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[Qemu-devel] [PATCH] iscsi: partly avoid iovec linearization in iscsi_ai
From: |
Peter Lieven |
Subject: |
[Qemu-devel] [PATCH] iscsi: partly avoid iovec linearization in iscsi_aio_writev |
Date: |
Mon, 19 Nov 2012 15:58:31 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2 |
libiscsi expects all write16 data in a linear buffer. If the
iovec only contains one buffer we can skip the linearization
step as well as the additional malloc/free and pass the
buffer directly.
Reported-by: Ronnie Sahlberg <address@hidden>
Signed-off-by: Peter Lieven <address@hidden>
---
block/iscsi.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/block/iscsi.c b/block/iscsi.c
index d0b1a10..f12148e 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -199,8 +199,10 @@ iscsi_aio_write16_cb(struct iscsi_context *iscsi, int
status,
trace_iscsi_aio_write16_cb(iscsi, status, acb, acb->canceled);
- g_free(acb->buf);
-
+ if (acb->buf != NULL) {
+ g_free(acb->buf);
+ }
+
if (acb->canceled != 0) {
return;
}
@@ -244,11 +246,18 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num,
acb->bh = NULL;
acb->status = -EINPROGRESS;
- /* XXX we should pass the iovec to write16 to avoid the extra copy */
- /* this will allow us to get rid of 'buf' completely */
size = nb_sectors * BDRV_SECTOR_SIZE;
- acb->buf = g_malloc(size);
- qemu_iovec_to_buf(acb->qiov, 0, acb->buf, size);
+ data.size = size;
+
+ /* if the iovec only contains one buffer we can pass it directly */
+ if (acb->qiov->niov == 1) {
+ acb->buf = NULL;
+ data.data = acb->qiov->iov[0].iov_base;
+ } else {
+ acb->buf = g_malloc(size);
+ qemu_iovec_to_buf(acb->qiov, 0, acb->buf, size);
+ data.data = acb->buf;
+ }
acb->task = malloc(sizeof(struct scsi_task));
if (acb->task == NULL) {
@@ -269,9 +278,6 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num,
*(uint32_t *)&acb->task->cdb[10] = htonl(num_sectors);
acb->task->expxferlen = size;
- data.data = acb->buf;
- data.size = size;
-
if (iscsi_scsi_command_async(iscsi, iscsilun->lun, acb->task,
iscsi_aio_write16_cb,
&data,
--
1.7.9.5
- [Qemu-devel] [PATCH] iscsi: partly avoid iovec linearization in iscsi_aio_writev,
Peter Lieven <=