motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-02 23:33:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

qcow2: add shrink image support

Browse source 
This patch add shrinking of the image file for qcow2. As a result, this allows
us to reduce the virtual image size and free up space on the disk without
copying the image. Image can be fragmented and shrink is done by punching holes
in the image file.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170918124230.8152-4-pbutsykin@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Pavel Butsykin 2017-09-18 15:42:29 +03:00 • committed by Max Reitz
parent f71c08ea8e
commit 46b732cdf3
5 changed files with 227 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

50
block/qcow2-cluster.c
View file

@ -32,6 +32,56 @@
#include "qemu/bswap.h"
#include "trace.h"
int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t exact_size)
{
BDRVQcow2State *s = bs->opaque;
int new_l1_size, i, ret;
if (exact_size >= s->l1_size) {
return 0;
}
new_l1_size = exact_size;
#ifdef DEBUG_ALLOC2
fprintf(stderr, "shrink l1_table from %d to %d\n", s->l1_size, new_l1_size);
#endif
BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_WRITE_TABLE);
ret = bdrv_pwrite_zeroes(bs->file, s->l1_table_offset +
new_l1_size * sizeof(uint64_t),
(s->l1_size - new_l1_size) * sizeof(uint64_t), 0);
if (ret < 0) {
goto fail;
}
ret = bdrv_flush(bs->file->bs);
if (ret < 0) {
goto fail;
}
BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS);
for (i = s->l1_size - 1; i > new_l1_size - 1; i--) {
if ((s->l1_table[i] & L1E_OFFSET_MASK) == 0) {
continue;
}
qcow2_free_clusters(bs, s->l1_table[i] & L1E_OFFSET_MASK,
s->cluster_size, QCOW2_DISCARD_ALWAYS);
s->l1_table[i] = 0;
}
return 0;
fail:
/*
* If the write in the l1_table failed the image may contain a partially
* overwritten l1_table. In this case it would be better to clear the
* l1_table in memory to avoid possible image corruption.
*/
memset(s->l1_table + new_l1_size, 0,
(s->l1_size - new_l1_size) * sizeof(uint64_t));
return ret;
}
int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
bool exact_size)
{