block: vdi - use block layer ops in vdi_create, instead of posix calls

Use the block layer to create, and write to, the image file in the
VDI .bdrv_create() operation.

This has a couple of benefits: Images can now be created over protocols,
and hacks such as NOCOW are not needed in the image format driver, and
the underlying file protocol appropriate for the host OS can be relied
upon.

Also some minor cleanup for error handling.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/vdi.c

@@ -53,13 +53,6 @@
 #include "block/block_int.h"
 #include "qemu/module.h"
 #include "migration/migration.h"
-#ifdef __linux__
-#include <linux/fs.h>
-#include <sys/ioctl.h>
-#ifndef FS_NOCOW_FL
-#define FS_NOCOW_FL                     0x00800000 /* Do not cow file */
-#endif
-#endif
 
 #if defined(CONFIG_UUID)
 #include <uuid/uuid.h>
@@ -681,7 +674,6 @@ static int vdi_co_write(BlockDriverState *bs,
 
 static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
 {
-    int fd;
     int result = 0;
     uint64_t bytes = 0;
     uint32_t blocks;
@@ -690,7 +682,10 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
     VdiHeader header;
     size_t i;
     size_t bmap_size;
-    bool nocow = false;
+    int64_t offset = 0;
+    Error *local_err = NULL;
+    BlockDriverState *bs = NULL;
+    uint32_t *bmap = NULL;
 
     logout("\n");
 
@@ -707,7 +702,6 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
         image_type = VDI_TYPE_STATIC;
     }
 #endif
-    nocow = qemu_opt_get_bool_del(opts, BLOCK_OPT_NOCOW, false);
 
     if (bytes > VDI_DISK_SIZE_MAX) {
         result = -ENOTSUP;
@@ -717,27 +711,16 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
         goto exit;
     }
 
-    fd = qemu_open(filename,
-                   O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
-                   0644);
-    if (fd < 0) {
-        result = -errno;
+    result = bdrv_create_file(filename, opts, &local_err);
+    if (result < 0) {
+        error_propagate(errp, local_err);
         goto exit;
     }
-
-    if (nocow) {
-#ifdef __linux__
-        /* Set NOCOW flag to solve performance issue on fs like btrfs.
-         * This is an optimisation. The FS_IOC_SETFLAGS ioctl return value will
-         * be ignored since any failure of this operation should not block the
-         * left work.
-         */
-        int attr;
-        if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
-            attr |= FS_NOCOW_FL;
-            ioctl(fd, FS_IOC_SETFLAGS, &attr);
-        }
-#endif
+    result = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
+                       NULL, &local_err);
+    if (result < 0) {
+        error_propagate(errp, local_err);
+        goto exit;
     }
 
     /* We need enough blocks to store the given disk size,
@@ -769,41 +752,41 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
     vdi_header_print(&header);
 #endif
     vdi_header_to_le(&header);
-    if (write(fd, &header, sizeof(header)) < 0) {
-        result = -errno;
-        goto close_and_exit;
+    result = bdrv_pwrite_sync(bs, offset, &header, sizeof(header));
+    if (result < 0) {
+        error_setg(errp, "Error writing header to %s", filename);
+        goto exit;
     }
+    offset += sizeof(header);
 
     if (bmap_size > 0) {
-        uint32_t *bmap = g_malloc0(bmap_size);
+        bmap = g_malloc0(bmap_size);
         for (i = 0; i < blocks; i++) {
             if (image_type == VDI_TYPE_STATIC) {
                 bmap[i] = i;
             } else {
                 bmap[i] = VDI_UNALLOCATED;
             }
         }
-        if (write(fd, bmap, bmap_size) < 0) {
-            result = -errno;
-            g_free(bmap);
-            goto close_and_exit;
+        result = bdrv_pwrite_sync(bs, offset, bmap, bmap_size);
+        if (result < 0) {
+            error_setg(errp, "Error writing bmap to %s", filename);
+            goto exit;
         }
-        g_free(bmap);
+        offset += bmap_size;
     }
 
     if (image_type == VDI_TYPE_STATIC) {
-        if (ftruncate(fd, sizeof(header) + bmap_size + blocks * block_size)) {
-            result = -errno;
-            goto close_and_exit;
+        result = bdrv_truncate(bs, offset + blocks * block_size);
+        if (result < 0) {
+            error_setg(errp, "Failed to statically allocate %s", filename);
+            goto exit;
         }
     }
 
-close_and_exit:
-    if ((close(fd) < 0) && !result) {
-        result = -errno;
-    }
-
 exit:
+    bdrv_unref(bs);
+    g_free(bmap);
     return result;
 }