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handle read outside the backing file

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git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2093 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
bellard 2006-08-06 13:34:04 +00:00
parent 1aacf3489b
commit a946592212
1 changed files with 33 additions and 9 deletions
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42
block-qcow2.c
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@ -696,11 +696,26 @@ static int decompress_cluster(BDRVQcowState *s, uint64_t cluster_offset)
return 0;
}
/* handle reading after the end of the backing file */
static int backing_read1(BlockDriverState *bs,
int64_t sector_num, uint8_t *buf, int nb_sectors)
{
int n1;
if ((sector_num + nb_sectors) <= bs->total_sectors)
return nb_sectors;
if (sector_num >= bs->total_sectors)
n1 = 0;
else
n1 = bs->total_sectors - sector_num;
memset(buf + n1 * 512, 0, 512 * (nb_sectors - n1));
return n1;
}
static int qcow_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
int ret, index_in_cluster, n;
int ret, index_in_cluster, n, n1;
uint64_t cluster_offset;
while (nb_sectors > 0) {
@ -712,9 +727,12 @@ static int qcow_read(BlockDriverState *bs, int64_t sector_num,
if (!cluster_offset) {
if (bs->backing_hd) {
/* read from the base image */
ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
if (ret < 0)
return -1;
n1 = backing_read1(bs->backing_hd, sector_num, buf, n);
if (n1 > 0) {
ret = bdrv_read(bs->backing_hd, sector_num, buf, n1);
if (ret < 0)
return -1;
}
} else {
memset(buf, 0, 512 * n);
}
@ -815,7 +833,7 @@ static void qcow_aio_read_cb(void *opaque, int ret)
BlockDriverState *bs = acb->bs;
BDRVQcowState *s = bs->opaque;
QCowAIOCB *acb1 = acb->opaque;
int index_in_cluster;
int index_in_cluster, n1;
if (ret < 0) {
fail:
@ -859,10 +877,16 @@ static void qcow_aio_read_cb(void *opaque, int ret)
if (!acb1->cluster_offset) {
if (bs->backing_hd) {
/* read from the base image */
ret = bdrv_aio_read(acb1->backing_hd_aiocb, acb1->sector_num,
acb1->buf, acb1->n, qcow_aio_read_cb, acb);
if (ret < 0)
goto fail;
n1 = backing_read1(bs->backing_hd, acb1->sector_num,
acb1->buf, acb1->n);
if (n1 > 0) {
ret = bdrv_aio_read(acb1->backing_hd_aiocb, acb1->sector_num,
acb1->buf, n1, qcow_aio_read_cb, acb);
if (ret < 0)
goto fail;
} else {
goto redo;
}
} else {
/* Note: in this case, no need to wait */
memset(acb1->buf, 0, 512 * acb1->n);