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qcow2: Allow requests with multiple l2metas 

Instead of expecting a single l2meta, have a list of them. This allows
to still have a single I/O request for the guest data, even though
multiple l2meta may be needed in order to describe both a COW overwrite
and a new cluster allocation (typical sequential write case).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2013-03-26 17:50:11 +01:00 committed by Stefan Hajnoczi
parent 710c2496d8
commit 88c6588c51
3 changed files with 17 additions and 3 deletions
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3
block/qcow2-cluster.c
View File

@ -1069,10 +1069,13 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
int alloc_n_start = offset_into_cluster(s, guest_offset) int alloc_n_start = offset_into_cluster(s, guest_offset)
>> BDRV_SECTOR_BITS; >> BDRV_SECTOR_BITS;
int nb_sectors = MIN(requested_sectors, avail_sectors); int nb_sectors = MIN(requested_sectors, avail_sectors);
QCowL2Meta *old_m = *m;
*m = g_malloc0(sizeof(**m)); *m = g_malloc0(sizeof(**m));
**m = (QCowL2Meta) { **m = (QCowL2Meta) {
.next = old_m,
.alloc_offset = alloc_cluster_offset, .alloc_offset = alloc_cluster_offset,
.offset = start_of_cluster(s, guest_offset), .offset = start_of_cluster(s, guest_offset),
.nb_clusters = nb_clusters, .nb_clusters = nb_clusters,

14
block/qcow2.c
View File

@ -858,7 +858,9 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
goto fail; goto fail;
} }
if (l2meta != NULL) { while (l2meta != NULL) {
QCowL2Meta *next;
ret = qcow2_alloc_cluster_link_l2(bs, l2meta); ret = qcow2_alloc_cluster_link_l2(bs, l2meta);
if (ret < 0) { if (ret < 0) {
goto fail; goto fail;
@ -871,8 +873,9 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
qemu_co_queue_restart_all(&l2meta->dependent_requests); qemu_co_queue_restart_all(&l2meta->dependent_requests);
next = l2meta->next;
g_free(l2meta); g_free(l2meta);
l2meta = NULL; l2meta = next;
} }
remaining_sectors -= cur_nr_sectors; remaining_sectors -= cur_nr_sectors;
@ -885,12 +888,17 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
fail: fail:
qemu_co_mutex_unlock(&s->lock); qemu_co_mutex_unlock(&s->lock);
if (l2meta != NULL) { while (l2meta != NULL) {
QCowL2Meta *next;
if (l2meta->nb_clusters != 0) { if (l2meta->nb_clusters != 0) {
QLIST_REMOVE(l2meta, next_in_flight); QLIST_REMOVE(l2meta, next_in_flight);
} }
qemu_co_queue_restart_all(&l2meta->dependent_requests); qemu_co_queue_restart_all(&l2meta->dependent_requests);
next = l2meta->next;
g_free(l2meta); g_free(l2meta);
l2meta = next;
} }
qemu_iovec_destroy(&hd_qiov); qemu_iovec_destroy(&hd_qiov);

3
block/qcow2.h
View File

@ -250,6 +250,9 @@ typedef struct QCowL2Meta
*/ */
Qcow2COWRegion cow_end; Qcow2COWRegion cow_end;
/** Pointer to next L2Meta of the same write request */
struct QCowL2Meta *next;
QLIST_ENTRY(QCowL2Meta) next_in_flight; QLIST_ENTRY(QCowL2Meta) next_in_flight;
} QCowL2Meta; } QCowL2Meta;