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7454d60045
xemu/block/qcow2-refcount.c
Max Reitz 7454d60045 qcow2: Don't shadow return value 
When trying to update the refcounts for a snapshot, the return value of
update_refcount on a compressed cluster was pretty much ignored,
cancelling the update on error but returning 0. This is caused by an
inner "ret" variable shadowing the outer one (the latter is used in the
return statement).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 10:08:56 +02:00

1804 lines
59 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/block_int.h"
#include "block/qcow2.h"
#include "qemu/range.h"
#include "qapi/qmp/types.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, enum qcow2_discard_type type);
/*********************************************************/
/* 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] & REFT_OFFSET_MASK;
/* 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 */
ret = qcow2_cache_flush(bs, s->l2_table_cache);
if (ret < 0) {
return ret;
}
/* 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,
QCOW2_DISCARD_NEVER);
if (ret < 0) {
goto fail_block;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
goto fail_block;
}
/* 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 * sizeof(uint64_t));
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++) {
be64_to_cpus(&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),
QCOW2_DISCARD_OTHER);
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;
}
void qcow2_process_discards(BlockDriverState *bs, int ret)
{
BDRVQcowState *s = bs->opaque;
Qcow2DiscardRegion *d, *next;
QTAILQ_FOREACH_SAFE(d, &s->discards, next, next) {
QTAILQ_REMOVE(&s->discards, d, next);
/* Discard is optional, ignore the return value */
if (ret >= 0) {
bdrv_discard(bs->file,
d->offset >> BDRV_SECTOR_BITS,
d->bytes >> BDRV_SECTOR_BITS);
}
g_free(d);
}
}
static void update_refcount_discard(BlockDriverState *bs,
uint64_t offset, uint64_t length)
{
BDRVQcowState *s = bs->opaque;
Qcow2DiscardRegion *d, *p, *next;
QTAILQ_FOREACH(d, &s->discards, next) {
uint64_t new_start = MIN(offset, d->offset);
uint64_t new_end = MAX(offset + length, d->offset + d->bytes);
if (new_end - new_start <= length + d->bytes) {
/* There can't be any overlap, areas ending up here have no
* references any more and therefore shouldn't get freed another
* time. */
assert(d->bytes + length == new_end - new_start);
d->offset = new_start;
d->bytes = new_end - new_start;
goto found;
}
}
d = g_malloc(sizeof(*d));
*d = (Qcow2DiscardRegion) {
.bs = bs,
.offset = offset,
.bytes = length,
};
QTAILQ_INSERT_TAIL(&s->discards, d, next);
found:
/* Merge discard requests if they are adjacent now */
QTAILQ_FOREACH_SAFE(p, &s->discards, next, next) {
if (p == d
|| p->offset > d->offset + d->bytes
|| d->offset > p->offset + p->bytes)
{
continue;
}
/* Still no overlap possible */
assert(p->offset == d->offset + d->bytes
|| d->offset == p->offset + p->bytes);
QTAILQ_REMOVE(&s->discards, p, next);
d->offset = MIN(d->offset, p->offset);
d->bytes += p->bytes;
}
}
/* XXX: cache several refcount block clusters ? */
static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
int64_t offset, int64_t length, int addend, enum qcow2_discard_type type)
{
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);
if (refcount == 0 && s->discard_passthrough[type]) {
update_refcount_discard(bs, cluster_offset, s->cluster_size);
}
}
ret = 0;
fail:
if (!s->cache_discards) {
qcow2_process_discards(bs, ret);
}
/* 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,
QCOW2_DISCARD_NEVER);
(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.
*/
int qcow2_update_cluster_refcount(BlockDriverState *bs,
int64_t cluster_index,
int addend,
enum qcow2_discard_type type)
{
BDRVQcowState *s = bs->opaque;
int ret;
ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend,
type);
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, 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, QCOW2_DISCARD_NEVER);
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;
uint64_t old_free_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 */
old_free_cluster_index = s->free_cluster_index;
s->free_cluster_index = cluster_index + i;
ret = update_refcount(bs, offset, i << s->cluster_bits, 1,
QCOW2_DISCARD_NEVER);
if (ret < 0) {
return ret;
}
s->free_cluster_index = old_free_cluster_index;
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) {
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
return offset;
}
s->free_byte_offset = 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)
qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
QCOW2_DISCARD_NEVER);
} 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;
qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
QCOW2_DISCARD_NEVER);
s->free_byte_offset += size;
} else {
s->free_byte_offset = offset;
goto redo;
}
}
/* The cluster refcount was incremented, either by qcow2_alloc_clusters()
* or explicitly by qcow2_update_cluster_refcount(). Refcount blocks must
* be flushed before the caller's L2 table updates.
*/
qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
return offset;
}
void qcow2_free_clusters(BlockDriverState *bs,
int64_t offset, int64_t size,
enum qcow2_discard_type type)
{
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE);
ret = update_refcount(bs, offset, size, -1, type);
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 a cluster using its L2 entry (handles clusters of all types, e.g.
* normal cluster, compressed cluster, etc.)
*/
void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t l2_entry,
int nb_clusters, enum qcow2_discard_type type)
{
BDRVQcowState *s = bs->opaque;
switch (qcow2_get_cluster_type(l2_entry)) {
case QCOW2_CLUSTER_COMPRESSED:
{
int nb_csectors;
nb_csectors = ((l2_entry >> s->csize_shift) &
s->csize_mask) + 1;
qcow2_free_clusters(bs,
(l2_entry & s->cluster_offset_mask) & ~511,
nb_csectors * 512, type);
}
break;
case QCOW2_CLUSTER_NORMAL:
qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
nb_clusters << s->cluster_bits, type);
break;
case QCOW2_CLUSTER_UNALLOCATED:
case QCOW2_CLUSTER_ZERO:
break;
default:
abort();
}
}
/*********************************************************/
/* 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;
l2_table = NULL;
l1_table = NULL;
l1_size2 = l1_size * sizeof(uint64_t);
s->cache_discards = true;
/* 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) {
l1_table = g_malloc0(align_offset(l1_size2, 512));
l1_allocated = 1;
ret = bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2);
if (ret < 0) {
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 &= L1E_OFFSET_MASK;
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++) {
uint64_t cluster_index;
offset = be64_to_cpu(l2_table[j]);
old_offset = offset;
offset &= ~QCOW_OFLAG_COPIED;
switch (qcow2_get_cluster_type(offset)) {
case QCOW2_CLUSTER_COMPRESSED:
nb_csectors = ((offset >> s->csize_shift) &
s->csize_mask) + 1;
if (addend != 0) {
ret = update_refcount(bs,
(offset & s->cluster_offset_mask) & ~511,
nb_csectors * 512, addend,
QCOW2_DISCARD_SNAPSHOT);
if (ret < 0) {
goto fail;
}
}
/* compressed clusters are never modified */
refcount = 2;
break;
case QCOW2_CLUSTER_NORMAL:
case QCOW2_CLUSTER_ZERO:
cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;
if (!cluster_index) {
/* unallocated */
refcount = 0;
break;
}
if (addend != 0) {
refcount = qcow2_update_cluster_refcount(bs,
cluster_index, addend,
QCOW2_DISCARD_SNAPSHOT);
} else {
refcount = get_refcount(bs, cluster_index);
}
if (refcount < 0) {
ret = refcount;
goto fail;
}
break;
case QCOW2_CLUSTER_UNALLOCATED:
refcount = 0;
break;
default:
abort();
}
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 = qcow2_update_cluster_refcount(bs, l2_offset >>
s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT);
} else {
refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
}
if (refcount < 0) {
ret = refcount;
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 = bdrv_flush(bs);
fail:
if (l2_table) {
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
}
s->cache_discards = false;
qcow2_process_discards(bs, ret);
/* Update L1 only if it isn't deleted anyway (addend = -1) */
if (ret == 0 && addend >= 0 && l1_modified) {
for (i = 0; i < l1_size; i++) {
cpu_to_be64s(&l1_table[i]);
}
ret = bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, l1_size2);
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++;
}
}
}
}
/* Flags for check_refcounts_l1() and check_refcounts_l2() */
enum {
CHECK_OFLAG_COPIED = 0x1, /* check QCOW_OFLAG_COPIED matches refcount */
CHECK_FRAG_INFO = 0x2, /* update BlockFragInfo counters */
};
/*
* 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 flags)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l2_table, l2_entry;
uint64_t next_contiguous_offset = 0;
int i, l2_size, nb_csectors;
/* 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++) {
l2_entry = be64_to_cpu(l2_table[i]);
switch (qcow2_get_cluster_type(l2_entry)) {
case QCOW2_CLUSTER_COMPRESSED:
/* Compressed clusters don't have QCOW_OFLAG_COPIED */
if (l2_entry & QCOW_OFLAG_COPIED) {
fprintf(stderr, "ERROR: cluster %" PRId64 ": "
"copied flag must never be set for compressed "
"clusters\n", l2_entry >> s->cluster_bits);
l2_entry &= ~QCOW_OFLAG_COPIED;
res->corruptions++;
}
/* Mark cluster as used */
nb_csectors = ((l2_entry >> s->csize_shift) &
s->csize_mask) + 1;
l2_entry &= s->cluster_offset_mask;
inc_refcounts(bs, res, refcount_table, refcount_table_size,
l2_entry & ~511, nb_csectors * 512);
if (flags & CHECK_FRAG_INFO) {
res->bfi.allocated_clusters++;
res->bfi.compressed_clusters++;
/* Compressed clusters are fragmented by nature. Since they
* take up sub-sector space but we only have sector granularity
* I/O we need to re-read the same sectors even for adjacent
* compressed clusters.
*/
res->bfi.fragmented_clusters++;
}
break;
case QCOW2_CLUSTER_ZERO:
if ((l2_entry & L2E_OFFSET_MASK) == 0) {
break;
}
/* fall through */
case QCOW2_CLUSTER_NORMAL:
{
uint64_t offset = l2_entry & L2E_OFFSET_MASK;
if (flags & CHECK_FRAG_INFO) {
res->bfi.allocated_clusters++;
if (next_contiguous_offset &&
offset != next_contiguous_offset) {
res->bfi.fragmented_clusters++;
}
next_contiguous_offset = offset + s->cluster_size;
}
/* Mark cluster as used */
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++;
}
break;
}
case QCOW2_CLUSTER_UNALLOCATED:
break;
default:
abort();
}
}
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 flags)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l1_table, l2_offset, l1_size2;
int i, 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) {
/* Mark L2 table as used */
l2_offset &= L1E_OFFSET_MASK;
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, flags);
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 the OFLAG_COPIED flag for all L1 and L2 entries.
*
* This function does not print an error message nor does it increment
* check_errors if get_refcount fails (this is because such an error will have
* been already detected and sufficiently signaled by the calling function
* (qcow2_check_refcounts) by the time this function is called).
*/
static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res,
BdrvCheckMode fix)
{
BDRVQcowState *s = bs->opaque;
uint64_t *l2_table = qemu_blockalign(bs, s->cluster_size);
int ret;
int refcount;
int i, j;
for (i = 0; i < s->l1_size; i++) {
uint64_t l1_entry = s->l1_table[i];
uint64_t l2_offset = l1_entry & L1E_OFFSET_MASK;
bool l2_dirty = false;
if (!l2_offset) {
continue;
}
refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
if (refcount < 0) {
/* don't print message nor increment check_errors */
continue;
}
if ((refcount == 1) != ((l1_entry & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "%s OFLAG_COPIED L2 cluster: l1_index=%d "
"l1_entry=%" PRIx64 " refcount=%d\n",
fix & BDRV_FIX_ERRORS ? "Repairing" :
"ERROR",
i, l1_entry, refcount);
if (fix & BDRV_FIX_ERRORS) {
s->l1_table[i] = refcount == 1
? l1_entry | QCOW_OFLAG_COPIED
: l1_entry & ~QCOW_OFLAG_COPIED;
ret = qcow2_write_l1_entry(bs, i);
if (ret < 0) {
res->check_errors++;
goto fail;
}
res->corruptions_fixed++;
} else {
res->corruptions++;
}
}
ret = bdrv_pread(bs->file, l2_offset, l2_table,
s->l2_size * sizeof(uint64_t));
if (ret < 0) {
fprintf(stderr, "ERROR: Could not read L2 table: %s\n",
strerror(-ret));
res->check_errors++;
goto fail;
}
for (j = 0; j < s->l2_size; j++) {
uint64_t l2_entry = be64_to_cpu(l2_table[j]);
uint64_t data_offset = l2_entry & L2E_OFFSET_MASK;
int cluster_type = qcow2_get_cluster_type(l2_entry);
if ((cluster_type == QCOW2_CLUSTER_NORMAL) ||
((cluster_type == QCOW2_CLUSTER_ZERO) && (data_offset != 0))) {
refcount = get_refcount(bs, data_offset >> s->cluster_bits);
if (refcount < 0) {
/* don't print message nor increment check_errors */
continue;
}
if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "%s OFLAG_COPIED data cluster: "
"l2_entry=%" PRIx64 " refcount=%d\n",
fix & BDRV_FIX_ERRORS ? "Repairing" :
"ERROR",
l2_entry, refcount);
if (fix & BDRV_FIX_ERRORS) {
l2_table[j] = cpu_to_be64(refcount == 1
? l2_entry | QCOW_OFLAG_COPIED
: l2_entry & ~QCOW_OFLAG_COPIED);
l2_dirty = true;
res->corruptions_fixed++;
} else {
res->corruptions++;
}
}
}
}
if (l2_dirty) {
ret = qcow2_pre_write_overlap_check(bs,
QCOW2_OL_DEFAULT & ~QCOW2_OL_ACTIVE_L2, l2_offset,
s->cluster_size);
if (ret < 0) {
fprintf(stderr, "ERROR: Could not write L2 table; metadata "
"overlap check failed: %s\n", strerror(-ret));
res->check_errors++;
goto fail;
}
ret = bdrv_pwrite(bs->file, l2_offset, l2_table, s->cluster_size);
if (ret < 0) {
fprintf(stderr, "ERROR: Could not write L2 table: %s\n",
strerror(-ret));
res->check_errors++;
goto fail;
}
}
}
ret = 0;
fail:
qemu_vfree(l2_table);
return ret;
}
/*
* Writes one sector of the refcount table to the disk
*/
#define RT_ENTRIES_PER_SECTOR (512 / sizeof(uint64_t))
static int write_reftable_entry(BlockDriverState *bs, int rt_index)
{
BDRVQcowState *s = bs->opaque;
uint64_t buf[RT_ENTRIES_PER_SECTOR];
int rt_start_index;
int i, ret;
rt_start_index = rt_index & ~(RT_ENTRIES_PER_SECTOR - 1);
for (i = 0; i < RT_ENTRIES_PER_SECTOR; i++) {
buf[i] = cpu_to_be64(s->refcount_table[rt_start_index + i]);
}
ret = qcow2_pre_write_overlap_check(bs,
QCOW2_OL_DEFAULT & ~QCOW2_OL_REFCOUNT_TABLE,
s->refcount_table_offset + rt_start_index * sizeof(uint64_t),
sizeof(buf));
if (ret < 0) {
return ret;
}
BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_UPDATE);
ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset +
rt_start_index * sizeof(uint64_t), buf, sizeof(buf));
if (ret < 0) {
return ret;
}
return 0;
}
/*
* Allocates a new cluster for the given refcount block (represented by its
* offset in the image file) and copies the current content there. This function
* does _not_ decrement the reference count for the currently occupied cluster.
*
* This function prints an informative message to stderr on error (and returns
* -errno); on success, 0 is returned.
*/
static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index,
uint64_t offset)
{
BDRVQcowState *s = bs->opaque;
int64_t new_offset = 0;
void *refcount_block = NULL;
int ret;
/* allocate new refcount block */
new_offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (new_offset < 0) {
fprintf(stderr, "Could not allocate new cluster: %s\n",
strerror(-new_offset));
ret = new_offset;
goto fail;
}
/* fetch current refcount block content */
ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block);
if (ret < 0) {
fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret));
goto fail;
}
/* new block has not yet been entered into refcount table, therefore it is
* no refcount block yet (regarding this check) */
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT, new_offset,
s->cluster_size);
if (ret < 0) {
fprintf(stderr, "Could not write refcount block; metadata overlap "
"check failed: %s\n", strerror(-ret));
/* the image will be marked corrupt, so don't even attempt on freeing
* the cluster */
new_offset = 0;
goto fail;
}
/* write to new block */
ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block,
s->cluster_sectors);
if (ret < 0) {
fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret));
goto fail;
}
/* update refcount table */
assert(!(new_offset & (s->cluster_size - 1)));
s->refcount_table[reftable_index] = new_offset;
ret = write_reftable_entry(bs, reftable_index);
if (ret < 0) {
fprintf(stderr, "Could not update refcount table: %s\n",
strerror(-ret));
goto fail;
}
fail:
if (new_offset && (ret < 0)) {
qcow2_free_clusters(bs, new_offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
if (refcount_block) {
if (ret < 0) {
qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
} else {
ret = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
}
}
if (ret < 0) {
return ret;
}
return new_offset;
}
/*
* 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,
BdrvCheckMode fix)
{
BDRVQcowState *s = bs->opaque;
int64_t size, i, highest_cluster;
int nb_clusters, refcount1, refcount2;
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));
res->bfi.total_clusters =
size_to_clusters(s, bs->total_sectors * BDRV_SECTOR_SIZE);
/* 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,
CHECK_OFLAG_COPIED | CHECK_FRAG_INFO);
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 %" PRId64 " is not "
"cluster aligned; refcount table entry corrupted\n", i);
res->corruptions++;
continue;
}
if (cluster >= nb_clusters) {
fprintf(stderr, "ERROR refcount block %" PRId64
" 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, "%s refcount block %" PRId64
" refcount=%d\n",
fix & BDRV_FIX_ERRORS ? "Repairing" :
"ERROR",
i, refcount_table[cluster]);
if (fix & BDRV_FIX_ERRORS) {
int64_t new_offset;
new_offset = realloc_refcount_block(bs, i, offset);
if (new_offset < 0) {
res->corruptions++;
continue;
}
/* update refcounts */
if ((new_offset >> s->cluster_bits) >= nb_clusters) {
/* increase refcount_table size if necessary */
int old_nb_clusters = nb_clusters;
nb_clusters = (new_offset >> s->cluster_bits) + 1;
refcount_table = g_realloc(refcount_table,
nb_clusters * sizeof(uint16_t));
memset(&refcount_table[old_nb_clusters], 0, (nb_clusters
- old_nb_clusters) * sizeof(uint16_t));
}
refcount_table[cluster]--;
inc_refcounts(bs, res, refcount_table, nb_clusters,
new_offset, s->cluster_size);
res->corruptions_fixed++;
} else {
res->corruptions++;
}
}
}
}
/* compare ref counts */
for (i = 0, highest_cluster = 0; i < nb_clusters; i++) {
refcount1 = get_refcount(bs, i);
if (refcount1 < 0) {
fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
i, strerror(-refcount1));
res->check_errors++;
continue;
}
refcount2 = refcount_table[i];
if (refcount1 > 0 || refcount2 > 0) {
highest_cluster = i;
}
if (refcount1 != refcount2) {
/* Check if we're allowed to fix the mismatch */
int *num_fixed = NULL;
if (refcount1 > refcount2 && (fix & BDRV_FIX_LEAKS)) {
num_fixed = &res->leaks_fixed;
} else if (refcount1 < refcount2 && (fix & BDRV_FIX_ERRORS)) {
num_fixed = &res->corruptions_fixed;
}
fprintf(stderr, "%s cluster %" PRId64 " refcount=%d reference=%d\n",
num_fixed != NULL ? "Repairing" :
refcount1 < refcount2 ? "ERROR" :
"Leaked",
i, refcount1, refcount2);
if (num_fixed) {
ret = update_refcount(bs, i << s->cluster_bits, 1,
refcount2 - refcount1,
QCOW2_DISCARD_ALWAYS);
if (ret >= 0) {
(*num_fixed)++;
continue;
}
}
/* And if we couldn't, print an error */
if (refcount1 < refcount2) {
res->corruptions++;
} else {
res->leaks++;
}
}
}
/* check OFLAG_COPIED */
ret = check_oflag_copied(bs, res, fix);
if (ret < 0) {
goto fail;
}
res->image_end_offset = (highest_cluster + 1) * s->cluster_size;
ret = 0;
fail:
g_free(refcount_table);
return ret;
}
#define overlaps_with(ofs, sz) \
ranges_overlap(offset, size, ofs, sz)
/*
* Checks if the given offset into the image file is actually free to use by
* looking for overlaps with important metadata sections (L1/L2 tables etc.),
* i.e. a sanity check without relying on the refcount tables.
*
* The chk parameter specifies exactly what checks to perform (being a bitmask
* of QCow2MetadataOverlap values).
*
* Returns:
* - 0 if writing to this offset will not affect the mentioned metadata
* - a positive QCow2MetadataOverlap value indicating one overlapping section
* - a negative value (-errno) indicating an error while performing a check,
* e.g. when bdrv_read failed on QCOW2_OL_INACTIVE_L2
*/
int qcow2_check_metadata_overlap(BlockDriverState *bs, int chk, int64_t offset,
int64_t size)
{
BDRVQcowState *s = bs->opaque;
int i, j;
if (!size) {
return 0;
}
if (chk & QCOW2_OL_MAIN_HEADER) {
if (offset < s->cluster_size) {
return QCOW2_OL_MAIN_HEADER;
}
}
/* align range to test to cluster boundaries */
size = align_offset(offset_into_cluster(s, offset) + size, s->cluster_size);
offset = start_of_cluster(s, offset);
if ((chk & QCOW2_OL_ACTIVE_L1) && s->l1_size) {
if (overlaps_with(s->l1_table_offset, s->l1_size * sizeof(uint64_t))) {
return QCOW2_OL_ACTIVE_L1;
}
}
if ((chk & QCOW2_OL_REFCOUNT_TABLE) && s->refcount_table_size) {
if (overlaps_with(s->refcount_table_offset,
s->refcount_table_size * sizeof(uint64_t))) {
return QCOW2_OL_REFCOUNT_TABLE;
}
}
if ((chk & QCOW2_OL_SNAPSHOT_TABLE) && s->snapshots_size) {
if (overlaps_with(s->snapshots_offset, s->snapshots_size)) {
return QCOW2_OL_SNAPSHOT_TABLE;
}
}
if ((chk & QCOW2_OL_INACTIVE_L1) && s->snapshots) {
for (i = 0; i < s->nb_snapshots; i++) {
if (s->snapshots[i].l1_size &&
overlaps_with(s->snapshots[i].l1_table_offset,
s->snapshots[i].l1_size * sizeof(uint64_t))) {
return QCOW2_OL_INACTIVE_L1;
}
}
}
if ((chk & QCOW2_OL_ACTIVE_L2) && s->l1_table) {
for (i = 0; i < s->l1_size; i++) {
if ((s->l1_table[i] & L1E_OFFSET_MASK) &&
overlaps_with(s->l1_table[i] & L1E_OFFSET_MASK,
s->cluster_size)) {
return QCOW2_OL_ACTIVE_L2;
}
}
}
if ((chk & QCOW2_OL_REFCOUNT_BLOCK) && s->refcount_table) {
for (i = 0; i < s->refcount_table_size; i++) {
if ((s->refcount_table[i] & REFT_OFFSET_MASK) &&
overlaps_with(s->refcount_table[i] & REFT_OFFSET_MASK,
s->cluster_size)) {
return QCOW2_OL_REFCOUNT_BLOCK;
}
}
}
if ((chk & QCOW2_OL_INACTIVE_L2) && s->snapshots) {
for (i = 0; i < s->nb_snapshots; i++) {
uint64_t l1_ofs = s->snapshots[i].l1_table_offset;
uint32_t l1_sz = s->snapshots[i].l1_size;
uint64_t *l1 = g_malloc(l1_sz * sizeof(uint64_t));
int ret;
ret = bdrv_read(bs->file, l1_ofs / BDRV_SECTOR_SIZE, (uint8_t *)l1,
l1_sz * sizeof(uint64_t) / BDRV_SECTOR_SIZE);
if (ret < 0) {
g_free(l1);
return ret;
}
for (j = 0; j < l1_sz; j++) {
if ((l1[j] & L1E_OFFSET_MASK) &&
overlaps_with(l1[j] & L1E_OFFSET_MASK, s->cluster_size)) {
g_free(l1);
return QCOW2_OL_INACTIVE_L2;
}
}
g_free(l1);
}
}
return 0;
}
static const char *metadata_ol_names[] = {
[QCOW2_OL_MAIN_HEADER_BITNR] = "qcow2_header",
[QCOW2_OL_ACTIVE_L1_BITNR] = "active L1 table",
[QCOW2_OL_ACTIVE_L2_BITNR] = "active L2 table",
[QCOW2_OL_REFCOUNT_TABLE_BITNR] = "refcount table",
[QCOW2_OL_REFCOUNT_BLOCK_BITNR] = "refcount block",
[QCOW2_OL_SNAPSHOT_TABLE_BITNR] = "snapshot table",
[QCOW2_OL_INACTIVE_L1_BITNR] = "inactive L1 table",
[QCOW2_OL_INACTIVE_L2_BITNR] = "inactive L2 table",
};
/*
* First performs a check for metadata overlaps (through
* qcow2_check_metadata_overlap); if that fails with a negative value (error
* while performing a check), that value is returned. If an impending overlap
* is detected, the BDS will be made unusable, the qcow2 file marked corrupt
* and -EIO returned.
*
* Returns 0 if there were neither overlaps nor errors while checking for
* overlaps; or a negative value (-errno) on error.
*/
int qcow2_pre_write_overlap_check(BlockDriverState *bs, int chk, int64_t offset,
int64_t size)
{
int ret = qcow2_check_metadata_overlap(bs, chk, offset, size);
if (ret < 0) {
return ret;
} else if (ret > 0) {
int metadata_ol_bitnr = ffs(ret) - 1;
char *message;
QObject *data;
assert(metadata_ol_bitnr < QCOW2_OL_MAX_BITNR);
fprintf(stderr, "qcow2: Preventing invalid write on metadata (overlaps "
"with %s); image marked as corrupt.\n",
metadata_ol_names[metadata_ol_bitnr]);
message = g_strdup_printf("Prevented %s overwrite",
metadata_ol_names[metadata_ol_bitnr]);
data = qobject_from_jsonf("{ 'device': %s, 'msg': %s, 'offset': %"
PRId64 ", 'size': %" PRId64 " }", bs->device_name, message,
offset, size);
monitor_protocol_event(QEVENT_BLOCK_IMAGE_CORRUPTED, data);
g_free(message);
qobject_decref(data);
qcow2_mark_corrupt(bs);
bs->drv = NULL; /* make BDS unusable */
return -EIO;
}
return 0;
}
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