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authorKevin Wolf <kwolf@redhat.com>2010-09-13 18:24:10 +0200
committerKevin Wolf <kwolf@redhat.com>2010-09-21 15:39:43 +0200
commit6f5f060b736cedc2d962114d20805fdd2889513a (patch)
tree8589b132acaa662598a1954c4cc5461ed6b204f2
parentbd28f835652e396841bb73080a07bcc08fe21bf0 (diff)
qcow2: Avoid bounce buffers for AIO write requests
qcow2 used to use bounce buffers for any AIO requests. This does not only imply unnecessary copying, but also unbounded allocations which should be avoided. This patch removes bounce buffers from the normal AIO write path. Encrypted images continue to use a bounce buffer, however with constant size. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/qcow2.c41
1 files changed, 18 insertions, 23 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 4a688b4863..ee3481b786 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -331,15 +331,12 @@ typedef struct QCowAIOCB {
BlockDriverAIOCB common;
int64_t sector_num;
QEMUIOVector *qiov;
- uint8_t *buf;
- void *orig_buf;
int remaining_sectors;
int cur_nr_sectors; /* number of sectors in current iteration */
uint64_t bytes_done;
uint64_t cluster_offset;
uint8_t *cluster_data;
BlockDriverAIOCB *hd_aiocb;
- struct iovec hd_iov;
QEMUIOVector hd_qiov;
QEMUBH *bh;
QCowL2Meta l2meta;
@@ -530,14 +527,7 @@ static QCowAIOCB *qcow_aio_setup(BlockDriverState *bs,
acb->sector_num = sector_num;
acb->qiov = qiov;
- if (!is_write) {
- qemu_iovec_init(&acb->hd_qiov, qiov->niov);
- } else if (qiov->niov == 1) {
- acb->buf = (uint8_t *)qiov->iov->iov_base;
- } else {
- acb->buf = acb->orig_buf = qemu_blockalign(bs, qiov->size);
- qemu_iovec_to_buffer(qiov, acb->buf);
- }
+ qemu_iovec_init(&acb->hd_qiov, qiov->niov);
acb->bytes_done = 0;
acb->remaining_sectors = nb_sectors;
@@ -589,7 +579,6 @@ static void qcow_aio_write_cb(void *opaque, int ret)
BlockDriverState *bs = acb->common.bs;
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
- const uint8_t *src_buf;
int n_end;
acb->hd_aiocb = NULL;
@@ -605,7 +594,7 @@ static void qcow_aio_write_cb(void *opaque, int ret)
acb->remaining_sectors -= acb->cur_nr_sectors;
acb->sector_num += acb->cur_nr_sectors;
- acb->buf += acb->cur_nr_sectors * 512;
+ acb->bytes_done += acb->cur_nr_sectors * 512;
if (acb->remaining_sectors == 0) {
/* request completed */
@@ -636,20 +625,27 @@ static void qcow_aio_write_cb(void *opaque, int ret)
assert((acb->cluster_offset & 511) == 0);
+ qemu_iovec_reset(&acb->hd_qiov);
+ qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
+ acb->cur_nr_sectors * 512);
+
if (s->crypt_method) {
if (!acb->cluster_data) {
acb->cluster_data = qemu_mallocz(QCOW_MAX_CRYPT_CLUSTERS *
s->cluster_size);
}
- qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data, acb->buf,
- acb->cur_nr_sectors, 1, &s->aes_encrypt_key);
- src_buf = acb->cluster_data;
- } else {
- src_buf = acb->buf;
+
+ assert(acb->hd_qiov.size <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
+ qemu_iovec_to_buffer(&acb->hd_qiov, acb->cluster_data);
+
+ qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data,
+ acb->cluster_data, acb->cur_nr_sectors, 1, &s->aes_encrypt_key);
+
+ qemu_iovec_reset(&acb->hd_qiov);
+ qemu_iovec_add(&acb->hd_qiov, acb->cluster_data,
+ acb->cur_nr_sectors * 512);
}
- acb->hd_iov.iov_base = (void *)src_buf;
- acb->hd_iov.iov_len = acb->cur_nr_sectors * 512;
- qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);
+
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
acb->hd_aiocb = bdrv_aio_writev(bs->file,
(acb->cluster_offset >> 9) + index_in_cluster,
@@ -667,9 +663,8 @@ fail:
QLIST_REMOVE(&acb->l2meta, next_in_flight);
}
done:
- if (acb->qiov->niov > 1)
- qemu_vfree(acb->orig_buf);
acb->common.cb(acb->common.opaque, ret);
+ qemu_iovec_destroy(&acb->hd_qiov);
qemu_aio_release(acb);
}