On Fri, 15 Apr 2011, Prasad Joshi wrote:
-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;
+}
Wouldn't it be better to put this in 'struct disk_image'? We do fstat()
upon startup anyway.
+
+static inline u64 align(u64 address, uint32_t size)
+{
+ return (address + size) & (~(size - 1));
+}
There's ALIGN macro somewhere in include/linux. Use that.
+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;
Please use u32, u64, and friends.
+
+ 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;
+ }
Maybe it's best to split this in a separate function?
qcow_write_l2_table() or something?
It would also nice to have some comments explaining what exactly you're
trying to do with fsync() calls there.
+
+ 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;
You can get rid of some duplication with:
clust_start = be64_to_cpu(l2_table[l2_idx]);
if (!clust_start) {
clust_start = ALIGN(...);
update_metadata = true;
}
if (qcow_pwrite_with_sync(....) < 0)
goto error;
if (update_metadata) {
// ...
}
Pekka
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