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alloc_cluster_link_l2: Write complete sectors

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When updating the L2 tables in alloc_cluster_link_l2(), write complete
sectors instead of updating single entries.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Kevin Wolf 2009-06-16 11:31:29 +02:00 committed by Anthony Liguori
parent 6583e3c7e8
commit 4c1612d954
1 changed files with 25 additions and 3 deletions
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28
block/qcow2-cluster.c
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@ -578,6 +578,28 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
return cluster_offset; return cluster_offset;
} }
/*
* Write L2 table updates to disk, writing whole sectors to avoid a
* read-modify-write in bdrv_pwrite
*/
#define L2_ENTRIES_PER_SECTOR (512 / 8)
static int write_l2_entries(BDRVQcowState *s, uint64_t *l2_table,
uint64_t l2_offset, int l2_index, int num)
{
int l2_start_index = l2_index & ~(L1_ENTRIES_PER_SECTOR - 1);
int start_offset = (8 * l2_index) & ~511;
int end_offset = (8 * (l2_index + num) + 511) & ~511;
size_t len = end_offset - start_offset;
if (bdrv_pwrite(s->hd, l2_offset + start_offset, &l2_table[l2_start_index],
len) != len)
{
return -1;
}
return 0;
}
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset, int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
QCowL2Meta *m) QCowL2Meta *m)
{ {
@ -625,10 +647,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
(i << s->cluster_bits)) | QCOW_OFLAG_COPIED); (i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
} }
if (bdrv_pwrite(s->hd, l2_offset + l2_index * sizeof(uint64_t), if (write_l2_entries(s, l2_table, l2_offset, l2_index, m->nb_clusters) < 0) {
l2_table + l2_index, m->nb_clusters * sizeof(uint64_t)) != ret = -1;
m->nb_clusters * sizeof(uint64_t))
goto err; goto err;
}
for (i = 0; i < j; i++) for (i = 0; i < j; i++)
qcow2_free_any_clusters(bs, qcow2_free_any_clusters(bs,