gwj / at91sam9263 · Commits

Commit 4c1612d95412bcc487e0c734ad5b738105b67b19

Authored by Kevin Wolf
Committed by Anthony Liguori
1 parent 6583e3c7

alloc_cluster_link_l2: Write complete sectors 

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>
Inline Side-by-side
Showing 1 changed file with 25 additions and 3 deletions
block/qcow2-cluster.c
  View file @4c1612d
... ... @@ -578,6 +578,28 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
578 578 return cluster_offset;
579 579 }
580 580  
  581 +/*
  582 + * Write L2 table updates to disk, writing whole sectors to avoid a
  583 + * read-modify-write in bdrv_pwrite
  584 + */
  585 +#define L2_ENTRIES_PER_SECTOR (512 / 8)
  586 +static int write_l2_entries(BDRVQcowState *s, uint64_t *l2_table,
  587 + uint64_t l2_offset, int l2_index, int num)
  588 +{
  589 + int l2_start_index = l2_index & ~(L1_ENTRIES_PER_SECTOR - 1);
  590 + int start_offset = (8 * l2_index) & ~511;
  591 + int end_offset = (8 * (l2_index + num) + 511) & ~511;
  592 + size_t len = end_offset - start_offset;
  593 +
  594 + if (bdrv_pwrite(s->hd, l2_offset + start_offset, &l2_table[l2_start_index],
  595 + len) != len)
  596 + {
  597 + return -1;
  598 + }
  599 +
  600 + return 0;
  601 +}
  602 +
581 603 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
582 604 QCowL2Meta *m)
583 605 {
... ... @@ -625,10 +647,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
625 647 (i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
626 648 }
627 649  
628   - if (bdrv_pwrite(s->hd, l2_offset + l2_index * sizeof(uint64_t),
629   - l2_table + l2_index, m->nb_clusters * sizeof(uint64_t)) !=
630   - m->nb_clusters * sizeof(uint64_t))
  650 + if (write_l2_entries(s, l2_table, l2_offset, l2_index, m->nb_clusters) < 0) {
  651 + ret = -1;
631 652 goto err;
  653 + }
632 654  
633 655 for (i = 0; i < j; i++)
634 656 qcow2_free_any_clusters(bs,
... ...