[Qemu-devel] [PULL 37/62] block: vpc - use block layer ops in vpc_create, instead of posix calls

[Kevin Wolf <kwolf@redhat.com>]

From: Jeff Cody <jcody@redhat.com>

Use the block layer to create, and write to, the image file in the VPC
.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.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vpc.c | 106 ++++++++++++++++++++++++------------------------------------
 1 file changed, 43 insertions(+), 63 deletions(-)

diff --git a/block/vpc.c b/block/vpc.c
index 8b376a4..9690344 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -29,13 +29,6 @@
 #if defined(CONFIG_UUID)
 #include <uuid/uuid.h>
 #endif
-#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
 
 /**************************************************************/
 
@@ -656,39 +649,41 @@ static int calculate_geometry(int64_t total_sectors, uint16_t* cyls,
     return 0;
 }
 
-static int create_dynamic_disk(int fd, uint8_t *buf, int64_t total_sectors)
+static int create_dynamic_disk(BlockDriverState *bs, uint8_t *buf,
+                               int64_t total_sectors)
 {
     VHDDynDiskHeader *dyndisk_header =
         (VHDDynDiskHeader *) buf;
     size_t block_size, num_bat_entries;
     int i;
-    int ret = -EIO;
+    int ret;
+    int64_t offset = 0;
 
     // Write the footer (twice: at the beginning and at the end)
     block_size = 0x200000;
     num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
 
-    if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
+    ret = bdrv_pwrite_sync(bs, offset, buf, HEADER_SIZE);
+    if (ret) {
         goto fail;
     }
 
-    if (lseek(fd, 1536 + ((num_bat_entries * 4 + 511) & ~511), SEEK_SET) < 0) {
-        goto fail;
-    }
-    if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
+    offset = 1536 + ((num_bat_entries * 4 + 511) & ~511);
+    ret = bdrv_pwrite_sync(bs, offset, buf, HEADER_SIZE);
+    if (ret < 0) {
         goto fail;
     }
 
     // Write the initial BAT
-    if (lseek(fd, 3 * 512, SEEK_SET) < 0) {
-        goto fail;
-    }
+    offset = 3 * 512;
 
     memset(buf, 0xFF, 512);
     for (i = 0; i < (num_bat_entries * 4 + 511) / 512; i++) {
-        if (write(fd, buf, 512) != 512) {
+        ret = bdrv_pwrite_sync(bs, offset, buf, 512);
+        if (ret < 0) {
             goto fail;
         }
+        offset += 512;
     }
 
     // Prepare the Dynamic Disk Header
@@ -709,39 +704,35 @@ static int create_dynamic_disk(int fd, uint8_t *buf, int64_t total_sectors)
     dyndisk_header->checksum = be32_to_cpu(vpc_checksum(buf, 1024));
 
     // Write the header
-    if (lseek(fd, 512, SEEK_SET) < 0) {
-        goto fail;
-    }
+    offset = 512;
 
-    if (write(fd, buf, 1024) != 1024) {
+    ret = bdrv_pwrite_sync(bs, offset, buf, 1024);
+    if (ret < 0) {
         goto fail;
     }
-    ret = 0;
 
  fail:
     return ret;
 }
 
-static int create_fixed_disk(int fd, uint8_t *buf, int64_t total_size)
+static int create_fixed_disk(BlockDriverState *bs, uint8_t *buf,
+                             int64_t total_size)
 {
-    int ret = -EIO;
+    int ret;
 
     /* Add footer to total size */
-    total_size += 512;
-    if (ftruncate(fd, total_size) != 0) {
-        ret = -errno;
-        goto fail;
-    }
-    if (lseek(fd, -512, SEEK_END) < 0) {
-        goto fail;
-    }
-    if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
-        goto fail;
+    total_size += HEADER_SIZE;
+
+    ret = bdrv_truncate(bs, total_size);
+    if (ret < 0) {
+        return ret;
     }
 
-    ret = 0;
+    ret = bdrv_pwrite_sync(bs, total_size - HEADER_SIZE, buf, HEADER_SIZE);
+    if (ret < 0) {
+        return ret;
+    }
 
- fail:
     return ret;
 }
 
@@ -750,7 +741,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     uint8_t buf[1024];
     VHDFooter *footer = (VHDFooter *) buf;
     char *disk_type_param;
-    int fd, i;
+    int i;
     uint16_t cyls = 0;
     uint8_t heads = 0;
     uint8_t secs_per_cyl = 0;
@@ -758,7 +749,8 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     int64_t total_size;
     int disk_type;
     int ret = -EIO;
-    bool nocow = false;
+    Error *local_err = NULL;
+    BlockDriverState *bs = NULL;
 
     /* Read out options */
     total_size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
@@ -775,28 +767,17 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     } else {
         disk_type = VHD_DYNAMIC;
     }
-    nocow = qemu_opt_get_bool_del(opts, BLOCK_OPT_NOCOW, false);
 
-    /* Create the file */
-    fd = qemu_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
-    if (fd < 0) {
-        ret = -EIO;
+    ret = bdrv_create_file(filename, opts, &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
         goto out;
     }
-
-    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
+    ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
+                    NULL, &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
+        goto out;
     }
 
     /*
@@ -810,7 +791,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
                                &secs_per_cyl))
         {
             ret = -EFBIG;
-            goto fail;
+            goto out;
         }
     }
 
@@ -856,14 +837,13 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE));
 
     if (disk_type == VHD_DYNAMIC) {
-        ret = create_dynamic_disk(fd, buf, total_sectors);
+        ret = create_dynamic_disk(bs, buf, total_sectors);
     } else {
-        ret = create_fixed_disk(fd, buf, total_size);
+        ret = create_fixed_disk(bs, buf, total_size);
     }
 
-fail:
-    qemu_close(fd);
 out:
+    bdrv_unref(bs);
     g_free(disk_type_param);
     return ret;
 }
-- 
1.8.3.1