[Qemu-devel] [PATCH 6/7] vdi: do not create useless iovecs

[Paolo Bonzini <pbonzini@redhat.com>]

Reads and writes to the underlying file can also occur with the simple
non-vectored I/O interfaces.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/vdi.c |   79 ++++++++++++++++++++++++----------------------------------
 1 files changed, 33 insertions(+), 46 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index 5070f91..c192c7e 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -474,8 +474,6 @@ static int vdi_co_read(BlockDriverState *bs,
     uint32_t block_index;
     uint32_t sector_in_block;
     uint32_t n_sectors;
-    struct iovec hd_iov;
-    QEMUIOVector hd_qiov;
     int ret;
 
     logout("\n");
@@ -501,10 +499,7 @@ restart:
         uint64_t offset = s->header.offset_data / SECTOR_SIZE +
                           (uint64_t)bmap_entry * s->block_sectors +
                           sector_in_block;
-        hd_iov.iov_base = (void *)buf;
-        hd_iov.iov_len = n_sectors * SECTOR_SIZE;
-        qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
-        ret = bdrv_co_readv(bs->file, offset, n_sectors, &hd_qiov);
+        ret = bdrv_read(bs->file, offset, buf, n_sectors);
     }
     logout("%u sectors read\n", n_sectors);
 
@@ -529,8 +524,6 @@ static int vdi_co_write(BlockDriverState *bs,
     uint32_t n_sectors;
     uint32_t bmap_first;
     uint32_t bmap_last;
-    struct iovec hd_iov;
-    QEMUIOVector hd_qiov;
     uint8_t *block = NULL;
     int ret;
 
@@ -568,18 +561,12 @@ restart:
                buf, n_sectors * SECTOR_SIZE);
         memset(block + (sector_in_block + n_sectors) * SECTOR_SIZE, 0,
                (s->block_sectors - n_sectors - sector_in_block) * SECTOR_SIZE);
-        hd_iov.iov_base = (void *)block;
-        hd_iov.iov_len = s->block_size;
-        qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
-        ret = bdrv_co_writev(bs->file, offset, s->block_sectors, &hd_qiov);
+        ret = bdrv_write(bs->file, offset, block, s->block_sectors);
     } else {
         uint64_t offset = s->header.offset_data / SECTOR_SIZE +
                           (uint64_t)bmap_entry * s->block_sectors +
                           sector_in_block;
-        hd_iov.iov_base = (void *)buf;
-        hd_iov.iov_len = n_sectors * SECTOR_SIZE;
-        qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
-        ret = bdrv_co_writev(bs->file, offset, n_sectors, &hd_qiov);
+        ret = bdrv_write(bs->file, offset, buf, n_sectors);
     }
 
     nb_sectors -= n_sectors;
@@ -592,39 +579,39 @@ restart:
     }
 
     logout("finished data write\n");
-    if (ret >= 0) {
-        ret = 0;
-        if (block) {
-            VdiHeader *header = (VdiHeader *) block;
-            logout("now writing modified header\n");
-            assert(VDI_IS_ALLOCATED(bmap_first));
-            *header = s->header;
-            vdi_header_to_le(header);
-            hd_iov.iov_base = block;
-            hd_iov.iov_len = SECTOR_SIZE;
-            qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
-            ret = bdrv_co_writev(bs->file, 0, 1, &hd_qiov);
-        }
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (block) {
+        /* One or more new blocks were allocated. */
+        VdiHeader *header = (VdiHeader *) block;
+        uint8_t *base;
+        uint64_t offset;
+
+        logout("now writing modified header\n");
+        assert(VDI_IS_ALLOCATED(bmap_first));
+        *header = s->header;
+        vdi_header_to_le(header);
+        ret = bdrv_write(bs->file, 0, block, 1);
         g_free(block);
         block = NULL;
-        if (ret >= 0 && VDI_IS_ALLOCATED(bmap_first)) {
-            /* One or more new blocks were allocated. */
-            uint64_t offset;
-            logout("now writing modified block map entry %u...%u\n",
-                   bmap_first, bmap_last);
-            /* Write modified sectors from block map. */
-            bmap_first /= (SECTOR_SIZE / sizeof(uint32_t));
-            bmap_last /= (SECTOR_SIZE / sizeof(uint32_t));
-            n_sectors = bmap_last - bmap_first + 1;
-            offset = s->bmap_sector + bmap_first;
-            hd_iov.iov_base = (void *)((uint8_t *)&s->bmap[0] +
-                                            bmap_first * SECTOR_SIZE);
-            hd_iov.iov_len = n_sectors * SECTOR_SIZE;
-            qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
-            logout("will write %u block map sectors starting from entry %u\n",
-                   n_sectors, bmap_first);
-            ret = bdrv_co_writev(bs->file, offset, n_sectors, &hd_qiov);
+
+        if (ret < 0) {
+            return ret;
         }
+
+        logout("now writing modified block map entry %u...%u\n",
+               bmap_first, bmap_last);
+        /* Write modified sectors from block map. */
+        bmap_first /= (SECTOR_SIZE / sizeof(uint32_t));
+        bmap_last /= (SECTOR_SIZE / sizeof(uint32_t));
+        n_sectors = bmap_last - bmap_first + 1;
+        offset = s->bmap_sector + bmap_first;
+        base = ((uint8_t *)&s->bmap[0]) + bmap_first * SECTOR_SIZE;
+        logout("will write %u block map sectors starting from entry %u\n",
+               n_sectors, bmap_first);
+        ret = bdrv_write(bs->file, offset, base, n_sectors);
     }
 
     return ret;
-- 
1.7.7.6