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qemu/block/qcow2-refcount.c
Kevin Wolf 746c3cb5d5 qcow2: More checks for qemu-img check 
Implement some more refcount block related checks

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2010-02-23 13:23:29 -06:00

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/*
* Block driver for the QCOW version 2 format
*
* Copyright (c) 2004-2006 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block_int.h"
#include "block/qcow2.h"
static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size);
static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
int64_t offset, int64_t length,
int addend);
static int cache_refcount_updates = 0;
static int write_refcount_block(BDRVQcowState *s)
{
size_t size = s->cluster_size;
if (s->refcount_block_cache_offset == 0) {
return 0;
}
if (bdrv_pwrite(s->hd, s->refcount_block_cache_offset,
s->refcount_block_cache, size) != size)
{
return -EIO;
}
return 0;
}
/*********************************************************/
/* refcount handling */
int qcow2_refcount_init(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int ret, refcount_table_size2, i;
s->refcount_block_cache = qemu_malloc(s->cluster_size);
refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
s->refcount_table = qemu_malloc(refcount_table_size2);
if (s->refcount_table_size > 0) {
ret = bdrv_pread(s->hd, s->refcount_table_offset,
s->refcount_table, refcount_table_size2);
if (ret != refcount_table_size2)
goto fail;
for(i = 0; i < s->refcount_table_size; i++)
be64_to_cpus(&s->refcount_table[i]);
}
return 0;
fail:
return -ENOMEM;
}
void qcow2_refcount_close(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
qemu_free(s->refcount_block_cache);
qemu_free(s->refcount_table);
}
static int load_refcount_block(BlockDriverState *bs,
int64_t refcount_block_offset)
{
BDRVQcowState *s = bs->opaque;
int ret;
if (cache_refcount_updates) {
write_refcount_block(s);
}
ret = bdrv_pread(s->hd, refcount_block_offset, s->refcount_block_cache,
s->cluster_size);
if (ret != s->cluster_size)
return -EIO;
s->refcount_block_cache_offset = refcount_block_offset;
return 0;
}
static int get_refcount(BlockDriverState *bs, int64_t cluster_index)
{
BDRVQcowState *s = bs->opaque;
int refcount_table_index, block_index;
int64_t refcount_block_offset;
refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
if (refcount_table_index >= s->refcount_table_size)
return 0;
refcount_block_offset = s->refcount_table[refcount_table_index];
if (!refcount_block_offset)
return 0;
if (refcount_block_offset != s->refcount_block_cache_offset) {
/* better than nothing: return allocated if read error */
if (load_refcount_block(bs, refcount_block_offset) < 0)
return 1;
}
block_index = cluster_index &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
return be16_to_cpu(s->refcount_block_cache[block_index]);
}
/*
* Rounds the refcount table size up to avoid growing the table for each single
* refcount block that is allocated.
*/
static unsigned int next_refcount_table_size(BDRVQcowState *s,
unsigned int min_size)
{
unsigned int min_clusters = (min_size >> (s->cluster_bits - 3)) + 1;
unsigned int refcount_table_clusters =
MAX(1, s->refcount_table_size >> (s->cluster_bits - 3));
while (min_clusters > refcount_table_clusters) {
refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2;
}
return refcount_table_clusters << (s->cluster_bits - 3);
}
/* Checks if two offsets are described by the same refcount block */
static int in_same_refcount_block(BDRVQcowState *s, uint64_t offset_a,
uint64_t offset_b)
{
uint64_t block_a = offset_a >> (2 * s->cluster_bits - REFCOUNT_SHIFT);
uint64_t block_b = offset_b >> (2 * s->cluster_bits - REFCOUNT_SHIFT);
return (block_a == block_b);
}
/*
* Loads a refcount block. If it doesn't exist yet, it is allocated first
* (including growing the refcount table if needed).
*
* Returns the offset of the refcount block on success or -errno in error case
*/
static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index)
{
BDRVQcowState *s = bs->opaque;
unsigned int refcount_table_index;
int ret;
/* Find the refcount block for the given cluster */
refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
if (refcount_table_index < s->refcount_table_size) {
uint64_t refcount_block_offset =
s->refcount_table[refcount_table_index];
/* If it's already there, we're done */
if (refcount_block_offset) {
if (refcount_block_offset != s->refcount_block_cache_offset) {
ret = load_refcount_block(bs, refcount_block_offset);
if (ret < 0) {
return ret;
}
}
return refcount_block_offset;
}
}
/*
* If we came here, we need to allocate something. Something is at least
* a cluster for the new refcount block. It may also include a new refcount
* table if the old refcount table is too small.
*
* Note that allocating clusters here needs some special care:
*
* - We can't use the normal qcow2_alloc_clusters(), it would try to
* increase the refcount and very likely we would end up with an endless
* recursion. Instead we must place the refcount blocks in a way that
* they can describe them themselves.
*
* - We need to consider that at this point we are inside update_refcounts
* and doing the initial refcount increase. This means that some clusters
* have already been allocated by the caller, but their refcount isn't
* accurate yet. free_cluster_index tells us where this allocation ends
* as long as we don't overwrite it by freeing clusters.
*
* - alloc_clusters_noref and qcow2_free_clusters may load a different
* refcount block into the cache
*/
if (cache_refcount_updates) {
ret = write_refcount_block(s);
if (ret < 0) {
return ret;
}
}
/* Allocate the refcount block itself and mark it as used */
uint64_t new_block = alloc_clusters_noref(bs, s->cluster_size);
memset(s->refcount_block_cache, 0, s->cluster_size);
s->refcount_block_cache_offset = new_block;
#ifdef DEBUG_ALLOC2
fprintf(stderr, "qcow2: Allocate refcount block %d for %" PRIx64
" at %" PRIx64 "\n",
refcount_table_index, cluster_index << s->cluster_bits, new_block);
#endif
if (in_same_refcount_block(s, new_block, cluster_index << s->cluster_bits)) {
/* The block describes itself, need to update the cache */
int block_index = (new_block >> s->cluster_bits) &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
s->refcount_block_cache[block_index] = cpu_to_be16(1);
} else {
/* Described somewhere else. This can recurse at most twice before we
* arrive at a block that describes itself. */
ret = update_refcount(bs, new_block, s->cluster_size, 1);
if (ret < 0) {
goto fail_block;
}
}
/* Now the new refcount block needs to be written to disk */
ret = bdrv_pwrite(s->hd, new_block, s->refcount_block_cache,
s->cluster_size);
if (ret < 0) {
goto fail_block;
}
/* If the refcount table is big enough, just hook the block up there */
if (refcount_table_index < s->refcount_table_size) {
uint64_t data64 = cpu_to_be64(new_block);
ret = bdrv_pwrite(s->hd,
s->refcount_table_offset + refcount_table_index * sizeof(uint64_t),
&data64, sizeof(data64));
if (ret < 0) {
goto fail_block;
}
s->refcount_table[refcount_table_index] = new_block;
return new_block;
}
/*
* If we come here, we need to grow the refcount table. Again, a new
* refcount table needs some space and we can't simply allocate to avoid
* endless recursion.
*
* Therefore let's grab new refcount blocks at the end of the image, which
* will describe themselves and the new refcount table. This way we can
* reference them only in the new table and do the switch to the new
* refcount table at once without producing an inconsistent state in
* between.
*/
/* Calculate the number of refcount blocks needed so far */
uint64_t refcount_block_clusters = 1 << (s->cluster_bits - REFCOUNT_SHIFT);
uint64_t blocks_used = (s->free_cluster_index +
refcount_block_clusters - 1) / refcount_block_clusters;
/* And now we need at least one block more for the new metadata */
uint64_t table_size = next_refcount_table_size(s, blocks_used + 1);
uint64_t last_table_size;
uint64_t blocks_clusters;
do {
uint64_t table_clusters = size_to_clusters(s, table_size);
blocks_clusters = 1 +
((table_clusters + refcount_block_clusters - 1)
/ refcount_block_clusters);
uint64_t meta_clusters = table_clusters + blocks_clusters;
last_table_size = table_size;
table_size = next_refcount_table_size(s, blocks_used +
((meta_clusters + refcount_block_clusters - 1)
/ refcount_block_clusters));
} while (last_table_size != table_size);
#ifdef DEBUG_ALLOC2
fprintf(stderr, "qcow2: Grow refcount table %" PRId32 " => %" PRId64 "\n",
s->refcount_table_size, table_size);
#endif
/* Create the new refcount table and blocks */
uint64_t meta_offset = (blocks_used * refcount_block_clusters) *
s->cluster_size;
uint64_t table_offset = meta_offset + blocks_clusters * s->cluster_size;
uint16_t *new_blocks = qemu_mallocz(blocks_clusters * s->cluster_size);
uint64_t *new_table = qemu_mallocz(table_size * sizeof(uint64_t));
assert(meta_offset >= (s->free_cluster_index * s->cluster_size));
/* Fill the new refcount table */
memcpy(new_table, s->refcount_table,
s->refcount_table_size * sizeof(uint64_t));
new_table[refcount_table_index] = new_block;
int i;
for (i = 0; i < blocks_clusters; i++) {
new_table[blocks_used + i] = meta_offset + (i * s->cluster_size);
}
/* Fill the refcount blocks */
uint64_t table_clusters = size_to_clusters(s, table_size * sizeof(uint64_t));
int block = 0;
for (i = 0; i < table_clusters + blocks_clusters; i++) {
new_blocks[block++] = cpu_to_be16(1);
}
/* Write refcount blocks to disk */
ret = bdrv_pwrite(s->hd, meta_offset, new_blocks,
blocks_clusters * s->cluster_size);
qemu_free(new_blocks);
if (ret < 0) {
goto fail_table;
}
/* Write refcount table to disk */
for(i = 0; i < table_size; i++) {
cpu_to_be64s(&new_table[i]);
}
ret = bdrv_pwrite(s->hd, table_offset, new_table,
table_size * sizeof(uint64_t));
if (ret < 0) {
goto fail_table;
}
for(i = 0; i < table_size; i++) {
cpu_to_be64s(&new_table[i]);
}
/* Hook up the new refcount table in the qcow2 header */
uint8_t data[12];
cpu_to_be64w((uint64_t*)data, table_offset);
cpu_to_be32w((uint32_t*)(data + 8), table_clusters);
ret = bdrv_pwrite(s->hd, offsetof(QCowHeader, refcount_table_offset),
data, sizeof(data));
if (ret < 0) {
goto fail_table;
}
/* And switch it in memory */
uint64_t old_table_offset = s->refcount_table_offset;
uint64_t old_table_size = s->refcount_table_size;
qemu_free(s->refcount_table);
s->refcount_table = new_table;
s->refcount_table_size = table_size;
s->refcount_table_offset = table_offset;
/* Free old table. Remember, we must not change free_cluster_index */
uint64_t old_free_cluster_index = s->free_cluster_index;
qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t));
s->free_cluster_index = old_free_cluster_index;
ret = load_refcount_block(bs, new_block);
if (ret < 0) {
goto fail_block;
}
return new_block;
fail_table:
qemu_free(new_table);
fail_block:
s->refcount_block_cache_offset = 0;
return ret;
}
#define REFCOUNTS_PER_SECTOR (512 >> REFCOUNT_SHIFT)
static int write_refcount_block_entries(BDRVQcowState *s,
int64_t refcount_block_offset, int first_index, int last_index)
{
size_t size;
if (cache_refcount_updates) {
return 0;
}
first_index &= ~(REFCOUNTS_PER_SECTOR - 1);
last_index = (last_index + REFCOUNTS_PER_SECTOR)
& ~(REFCOUNTS_PER_SECTOR - 1);
size = (last_index - first_index) << 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;
}
/* XXX: cache several refcount block clusters ? */
static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
int64_t offset, int64_t length, int addend)
{
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;
int ret;
#ifdef DEBUG_ALLOC2
printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
offset, length, addend);
#endif
if (length < 0) {
return -EINVAL;
} else if (length == 0) {
return 0;
}
start = offset & ~(s->cluster_size - 1);
last = (offset + length - 1) & ~(s->cluster_size - 1);
for(cluster_offset = start; cluster_offset <= last;
cluster_offset += s->cluster_size)
{
int block_index, refcount;
int64_t cluster_index = cluster_offset >> s->cluster_bits;
int64_t new_block;
/* 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)) {
if (write_refcount_block_entries(s, refcount_block_offset,
first_index, last_index) < 0)
{
return -EIO;
}
first_index = -1;
last_index = -1;
}
/* Load the refcount block and allocate it if needed */
new_block = alloc_refcount_block(bs, cluster_index);
if (new_block < 0) {
ret = new_block;
goto fail;
}
refcount_block_offset = new_block;
/* 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) {
ret = -EINVAL;
goto fail;
}
if (refcount == 0 && cluster_index < s->free_cluster_index) {
s->free_cluster_index = cluster_index;
}
s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
}
ret = 0;
fail:
/* Write last changed block to disk */
if (refcount_block_offset != 0) {
if (write_refcount_block_entries(s, refcount_block_offset,
first_index, last_index) < 0)
{
return ret < 0 ? ret : -EIO;
}
}
/*
* Try do undo any updates if an error is returned (This may succeed in
* some cases like ENOSPC for allocating a new refcount block)
*/
if (ret < 0) {
int dummy;
dummy = update_refcount(bs, offset, cluster_offset - offset, -addend);
}
return ret;
}
/* addend must be 1 or -1 */
static int update_cluster_refcount(BlockDriverState *bs,
int64_t cluster_index,
int addend)
{
BDRVQcowState *s = bs->opaque;
int ret;
ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend);
if (ret < 0) {
return ret;
}
return get_refcount(bs, cluster_index);
}
/*********************************************************/
/* cluster allocation functions */
/* return < 0 if error */
static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size)
{
BDRVQcowState *s = bs->opaque;
int i, nb_clusters;
nb_clusters = size_to_clusters(s, size);
retry:
for(i = 0; i < nb_clusters; i++) {
int64_t i = s->free_cluster_index++;
if (get_refcount(bs, i) != 0)
goto retry;
}
#ifdef DEBUG_ALLOC2
printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",
size,
(s->free_cluster_index - nb_clusters) << s->cluster_bits);
#endif
return (s->free_cluster_index - nb_clusters) << s->cluster_bits;
}
int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size)
{
int64_t offset;
int ret;
offset = alloc_clusters_noref(bs, size);
ret = update_refcount(bs, offset, size, 1);
if (ret < 0) {
return ret;
}
return offset;
}
/* only used to allocate compressed sectors. We try to allocate
contiguous sectors. size must be <= cluster_size */
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
{
BDRVQcowState *s = bs->opaque;
int64_t offset, cluster_offset;
int free_in_cluster;
assert(size > 0 && size <= s->cluster_size);
if (s->free_byte_offset == 0) {
s->free_byte_offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (s->free_byte_offset < 0) {
return s->free_byte_offset;
}
}
redo:
free_in_cluster = s->cluster_size -
(s->free_byte_offset & (s->cluster_size - 1));
if (size <= free_in_cluster) {
/* enough space in current cluster */
offset = s->free_byte_offset;
s->free_byte_offset += size;
free_in_cluster -= size;
if (free_in_cluster == 0)
s->free_byte_offset = 0;
if ((offset & (s->cluster_size - 1)) != 0)
update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
} else {
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
return offset;
}
cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1);
if ((cluster_offset + s->cluster_size) == offset) {
/* we are lucky: contiguous data */
offset = s->free_byte_offset;
update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
s->free_byte_offset += size;
} else {
s->free_byte_offset = offset;
goto redo;
}
}
return offset;
}
void qcow2_free_clusters(BlockDriverState *bs,
int64_t offset, int64_t size)
{
int ret;
ret = update_refcount(bs, offset, size, -1);
if (ret < 0) {
fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret));
abort();
}
}
/*
* free_any_clusters
*
* free clusters according to its type: compressed or not
*
*/
void qcow2_free_any_clusters(BlockDriverState *bs,
uint64_t cluster_offset, int nb_clusters)
{
BDRVQcowState *s = bs->opaque;
/* free the cluster */
if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
int nb_csectors;
nb_csectors = ((cluster_offset >> s->csize_shift) &
s->csize_mask) + 1;
qcow2_free_clusters(bs,
(cluster_offset & s->cluster_offset_mask) & ~511,
nb_csectors * 512);
return;
}
qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits);
return;
}
/*********************************************************/
/* snapshots and image creation */
void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset,
int64_t size)
{
int refcount;
int64_t start, last, cluster_offset;
uint16_t *p;
start = offset & ~(s->cluster_size - 1);
last = (offset + size - 1) & ~(s->cluster_size - 1);
for(cluster_offset = start; cluster_offset <= last;
cluster_offset += s->cluster_size) {
p = &s->refcount_block[cluster_offset >> s->cluster_bits];
refcount = be16_to_cpu(*p);
refcount++;
*p = cpu_to_be16(refcount);
}
}
/* update the refcounts of snapshots and the copied flag */
int qcow2_update_snapshot_refcount(BlockDriverState *bs,
int64_t l1_table_offset, int l1_size, int addend)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated;
int64_t old_offset, old_l2_offset;
int l2_size, i, j, l1_modified, l2_modified, nb_csectors, refcount;
qcow2_l2_cache_reset(bs);
cache_refcount_updates = 1;
l2_table = NULL;
l1_table = NULL;
l1_size2 = l1_size * sizeof(uint64_t);
if (l1_table_offset != s->l1_table_offset) {
if (l1_size2 != 0) {
l1_table = qemu_mallocz(align_offset(l1_size2, 512));
} else {
l1_table = NULL;
}
l1_allocated = 1;
if (bdrv_pread(s->hd, l1_table_offset,
l1_table, l1_size2) != l1_size2)
goto fail;
for(i = 0;i < l1_size; i++)
be64_to_cpus(&l1_table[i]);
} else {
assert(l1_size == s->l1_size);
l1_table = s->l1_table;
l1_allocated = 0;
}
l2_size = s->l2_size * sizeof(uint64_t);
l2_table = qemu_malloc(l2_size);
l1_modified = 0;
for(i = 0; i < l1_size; i++) {
l2_offset = l1_table[i];
if (l2_offset) {
old_l2_offset = l2_offset;
l2_offset &= ~QCOW_OFLAG_COPIED;
l2_modified = 0;
if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)
goto fail;
for(j = 0; j < s->l2_size; j++) {
offset = be64_to_cpu(l2_table[j]);
if (offset != 0) {
old_offset = offset;
offset &= ~QCOW_OFLAG_COPIED;
if (offset & QCOW_OFLAG_COMPRESSED) {
nb_csectors = ((offset >> s->csize_shift) &
s->csize_mask) + 1;
if (addend != 0) {
int ret;
ret = update_refcount(bs,
(offset & s->cluster_offset_mask) & ~511,
nb_csectors * 512, addend);
if (ret < 0) {
goto fail;
}
}
/* compressed clusters are never modified */
refcount = 2;
} else {
if (addend != 0) {
refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend);
} else {
refcount = get_refcount(bs, offset >> s->cluster_bits);
}
}
if (refcount == 1) {
offset |= QCOW_OFLAG_COPIED;
}
if (offset != old_offset) {
l2_table[j] = cpu_to_be64(offset);
l2_modified = 1;
}
}
}
if (l2_modified) {
if (bdrv_pwrite(s->hd,
l2_offset, l2_table, l2_size) != l2_size)
goto fail;
}
if (addend != 0) {
refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend);
} else {
refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
}
if (refcount == 1) {
l2_offset |= QCOW_OFLAG_COPIED;
}
if (l2_offset != old_l2_offset) {
l1_table[i] = l2_offset;
l1_modified = 1;
}
}
}
if (l1_modified) {
for(i = 0; i < l1_size; i++)
cpu_to_be64s(&l1_table[i]);
if (bdrv_pwrite(s->hd, l1_table_offset, l1_table,
l1_size2) != l1_size2)
goto fail;
for(i = 0; i < l1_size; i++)
be64_to_cpus(&l1_table[i]);
}
if (l1_allocated)
qemu_free(l1_table);
qemu_free(l2_table);
cache_refcount_updates = 0;
write_refcount_block(s);
return 0;
fail:
if (l1_allocated)
qemu_free(l1_table);
qemu_free(l2_table);
cache_refcount_updates = 0;
write_refcount_block(s);
return -EIO;
}
/*********************************************************/
/* refcount checking functions */
/*
* Increases the refcount for a range of clusters in a given refcount table.
* This is used to construct a temporary refcount table out of L1 and L2 tables
* which can be compared the the refcount table saved in the image.
*
* Returns the number of errors in the image that were found
*/
static int inc_refcounts(BlockDriverState *bs,
uint16_t *refcount_table,
int refcount_table_size,
int64_t offset, int64_t size)
{
BDRVQcowState *s = bs->opaque;
int64_t start, last, cluster_offset;
int k;
int errors = 0;
if (size <= 0)
return 0;
start = offset & ~(s->cluster_size - 1);
last = (offset + size - 1) & ~(s->cluster_size - 1);
for(cluster_offset = start; cluster_offset <= last;
cluster_offset += s->cluster_size) {
k = cluster_offset >> s->cluster_bits;
if (k < 0 || k >= refcount_table_size) {
fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",
cluster_offset);
errors++;
} else {
if (++refcount_table[k] == 0) {
fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
"\n", cluster_offset);
errors++;
}
}
}
return errors;
}
/*
* Increases the refcount in the given refcount table for the all clusters
* referenced in the L2 table. While doing so, performs some checks on L2
* entries.
*
* Returns the number of errors found by the checks or -errno if an internal
* error occurred.
*/
static int check_refcounts_l2(BlockDriverState *bs,
uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,
int check_copied)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l2_table, offset;
int i, l2_size, nb_csectors, refcount;
int errors = 0;
/* Read L2 table from disk */
l2_size = s->l2_size * sizeof(uint64_t);
l2_table = qemu_malloc(l2_size);
if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)
goto fail;
/* Do the actual checks */
for(i = 0; i < s->l2_size; i++) {
offset = be64_to_cpu(l2_table[i]);
if (offset != 0) {
if (offset & QCOW_OFLAG_COMPRESSED) {
/* Compressed clusters don't have QCOW_OFLAG_COPIED */
if (offset & QCOW_OFLAG_COPIED) {
fprintf(stderr, "ERROR: cluster %" PRId64 ": "
"copied flag must never be set for compressed "
"clusters\n", offset >> s->cluster_bits);
offset &= ~QCOW_OFLAG_COPIED;
errors++;
}
/* Mark cluster as used */
nb_csectors = ((offset >> s->csize_shift) &
s->csize_mask) + 1;
offset &= s->cluster_offset_mask;
errors += inc_refcounts(bs, refcount_table,
refcount_table_size,
offset & ~511, nb_csectors * 512);
} else {
/* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
if (check_copied) {
uint64_t entry = offset;
offset &= ~QCOW_OFLAG_COPIED;
refcount = get_refcount(bs, offset >> s->cluster_bits);
if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
PRIx64 " refcount=%d\n", entry, refcount);
errors++;
}
}
/* Mark cluster as used */
offset &= ~QCOW_OFLAG_COPIED;
errors += inc_refcounts(bs, refcount_table,
refcount_table_size,
offset, s->cluster_size);
/* Correct offsets are cluster aligned */
if (offset & (s->cluster_size - 1)) {
fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
"properly aligned; L2 entry corrupted.\n", offset);
errors++;
}
}
}
}
qemu_free(l2_table);
return errors;
fail:
fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
qemu_free(l2_table);
return -EIO;
}
/*
* Increases the refcount for the L1 table, its L2 tables and all referenced
* clusters in the given refcount table. While doing so, performs some checks
* on L1 and L2 entries.
*
* Returns the number of errors found by the checks or -errno if an internal
* error occurred.
*/
static int check_refcounts_l1(BlockDriverState *bs,
uint16_t *refcount_table,
int refcount_table_size,
int64_t l1_table_offset, int l1_size,
int check_copied)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l1_table, l2_offset, l1_size2;
int i, refcount, ret;
int errors = 0;
l1_size2 = l1_size * sizeof(uint64_t);
/* Mark L1 table as used */
errors += inc_refcounts(bs, refcount_table, refcount_table_size,
l1_table_offset, l1_size2);
/* Read L1 table entries from disk */
if (l1_size2 == 0) {
l1_table = NULL;
} else {
l1_table = qemu_malloc(l1_size2);
if (bdrv_pread(s->hd, l1_table_offset,
l1_table, l1_size2) != l1_size2)
goto fail;
for(i = 0;i < l1_size; i++)
be64_to_cpus(&l1_table[i]);
}
/* Do the actual checks */
for(i = 0; i < l1_size; i++) {
l2_offset = l1_table[i];
if (l2_offset) {
/* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
if (check_copied) {
refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED)
>> s->cluster_bits);
if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
" refcount=%d\n", l2_offset, refcount);
errors++;
}
}
/* Mark L2 table as used */
l2_offset &= ~QCOW_OFLAG_COPIED;
errors += inc_refcounts(bs, refcount_table,
refcount_table_size,
l2_offset,
s->cluster_size);
/* L2 tables are cluster aligned */
if (l2_offset & (s->cluster_size - 1)) {
fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
"cluster aligned; L1 entry corrupted\n", l2_offset);
errors++;
}
/* Process and check L2 entries */
ret = check_refcounts_l2(bs, refcount_table, refcount_table_size,
l2_offset, check_copied);
if (ret < 0) {
goto fail;
}
errors += ret;
}
}
qemu_free(l1_table);
return errors;
fail:
fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
qemu_free(l1_table);
return -EIO;
}
/*
* Checks an image for refcount consistency.
*
* Returns 0 if no errors are found, the number of errors in case the image is
* detected as corrupted, and -errno when an internal error occured.
*/
int qcow2_check_refcounts(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int64_t size;
int nb_clusters, refcount1, refcount2, i;
QCowSnapshot *sn;
uint16_t *refcount_table;
int ret, errors = 0;
size = bdrv_getlength(s->hd);
nb_clusters = size_to_clusters(s, size);
refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t));
/* header */
errors += inc_refcounts(bs, refcount_table, nb_clusters,
0, s->cluster_size);
/* current L1 table */
ret = check_refcounts_l1(bs, refcount_table, nb_clusters,
s->l1_table_offset, s->l1_size, 1);
if (ret < 0) {
return ret;
}
errors += ret;
/* snapshots */
for(i = 0; i < s->nb_snapshots; i++) {
sn = s->snapshots + i;
check_refcounts_l1(bs, refcount_table, nb_clusters,
sn->l1_table_offset, sn->l1_size, 0);
}
errors += inc_refcounts(bs, refcount_table, nb_clusters,
s->snapshots_offset, s->snapshots_size);
/* refcount data */
errors += inc_refcounts(bs, refcount_table, nb_clusters,
s->refcount_table_offset,
s->refcount_table_size * sizeof(uint64_t));
for(i = 0; i < s->refcount_table_size; i++) {
int64_t offset;
offset = s->refcount_table[i];
/* Refcount blocks are cluster aligned */
if (offset & (s->cluster_size - 1)) {
fprintf(stderr, "ERROR refcount block %d is not "
"cluster aligned; refcount table entry corrupted\n", i);
errors++;
}
if (offset != 0) {
errors += inc_refcounts(bs, refcount_table, nb_clusters,
offset, s->cluster_size);
if (refcount_table[offset / s->cluster_size] != 1) {
fprintf(stderr, "ERROR refcount block %d refcount=%d\n",
i, refcount_table[offset / s->cluster_size]);
}
}
}
/* compare ref counts */
for(i = 0; i < nb_clusters; i++) {
refcount1 = get_refcount(bs, i);
refcount2 = refcount_table[i];
if (refcount1 != refcount2) {
fprintf(stderr, "ERROR cluster %d refcount=%d reference=%d\n",
i, refcount1, refcount2);
errors++;
}
}
qemu_free(refcount_table);
return errors;
}
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