block: Use bdrv functions to replace file operation in cow.c

Since common file operation functions lack of error detection,
so change them to bdrv series functions.
Signed-off-by: NLi Zhi Hui <zhihuili@linux.vnet.ibm.com>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/cow.c

@@ -243,12 +243,12 @@ static void cow_close(BlockDriverState *bs)
 
 static int cow_create(const char *filename, QEMUOptionParameter *options)
 {
-    int fd, cow_fd;
     struct cow_header_v2 cow_header;
     struct stat st;
     int64_t image_sectors = 0;
     const char *image_filename = NULL;
     int ret;
+    BlockDriverState *cow_bs;
 
     /* Read out options */
     while (options && options->name) {
@@ -260,10 +260,16 @@ static int cow_create(const char *filename, QEMUOptionParameter *options)
         options++;
     }
 
-    cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
-              0644);
-    if (cow_fd < 0)
-        return -errno;
+    ret = bdrv_create_file(filename, options);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = bdrv_file_open(&cow_bs, filename, BDRV_O_RDWR);
+    if (ret < 0) {
+        return ret;
+    }
+
     memset(&cow_header, 0, sizeof(cow_header));
     cow_header.magic = cpu_to_be32(COW_MAGIC);
     cow_header.version = cpu_to_be32(COW_VERSION);
@@ -271,16 +277,9 @@ static int cow_create(const char *filename, QEMUOptionParameter *options)
         /* Note: if no file, we put a dummy mtime */
         cow_header.mtime = cpu_to_be32(0);
 
-        fd = open(image_filename, O_RDONLY | O_BINARY);
-        if (fd < 0) {
-            close(cow_fd);
-            goto mtime_fail;
-        }
-        if (fstat(fd, &st) != 0) {
-            close(fd);
+        if (stat(image_filename, &st) != 0) {
             goto mtime_fail;
         }
-        close(fd);
         cow_header.mtime = cpu_to_be32(st.st_mtime);
     mtime_fail:
         pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
@@ -288,21 +287,20 @@ static int cow_create(const char *filename, QEMUOptionParameter *options)
     }
     cow_header.sectorsize = cpu_to_be32(512);
     cow_header.size = cpu_to_be64(image_sectors * 512);
-    ret = qemu_write_full(cow_fd, &cow_header, sizeof(cow_header));
+    ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
     if (ret != sizeof(cow_header)) {
-        ret = -errno;
         goto exit;
     }
 
     /* resize to include at least all the bitmap */
-    ret = ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
+    ret = bdrv_truncate(cow_bs,
+        sizeof(cow_header) + ((image_sectors + 7) >> 3));
     if (ret) {
-        ret = -errno;
         goto exit;
     }
 
 exit:
-    close(cow_fd);
+    bdrv_delete(cow_bs);
     return ret;
 }