From 2f51b8136807041d1585dd5a740190c15dfbadd1 Mon Sep 17 00:00:00 2001 From: Stefan Weil Date: Wed, 30 Jan 2013 16:24:34 +0100 Subject: [PATCH 2/2] block/vpc: Improve code Signed-off-by: Stefan Weil --- block/vpc.c | 98 +++++++++++++++++++++++++++++----------------------------- 1 files changed, 49 insertions(+), 49 deletions(-) diff --git a/block/vpc.c b/block/vpc.c index 7948609..5e43934 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -21,6 +21,9 @@ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. + * + * See http://en.wikipedia.org/wiki/VHD_(file_format) for more information + * and links to the VHD specification. */ #include "qemu-common.h" #include "block/block_int.h" @@ -32,10 +35,13 @@ /**************************************************************/ -#define HEADER_SIZE 512 +#define FOOTER_SIZE 512 //#define CACHE +/* By default, VHD uses a block size of 2 MiB for dynamic disk images. */ +#define VHD_DEFAULT_BLOCK_SIZE 0x200000 + enum vhd_type { VHD_FIXED = 2, VHD_DYNAMIC = 3, @@ -51,7 +57,7 @@ struct vhd_footer { uint32_t features; uint32_t version; - // Offset of next header structure, 0xFFFFFFFF if none + // Offset of first dyndisk header structure, 0xFFFFFFFF if none uint64_t data_offset; // Seconds since Jan 1, 2000 0:00:00 (UTC) @@ -115,7 +121,7 @@ struct vhd_dyndisk_header { typedef struct BDRVVPCState { CoMutex lock; - uint8_t footer_buf[HEADER_SIZE]; + uint8_t footer_buf[FOOTER_SIZE]; uint64_t free_data_block_offset; int max_table_entries; uint32_t *pagetable; @@ -141,8 +147,9 @@ static uint32_t vpc_checksum(uint8_t* buf, size_t size) uint32_t res = 0; int i; - for (i = 0; i < size; i++) + for (i = 0; i < size; i++) { res += buf[i]; + } return ~res; } @@ -150,8 +157,9 @@ static uint32_t vpc_checksum(uint8_t* buf, size_t size) static int vpc_probe(const uint8_t *buf, int buf_size, const char *filename) { - if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8)) - return 100; + if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8)) { + return 100; + } return 0; } @@ -159,47 +167,47 @@ static int vpc_open(BlockDriverState *bs, int flags) { BDRVVPCState *s = bs->opaque; int i; - struct vhd_footer* footer; + struct vhd_footer* footer = s->footer_buf; struct vhd_dyndisk_header* dyndisk_header; - uint8_t buf[HEADER_SIZE]; + uint8_t buf[FOOTER_SIZE]; uint32_t checksum; int err = -1; int disk_type = VHD_DYNAMIC; + int64_t offset = bdrv_getlength(bs->file); - if (bdrv_pread(bs->file, 0, s->footer_buf, HEADER_SIZE) != HEADER_SIZE) + if (offset < FOOTER_SIZE) { goto fail; + } + + /* The footer is always found at the end of the file. */ + if (bdrv_pread(bs->file, offset-FOOTER_SIZE, s->footer_buf, FOOTER_SIZE) + != FOOTER_SIZE) { + goto fail; + } - footer = (struct vhd_footer*) s->footer_buf; 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; - } + /* Some VHD versions use a footer with only 511 byte. Try it, too. */ + memmove(s->footer_buf, s->footer_buf + 1, FOOTER_SIZE - 1); if (strncmp(footer->creator, "conectix", 8)) { goto fail; } - disk_type = VHD_FIXED; } + disk_type = be32_to_cpu(footer->type); checksum = be32_to_cpu(footer->checksum); footer->checksum = 0; - if (vpc_checksum(s->footer_buf, HEADER_SIZE) != checksum) - fprintf(stderr, "block-vpc: The header checksum of '%s' is " + if (vpc_checksum(s->footer_buf, FOOTER_SIZE) != checksum) { + fprintf(stderr, "block-vpc: The footer checksum of '%s' is " "incorrect.\n", bs->filename); + } /* Write 'checksum' back to footer, or else will leave it with zero. */ footer->checksum = be32_to_cpu(checksum); - // The visible size of a image in Virtual PC depends on the geometry + // The visible size of an image in Virtual PC may depend on the geometry // rather than on the size stored in the footer (the size in the footer - // is too large usually) - bs->total_sectors = (int64_t) - be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl; + // is usually larger). Nevertheless we must use the real size here. + bs->total_sectors = be64_to_cpu(footer->size) / 512; /* Allow a maximum disk size of approximately 2 TB */ if (bs->total_sectors >= 65535LL * 255 * 255) { @@ -209,7 +217,7 @@ static int vpc_open(BlockDriverState *bs, int flags) if (disk_type == VHD_DYNAMIC) { if (bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf, - HEADER_SIZE) != HEADER_SIZE) { + FOOTER_SIZE) != FOOTER_SIZE) { goto fail; } @@ -359,7 +367,7 @@ static int rewrite_footer(BlockDriverState* bs) BDRVVPCState *s = bs->opaque; int64_t offset = s->free_data_block_offset; - ret = bdrv_pwrite_sync(bs->file, offset, s->footer_buf, HEADER_SIZE); + ret = bdrv_pwrite_sync(bs->file, offset, s->footer_buf, FOOTER_SIZE); if (ret < 0) return ret; @@ -585,17 +593,17 @@ static int create_dynamic_disk(int fd, uint8_t *buf, int64_t total_sectors) int ret = -EIO; // Write the footer (twice: at the beginning and at the end) - block_size = 0x200000; + block_size = VHD_DEFAULT_BLOCK_SIZE; num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512); - if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) { + if (write(fd, buf, FOOTER_SIZE) != FOOTER_SIZE) { 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) { + if (write(fd, buf, FOOTER_SIZE) != FOOTER_SIZE) { goto fail; } @@ -655,7 +663,7 @@ static int create_fixed_disk(int fd, uint8_t *buf, int64_t total_size) if (lseek(fd, -512, SEEK_END) < 0) { goto fail; } - if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) { + if (write(fd, buf, FOOTER_SIZE) != FOOTER_SIZE) { goto fail; } @@ -670,7 +678,7 @@ 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; + int fd; uint16_t cyls = 0; uint8_t heads = 0; uint8_t secs_per_cyl = 0; @@ -702,22 +710,15 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options) } /* - * Calculate matching total_size and geometry. Increase the number of - * sectors requested until we get enough (or fail). This ensures that - * qemu-img convert doesn't truncate images, but rather rounds up. + * Calculate geometry. For guests which use the geometry values, + * the last blocks may be invisible. */ total_sectors = total_size / BDRV_SECTOR_SIZE; - 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; - } + if (calculate_geometry(total_sectors, &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); @@ -729,7 +730,7 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options) 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); + footer->data_offset = be64_to_cpu(FOOTER_SIZE); } else { footer->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL); } @@ -740,11 +741,10 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options) 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->size = footer->orig_size; footer->cyls = be16_to_cpu(cyls); footer->heads = heads; footer->secs_per_cyl = secs_per_cyl; @@ -755,7 +755,7 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options) uuid_generate(footer->uuid); #endif - footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE)); + footer->checksum = be32_to_cpu(vpc_checksum(buf, FOOTER_SIZE)); if (disk_type == VHD_DYNAMIC) { ret = create_dynamic_disk(fd, buf, total_sectors); -- 1.7.6.msysgit.0