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qemu/block/qcow2-refcount.c
Kevin Wolf 66f82ceed6 block: Open the underlying image file in generic code 
Format drivers shouldn't need to bother with things like file names, but rather
just get an open BlockDriverState for the underlying protocol. This patch
introduces this behaviour for bdrv_open implementation. For protocols which
need to access the filename to open their file/device/connection/... a new
callback bdrv_file_open is introduced which doesn't get an underlying file
opened.

For now, also some of the more obscure formats use bdrv_file_open because they
open() the file themselves instead of using the block.c functions. They need to
be fixed in later patches.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-05-03 10:07:30 +02:00

1119 lines
36 KiB
C
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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(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
size_t size = s->cluster_size;
if (s->refcount_block_cache_offset == 0) {
return 0;
}
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE);
if (bdrv_pwrite(bs->file, 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) {
BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_LOAD);
ret = bdrv_pread(bs->file, 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(bs);
}
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD);
ret = bdrv_pread(bs->file, 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;
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC);
/* 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(bs);
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 */
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE);
ret = bdrv_pwrite(bs->file, 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);
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_HOOKUP);
ret = bdrv_pwrite(bs->file,
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.
*/
BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW);
/* 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 */
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_BLOCKS);
ret = bdrv_pwrite(bs->file, 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]);
}
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_TABLE);
ret = bdrv_pwrite(bs->file, 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);
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE);
ret = bdrv_pwrite(bs->file, 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(BlockDriverState *bs,
int64_t refcount_block_offset, int first_index, int last_index)
{
BDRVQcowState *s = bs->opaque;
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;
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
if (bdrv_pwrite(bs->file,
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(bs, 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(bs, 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;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC);
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;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);
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;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE);
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(bs->file, 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(bs->file, 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(bs->file,
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(bs->file, 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(bs);
return 0;
fail:
if (l1_allocated)
qemu_free(l1_table);
qemu_free(l2_table);
cache_refcount_updates = 0;
write_refcount_block(bs);
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(bs->file, 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(bs->file, 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(bs->file);
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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