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qemu-e2k/block/qcow2-refcount.c
Kevin Wolf 0b919fae31 qcow2: Batch discards 
This optimises the discard operation for freed clusters by batching
discard requests (both snapshot deletion and bdrv_discard end up
updating the refcounts cluster by cluster).

Note that we don't discard asynchronously, but keep s->lock held. This
is to avoid that a freed cluster is reallocated and written to while the
discard is still in flight.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-06-24 10:25:17 +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/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, 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.
*/
static int 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)
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;
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 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++) {
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,
QCOW2_DISCARD_SNAPSHOT);
if (ret < 0) {
goto fail;
}
}
/* compressed clusters are never modified */
refcount = 2;
} else {
uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;
if (addend != 0) {
refcount = update_cluster_refcount(bs, cluster_index, addend,
QCOW2_DISCARD_SNAPSHOT);
} else {
refcount = get_refcount(bs, cluster_index);
}
if (refcount < 0) {
ret = refcount;
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,
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, 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++) {
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:
{
/* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
uint64_t offset = l2_entry & L2E_OFFSET_MASK;
if (flags & CHECK_OFLAG_COPIED) {
refcount = get_refcount(bs, offset >> s->cluster_bits);
if (refcount < 0) {
fprintf(stderr, "Can't get refcount for offset %"
PRIx64 ": %s\n", l2_entry, strerror(-refcount));
goto fail;
}
if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) {
fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
PRIx64 " refcount=%d\n", l2_entry, refcount);
res->corruptions++;
}
}
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, 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 (flags & CHECK_OFLAG_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 &= 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 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, "ERROR refcount block %" PRId64
" refcount=%d\n",
i, refcount_table[cluster]);
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++;
}
}
}
res->image_end_offset = (highest_cluster + 1) * s->cluster_size;
ret = 0;
fail:
g_free(refcount_table);
return ret;
}
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