diff options
| -rw-r--r-- | block-qcow2.c | 55 |
1 files changed, 53 insertions, 2 deletions
diff --git a/block-qcow2.c b/block-qcow2.c index 6d07f9dab1..7759d34d54 100644 --- a/block-qcow2.c +++ b/block-qcow2.c @@ -84,6 +84,7 @@ typedef struct { uint32_t len; } QCowExtension; #define QCOW_EXT_MAGIC_END 0 +#define QCOW_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA typedef struct __attribute__((packed)) QCowSnapshotHeader { @@ -235,6 +236,24 @@ static int qcow_read_extensions(BlockDriverState *bs, uint64_t start_offset, switch (ext.magic) { case QCOW_EXT_MAGIC_END: return 0; + + case QCOW_EXT_MAGIC_BACKING_FORMAT: + if (ext.len >= sizeof(bs->backing_format)) { + fprintf(stderr, "ERROR: ext_backing_format: len=%u too large" + " (>=%lu)\n", + ext.len, sizeof(bs->backing_format)); + return 2; + } + if (bdrv_pread(s->hd, offset , bs->backing_format, + ext.len) != ext.len) + return 3; + bs->backing_format[ext.len] = '\0'; +#ifdef DEBUG_EXT + printf("Qcow2: Got format extension %s\n", bs->backing_format); +#endif + offset += ((ext.len + 7) & ~7); + break; + default: /* unknown magic -- just skip it */ offset += ((ext.len + 7) & ~7); @@ -1526,13 +1545,18 @@ static void create_refcount_update(QCowCreateState *s, } } -static int qcow_create(const char *filename, int64_t total_size, - const char *backing_file, int flags) +static int qcow_create2(const char *filename, int64_t total_size, + const char *backing_file, const char *backing_format, + int flags) { + int fd, header_size, backing_filename_len, l1_size, i, shift, l2_bits; + int backing_format_len = 0; QCowHeader header; uint64_t tmp, offset; QCowCreateState s1, *s = &s1; + QCowExtension ext_bf = {0, 0}; + memset(s, 0, sizeof(*s)); @@ -1546,6 +1570,12 @@ static int qcow_create(const char *filename, int64_t total_size, header_size = sizeof(header); backing_filename_len = 0; if (backing_file) { + if (backing_format) { + ext_bf.magic = QCOW_EXT_MAGIC_BACKING_FORMAT; + backing_format_len = strlen(backing_format); + ext_bf.len = (backing_format_len + 7) & ~7; + header_size += ((sizeof(ext_bf) + ext_bf.len + 7) & ~7); + } header.backing_file_offset = cpu_to_be64(header_size); backing_filename_len = strlen(backing_file); header.backing_file_size = cpu_to_be32(backing_filename_len); @@ -1590,6 +1620,19 @@ static int qcow_create(const char *filename, int64_t total_size, /* write all the data */ write(fd, &header, sizeof(header)); if (backing_file) { + if (backing_format_len) { + char zero[16]; + int d = ext_bf.len - backing_format_len; + + memset(zero, 0, sizeof(zero)); + cpu_to_be32s(&ext_bf.magic); + cpu_to_be32s(&ext_bf.len); + write(fd, &ext_bf, sizeof(ext_bf)); + write(fd, backing_format, backing_format_len); + if (d>0) { + write(fd, zero, d); + } + } write(fd, backing_file, backing_filename_len); } lseek(fd, s->l1_table_offset, SEEK_SET); @@ -1609,6 +1652,12 @@ static int qcow_create(const char *filename, int64_t total_size, return 0; } +static int qcow_create(const char *filename, int64_t total_size, + const char *backing_file, int flags) +{ + return qcow_create2(filename, total_size, backing_file, NULL, flags); +} + static int qcow_make_empty(BlockDriverState *bs) { #if 0 @@ -2685,4 +2734,6 @@ BlockDriver bdrv_qcow2 = { .bdrv_snapshot_delete = qcow_snapshot_delete, .bdrv_snapshot_list = qcow_snapshot_list, .bdrv_get_info = qcow_get_info, + + .bdrv_create2 = qcow_create2, }; |