* Complete now if there are no backing file sectors to read */
- if (pos >= backing_length) {
- return 0;
- }
-
- /* If the read straddles the end of the backing file, shorten it */
- size = MIN((uint64_t)backing_length - pos, qiov->size);
-
- assert(*backing_qiov == NULL);
- *backing_qiov = g_new(QEMUIOVector, 1);
- qemu_iovec_init(*backing_qiov, qiov->niov);
- qemu_iovec_concat(*backing_qiov, qiov, 0, size);
-
- BLKDBG_EVENT(s->bs->file, BLKDBG_READ_BACKING_AIO);
- ret = bdrv_co_preadv(s->bs->backing, pos, size, *backing_qiov, 0);
- if (ret < 0) {
- return ret;
+ BLKDBG_EVENT(s->bs->file, BLKDBG_READ_BACKING_AIO);
+ return bdrv_co_preadv(s->bs->backing, pos, qiov->size, qiov, 0);
}
+ qemu_iovec_memset(qiov, 0, 0, qiov->size);
return 0;
}
@@ -915,7 +877,6 @@ static int coroutine_fn qed_copy_from_backing_file(BDRVQEDState *s,
uint64_t offset)
{
QEMUIOVector qiov;
- QEMUIOVector *backing_qiov = NULL;
int ret;
/* Skip copy entirely if there is no work to do */
@@ -925,13 +886,7 @@ static int coroutine_fn qed_copy_from_backing_file(BDRVQEDState *s,
qemu_iovec_init_buf(&qiov, qemu_blockalign(s->bs, len), len);
- ret = qed_read_backing_file(s, pos, &qiov, &backing_qiov);
-
- if (backing_qiov) {
- qemu_iovec_destroy(backing_qiov);
- g_free(backing_qiov);
- backing_qiov = NULL;
- }
+ ret = qed_read_backing_file(s, pos, &qiov);
if (ret) {
goto out;
@@ -1339,8 +1294,7 @@ static int coroutine_fn qed_aio_read_data(void *opaque, int ret,
qemu_iovec_memset(&acb->cur_qiov, 0, 0, acb->cur_qiov.size);
r = 0;
} else if (ret != QED_CLUSTER_FOUND) {
- r = qed_read_backing_file(s, acb->cur_pos, &acb->cur_qiov,
- &acb->backing_qiov);
+ r = qed_read_backing_file(s, acb->cur_pos, &acb->cur_qiov);
} else {
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
r = bdrv_co_preadv(bs->file, offset, acb->cur_qiov.size,
@@ -1365,12 +1319,6 @@ static int coroutine_fn qed_aio_next_io(QEDAIOCB *acb)
while (1) {
trace_qed_aio_next_io(s, acb, 0, acb->cur_pos + acb->cur_qiov.size);
- if (acb->backing_qiov) {
- qemu_iovec_destroy(acb->backing_qiov);
- g_free(acb->backing_qiov);
- acb->backing_qiov = NULL;
- }
-
acb->qiov_offset += acb->cur_qiov.size;
acb->cur_pos += acb->cur_qiov.size;
qemu_iovec_reset(&acb->cur_qiov);
--
2.26.2