The code is based on the following QCOW 1 image format specification: http://people.gnome.org/~markmc/qcow-image-format-version-1.html
Signed-off-by: Prasad Joshi <[email protected]> --- tools/kvm/qcow.c | 148 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 147 insertions(+), 1 deletions(-) diff --git a/tools/kvm/qcow.c b/tools/kvm/qcow.c index e6d5897..ff73c55 100644 --- a/tools/kvm/qcow.c +++ b/tools/kvm/qcow.c @@ -134,8 +134,154 @@ error: return -1; } -static int qcow1_write_sector(struct disk_image *self, uint64_t sector, void *src, uint32_t src_len) +static inline u64 get_file_length(int fd) { + struct stat st; + + if (fstat(fd, &st) < 0) + return 0; + return st.st_size; +} + +static inline u64 align(u64 address, uint32_t size) +{ + return (address + size) & (~(size - 1)); +} + +static int qcow_pwrite_with_sync(int fd, void *buf, size_t count, off_t offset) +{ + if (pwrite_in_full(fd, buf, count, offset) < 0) + return -1; + + if (fsync(fd) < 0) + return -1; + + return 0; +} + +static uint32_t qcow1_write_cluster(struct qcow *q, uint64_t offset, void *buf, + uint32_t src_len) +{ + struct qcow1_header *header = q->header; + struct qcow_table *table = &q->table; + uint32_t length; + + uint32_t l2_table_size; + u64 l2_table_offset; + u64 *l2_table; + u64 l2_idx; + + uint32_t clust_size; + u64 clust_offset; + u64 clust_start; + + u64 l1_idx; + u64 tmp; + + l2_table_size = 1 << header->l2_bits; + clust_size = 1 << header->cluster_bits; + + l1_idx = get_l1_index(q, offset); + if (l1_idx >= table->table_size) + goto error; + + l2_idx = get_l2_index(q, offset); + if (l2_idx >= l2_table_size) + goto error; + + clust_offset = get_cluster_offset(q, offset); + if (clust_offset >= clust_size) + goto error; + + length = clust_size - clust_offset; + if (length > src_len) + length = src_len; + + l2_table = calloc(l2_table_size, sizeof(u64)); + if (!l2_table) + goto error; + + l2_table_offset = table->l1_table[l1_idx]; + if (l2_table_offset) { + if (pread_in_full(q->fd, l2_table, l2_table_size * sizeof(u64), + l2_table_offset) < 0) + goto free_l2; + } else { + /* + * 1. write a level 2 table of zeros at the end of the file + * 2. update the level1 table + */ + l2_table_offset = align(get_file_length(q->fd), clust_size); + table->l1_table[l1_idx] = l2_table_offset; + + if (qcow_pwrite_with_sync(q->fd, l2_table, + l2_table_size * sizeof(u64), + l2_table_offset) < 0) + goto free_l2; + + tmp = cpu_to_be64(l2_table_offset); + if (qcow_pwrite_with_sync(q->fd, &tmp, sizeof(tmp), + header->l1_table_offset + + (l1_idx * sizeof(u64))) < 0) + goto free_l2; + } + + clust_start = be64_to_cpu(l2_table[l2_idx]); + free(l2_table); + if (clust_start) { + if (qcow_pwrite_with_sync(q->fd, buf, length, + clust_start + clust_offset) < 0) + goto error; + } else { + /* + * Follow the write order to avoid metadata loss + * 1. write the data at the end of the file + * 2. update the l2_table with new + */ + clust_start = align(get_file_length(q->fd), clust_size); + if (qcow_pwrite_with_sync(q->fd, buf, length, + clust_start + clust_offset) < 0) + goto error; + + tmp = cpu_to_be64(clust_start); + if (qcow_pwrite_with_sync(q->fd, &tmp, sizeof(tmp), + l2_table_offset + + (l2_idx * sizeof(u64))) < 0) + goto error; + } + return length; +free_l2: + free(l2_table); +error: + return 0; +} + +static int qcow1_write_sector(struct disk_image *self, uint64_t sector, + void *src, uint32_t src_len) +{ + struct qcow *q = self->priv; + struct qcow1_header *header = q->header; + uint32_t length = 0; + char *buf = src; + uint64_t offset; + uint32_t nr; + + while (length < src_len) { + offset = sector << SECTOR_SHIFT; + if (offset >= header->size) + goto error; + + nr = qcow1_write_cluster(q, offset, buf, src_len - length); + if (!nr) + goto error; + + length += nr; + buf += nr; + sector += (nr >> SECTOR_SHIFT); + } + + return 0; +error: return -1; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
