gwj / at91sam9263 · Commits

Commit a980c98cf1acb3e813428d4f783a8ebd153ef036

Authored by Kevin Wolf
Committed by Anthony Liguori
1 parent 44ff42de

qcow2: Update multiple refcounts at once 

Don't write each single changed refcount block entry to the disk after it is
written, but update all entries of the block and write all of them at once.

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 36 additions and 4 deletions
block/qcow2.c
  View file @a980c98
... ... @@ -2578,6 +2578,9 @@ static int update_refcount(BlockDriverState *bs,
2578 2578 {
2579 2579 BDRVQcowState *s = bs->opaque;
2580 2580 int64_t start, last, cluster_offset;
  2581 + int64_t refcount_block_offset = 0;
  2582 + int64_t table_index = -1, old_table_index;
  2583 + int first_index = -1, last_index = -1;
2581 2584  
2582 2585 #ifdef DEBUG_ALLOC2
2583 2586 printf("update_refcount: offset=%lld size=%lld addend=%d\n",
... ... @@ -2590,10 +2593,25 @@ static int update_refcount(BlockDriverState *bs,
2590 2593 for(cluster_offset = start; cluster_offset <= last;
2591 2594 cluster_offset += s->cluster_size)
2592 2595 {
2593   - int64_t refcount_block_offset;
2594 2596 int block_index, refcount;
2595 2597 int64_t cluster_index = cluster_offset >> s->cluster_bits;
2596 2598  
  2599 + /* Only write refcount block to disk when we are done with it */
  2600 + old_table_index = table_index;
  2601 + table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
  2602 + if ((old_table_index >= 0) && (table_index != old_table_index)) {
  2603 + size_t size = (last_index - first_index + 1) << REFCOUNT_SHIFT;
  2604 + if (bdrv_pwrite(s->hd,
  2605 + refcount_block_offset + (first_index << REFCOUNT_SHIFT),
  2606 + &s->refcount_block_cache[first_index], size) != size)
  2607 + {
  2608 + return -EIO;
  2609 + }
  2610 +
  2611 + first_index = -1;
  2612 + last_index = -1;
  2613 + }
  2614 +
2597 2615 /* Load the refcount block and allocate it if needed */
2598 2616 refcount_block_offset = alloc_refcount_block(bs, cluster_index);
2599 2617 if (refcount_block_offset < 0) {
... ... @@ -2603,6 +2621,13 @@ static int update_refcount(BlockDriverState *bs,
2603 2621 /* we can update the count and save it */
2604 2622 block_index = cluster_index &
2605 2623 ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
  2624 + if (first_index == -1 || block_index < first_index) {
  2625 + first_index = block_index;
  2626 + }
  2627 + if (block_index > last_index) {
  2628 + last_index = block_index;
  2629 + }
  2630 +
2606 2631 refcount = be16_to_cpu(s->refcount_block_cache[block_index]);
2607 2632 refcount += addend;
2608 2633 if (refcount < 0 || refcount > 0xffff)
... ... @@ -2611,12 +2636,19 @@ static int update_refcount(BlockDriverState *bs,
2611 2636 s->free_cluster_index = cluster_index;
2612 2637 }
2613 2638 s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
  2639 + }
  2640 +
  2641 + /* Write last changed block to disk */
  2642 + if (refcount_block_offset != 0) {
  2643 + size_t size = (last_index - first_index + 1) << REFCOUNT_SHIFT;
2614 2644 if (bdrv_pwrite(s->hd,
2615   - refcount_block_offset + (block_index << REFCOUNT_SHIFT),
2616   - &s->refcount_block_cache[block_index], 2) != 2)
  2645 + refcount_block_offset + (first_index << REFCOUNT_SHIFT),
  2646 + &s->refcount_block_cache[first_index], size) != size)
  2647 + {
2617 2648 return -EIO;
2618   -
  2649 + }
2619 2650 }
  2651 +
2620 2652 return 0;
2621 2653 }
2622 2654  
... ...