[Qemu-devel] [PATCHv3 3/9] allow qemu_iovec_from_buffer() to specify offset from which to start copying

[Michael Tokarev <mjt@tls.msk.ru>]

Similar to
 qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                   int c, size_t bytes);
the new prototype is:
 qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
                     const void *buf, size_t bytes);

The processing starts at offset bytes within qiov.

This way, we may copy a bounce buffer directly to
a middle of qiov.

This is exactly the same function as iov_from_buf() from
iov.c, so use the existing implementation and rename it
to qemu_iovec_from_buf() to be shorter and to match the
utility function.

As with utility implementation, we now assert that the
offset is inside actual iovec.  Nothing changed for
current callers, because `offset' parameter is new.

While at it, stop using "bounce-qiov" in block/qcow2.c
and copy decrypted data directly from cluster_data
instead of recreating a temp qiov for doing that
(Cc'ing kwolf for this change).

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Kevin Wolf <kwolf@redhat.com>
---
 block.c       |    6 +++---
 block/curl.c  |    6 +++---
 block/qcow.c  |    2 +-
 block/qcow2.c |    9 +++------
 block/vdi.c   |    2 +-
 cutils.c      |   16 +++-------------
 qemu-common.h |    3 ++-
 7 files changed, 16 insertions(+), 28 deletions(-)

diff --git a/block.c b/block.c
index 52ffe14..f4320be 100644
--- a/block.c
+++ b/block.c
@@ -1692,8 +1692,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
     }
 
     skip_bytes = (sector_num - cluster_sector_num) * BDRV_SECTOR_SIZE;
-    qemu_iovec_from_buffer(qiov, bounce_buffer + skip_bytes,
-                           nb_sectors * BDRV_SECTOR_SIZE);
+    qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes,
+                        nb_sectors * BDRV_SECTOR_SIZE);
 
 err:
     qemu_vfree(bounce_buffer);
@@ -3240,7 +3240,7 @@ static void bdrv_aio_bh_cb(void *opaque)
     BlockDriverAIOCBSync *acb = opaque;
 
     if (!acb->is_write)
-        qemu_iovec_from_buffer(acb->qiov, acb->bounce, acb->qiov->size);
+        qemu_iovec_from_buf(acb->qiov, 0, acb->bounce, acb->qiov->size);
     qemu_vfree(acb->bounce);
     acb->common.cb(acb->common.opaque, acb->ret);
     qemu_bh_delete(acb->bh);
diff --git a/block/curl.c b/block/curl.c
index e9102e3..cfc2ced 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -142,8 +142,8 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
             continue;
 
         if ((s->buf_off >= acb->end)) {
-            qemu_iovec_from_buffer(acb->qiov, s->orig_buf + acb->start,
-                                   acb->end - acb->start);
+            qemu_iovec_from_buf(acb->qiov, 0, s->orig_buf + acb->start,
+                                acb->end - acb->start);
             acb->common.cb(acb->common.opaque, 0);
             qemu_aio_release(acb);
             s->acb[i] = NULL;
@@ -178,7 +178,7 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
         {
             char *buf = state->orig_buf + (start - state->buf_start);
 
-            qemu_iovec_from_buffer(acb->qiov, buf, len);
+            qemu_iovec_from_buf(acb->qiov, 0, buf, len);
             acb->common.cb(acb->common.opaque, 0);
 
             return FIND_RET_OK;
diff --git a/block/qcow.c b/block/qcow.c
index b1cfe1f..562a19c 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -540,7 +540,7 @@ done:
     qemu_co_mutex_unlock(&s->lock);
 
     if (qiov->niov > 1) {
-        qemu_iovec_from_buffer(qiov, orig_buf, qiov->size);
+        qemu_iovec_from_buf(qiov, 0, orig_buf, qiov->size);
         qemu_vfree(orig_buf);
     }
 
diff --git a/block/qcow2.c b/block/qcow2.c
index d46ca70..106f2ce 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -475,7 +475,7 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
                 goto fail;
             }
 
-            qemu_iovec_from_buffer(&hd_qiov,
+            qemu_iovec_from_buf(&hd_qiov, 0,
                 s->cluster_cache + index_in_cluster * 512,
                 512 * cur_nr_sectors);
         } else {
@@ -513,11 +513,8 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
             if (s->crypt_method) {
                 qcow2_encrypt_sectors(s, sector_num,  cluster_data,
                     cluster_data, cur_nr_sectors, 0, &s->aes_decrypt_key);
-                qemu_iovec_reset(&hd_qiov);
-                qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
-                    cur_nr_sectors * 512);
-                qemu_iovec_from_buffer(&hd_qiov, cluster_data,
-                    512 * cur_nr_sectors);
+                qemu_iovec_from_buf(qiov, bytes_done,
+                    cluster_data, 512 * cur_nr_sectors);
             }
         }
 
diff --git a/block/vdi.c b/block/vdi.c
index 6a0011f..24f4027 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -635,7 +635,7 @@ static void vdi_aio_read_cb(void *opaque, int ret)
     return;
 done:
     if (acb->qiov->niov > 1) {
-        qemu_iovec_from_buffer(acb->qiov, acb->orig_buf, acb->qiov->size);
+        qemu_iovec_from_buf(acb->qiov, 0, acb->orig_buf, acb->qiov->size);
         qemu_vfree(acb->orig_buf);
     }
     acb->common.cb(acb->common.opaque, ret);
diff --git a/cutils.c b/cutils.c
index 53ff825..1c93ed4 100644
--- a/cutils.c
+++ b/cutils.c
@@ -245,20 +245,10 @@ void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf)
     }
 }
 
-void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count)
+size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
+                           const void *buf, size_t bytes)
 {
-    const uint8_t *p = (const uint8_t *)buf;
-    size_t copy;
-    int i;
-
-    for (i = 0; i < qiov->niov && count; ++i) {
-        copy = count;
-        if (copy > qiov->iov[i].iov_len)
-            copy = qiov->iov[i].iov_len;
-        memcpy(qiov->iov[i].iov_base, p, copy);
-        p     += copy;
-        count -= copy;
-    }
+    return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 }
 
 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
diff --git a/qemu-common.h b/qemu-common.h
index 90f17fe..2cbb513 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -339,7 +339,8 @@ void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size);
 void qemu_iovec_destroy(QEMUIOVector *qiov);
 void qemu_iovec_reset(QEMUIOVector *qiov);
 void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf);
-void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count);
+size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
+                           const void *buf, size_t bytes);
 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                          int c, size_t bytes);
 
-- 
1.7.9.1