Re: [Qemu-devel] [PATCH] block: Add support for vpc Fixed Disk type

[Charles Arnold]

Next version of the patch with fixes, cleanups, and suggestions.
- Charles


The Virtual Hard Disk Image Format Specification allows for three
types of hard disk formats, Fixed, Dynamic, and Differencing.  Qemu 
currently only supports Dynamic disks.  This patch adds support for
the Fixed Disk format.

Usage:
    Example 1: qemu-img create -f vpc -o type=fixed <filename> [size]
    Example 2: qemu-img convert -O vpc -o type=fixed <input filename> <output 
filename>

While it is also allowed to specify '-o type=dynamic', the default disk type 
remains Dynamic and is what is used when the type is left unspecified.

Signed-off-by: Charles Arnold <address@hidden>

diff --git a/block/vpc.c b/block/vpc.c
index 89a5ee2..d9a1c44 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -161,13 +161,27 @@ static int vpc_open(BlockDriverState *bs, int flags)
     uint8_t buf[HEADER_SIZE];
     uint32_t checksum;
     int err = -1;
+    int disk_type = VHD_DYNAMIC;
 
     if (bdrv_pread(bs->file, 0, s->footer_buf, HEADER_SIZE) != HEADER_SIZE)
         goto fail;
 
     footer = (struct vhd_footer*) s->footer_buf;
-    if (strncmp(footer->creator, "conectix", 8))
-        goto fail;
+    if (strncmp(footer->creator, "conectix", 8)) {
+        int64_t offset = bdrv_getlength(bs->file);
+        if (offset < HEADER_SIZE) {
+            goto fail;
+        }
+        /* If a fixed disk, the footer is found only at the end of the file */
+        if (bdrv_pread(bs->file, offset-HEADER_SIZE, s->footer_buf, 
HEADER_SIZE)
+                != HEADER_SIZE) {
+            goto fail;
+        }
+        if (strncmp(footer->creator, "conectix", 8)) {
+            goto fail;
+        }
+        disk_type = VHD_FIXED;
+    }
 
     checksum = be32_to_cpu(footer->checksum);
     footer->checksum = 0;
@@ -186,49 +200,54 @@ static int vpc_open(BlockDriverState *bs, int flags)
         goto fail;
     }
 
-    if (bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf, 
HEADER_SIZE)
-            != HEADER_SIZE)
-        goto fail;
-
-    dyndisk_header = (struct vhd_dyndisk_header*) buf;
+    if (disk_type == VHD_DYNAMIC) {
+        if (bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf,
+                HEADER_SIZE) != HEADER_SIZE) {
+            goto fail;
+        }
 
-    if (strncmp(dyndisk_header->magic, "cxsparse", 8))
-        goto fail;
+        dyndisk_header = (struct vhd_dyndisk_header *) buf;
 
+        if (strncmp(dyndisk_header->magic, "cxsparse", 8)) {
+            goto fail;
+        }
 
-    s->block_size = be32_to_cpu(dyndisk_header->block_size);
-    s->bitmap_size = ((s->block_size / (8 * 512)) + 511) & ~511;
+        s->block_size = be32_to_cpu(dyndisk_header->block_size);
+        s->bitmap_size = ((s->block_size / (8 * 512)) + 511) & ~511;
 
-    s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries);
-    s->pagetable = g_malloc(s->max_table_entries * 4);
+        s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries);
+        s->pagetable = g_malloc(s->max_table_entries * 4);
 
-    s->bat_offset = be64_to_cpu(dyndisk_header->table_offset);
-    if (bdrv_pread(bs->file, s->bat_offset, s->pagetable,
-            s->max_table_entries * 4) != s->max_table_entries * 4)
-           goto fail;
+        s->bat_offset = be64_to_cpu(dyndisk_header->table_offset);
+        if (bdrv_pread(bs->file, s->bat_offset, s->pagetable,
+                s->max_table_entries * 4) != s->max_table_entries * 4) {
+            goto fail;
+        }
 
-    s->free_data_block_offset =
-        (s->bat_offset + (s->max_table_entries * 4) + 511) & ~511;
+        s->free_data_block_offset =
+            (s->bat_offset + (s->max_table_entries * 4) + 511) & ~511;
 
-    for (i = 0; i < s->max_table_entries; i++) {
-        be32_to_cpus(&s->pagetable[i]);
-        if (s->pagetable[i] != 0xFFFFFFFF) {
-            int64_t next = (512 * (int64_t) s->pagetable[i]) +
-                s->bitmap_size + s->block_size;
+        for (i = 0; i < s->max_table_entries; i++) {
+            be32_to_cpus(&s->pagetable[i]);
+            if (s->pagetable[i] != 0xFFFFFFFF) {
+                int64_t next = (512 * (int64_t) s->pagetable[i]) +
+                    s->bitmap_size + s->block_size;
 
-            if (next> s->free_data_block_offset)
-                s->free_data_block_offset = next;
+                if (next > s->free_data_block_offset) {
+                    s->free_data_block_offset = next;
+                }
+            }
         }
-    }
 
-    s->last_bitmap_offset = (int64_t) -1;
+        s->last_bitmap_offset = (int64_t) -1;
 
 #ifdef CACHE
-    s->pageentry_u8 = g_malloc(512);
-    s->pageentry_u32 = s->pageentry_u8;
-    s->pageentry_u16 = s->pageentry_u8;
-    s->last_pagetable = -1;
+        s->pageentry_u8 = g_malloc(512);
+        s->pageentry_u32 = s->pageentry_u8;
+        s->pageentry_u16 = s->pageentry_u8;
+        s->last_pagetable = -1;
 #endif
+    }
 
     qemu_co_mutex_init(&s->lock);
 
@@ -395,7 +414,11 @@ static int vpc_read(BlockDriverState *bs, int64_t 
sector_num,
     int ret;
     int64_t offset;
     int64_t sectors, sectors_per_block;
+    struct vhd_footer *footer = (struct vhd_footer *) s->footer_buf;
 
+    if (cpu_to_be32(footer->type) == VHD_FIXED) {
+        return bdrv_read(bs->file, sector_num, buf, nb_sectors);
+    }
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 0);
 
@@ -440,7 +463,11 @@ static int vpc_write(BlockDriverState *bs, int64_t 
sector_num,
     int64_t offset;
     int64_t sectors, sectors_per_block;
     int ret;
+    struct vhd_footer *footer =  (struct vhd_footer *) s->footer_buf;
 
+    if (cpu_to_be32(footer->type) == VHD_FIXED) {
+        return bdrv_write(bs->file, sector_num, buf, nb_sectors);
+    }
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 1);
 
@@ -533,70 +560,14 @@ static int calculate_geometry(int64_t total_sectors, 
uint16_t* cyls,
     return 0;
 }
 
-static int vpc_create(const char *filename, QEMUOptionParameter *options)
+static int create_dynamic_disk(int fd, uint8_t *buf, int64_t total_sectors)
 {
-    uint8_t buf[1024];
-    struct vhd_footer* footer = (struct vhd_footer*) buf;
     struct vhd_dyndisk_header* dyndisk_header =
         (struct vhd_dyndisk_header*) buf;
-    int fd, i;
-    uint16_t cyls = 0;
-    uint8_t heads = 0;
-    uint8_t secs_per_cyl = 0;
     size_t block_size, num_bat_entries;
-    int64_t total_sectors = 0;
+    int i;
     int ret = -EIO;
 
-    // Read out options
-    total_sectors = get_option_parameter(options, BLOCK_OPT_SIZE)->value.n /
-                    BDRV_SECTOR_SIZE;
-
-    // Create the file
-    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
-    if (fd < 0)
-        return -EIO;
-
-    /* Calculate matching total_size and geometry. Increase the number of
-       sectors requested until we get enough (or fail). */
-    for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
-        if (calculate_geometry(total_sectors + i,
-                               &cyls, &heads, &secs_per_cyl)) {
-            ret = -EFBIG;
-            goto fail;
-        }
-    }
-    total_sectors = (int64_t) cyls * heads * secs_per_cyl;
-
-    // Prepare the Hard Disk Footer
-    memset(buf, 0, 1024);
-
-    memcpy(footer->creator, "conectix", 8);
-    // TODO Check if "qemu" creator_app is ok for VPC
-    memcpy(footer->creator_app, "qemu", 4);
-    memcpy(footer->creator_os, "Wi2k", 4);
-
-    footer->features = be32_to_cpu(0x02);
-    footer->version = be32_to_cpu(0x00010000);
-    footer->data_offset = be64_to_cpu(HEADER_SIZE);
-    footer->timestamp = be32_to_cpu(time(NULL) - VHD_TIMESTAMP_BASE);
-
-    // Version of Virtual PC 2007
-    footer->major = be16_to_cpu(0x0005);
-    footer->minor =be16_to_cpu(0x0003);
-
-    footer->orig_size = be64_to_cpu(total_sectors * 512);
-    footer->size = be64_to_cpu(total_sectors * 512);
-
-    footer->cyls = be16_to_cpu(cyls);
-    footer->heads = heads;
-    footer->secs_per_cyl = secs_per_cyl;
-
-    footer->type = be32_to_cpu(VHD_DYNAMIC);
-
-    // TODO uuid is missing
-
-    footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE));
-
     // 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);
@@ -624,7 +595,6 @@ static int vpc_create(const char *filename, 
QEMUOptionParameter *options)
         }
     }
 
-
     // Prepare the Dynamic Disk Header
     memset(buf, 0, 1024);
 
@@ -653,6 +623,130 @@ static int vpc_create(const char *filename, 
QEMUOptionParameter *options)
     ret = 0;
 
  fail:
+    return ret;
+}
+
+static int create_fixed_disk(int fd, uint8_t *buf, int64_t total_size)
+{
+    int ret = -EIO;
+
+    /* 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;
+    }
+
+    ret = 0;
+
+ fail:
+    return ret;
+}
+
+static int vpc_create(const char *filename, QEMUOptionParameter *options)
+{
+    uint8_t buf[1024];
+    struct vhd_footer *footer = (struct vhd_footer *) buf;
+    QEMUOptionParameter *disk_type_param;
+    int fd, i;
+    uint16_t cyls = 0;
+    uint8_t heads = 0;
+    uint8_t secs_per_cyl = 0;
+    int64_t total_sectors;
+    int64_t total_size;
+    int disk_type;
+    int ret = -EIO;
+
+    /* Read out options */
+    total_size = get_option_parameter(options, BLOCK_OPT_SIZE)->value.n;
+
+    disk_type_param = get_option_parameter(options, BLOCK_OPT_SUBFMT);
+    if (disk_type_param && disk_type_param->value.s) {
+        if (!strcmp(disk_type_param->value.s, "dynamic")) {
+            disk_type = VHD_DYNAMIC;
+        } else if (!strcmp(disk_type_param->value.s, "fixed")) {
+            disk_type = VHD_FIXED;
+        } else {
+            return -EINVAL;
+        }
+    } else {
+        disk_type = VHD_DYNAMIC;
+    }
+
+    /* Create the file */
+    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
+    if (fd < 0) {
+        return -EIO;
+    }
+
+    total_sectors = total_size / BDRV_SECTOR_SIZE;
+    if (disk_type == VHD_DYNAMIC) {
+        /* Calculate matching total_size and geometry. Increase the number of
+           sectors requested until we get enough (or fail). */
+        for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl;
+             i++) {
+            if (calculate_geometry(total_sectors + i,
+                                   &cyls, &heads, &secs_per_cyl)) {
+                goto fail;
+            }
+        }
+    } else {
+        if (calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl)) {
+            goto fail;
+        }
+    }
+    total_sectors = (int64_t) cyls * heads * secs_per_cyl;
+
+    /* Prepare the Hard Disk Footer */
+    memset(buf, 0, 1024);
+
+    memcpy(footer->creator, "conectix", 8);
+    /* TODO Check if "qemu" creator_app is ok for VPC */
+    memcpy(footer->creator_app, "qemu", 4);
+    memcpy(footer->creator_os, "Wi2k", 4);
+
+    footer->features = be32_to_cpu(0x02);
+    footer->version = be32_to_cpu(0x00010000);
+    if (disk_type == VHD_DYNAMIC) {
+        footer->data_offset = be64_to_cpu(HEADER_SIZE);
+    } else {
+        footer->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL);
+    }
+    footer->timestamp = be32_to_cpu(time(NULL) - VHD_TIMESTAMP_BASE);
+
+    /* Version of Virtual PC 2007 */
+    footer->major = be16_to_cpu(0x0005);
+    footer->minor = be16_to_cpu(0x0003);
+    if (disk_type == VHD_DYNAMIC) {
+        footer->orig_size = be64_to_cpu(total_sectors * 512);
+        footer->size = be64_to_cpu(total_sectors * 512);
+    } else {
+        footer->orig_size = be64_to_cpu(total_size);
+        footer->size = be64_to_cpu(total_size);
+    }
+    footer->cyls = be16_to_cpu(cyls);
+    footer->heads = heads;
+    footer->secs_per_cyl = secs_per_cyl;
+
+    footer->type = be32_to_cpu(disk_type);
+
+    /* TODO uuid is missing */
+
+    footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE));
+
+    if (disk_type == VHD_DYNAMIC) {
+        ret = create_dynamic_disk(fd, buf, total_sectors);
+    } else {
+        ret = create_fixed_disk(fd, buf, total_size);
+    }
+
+ fail:
     close(fd);
     return ret;
 }
@@ -675,6 +769,13 @@ static QEMUOptionParameter vpc_create_options[] = {
         .type = OPT_SIZE,
         .help = "Virtual disk size"
     },
+    {
+        .name = BLOCK_OPT_SUBFMT,
+        .type = OPT_STRING,
+        .help =
+            "Type of virtual hard disk format. Supported formats are "
+            "{dynamic (default) | fixed} "
+    },
     { NULL }
 };