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2795ecf681
xemu/block/qcow2-refcount.c
Kevin Wolf 2795ecf681 qcow2: Fix return value of alloc_refcount_block 
Someone forgot something in commit 29c1a730... Documenting the right
return value is not enough, you also need to actually return it in the
code.

This bug sometimes causes error return values even when everything has
succeeded: The new offset of the refcount block is truncated to 32 bits
and interpreted as signed. At least with small cluster sizes it's easy
to get a negative return value this way.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2012-04-19 16:03:27 +02:00

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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);
/*********************************************************/
/* refcount handling */
int qcow2_refcount_init(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int ret, refcount_table_size2, i;
refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
s->refcount_table = g_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;
g_free(s->refcount_table);
}
static int load_refcount_block(BlockDriverState *bs,
int64_t refcount_block_offset,
void **refcount_block)
{
BDRVQcowState *s = bs->opaque;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD);
ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
refcount_block);
return ret;
}
/*
* Returns the refcount of the cluster given by its index. Any non-negative
* return value is the refcount of the cluster, negative values are -errno
* and indicate an error.
*/
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;
int ret;
uint16_t *refcount_block;
uint16_t refcount;
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;
ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
(void**) &refcount_block);
if (ret < 0) {
return ret;
}
block_index = cluster_index &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
refcount = be16_to_cpu(refcount_block[block_index]);
ret = qcow2_cache_put(bs, s->refcount_block_cache,
(void**) &refcount_block);
if (ret < 0) {
return ret;
}
return refcount;
}
/*
* 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 0 on success or -errno in error case
*/
static int alloc_refcount_block(BlockDriverState *bs,
int64_t cluster_index, uint16_t **refcount_block)
{
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) {
return load_refcount_block(bs, refcount_block_offset,
(void**) refcount_block);
}
}
/*
* 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
*/
*refcount_block = NULL;
/* We write to the refcount table, so we might depend on L2 tables */
qcow2_cache_flush(bs, s->l2_table_cache);
/* Allocate the refcount block itself and mark it as used */
int64_t new_block = alloc_clusters_noref(bs, s->cluster_size);
if (new_block < 0) {
return 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)) {
/* Zero the new refcount block before updating it */
ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block,
(void**) refcount_block);
if (ret < 0) {
goto fail_block;
}
memset(*refcount_block, 0, s->cluster_size);
/* The block describes itself, need to update the cache */
int block_index = (new_block >> s->cluster_bits) &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
(*refcount_block)[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;
}
bdrv_flush(bs->file);
/* Initialize the new refcount block only after updating its refcount,
* update_refcount uses the refcount cache itself */
ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block,
(void**) refcount_block);
if (ret < 0) {
goto fail_block;
}
memset(*refcount_block, 0, s->cluster_size);
}
/* Now the new refcount block needs to be written to disk */
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE);
qcow2_cache_entry_mark_dirty(s->refcount_block_cache, *refcount_block);
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
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_sync(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 0;
}
ret = qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block);
if (ret < 0) {
goto fail_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 = g_malloc0(blocks_clusters * s->cluster_size);
uint64_t *new_table = g_malloc0(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_sync(bs->file, meta_offset, new_blocks,
blocks_clusters * s->cluster_size);
g_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_sync(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_sync(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;
g_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, (void**) refcount_block);
if (ret < 0) {
return ret;
}
return 0;
fail_table:
g_free(new_table);
fail_block:
if (*refcount_block != NULL) {
qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block);
}
return ret;
}
/* 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;
uint16_t *refcount_block = NULL;
int64_t old_table_index = -1;
int ret;
#ifdef DEBUG_ALLOC2
fprintf(stderr, "update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
offset, length, addend);
#endif
if (length < 0) {
return -EINVAL;
} else if (length == 0) {
return 0;
}
if (addend < 0) {
qcow2_cache_set_dependency(bs, s->refcount_block_cache,
s->l2_table_cache);
}
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 table_index =
cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
/* Load the refcount block and allocate it if needed */
if (table_index != old_table_index) {
if (refcount_block) {
ret = qcow2_cache_put(bs, s->refcount_block_cache,
(void**) &refcount_block);
if (ret < 0) {
goto fail;
}
}
ret = alloc_refcount_block(bs, cluster_index, &refcount_block);
if (ret < 0) {
goto fail;
}
}
old_table_index = table_index;
qcow2_cache_entry_mark_dirty(s->refcount_block_cache, refcount_block);
/* we can update the count and save it */
block_index = cluster_index &
((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
refcount = be16_to_cpu(refcount_block[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;
}
refcount_block[block_index] = cpu_to_be16(refcount);
}
ret = 0;
fail:
/* Write last changed block to disk */
if (refcount_block) {
int wret;
wret = qcow2_cache_put(bs, s->refcount_block_cache,
(void**) &refcount_block);
if (wret < 0) {
return ret < 0 ? ret : wret;
}
}
/*
* 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);
(void)dummy;
}
return ret;
}
/*
* Increases or decreases the refcount of a given cluster by one.
* addend must be 1 or -1.
*
* If the return value is non-negative, it is the new refcount of the cluster.
* If it is negative, it is -errno and indicates an error.
*/
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;
}
bdrv_flush(bs->file);
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, refcount;
nb_clusters = size_to_clusters(s, size);
retry:
for(i = 0; i < nb_clusters; i++) {
int64_t next_cluster_index = s->free_cluster_index++;
refcount = get_refcount(bs, next_cluster_index);
if (refcount < 0) {
return refcount;
} else if (refcount != 0) {
goto retry;
}
}
#ifdef DEBUG_ALLOC2
fprintf(stderr, "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);
if (offset < 0) {
return offset;
}
ret = update_refcount(bs, offset, size, 1);
if (ret < 0) {
return ret;
}
return offset;
}
int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
int nb_clusters)
{
BDRVQcowState *s = bs->opaque;
uint64_t cluster_index;
int i, refcount, ret;
/* Check how many clusters there are free */
cluster_index = offset >> s->cluster_bits;
for(i = 0; i < nb_clusters; i++) {
refcount = get_refcount(bs, cluster_index++);
if (refcount < 0) {
return refcount;
} else if (refcount != 0) {
break;
}
}
/* And then allocate them */
ret = update_refcount(bs, offset, i << s->cluster_bits, 1);
if (ret < 0) {
return ret;
}
return i;
}
/* 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;
}
}
bdrv_flush(bs->file);
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));
/* TODO Remember the clusters to free them later and avoid leaking */
}
}
/*
* 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 */
/* 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 i, j, l1_modified = 0, nb_csectors, refcount;
int ret;
bool old_l2_writethrough, old_refcount_writethrough;
/* Switch caches to writeback mode during update */
old_l2_writethrough =
qcow2_cache_set_writethrough(bs, s->l2_table_cache, false);
old_refcount_writethrough =
qcow2_cache_set_writethrough(bs, s->refcount_block_cache, false);
l2_table = NULL;
l1_table = NULL;
l1_size2 = l1_size * sizeof(uint64_t);
/* WARNING: qcow2_snapshot_goto relies on this function not using the
* l1_table_offset when it is the current s->l1_table_offset! Be careful
* when changing this! */
if (l1_table_offset != s->l1_table_offset) {
if (l1_size2 != 0) {
l1_table = g_malloc0(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)
{
ret = -EIO;
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;
}
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;
ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
(void**) &l2_table);
if (ret < 0) {
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;
}
/* TODO Flushing once for the whole function should
* be enough */
bdrv_flush(bs->file);
}
/* 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 < 0) {
ret = -EIO;
goto fail;
}
}
if (refcount == 1) {
offset |= QCOW_OFLAG_COPIED;
}
if (offset != old_offset) {
if (addend > 0) {
qcow2_cache_set_dependency(bs, s->l2_table_cache,
s->refcount_block_cache);
}
l2_table[j] = cpu_to_be64(offset);
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
}
}
}
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
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 < 0) {
ret = -EIO;
goto fail;
} else if (refcount == 1) {
l2_offset |= QCOW_OFLAG_COPIED;
}
if (l2_offset != old_l2_offset) {
l1_table[i] = l2_offset;
l1_modified = 1;
}
}
}
ret = 0;
fail:
if (l2_table) {
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
}
/* Enable writethrough cache mode again */
qcow2_cache_set_writethrough(bs, s->l2_table_cache, old_l2_writethrough);
qcow2_cache_set_writethrough(bs, s->refcount_block_cache,
old_refcount_writethrough);
/* Update L1 only if it isn't deleted anyway (addend = -1) */
if (addend >= 0 && l1_modified) {
for(i = 0; i < l1_size; i++)
cpu_to_be64s(&l1_table[i]);
if (bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table,
l1_size2) < 0)
goto fail;
for(i = 0; i < l1_size; i++)
be64_to_cpus(&l1_table[i]);
}
if (l1_allocated)
g_free(l1_table);
return ret;
}
/*********************************************************/
/* 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.
*
* Modifies the number of errors in res.
*/
static void inc_refcounts(BlockDriverState *bs,
BdrvCheckResult *res,
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;
if (size <= 0)
return;
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) {
fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",
cluster_offset);
res->corruptions++;
} else if (k >= refcount_table_size) {
fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after "
"the end of the image file, can't properly check refcounts.\n",
cluster_offset);
res->check_errors++;
} else {
if (++refcount_table[k] == 0) {
fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
"\n", cluster_offset);
res->corruptions++;
}
}
}
}
/*
* 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, BdrvCheckResult *res,
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;
/* Read L2 table from disk */
l2_size = s->l2_size * sizeof(uint64_t);
l2_table = g_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;
res->corruptions++;
}
/* Mark cluster as used */
nb_csectors = ((offset >> s->csize_shift) &
s->csize_mask) + 1;
offset &= s->cluster_offset_mask;
inc_refcounts(bs, res, 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 < 0) {
fprintf(stderr, "Can't get refcount for offset %"
PRIx64 ": %s\n", entry, strerror(-refcount));
goto fail;
}
if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
PRIx64 " refcount=%d\n", entry, refcount);
res->corruptions++;
}
}
/* Mark cluster as used */
offset &= ~QCOW_OFLAG_COPIED;
inc_refcounts(bs, res, 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);
res->corruptions++;
}
}
}
}
g_free(l2_table);
return 0;
fail:
fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n");
g_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,
BdrvCheckResult *res,
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;
l1_size2 = l1_size * sizeof(uint64_t);
/* Mark L1 table as used */
inc_refcounts(bs, res, 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 = g_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 < 0) {
fprintf(stderr, "Can't get refcount for l2_offset %"
PRIx64 ": %s\n", l2_offset, strerror(-refcount));
goto fail;
}
if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
" refcount=%d\n", l2_offset, refcount);
res->corruptions++;
}
}
/* Mark L2 table as used */
l2_offset &= ~QCOW_OFLAG_COPIED;
inc_refcounts(bs, res, 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);
res->corruptions++;
}
/* Process and check L2 entries */
ret = check_refcounts_l2(bs, res, refcount_table,
refcount_table_size, l2_offset, check_copied);
if (ret < 0) {
goto fail;
}
}
}
g_free(l1_table);
return 0;
fail:
fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
res->check_errors++;
g_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 occurred.
*/
int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res)
{
BDRVQcowState *s = bs->opaque;
int64_t size;
int nb_clusters, refcount1, refcount2, i;
QCowSnapshot *sn;
uint16_t *refcount_table;
int ret;
size = bdrv_getlength(bs->file);
nb_clusters = size_to_clusters(s, size);
refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t));
/* header */
inc_refcounts(bs, res, refcount_table, nb_clusters,
0, s->cluster_size);
/* current L1 table */
ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
s->l1_table_offset, s->l1_size, 1);
if (ret < 0) {
goto fail;
}
/* snapshots */
for(i = 0; i < s->nb_snapshots; i++) {
sn = s->snapshots + i;
ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
sn->l1_table_offset, sn->l1_size, 0);
if (ret < 0) {
goto fail;
}
}
inc_refcounts(bs, res, refcount_table, nb_clusters,
s->snapshots_offset, s->snapshots_size);
/* refcount data */
inc_refcounts(bs, res, refcount_table, nb_clusters,
s->refcount_table_offset,
s->refcount_table_size * sizeof(uint64_t));
for(i = 0; i < s->refcount_table_size; i++) {
uint64_t offset, cluster;
offset = s->refcount_table[i];
cluster = offset >> s->cluster_bits;
/* 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);
res->corruptions++;
continue;
}
if (cluster >= nb_clusters) {
fprintf(stderr, "ERROR refcount block %d is outside image\n", i);
res->corruptions++;
continue;
}
if (offset != 0) {
inc_refcounts(bs, res, refcount_table, nb_clusters,
offset, s->cluster_size);
if (refcount_table[cluster] != 1) {
fprintf(stderr, "ERROR refcount block %d refcount=%d\n",
i, refcount_table[cluster]);
res->corruptions++;
}
}
}
/* compare ref counts */
for(i = 0; i < nb_clusters; i++) {
refcount1 = get_refcount(bs, i);
if (refcount1 < 0) {
fprintf(stderr, "Can't get refcount for cluster %d: %s\n",
i, strerror(-refcount1));
res->check_errors++;
continue;
}
refcount2 = refcount_table[i];
if (refcount1 != refcount2) {
fprintf(stderr, "%s cluster %d refcount=%d reference=%d\n",
refcount1 < refcount2 ? "ERROR" : "Leaked",
i, refcount1, refcount2);
if (refcount1 < refcount2) {
res->corruptions++;
} else {
res->leaks++;
}
}
}
ret = 0;
fail:
g_free(refcount_table);
return ret;
}
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