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qcow2: Update multiple refcounts at once

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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>
This commit is contained in:
Kevin Wolf 2009-05-26 14:36:03 +02:00 committed by Anthony Liguori
parent 44ff42de1c
commit a980c98cf1
1 changed files with 38 additions and 6 deletions
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44
block/qcow2.c
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@ -2578,6 +2578,9 @@ static int update_refcount(BlockDriverState *bs,
{
BDRVQcowState *s = bs->opaque;
int64_t start, last, cluster_offset;
int64_t refcount_block_offset = 0;
int64_t table_index = -1, old_table_index;
int first_index = -1, last_index = -1;
#ifdef DEBUG_ALLOC2
printf("update_refcount: offset=%lld size=%lld addend=%d\n",
@ -2590,10 +2593,25 @@ static int update_refcount(BlockDriverState *bs,
for(cluster_offset = start; cluster_offset <= last;
cluster_offset += s->cluster_size)
{
int64_t refcount_block_offset;
int block_index, refcount;
int64_t cluster_index = cluster_offset >> s->cluster_bits;
/* Only write refcount block to disk when we are done with it */
old_table_index = table_index;
table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
if ((old_table_index >= 0) && (table_index != old_table_index)) {
size_t size = (last_index - first_index + 1) << REFCOUNT_SHIFT;
if (bdrv_pwrite(s->hd,
refcount_block_offset + (first_index << REFCOUNT_SHIFT),
&s->refcount_block_cache[first_index], size) != size)
{
return -EIO;
}
first_index = -1;
last_index = -1;
}
/* Load the refcount block and allocate it if needed */
refcount_block_offset = alloc_refcount_block(bs, cluster_index);
if (refcount_block_offset < 0) {
@ -2603,6 +2621,13 @@ static int update_refcount(BlockDriverState *bs,
/* we can update the count and save it */
block_index = cluster_index &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
if (first_index == -1 || block_index < first_index) {
first_index = block_index;
}
if (block_index > last_index) {
last_index = block_index;
}
refcount = be16_to_cpu(s->refcount_block_cache[block_index]);
refcount += addend;
if (refcount < 0 || refcount > 0xffff)
@ -2611,12 +2636,19 @@ static int update_refcount(BlockDriverState *bs,
s->free_cluster_index = cluster_index;
}
s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
if (bdrv_pwrite(s->hd,
refcount_block_offset + (block_index << REFCOUNT_SHIFT),
&s->refcount_block_cache[block_index], 2) != 2)
return -EIO;
}
/* Write last changed block to disk */
if (refcount_block_offset != 0) {
size_t size = (last_index - first_index + 1) << REFCOUNT_SHIFT;
if (bdrv_pwrite(s->hd,
refcount_block_offset + (first_index << REFCOUNT_SHIFT),
&s->refcount_block_cache[first_index], size) != size)
{
return -EIO;
}
}
return 0;
}