diff options
| -rw-r--r-- | block/qcow2-cluster.c | 33 |
1 files changed, 28 insertions, 5 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 99215fa856..1c70693e3a 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -171,6 +171,31 @@ static uint64_t *l2_load(BlockDriverState *bs, uint64_t l2_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) + */ +#define L1_ENTRIES_PER_SECTOR (512 / 8) +static int write_l1_entry(BDRVQcowState *s, int l1_index) +{ + uint64_t buf[L1_ENTRIES_PER_SECTOR]; + int l1_start_index; + int i; + + l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1); + for (i = 0; i < L1_ENTRIES_PER_SECTOR; i++) { + buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); + } + + if (bdrv_pwrite(s->hd, s->l1_table_offset + 8 * l1_start_index, + buf, sizeof(buf)) != sizeof(buf)) + { + return -1; + } + + return 0; +} + +/* * l2_allocate * * Allocate a new l2 entry in the file. If l1_index points to an already @@ -184,7 +209,7 @@ static uint64_t *l2_allocate(BlockDriverState *bs, int l1_index) { BDRVQcowState *s = bs->opaque; int min_index; - uint64_t old_l2_offset, tmp; + uint64_t old_l2_offset; uint64_t *l2_table, l2_offset; old_l2_offset = s->l1_table[l1_index]; @@ -196,11 +221,9 @@ static uint64_t *l2_allocate(BlockDriverState *bs, int l1_index) /* update the L1 entry */ s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; - - tmp = cpu_to_be64(l2_offset | QCOW_OFLAG_COPIED); - if (bdrv_pwrite(s->hd, s->l1_table_offset + l1_index * sizeof(tmp), - &tmp, sizeof(tmp)) != sizeof(tmp)) + if (write_l1_entry(s, l1_index) < 0) { return NULL; + } /* allocate a new entry in the l2 cache */ |