diff options
| -rw-r--r-- | block/qcow2-cluster.c | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 0384fb2339..1947f13a2d 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -216,26 +216,31 @@ static int l2_load(BlockDriverState *bs, uint64_t offset, } /* - * Writes one sector of the L1 table to the disk (can't update single entries - * and we really don't want bdrv_pread to perform a read-modify-write) + * Writes an L1 entry to disk (note that depending on the alignment + * requirements this function may write more that just one entry in + * order to prevent bdrv_pwrite from performing a read-modify-write) */ -#define L1_ENTRIES_PER_SECTOR (512 / 8) int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) { BDRVQcow2State *s = bs->opaque; - uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 }; int l1_start_index; int i, ret; + int bufsize = MAX(sizeof(uint64_t), + MIN(bs->file->bs->bl.request_alignment, s->cluster_size)); + int nentries = bufsize / sizeof(uint64_t); + g_autofree uint64_t *buf = g_try_new0(uint64_t, nentries); - l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1); - for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size; - i++) - { + if (buf == NULL) { + return -ENOMEM; + } + + l1_start_index = QEMU_ALIGN_DOWN(l1_index, nentries); + for (i = 0; i < MIN(nentries, s->l1_size - l1_start_index); i++) { buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); } ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, - s->l1_table_offset + 8 * l1_start_index, sizeof(buf), false); + s->l1_table_offset + 8 * l1_start_index, bufsize, false); if (ret < 0) { return ret; } @@ -243,7 +248,7 @@ int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset + 8 * l1_start_index, - buf, sizeof(buf)); + buf, bufsize); if (ret < 0) { return ret; } |