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qemu/block/qcow2-cluster.c
Alberto Garcia 3441ad4bc4 qcow2: Document and enforce the QCowL2Meta invariants 
The QCowL2Meta structure is used to store information about a part of
a write request that touches clusters that need changes in their L2
entries. This happens with newly-allocated clusters or subclusters.

This structure has changed a bit since it was first created and its
current documentation is not quite up-to-date.

A write request can span a region consisting of a combination of
clusters of different types, and qcow2_alloc_host_offset() can
repeatedly call handle_copied() and handle_alloc() to add more
clusters to the mix as long as they all are contiguous on the image
file.

Because of this a write request has a list of QCowL2Meta structures,
one for each part of the request that needs changes in the L2
metadata.

Each one of them spans nb_clusters and has two copy-on-write regions
located immediately before and after the middle region touched by that
part of the write request. Even when those regions themselves are
empty their offsets must be correct because they are used to know the
location of the middle region.

This was not always the case but it is not a problem anymore
because the only two places where QCowL2Meta structures are created
(calculate_l2_meta() and qcow2_co_truncate()) ensure that the
copy-on-write regions are correctly defined, and so do assertions like
the ones in perform_cow().

The conditional initialization of the 'written_to' variable is
therefore unnecessary and is removed by this patch.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201007161323.4667-1-berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-11-09 15:44:21 +01:00

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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/osdep.h"
#include <zlib.h>
#include "qapi/error.h"
#include "qcow2.h"
#include "qemu/bswap.h"
#include "trace.h"
int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t exact_size)
{
BDRVQcow2State *s = bs->opaque;
int new_l1_size, i, ret;
if (exact_size >= s->l1_size) {
return 0;
}
new_l1_size = exact_size;
#ifdef DEBUG_ALLOC2
fprintf(stderr, "shrink l1_table from %d to %d\n", s->l1_size, new_l1_size);
#endif
BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_WRITE_TABLE);
ret = bdrv_pwrite_zeroes(bs->file, s->l1_table_offset +
new_l1_size * L1E_SIZE,
(s->l1_size - new_l1_size) * L1E_SIZE, 0);
if (ret < 0) {
goto fail;
}
ret = bdrv_flush(bs->file->bs);
if (ret < 0) {
goto fail;
}
BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS);
for (i = s->l1_size - 1; i > new_l1_size - 1; i--) {
if ((s->l1_table[i] & L1E_OFFSET_MASK) == 0) {
continue;
}
qcow2_free_clusters(bs, s->l1_table[i] & L1E_OFFSET_MASK,
s->cluster_size, QCOW2_DISCARD_ALWAYS);
s->l1_table[i] = 0;
}
return 0;
fail:
/*
* If the write in the l1_table failed the image may contain a partially
* overwritten l1_table. In this case it would be better to clear the
* l1_table in memory to avoid possible image corruption.
*/
memset(s->l1_table + new_l1_size, 0,
(s->l1_size - new_l1_size) * L1E_SIZE);
return ret;
}
int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
bool exact_size)
{
BDRVQcow2State *s = bs->opaque;
int new_l1_size2, ret, i;
uint64_t *new_l1_table;
int64_t old_l1_table_offset, old_l1_size;
int64_t new_l1_table_offset, new_l1_size;
uint8_t data[12];
if (min_size <= s->l1_size)
return 0;
/* Do a sanity check on min_size before trying to calculate new_l1_size
* (this prevents overflows during the while loop for the calculation of
* new_l1_size) */
if (min_size > INT_MAX / L1E_SIZE) {
return -EFBIG;
}
if (exact_size) {
new_l1_size = min_size;
} else {
/* Bump size up to reduce the number of times we have to grow */
new_l1_size = s->l1_size;
if (new_l1_size == 0) {
new_l1_size = 1;
}
while (min_size > new_l1_size) {
new_l1_size = DIV_ROUND_UP(new_l1_size * 3, 2);
}
}
QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE > INT_MAX);
if (new_l1_size > QCOW_MAX_L1_SIZE / L1E_SIZE) {
return -EFBIG;
}
#ifdef DEBUG_ALLOC2
fprintf(stderr, "grow l1_table from %d to %" PRId64 "\n",
s->l1_size, new_l1_size);
#endif
new_l1_size2 = L1E_SIZE * new_l1_size;
new_l1_table = qemu_try_blockalign(bs->file->bs, new_l1_size2);
if (new_l1_table == NULL) {
return -ENOMEM;
}
memset(new_l1_table, 0, new_l1_size2);
if (s->l1_size) {
memcpy(new_l1_table, s->l1_table, s->l1_size * L1E_SIZE);
}
/* write new table (align to cluster) */
BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE);
new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2);
if (new_l1_table_offset < 0) {
qemu_vfree(new_l1_table);
return new_l1_table_offset;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
goto fail;
}
/* the L1 position has not yet been updated, so these clusters must
* indeed be completely free */
ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset,
new_l1_size2, false);
if (ret < 0) {
goto fail;
}
BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE);
for(i = 0; i < s->l1_size; i++)
new_l1_table[i] = cpu_to_be64(new_l1_table[i]);
ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset,
new_l1_table, new_l1_size2);
if (ret < 0)
goto fail;
for(i = 0; i < s->l1_size; i++)
new_l1_table[i] = be64_to_cpu(new_l1_table[i]);
/* set new table */
BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE);
stl_be_p(data, new_l1_size);
stq_be_p(data + 4, new_l1_table_offset);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size),
data, sizeof(data));
if (ret < 0) {
goto fail;
}
qemu_vfree(s->l1_table);
old_l1_table_offset = s->l1_table_offset;
s->l1_table_offset = new_l1_table_offset;
s->l1_table = new_l1_table;
old_l1_size = s->l1_size;
s->l1_size = new_l1_size;
qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * L1E_SIZE,
QCOW2_DISCARD_OTHER);
return 0;
fail:
qemu_vfree(new_l1_table);
qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2,
QCOW2_DISCARD_OTHER);
return ret;
}
/*
* l2_load
*
* @bs: The BlockDriverState
* @offset: A guest offset, used to calculate what slice of the L2
* table to load.
* @l2_offset: Offset to the L2 table in the image file.
* @l2_slice: Location to store the pointer to the L2 slice.
*
* Loads a L2 slice into memory (L2 slices are the parts of L2 tables
* that are loaded by the qcow2 cache). If the slice is in the cache,
* the cache is used; otherwise the L2 slice is loaded from the image
* file.
*/
static int l2_load(BlockDriverState *bs, uint64_t offset,
uint64_t l2_offset, uint64_t **l2_slice)
{
BDRVQcow2State *s = bs->opaque;
int start_of_slice = l2_entry_size(s) *
(offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset));
return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice,
(void **)l2_slice);
}
/*
* Writes an L1 entry to disk (note that depending on the alignment
* requirements this function may write more that just one entry in
* order to prevent bdrv_pwrite from performing a read-modify-write)
*/
int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
{
BDRVQcow2State *s = bs->opaque;
int l1_start_index;
int i, ret;
int bufsize = MAX(L1E_SIZE,
MIN(bs->file->bs->bl.request_alignment, s->cluster_size));
int nentries = bufsize / L1E_SIZE;
g_autofree uint64_t *buf = g_try_new0(uint64_t, nentries);
if (buf == NULL) {
return -ENOMEM;
}
l1_start_index = QEMU_ALIGN_DOWN(l1_index, nentries);
for (i = 0; i < MIN(nentries, s->l1_size - l1_start_index); i++) {
buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
}
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
s->l1_table_offset + L1E_SIZE * l1_start_index, bufsize, false);
if (ret < 0) {
return ret;
}
BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
ret = bdrv_pwrite_sync(bs->file,
s->l1_table_offset + L1E_SIZE * l1_start_index,
buf, bufsize);
if (ret < 0) {
return ret;
}
return 0;
}
/*
* l2_allocate
*
* Allocate a new l2 entry in the file. If l1_index points to an already
* used entry in the L2 table (i.e. we are doing a copy on write for the L2
* table) copy the contents of the old L2 table into the newly allocated one.
* Otherwise the new table is initialized with zeros.
*
*/
static int l2_allocate(BlockDriverState *bs, int l1_index)
{
BDRVQcow2State *s = bs->opaque;
uint64_t old_l2_offset;
uint64_t *l2_slice = NULL;
unsigned slice, slice_size2, n_slices;
int64_t l2_offset;
int ret;
old_l2_offset = s->l1_table[l1_index];
trace_qcow2_l2_allocate(bs, l1_index);
/* allocate a new l2 entry */
l2_offset = qcow2_alloc_clusters(bs, s->l2_size * l2_entry_size(s));
if (l2_offset < 0) {
ret = l2_offset;
goto fail;
}
/* The offset must fit in the offset field of the L1 table entry */
assert((l2_offset & L1E_OFFSET_MASK) == l2_offset);
/* If we're allocating the table at offset 0 then something is wrong */
if (l2_offset == 0) {
qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid "
"allocation of L2 table at offset 0");
ret = -EIO;
goto fail;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
goto fail;
}
/* allocate a new entry in the l2 cache */
slice_size2 = s->l2_slice_size * l2_entry_size(s);
n_slices = s->cluster_size / slice_size2;
trace_qcow2_l2_allocate_get_empty(bs, l1_index);
for (slice = 0; slice < n_slices; slice++) {
ret = qcow2_cache_get_empty(bs, s->l2_table_cache,
l2_offset + slice * slice_size2,
(void **) &l2_slice);
if (ret < 0) {
goto fail;
}
if ((old_l2_offset & L1E_OFFSET_MASK) == 0) {
/* if there was no old l2 table, clear the new slice */
memset(l2_slice, 0, slice_size2);
} else {
uint64_t *old_slice;
uint64_t old_l2_slice_offset =
(old_l2_offset & L1E_OFFSET_MASK) + slice * slice_size2;
/* if there was an old l2 table, read a slice from the disk */
BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ);
ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_slice_offset,
(void **) &old_slice);
if (ret < 0) {
goto fail;
}
memcpy(l2_slice, old_slice, slice_size2);
qcow2_cache_put(s->l2_table_cache, (void **) &old_slice);
}
/* write the l2 slice to the file */
BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE);
trace_qcow2_l2_allocate_write_l2(bs, l1_index);
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
}
ret = qcow2_cache_flush(bs, s->l2_table_cache);
if (ret < 0) {
goto fail;
}
/* update the L1 entry */
trace_qcow2_l2_allocate_write_l1(bs, l1_index);
s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
ret = qcow2_write_l1_entry(bs, l1_index);
if (ret < 0) {
goto fail;
}
trace_qcow2_l2_allocate_done(bs, l1_index, 0);
return 0;
fail:
trace_qcow2_l2_allocate_done(bs, l1_index, ret);
if (l2_slice != NULL) {
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
}
s->l1_table[l1_index] = old_l2_offset;
if (l2_offset > 0) {
qcow2_free_clusters(bs, l2_offset, s->l2_size * l2_entry_size(s),
QCOW2_DISCARD_ALWAYS);
}
return ret;
}
/*
* For a given L2 entry, count the number of contiguous subclusters of
* the same type starting from @sc_from. Compressed clusters are
* treated as if they were divided into subclusters of size
* s->subcluster_size.
*
* Return the number of contiguous subclusters and set @type to the
* subcluster type.
*
* If the L2 entry is invalid return -errno and set @type to
* QCOW2_SUBCLUSTER_INVALID.
*/
static int qcow2_get_subcluster_range_type(BlockDriverState *bs,
uint64_t l2_entry,
uint64_t l2_bitmap,
unsigned sc_from,
QCow2SubclusterType *type)
{
BDRVQcow2State *s = bs->opaque;
uint32_t val;
*type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_from);
if (*type == QCOW2_SUBCLUSTER_INVALID) {
return -EINVAL;
} else if (!has_subclusters(s) || *type == QCOW2_SUBCLUSTER_COMPRESSED) {
return s->subclusters_per_cluster - sc_from;
}
switch (*type) {
case QCOW2_SUBCLUSTER_NORMAL:
val = l2_bitmap | QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
return cto32(val) - sc_from;
case QCOW2_SUBCLUSTER_ZERO_PLAIN:
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
val = (l2_bitmap | QCOW_OFLAG_SUB_ZERO_RANGE(0, sc_from)) >> 32;
return cto32(val) - sc_from;
case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
val = ((l2_bitmap >> 32) | l2_bitmap)
& ~QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
return ctz32(val) - sc_from;
default:
g_assert_not_reached();
}
}
/*
* Return the number of contiguous subclusters of the exact same type
* in a given L2 slice, starting from cluster @l2_index, subcluster
* @sc_index. Allocated subclusters are required to be contiguous in
* the image file.
* At most @nb_clusters are checked (note that this means clusters,
* not subclusters).
* Compressed clusters are always processed one by one but for the
* purpose of this count they are treated as if they were divided into
* subclusters of size s->subcluster_size.
* On failure return -errno and update @l2_index to point to the
* invalid entry.
*/
static int count_contiguous_subclusters(BlockDriverState *bs, int nb_clusters,
unsigned sc_index, uint64_t *l2_slice,
unsigned *l2_index)
{
BDRVQcow2State *s = bs->opaque;
int i, count = 0;
bool check_offset = false;
uint64_t expected_offset = 0;
QCow2SubclusterType expected_type = QCOW2_SUBCLUSTER_NORMAL, type;
assert(*l2_index + nb_clusters <= s->l2_slice_size);
for (i = 0; i < nb_clusters; i++) {
unsigned first_sc = (i == 0) ? sc_index : 0;
uint64_t l2_entry = get_l2_entry(s, l2_slice, *l2_index + i);
uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, *l2_index + i);
int ret = qcow2_get_subcluster_range_type(bs, l2_entry, l2_bitmap,
first_sc, &type);
if (ret < 0) {
*l2_index += i; /* Point to the invalid entry */
return -EIO;
}
if (i == 0) {
if (type == QCOW2_SUBCLUSTER_COMPRESSED) {
/* Compressed clusters are always processed one by one */
return ret;
}
expected_type = type;
expected_offset = l2_entry & L2E_OFFSET_MASK;
check_offset = (type == QCOW2_SUBCLUSTER_NORMAL ||
type == QCOW2_SUBCLUSTER_ZERO_ALLOC ||
type == QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC);
} else if (type != expected_type) {
break;
} else if (check_offset) {
expected_offset += s->cluster_size;
if (expected_offset != (l2_entry & L2E_OFFSET_MASK)) {
break;
}
}
count += ret;
/* Stop if there are type changes before the end of the cluster */
if (first_sc + ret < s->subclusters_per_cluster) {
break;
}
}
return count;
}
static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
uint64_t src_cluster_offset,
unsigned offset_in_cluster,
QEMUIOVector *qiov)
{
int ret;
if (qiov->size == 0) {
return 0;
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_READ);
if (!bs->drv) {
return -ENOMEDIUM;
}
/* Call .bdrv_co_readv() directly instead of using the public block-layer
* interface. This avoids double I/O throttling and request tracking,
* which can lead to deadlock when block layer copy-on-read is enabled.
*/
ret = bs->drv->bdrv_co_preadv_part(bs,
src_cluster_offset + offset_in_cluster,
qiov->size, qiov, 0, 0);
if (ret < 0) {
return ret;
}
return 0;
}
static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
uint64_t cluster_offset,
unsigned offset_in_cluster,
QEMUIOVector *qiov)
{
BDRVQcow2State *s = bs->opaque;
int ret;
if (qiov->size == 0) {
return 0;
}
ret = qcow2_pre_write_overlap_check(bs, 0,
cluster_offset + offset_in_cluster, qiov->size, true);
if (ret < 0) {
return ret;
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
ret = bdrv_co_pwritev(s->data_file, cluster_offset + offset_in_cluster,
qiov->size, qiov, 0);
if (ret < 0) {
return ret;
}
return 0;
}
/*
* get_host_offset
*
* For a given offset of the virtual disk find the equivalent host
* offset in the qcow2 file and store it in *host_offset. Neither
* offset needs to be aligned to a cluster boundary.
*
* If the cluster is unallocated then *host_offset will be 0.
* If the cluster is compressed then *host_offset will contain the
* complete compressed cluster descriptor.
*
* On entry, *bytes is the maximum number of contiguous bytes starting at
* offset that we are interested in.
*
* On exit, *bytes is the number of bytes starting at offset that have the same
* subcluster type and (if applicable) are stored contiguously in the image
* file. The subcluster type is stored in *subcluster_type.
* Compressed clusters are always processed one by one.
*
* Returns 0 on success, -errno in error cases.
*/
int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
unsigned int *bytes, uint64_t *host_offset,
QCow2SubclusterType *subcluster_type)
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index, sc_index;
uint64_t l1_index, l2_offset, *l2_slice, l2_entry, l2_bitmap;
int sc;
unsigned int offset_in_cluster;
uint64_t bytes_available, bytes_needed, nb_clusters;
QCow2SubclusterType type;
int ret;
offset_in_cluster = offset_into_cluster(s, offset);
bytes_needed = (uint64_t) *bytes + offset_in_cluster;
/* compute how many bytes there are between the start of the cluster
* containing offset and the end of the l2 slice that contains
* the entry pointing to it */
bytes_available =
((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset)))
<< s->cluster_bits;
if (bytes_needed > bytes_available) {
bytes_needed = bytes_available;
}
*host_offset = 0;
/* seek to the l2 offset in the l1 table */
l1_index = offset_to_l1_index(s, offset);
if (l1_index >= s->l1_size) {
type = QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
if (!l2_offset) {
type = QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
if (offset_into_cluster(s, l2_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64
" unaligned (L1 index: %#" PRIx64 ")",
l2_offset, l1_index);
return -EIO;
}
/* load the l2 slice in memory */
ret = l2_load(bs, offset, l2_offset, &l2_slice);
if (ret < 0) {
return ret;
}
/* find the cluster offset for the given disk offset */
l2_index = offset_to_l2_slice_index(s, offset);
sc_index = offset_to_sc_index(s, offset);
l2_entry = get_l2_entry(s, l2_slice, l2_index);
l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
nb_clusters = size_to_clusters(s, bytes_needed);
/* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned
* integers; the minimum cluster size is 512, so this assertion is always
* true */
assert(nb_clusters <= INT_MAX);
type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
if (s->qcow_version < 3 && (type == QCOW2_SUBCLUSTER_ZERO_PLAIN ||
type == QCOW2_SUBCLUSTER_ZERO_ALLOC)) {
qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found"
" in pre-v3 image (L2 offset: %#" PRIx64
", L2 index: %#x)", l2_offset, l2_index);
ret = -EIO;
goto fail;
}
switch (type) {
case QCOW2_SUBCLUSTER_INVALID:
break; /* This is handled by count_contiguous_subclusters() below */
case QCOW2_SUBCLUSTER_COMPRESSED:
if (has_data_file(bs)) {
qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluster "
"entry found in image with external data "
"file (L2 offset: %#" PRIx64 ", L2 index: "
"%#x)", l2_offset, l2_index);
ret = -EIO;
goto fail;
}
*host_offset = l2_entry & L2E_COMPRESSED_OFFSET_SIZE_MASK;
break;
case QCOW2_SUBCLUSTER_ZERO_PLAIN:
case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
break;
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_NORMAL:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC: {
uint64_t host_cluster_offset = l2_entry & L2E_OFFSET_MASK;
*host_offset = host_cluster_offset + offset_in_cluster;
if (offset_into_cluster(s, host_cluster_offset)) {
qcow2_signal_corruption(bs, true, -1, -1,
"Cluster allocation offset %#"
PRIx64 " unaligned (L2 offset: %#" PRIx64
", L2 index: %#x)", host_cluster_offset,
l2_offset, l2_index);
ret = -EIO;
goto fail;
}
if (has_data_file(bs) && *host_offset != offset) {
qcow2_signal_corruption(bs, true, -1, -1,
"External data file host cluster offset %#"
PRIx64 " does not match guest cluster "
"offset: %#" PRIx64
", L2 index: %#x)", host_cluster_offset,
offset - offset_in_cluster, l2_index);
ret = -EIO;
goto fail;
}
break;
}
default:
abort();
}
sc = count_contiguous_subclusters(bs, nb_clusters, sc_index,
l2_slice, &l2_index);
if (sc < 0) {
qcow2_signal_corruption(bs, true, -1, -1, "Invalid cluster entry found "
" (L2 offset: %#" PRIx64 ", L2 index: %#x)",
l2_offset, l2_index);
ret = -EIO;
goto fail;
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
bytes_available = ((int64_t)sc + sc_index) << s->subcluster_bits;
out:
if (bytes_available > bytes_needed) {
bytes_available = bytes_needed;
}
/* bytes_available <= bytes_needed <= *bytes + offset_in_cluster;
* subtracting offset_in_cluster will therefore definitely yield something
* not exceeding UINT_MAX */
assert(bytes_available - offset_in_cluster <= UINT_MAX);
*bytes = bytes_available - offset_in_cluster;
*subcluster_type = type;
return 0;
fail:
qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice);
return ret;
}
/*
* get_cluster_table
*
* for a given disk offset, load (and allocate if needed)
* the appropriate slice of its l2 table.
*
* the cluster index in the l2 slice is given to the caller.
*
* Returns 0 on success, -errno in failure case
*/
static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
uint64_t **new_l2_slice,
int *new_l2_index)
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index;
uint64_t l1_index, l2_offset;
uint64_t *l2_slice = NULL;
int ret;
/* seek to the l2 offset in the l1 table */
l1_index = offset_to_l1_index(s, offset);
if (l1_index >= s->l1_size) {
ret = qcow2_grow_l1_table(bs, l1_index + 1, false);
if (ret < 0) {
return ret;
}
}
assert(l1_index < s->l1_size);
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
if (offset_into_cluster(s, l2_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64
" unaligned (L1 index: %#" PRIx64 ")",
l2_offset, l1_index);
return -EIO;
}
if (!(s->l1_table[l1_index] & QCOW_OFLAG_COPIED)) {
/* First allocate a new L2 table (and do COW if needed) */
ret = l2_allocate(bs, l1_index);
if (ret < 0) {
return ret;
}
/* Then decrease the refcount of the old table */
if (l2_offset) {
qcow2_free_clusters(bs, l2_offset, s->l2_size * l2_entry_size(s),
QCOW2_DISCARD_OTHER);
}
/* Get the offset of the newly-allocated l2 table */
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
assert(offset_into_cluster(s, l2_offset) == 0);
}
/* load the l2 slice in memory */
ret = l2_load(bs, offset, l2_offset, &l2_slice);
if (ret < 0) {
return ret;
}
/* find the cluster offset for the given disk offset */
l2_index = offset_to_l2_slice_index(s, offset);
*new_l2_slice = l2_slice;
*new_l2_index = l2_index;
return 0;
}
/*
* alloc_compressed_cluster_offset
*
* For a given offset on the virtual disk, allocate a new compressed cluster
* and put the host offset of the cluster into *host_offset. If a cluster is
* already allocated at the offset, return an error.
*
* Return 0 on success and -errno in error cases
*/
int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
uint64_t offset,
int compressed_size,
uint64_t *host_offset)
{
BDRVQcow2State *s = bs->opaque;
int l2_index, ret;
uint64_t *l2_slice;
int64_t cluster_offset;
int nb_csectors;
if (has_data_file(bs)) {
return 0;
}
ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
/* Compression can't overwrite anything. Fail if the cluster was already
* allocated. */
cluster_offset = get_l2_entry(s, l2_slice, l2_index);
if (cluster_offset & L2E_OFFSET_MASK) {
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return -EIO;
}
cluster_offset = qcow2_alloc_bytes(bs, compressed_size);
if (cluster_offset < 0) {
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return cluster_offset;
}
nb_csectors =
(cluster_offset + compressed_size - 1) / QCOW2_COMPRESSED_SECTOR_SIZE -
(cluster_offset / QCOW2_COMPRESSED_SECTOR_SIZE);
/* The offset and size must fit in their fields of the L2 table entry */
assert((cluster_offset & s->cluster_offset_mask) == cluster_offset);
assert((nb_csectors & s->csize_mask) == nb_csectors);
cluster_offset |= QCOW_OFLAG_COMPRESSED |
((uint64_t)nb_csectors << s->csize_shift);
/* update L2 table */
/* compressed clusters never have the copied flag */
BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED);
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
set_l2_entry(s, l2_slice, l2_index, cluster_offset);
if (has_subclusters(s)) {
set_l2_bitmap(s, l2_slice, l2_index, 0);
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
*host_offset = cluster_offset & s->cluster_offset_mask;
return 0;
}
static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
{
BDRVQcow2State *s = bs->opaque;
Qcow2COWRegion *start = &m->cow_start;
Qcow2COWRegion *end = &m->cow_end;
unsigned buffer_size;
unsigned data_bytes = end->offset - (start->offset + start->nb_bytes);
bool merge_reads;
uint8_t *start_buffer, *end_buffer;
QEMUIOVector qiov;
int ret;
assert(start->nb_bytes <= UINT_MAX - end->nb_bytes);
assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes);
assert(start->offset + start->nb_bytes <= end->offset);
if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) {
return 0;
}
/* If we have to read both the start and end COW regions and the
* middle region is not too large then perform just one read
* operation */
merge_reads = start->nb_bytes && end->nb_bytes && data_bytes <= 16384;
if (merge_reads) {
buffer_size = start->nb_bytes + data_bytes + end->nb_bytes;
} else {
/* If we have to do two reads, add some padding in the middle
* if necessary to make sure that the end region is optimally
* aligned. */
size_t align = bdrv_opt_mem_align(bs);
assert(align > 0 && align <= UINT_MAX);
assert(QEMU_ALIGN_UP(start->nb_bytes, align) <=
UINT_MAX - end->nb_bytes);
buffer_size = QEMU_ALIGN_UP(start->nb_bytes, align) + end->nb_bytes;
}
/* Reserve a buffer large enough to store all the data that we're
* going to read */
start_buffer = qemu_try_blockalign(bs, buffer_size);
if (start_buffer == NULL) {
return -ENOMEM;
}
/* The part of the buffer where the end region is located */
end_buffer = start_buffer + buffer_size - end->nb_bytes;
qemu_iovec_init(&qiov, 2 + (m->data_qiov ?
qemu_iovec_subvec_niov(m->data_qiov,
m->data_qiov_offset,
data_bytes)
: 0));
qemu_co_mutex_unlock(&s->lock);
/* First we read the existing data from both COW regions. We
* either read the whole region in one go, or the start and end
* regions separately. */
if (merge_reads) {
qemu_iovec_add(&qiov, start_buffer, buffer_size);
ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov);
} else {
qemu_iovec_add(&qiov, start_buffer, start->nb_bytes);
ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov);
if (ret < 0) {
goto fail;
}
qemu_iovec_reset(&qiov);
qemu_iovec_add(&qiov, end_buffer, end->nb_bytes);
ret = do_perform_cow_read(bs, m->offset, end->offset, &qiov);
}
if (ret < 0) {
goto fail;
}
/* Encrypt the data if necessary before writing it */
if (bs->encrypted) {
ret = qcow2_co_encrypt(bs,
m->alloc_offset + start->offset,
m->offset + start->offset,
start_buffer, start->nb_bytes);
if (ret < 0) {
goto fail;
}
ret = qcow2_co_encrypt(bs,
m->alloc_offset + end->offset,
m->offset + end->offset,
end_buffer, end->nb_bytes);
if (ret < 0) {
goto fail;
}
}
/* And now we can write everything. If we have the guest data we
* can write everything in one single operation */
if (m->data_qiov) {
qemu_iovec_reset(&qiov);
if (start->nb_bytes) {
qemu_iovec_add(&qiov, start_buffer, start->nb_bytes);
}
qemu_iovec_concat(&qiov, m->data_qiov, m->data_qiov_offset, data_bytes);
if (end->nb_bytes) {
qemu_iovec_add(&qiov, end_buffer, end->nb_bytes);
}
/* NOTE: we have a write_aio blkdebug event here followed by
* a cow_write one in do_perform_cow_write(), but there's only
* one single I/O operation */
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov);
} else {
/* If there's no guest data then write both COW regions separately */
qemu_iovec_reset(&qiov);
qemu_iovec_add(&qiov, start_buffer, start->nb_bytes);
ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov);
if (ret < 0) {
goto fail;
}
qemu_iovec_reset(&qiov);
qemu_iovec_add(&qiov, end_buffer, end->nb_bytes);
ret = do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov);
}
fail:
qemu_co_mutex_lock(&s->lock);
/*
* Before we update the L2 table to actually point to the new cluster, we
* need to be sure that the refcounts have been increased and COW was
* handled.
*/
if (ret == 0) {
qcow2_cache_depends_on_flush(s->l2_table_cache);
}
qemu_vfree(start_buffer);
qemu_iovec_destroy(&qiov);
return ret;
}
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
{
BDRVQcow2State *s = bs->opaque;
int i, j = 0, l2_index, ret;
uint64_t *old_cluster, *l2_slice;
uint64_t cluster_offset = m->alloc_offset;
trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters);
assert(m->nb_clusters > 0);
old_cluster = g_try_new(uint64_t, m->nb_clusters);
if (old_cluster == NULL) {
ret = -ENOMEM;
goto err;
}
/* copy content of unmodified sectors */
ret = perform_cow(bs, m);
if (ret < 0) {
goto err;
}
/* Update L2 table. */
if (s->use_lazy_refcounts) {
qcow2_mark_dirty(bs);
}
if (qcow2_need_accurate_refcounts(s)) {
qcow2_cache_set_dependency(bs, s->l2_table_cache,
s->refcount_block_cache);
}
ret = get_cluster_table(bs, m->offset, &l2_slice, &l2_index);
if (ret < 0) {
goto err;
}
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
assert(l2_index + m->nb_clusters <= s->l2_slice_size);
assert(m->cow_end.offset + m->cow_end.nb_bytes <=
m->nb_clusters << s->cluster_bits);
for (i = 0; i < m->nb_clusters; i++) {
uint64_t offset = cluster_offset + ((uint64_t)i << s->cluster_bits);
/* if two concurrent writes happen to the same unallocated cluster
* each write allocates separate cluster and writes data concurrently.
* The first one to complete updates l2 table with pointer to its
* cluster the second one has to do RMW (which is done above by
* perform_cow()), update l2 table with its cluster pointer and free
* old cluster. This is what this loop does */
if (get_l2_entry(s, l2_slice, l2_index + i) != 0) {
old_cluster[j++] = get_l2_entry(s, l2_slice, l2_index + i);
}
/* The offset must fit in the offset field of the L2 table entry */
assert((offset & L2E_OFFSET_MASK) == offset);
set_l2_entry(s, l2_slice, l2_index + i, offset | QCOW_OFLAG_COPIED);
/* Update bitmap with the subclusters that were just written */
if (has_subclusters(s) && !m->prealloc) {
uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
unsigned written_from = m->cow_start.offset;
unsigned written_to = m->cow_end.offset + m->cow_end.nb_bytes;
int first_sc, last_sc;
/* Narrow written_from and written_to down to the current cluster */
written_from = MAX(written_from, i << s->cluster_bits);
written_to = MIN(written_to, (i + 1) << s->cluster_bits);
assert(written_from < written_to);
first_sc = offset_to_sc_index(s, written_from);
last_sc = offset_to_sc_index(s, written_to - 1);
l2_bitmap |= QCOW_OFLAG_SUB_ALLOC_RANGE(first_sc, last_sc + 1);
l2_bitmap &= ~QCOW_OFLAG_SUB_ZERO_RANGE(first_sc, last_sc + 1);
set_l2_bitmap(s, l2_slice, l2_index + i, l2_bitmap);
}
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
/*
* If this was a COW, we need to decrease the refcount of the old cluster.
*
* Don't discard clusters that reach a refcount of 0 (e.g. compressed
* clusters), the next write will reuse them anyway.
*/
if (!m->keep_old_clusters && j != 0) {
for (i = 0; i < j; i++) {
qcow2_free_any_cluster(bs, old_cluster[i], QCOW2_DISCARD_NEVER);
}
}
ret = 0;
err:
g_free(old_cluster);
return ret;
}
/**
* Frees the allocated clusters because the request failed and they won't
* actually be linked.
*/
void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m)
{
BDRVQcow2State *s = bs->opaque;
if (!has_data_file(bs) && !m->keep_old_clusters) {
qcow2_free_clusters(bs, m->alloc_offset,
m->nb_clusters << s->cluster_bits,
QCOW2_DISCARD_NEVER);
}
}
/*
* For a given write request, create a new QCowL2Meta structure, add
* it to @m and the BDRVQcow2State.cluster_allocs list. If the write
* request does not need copy-on-write or changes to the L2 metadata
* then this function does nothing.
*
* @host_cluster_offset points to the beginning of the first cluster.
*
* @guest_offset and @bytes indicate the offset and length of the
* request.
*
* @l2_slice contains the L2 entries of all clusters involved in this
* write request.
*
* If @keep_old is true it means that the clusters were already
* allocated and will be overwritten. If false then the clusters are
* new and we have to decrease the reference count of the old ones.
*
* Returns 0 on success, -errno on failure.
*/
static int calculate_l2_meta(BlockDriverState *bs, uint64_t host_cluster_offset,
uint64_t guest_offset, unsigned bytes,
uint64_t *l2_slice, QCowL2Meta **m, bool keep_old)
{
BDRVQcow2State *s = bs->opaque;
int sc_index, l2_index = offset_to_l2_slice_index(s, guest_offset);
uint64_t l2_entry, l2_bitmap;
unsigned cow_start_from, cow_end_to;
unsigned cow_start_to = offset_into_cluster(s, guest_offset);
unsigned cow_end_from = cow_start_to + bytes;
unsigned nb_clusters = size_to_clusters(s, cow_end_from);
QCowL2Meta *old_m = *m;
QCow2SubclusterType type;
int i;
bool skip_cow = keep_old;
assert(nb_clusters <= s->l2_slice_size - l2_index);
/* Check the type of all affected subclusters */
for (i = 0; i < nb_clusters; i++) {
l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
if (skip_cow) {
unsigned write_from = MAX(cow_start_to, i << s->cluster_bits);
unsigned write_to = MIN(cow_end_from, (i + 1) << s->cluster_bits);
int first_sc = offset_to_sc_index(s, write_from);
int last_sc = offset_to_sc_index(s, write_to - 1);
int cnt = qcow2_get_subcluster_range_type(bs, l2_entry, l2_bitmap,
first_sc, &type);
/* Is any of the subclusters of type != QCOW2_SUBCLUSTER_NORMAL ? */
if (type != QCOW2_SUBCLUSTER_NORMAL || first_sc + cnt <= last_sc) {
skip_cow = false;
}
} else {
/* If we can't skip the cow we can still look for invalid entries */
type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, 0);
}
if (type == QCOW2_SUBCLUSTER_INVALID) {
int l1_index = offset_to_l1_index(s, guest_offset);
uint64_t l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
qcow2_signal_corruption(bs, true, -1, -1, "Invalid cluster "
"entry found (L2 offset: %#" PRIx64
", L2 index: %#x)",
l2_offset, l2_index + i);
return -EIO;
}
}
if (skip_cow) {
return 0;
}
/* Get the L2 entry of the first cluster */
l2_entry = get_l2_entry(s, l2_slice, l2_index);
l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
sc_index = offset_to_sc_index(s, guest_offset);
type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
if (!keep_old) {
switch (type) {
case QCOW2_SUBCLUSTER_COMPRESSED:
cow_start_from = 0;
break;
case QCOW2_SUBCLUSTER_NORMAL:
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
if (has_subclusters(s)) {
/* Skip all leading zero and unallocated subclusters */
uint32_t alloc_bitmap = l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC;
cow_start_from =
MIN(sc_index, ctz32(alloc_bitmap)) << s->subcluster_bits;
} else {
cow_start_from = 0;
}
break;
case QCOW2_SUBCLUSTER_ZERO_PLAIN:
case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
cow_start_from = sc_index << s->subcluster_bits;
break;
default:
g_assert_not_reached();
}
} else {
switch (type) {
case QCOW2_SUBCLUSTER_NORMAL:
cow_start_from = cow_start_to;
break;
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
cow_start_from = sc_index << s->subcluster_bits;
break;
default:
g_assert_not_reached();
}
}
/* Get the L2 entry of the last cluster */
l2_index += nb_clusters - 1;
l2_entry = get_l2_entry(s, l2_slice, l2_index);
l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
sc_index = offset_to_sc_index(s, guest_offset + bytes - 1);
type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
if (!keep_old) {
switch (type) {
case QCOW2_SUBCLUSTER_COMPRESSED:
cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
break;
case QCOW2_SUBCLUSTER_NORMAL:
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
if (has_subclusters(s)) {
/* Skip all trailing zero and unallocated subclusters */
uint32_t alloc_bitmap = l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC;
cow_end_to -=
MIN(s->subclusters_per_cluster - sc_index - 1,
clz32(alloc_bitmap)) << s->subcluster_bits;
}
break;
case QCOW2_SUBCLUSTER_ZERO_PLAIN:
case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
cow_end_to = ROUND_UP(cow_end_from, s->subcluster_size);
break;
default:
g_assert_not_reached();
}
} else {
switch (type) {
case QCOW2_SUBCLUSTER_NORMAL:
cow_end_to = cow_end_from;
break;
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
cow_end_to = ROUND_UP(cow_end_from, s->subcluster_size);
break;
default:
g_assert_not_reached();
}
}
*m = g_malloc0(sizeof(**m));
**m = (QCowL2Meta) {
.next = old_m,
.alloc_offset = host_cluster_offset,
.offset = start_of_cluster(s, guest_offset),
.nb_clusters = nb_clusters,
.keep_old_clusters = keep_old,
.cow_start = {
.offset = cow_start_from,
.nb_bytes = cow_start_to - cow_start_from,
},
.cow_end = {
.offset = cow_end_from,
.nb_bytes = cow_end_to - cow_end_from,
},
};
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
return 0;
}
/*
* Returns true if writing to the cluster pointed to by @l2_entry
* requires a new allocation (that is, if the cluster is unallocated
* or has refcount > 1 and therefore cannot be written in-place).
*/
static bool cluster_needs_new_alloc(BlockDriverState *bs, uint64_t l2_entry)
{
switch (qcow2_get_cluster_type(bs, l2_entry)) {
case QCOW2_CLUSTER_NORMAL:
case QCOW2_CLUSTER_ZERO_ALLOC:
if (l2_entry & QCOW_OFLAG_COPIED) {
return false;
}
/* fallthrough */
case QCOW2_CLUSTER_UNALLOCATED:
case QCOW2_CLUSTER_COMPRESSED:
case QCOW2_CLUSTER_ZERO_PLAIN:
return true;
default:
abort();
}
}
/*
* Returns the number of contiguous clusters that can be written to
* using one single write request, starting from @l2_index.
* At most @nb_clusters are checked.
*
* If @new_alloc is true this counts clusters that are either
* unallocated, or allocated but with refcount > 1 (so they need to be
* newly allocated and COWed).
*
* If @new_alloc is false this counts clusters that are already
* allocated and can be overwritten in-place (this includes clusters
* of type QCOW2_CLUSTER_ZERO_ALLOC).
*/
static int count_single_write_clusters(BlockDriverState *bs, int nb_clusters,
uint64_t *l2_slice, int l2_index,
bool new_alloc)
{
BDRVQcow2State *s = bs->opaque;
uint64_t l2_entry = get_l2_entry(s, l2_slice, l2_index);
uint64_t expected_offset = l2_entry & L2E_OFFSET_MASK;
int i;
for (i = 0; i < nb_clusters; i++) {
l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
if (cluster_needs_new_alloc(bs, l2_entry) != new_alloc) {
break;
}
if (!new_alloc) {
if (expected_offset != (l2_entry & L2E_OFFSET_MASK)) {
break;
}
expected_offset += s->cluster_size;
}
}
assert(i <= nb_clusters);
return i;
}
/*
* Check if there already is an AIO write request in flight which allocates
* the same cluster. In this case we need to wait until the previous
* request has completed and updated the L2 table accordingly.
*
* Returns:
* 0 if there was no dependency. *cur_bytes indicates the number of
* bytes from guest_offset that can be read before the next
* dependency must be processed (or the request is complete)
*
* -EAGAIN if we had to wait for another request, previously gathered
* information on cluster allocation may be invalid now. The caller
* must start over anyway, so consider *cur_bytes undefined.
*/
static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset,
uint64_t *cur_bytes, QCowL2Meta **m)
{
BDRVQcow2State *s = bs->opaque;
QCowL2Meta *old_alloc;
uint64_t bytes = *cur_bytes;
QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) {
uint64_t start = guest_offset;
uint64_t end = start + bytes;
uint64_t old_start = start_of_cluster(s, l2meta_cow_start(old_alloc));
uint64_t old_end = ROUND_UP(l2meta_cow_end(old_alloc), s->cluster_size);
if (end <= old_start || start >= old_end) {
/* No intersection */
} else {
if (start < old_start) {
/* Stop at the start of a running allocation */
bytes = old_start - start;
} else {
bytes = 0;
}
/* Stop if already an l2meta exists. After yielding, it wouldn't
* be valid any more, so we'd have to clean up the old L2Metas
* and deal with requests depending on them before starting to
* gather new ones. Not worth the trouble. */
if (bytes == 0 && *m) {
*cur_bytes = 0;
return 0;
}
if (bytes == 0) {
/* Wait for the dependency to complete. We need to recheck
* the free/allocated clusters when we continue. */
qemu_co_queue_wait(&old_alloc->dependent_requests, &s->lock);
return -EAGAIN;
}
}
}
/* Make sure that existing clusters and new allocations are only used up to
* the next dependency if we shortened the request above */
*cur_bytes = bytes;
return 0;
}
/*
* Checks how many already allocated clusters that don't require a new
* allocation there are at the given guest_offset (up to *bytes).
* If *host_offset is not INV_OFFSET, only physically contiguous clusters
* beginning at this host offset are counted.
*
* Note that guest_offset may not be cluster aligned. In this case, the
* returned *host_offset points to exact byte referenced by guest_offset and
* therefore isn't cluster aligned as well.
*
* Returns:
* 0: if no allocated clusters are available at the given offset.
* *bytes is normally unchanged. It is set to 0 if the cluster
* is allocated and can be overwritten in-place but doesn't have
* the right physical offset.
*
* 1: if allocated clusters that can be overwritten in place are
* available at the requested offset. *bytes may have decreased
* and describes the length of the area that can be written to.
*
* -errno: in error cases
*/
static int handle_copied(BlockDriverState *bs, uint64_t guest_offset,
uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m)
{
BDRVQcow2State *s = bs->opaque;
int l2_index;
uint64_t l2_entry, cluster_offset;
uint64_t *l2_slice;
uint64_t nb_clusters;
unsigned int keep_clusters;
int ret;
trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset,
*bytes);
assert(*host_offset == INV_OFFSET || offset_into_cluster(s, guest_offset)
== offset_into_cluster(s, *host_offset));
/*
* Calculate the number of clusters to look for. We stop at L2 slice
* boundaries to keep things simple.
*/
nb_clusters =
size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes);
l2_index = offset_to_l2_slice_index(s, guest_offset);
nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index);
/* Limit total byte count to BDRV_REQUEST_MAX_BYTES */
nb_clusters = MIN(nb_clusters, BDRV_REQUEST_MAX_BYTES >> s->cluster_bits);
/* Find L2 entry for the first involved cluster */
ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
l2_entry = get_l2_entry(s, l2_slice, l2_index);
cluster_offset = l2_entry & L2E_OFFSET_MASK;
if (!cluster_needs_new_alloc(bs, l2_entry)) {
if (offset_into_cluster(s, cluster_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "%s cluster offset "
"%#" PRIx64 " unaligned (guest offset: %#"
PRIx64 ")", l2_entry & QCOW_OFLAG_ZERO ?
"Preallocated zero" : "Data",
cluster_offset, guest_offset);
ret = -EIO;
goto out;
}
/* If a specific host_offset is required, check it */
if (*host_offset != INV_OFFSET && cluster_offset != *host_offset) {
*bytes = 0;
ret = 0;
goto out;
}
/* We keep all QCOW_OFLAG_COPIED clusters */
keep_clusters = count_single_write_clusters(bs, nb_clusters, l2_slice,
l2_index, false);
assert(keep_clusters <= nb_clusters);
*bytes = MIN(*bytes,
keep_clusters * s->cluster_size
- offset_into_cluster(s, guest_offset));
assert(*bytes != 0);
ret = calculate_l2_meta(bs, cluster_offset, guest_offset,
*bytes, l2_slice, m, true);
if (ret < 0) {
goto out;
}
ret = 1;
} else {
ret = 0;
}
/* Cleanup */
out:
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
/* Only return a host offset if we actually made progress. Otherwise we
* would make requirements for handle_alloc() that it can't fulfill */
if (ret > 0) {
*host_offset = cluster_offset + offset_into_cluster(s, guest_offset);
}
return ret;
}
/*
* Allocates new clusters for the given guest_offset.
*
* At most *nb_clusters are allocated, and on return *nb_clusters is updated to
* contain the number of clusters that have been allocated and are contiguous
* in the image file.
*
* If *host_offset is not INV_OFFSET, it specifies the offset in the image file
* at which the new clusters must start. *nb_clusters can be 0 on return in
* this case if the cluster at host_offset is already in use. If *host_offset
* is INV_OFFSET, the clusters can be allocated anywhere in the image file.
*
* *host_offset is updated to contain the offset into the image file at which
* the first allocated cluster starts.
*
* Return 0 on success and -errno in error cases. -EAGAIN means that the
* function has been waiting for another request and the allocation must be
* restarted, but the whole request should not be failed.
*/
static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,
uint64_t *host_offset, uint64_t *nb_clusters)
{
BDRVQcow2State *s = bs->opaque;
trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset,
*host_offset, *nb_clusters);
if (has_data_file(bs)) {
assert(*host_offset == INV_OFFSET ||
*host_offset == start_of_cluster(s, guest_offset));
*host_offset = start_of_cluster(s, guest_offset);
return 0;
}
/* Allocate new clusters */
trace_qcow2_cluster_alloc_phys(qemu_coroutine_self());
if (*host_offset == INV_OFFSET) {
int64_t cluster_offset =
qcow2_alloc_clusters(bs, *nb_clusters * s->cluster_size);
if (cluster_offset < 0) {
return cluster_offset;
}
*host_offset = cluster_offset;
return 0;
} else {
int64_t ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters);
if (ret < 0) {
return ret;
}
*nb_clusters = ret;
return 0;
}
}
/*
* Allocates new clusters for an area that is either still unallocated or
* cannot be overwritten in-place. If *host_offset is not INV_OFFSET,
* clusters are only allocated if the new allocation can match the specified
* host offset.
*
* Note that guest_offset may not be cluster aligned. In this case, the
* returned *host_offset points to exact byte referenced by guest_offset and
* therefore isn't cluster aligned as well.
*
* Returns:
* 0: if no clusters could be allocated. *bytes is set to 0,
* *host_offset is left unchanged.
*
* 1: if new clusters were allocated. *bytes may be decreased if the
* new allocation doesn't cover all of the requested area.
* *host_offset is updated to contain the host offset of the first
* newly allocated cluster.
*
* -errno: in error cases
*/
static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m)
{
BDRVQcow2State *s = bs->opaque;
int l2_index;
uint64_t *l2_slice;
uint64_t nb_clusters;
int ret;
uint64_t alloc_cluster_offset;
trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset,
*bytes);
assert(*bytes > 0);
/*
* Calculate the number of clusters to look for. We stop at L2 slice
* boundaries to keep things simple.
*/
nb_clusters =
size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes);
l2_index = offset_to_l2_slice_index(s, guest_offset);
nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index);
/* Limit total allocation byte count to BDRV_REQUEST_MAX_BYTES */
nb_clusters = MIN(nb_clusters, BDRV_REQUEST_MAX_BYTES >> s->cluster_bits);
/* Find L2 entry for the first involved cluster */
ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
nb_clusters = count_single_write_clusters(bs, nb_clusters,
l2_slice, l2_index, true);
/* This function is only called when there were no non-COW clusters, so if
* we can't find any unallocated or COW clusters either, something is
* wrong with our code. */
assert(nb_clusters > 0);
/* Allocate at a given offset in the image file */
alloc_cluster_offset = *host_offset == INV_OFFSET ? INV_OFFSET :
start_of_cluster(s, *host_offset);
ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset,
&nb_clusters);
if (ret < 0) {
goto out;
}
/* Can't extend contiguous allocation */
if (nb_clusters == 0) {
*bytes = 0;
ret = 0;
goto out;
}
assert(alloc_cluster_offset != INV_OFFSET);
/*
* Save info needed for meta data update.
*
* requested_bytes: Number of bytes from the start of the first
* newly allocated cluster to the end of the (possibly shortened
* before) write request.
*
* avail_bytes: Number of bytes from the start of the first
* newly allocated to the end of the last newly allocated cluster.
*
* nb_bytes: The number of bytes from the start of the first
* newly allocated cluster to the end of the area that the write
* request actually writes to (excluding COW at the end)
*/
uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset);
int avail_bytes = nb_clusters << s->cluster_bits;
int nb_bytes = MIN(requested_bytes, avail_bytes);
*host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset);
*bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset));
assert(*bytes != 0);
ret = calculate_l2_meta(bs, alloc_cluster_offset, guest_offset, *bytes,
l2_slice, m, false);
if (ret < 0) {
goto out;
}
ret = 1;
out:
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return ret;
}
/*
* For a given area on the virtual disk defined by @offset and @bytes,
* find the corresponding area on the qcow2 image, allocating new
* clusters (or subclusters) if necessary. The result can span a
* combination of allocated and previously unallocated clusters.
*
* Note that offset may not be cluster aligned. In this case, the returned
* *host_offset points to exact byte referenced by offset and therefore
* isn't cluster aligned as well.
*
* On return, @host_offset is set to the beginning of the requested
* area. This area is guaranteed to be contiguous on the qcow2 file
* but it can be smaller than initially requested. In this case @bytes
* is updated with the actual size.
*
* If any clusters or subclusters were allocated then @m contains a
* list with the information of all the affected regions. Note that
* this can happen regardless of whether this function succeeds or
* not. The caller is responsible for updating the L2 metadata of the
* allocated clusters (on success) or freeing them (on failure), and
* for clearing the contents of @m afterwards in both cases.
*
* If the request conflicts with another write request in flight, the coroutine
* is queued and will be reentered when the dependency has completed.
*
* Return 0 on success and -errno in error cases
*/
int qcow2_alloc_host_offset(BlockDriverState *bs, uint64_t offset,
unsigned int *bytes, uint64_t *host_offset,
QCowL2Meta **m)
{
BDRVQcow2State *s = bs->opaque;
uint64_t start, remaining;
uint64_t cluster_offset;
uint64_t cur_bytes;
int ret;
trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *bytes);
again:
start = offset;
remaining = *bytes;
cluster_offset = INV_OFFSET;
*host_offset = INV_OFFSET;
cur_bytes = 0;
*m = NULL;
while (true) {
if (*host_offset == INV_OFFSET && cluster_offset != INV_OFFSET) {
*host_offset = cluster_offset;
}
assert(remaining >= cur_bytes);
start += cur_bytes;
remaining -= cur_bytes;
if (cluster_offset != INV_OFFSET) {
cluster_offset += cur_bytes;
}
if (remaining == 0) {
break;
}
cur_bytes = remaining;
/*
* Now start gathering as many contiguous clusters as possible:
*
* 1. Check for overlaps with in-flight allocations
*
* a) Overlap not in the first cluster -> shorten this request and
* let the caller handle the rest in its next loop iteration.
*
* b) Real overlaps of two requests. Yield and restart the search
* for contiguous clusters (the situation could have changed
* while we were sleeping)
*
* c) TODO: Request starts in the same cluster as the in-flight
* allocation ends. Shorten the COW of the in-fight allocation,
* set cluster_offset to write to the same cluster and set up
* the right synchronisation between the in-flight request and
* the new one.
*/
ret = handle_dependencies(bs, start, &cur_bytes, m);
if (ret == -EAGAIN) {
/* Currently handle_dependencies() doesn't yield if we already had
* an allocation. If it did, we would have to clean up the L2Meta
* structs before starting over. */
assert(*m == NULL);
goto again;
} else if (ret < 0) {
return ret;
} else if (cur_bytes == 0) {
break;
} else {
/* handle_dependencies() may have decreased cur_bytes (shortened
* the allocations below) so that the next dependency is processed
* correctly during the next loop iteration. */
}
/*
* 2. Count contiguous COPIED clusters.
*/
ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
continue;
} else if (cur_bytes == 0) {
break;
}
/*
* 3. If the request still hasn't completed, allocate new clusters,
* considering any cluster_offset of steps 1c or 2.
*/
ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
continue;
} else {
assert(cur_bytes == 0);
break;
}
}
*bytes -= remaining;
assert(*bytes > 0);
assert(*host_offset != INV_OFFSET);
assert(offset_into_cluster(s, *host_offset) ==
offset_into_cluster(s, offset));
return 0;
}
/*
* This discards as many clusters of nb_clusters as possible at once (i.e.
* all clusters in the same L2 slice) and returns the number of discarded
* clusters.
*/
static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset,
uint64_t nb_clusters,
enum qcow2_discard_type type, bool full_discard)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l2_slice;
int l2_index;
int ret;
int i;
ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
/* Limit nb_clusters to one L2 slice */
nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index);
assert(nb_clusters <= INT_MAX);
for (i = 0; i < nb_clusters; i++) {
uint64_t old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
uint64_t old_l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
uint64_t new_l2_entry = old_l2_entry;
uint64_t new_l2_bitmap = old_l2_bitmap;
QCow2ClusterType cluster_type =
qcow2_get_cluster_type(bs, old_l2_entry);
/*
* If full_discard is true, the cluster should not read back as zeroes,
* but rather fall through to the backing file.
*
* If full_discard is false, make sure that a discarded area reads back
* as zeroes for v3 images (we cannot do it for v2 without actually
* writing a zero-filled buffer). We can skip the operation if the
* cluster is already marked as zero, or if it's unallocated and we
* don't have a backing file.
*
* TODO We might want to use bdrv_block_status(bs) here, but we're
* holding s->lock, so that doesn't work today.
*/
if (full_discard) {
new_l2_entry = new_l2_bitmap = 0;
} else if (bs->backing || qcow2_cluster_is_allocated(cluster_type)) {
if (has_subclusters(s)) {
new_l2_entry = 0;
new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES;
} else {
new_l2_entry = s->qcow_version >= 3 ? QCOW_OFLAG_ZERO : 0;
}
}
if (old_l2_entry == new_l2_entry && old_l2_bitmap == new_l2_bitmap) {
continue;
}
/* First remove L2 entries */
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry);
if (has_subclusters(s)) {
set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap);
}
/* Then decrease the refcount */
qcow2_free_any_cluster(bs, old_l2_entry, type);
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return nb_clusters;
}
int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, enum qcow2_discard_type type,
bool full_discard)
{
BDRVQcow2State *s = bs->opaque;
uint64_t end_offset = offset + bytes;
uint64_t nb_clusters;
int64_t cleared;
int ret;
/* Caller must pass aligned values, except at image end */
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
end_offset == bs->total_sectors << BDRV_SECTOR_BITS);
nb_clusters = size_to_clusters(s, bytes);
s->cache_discards = true;
/* Each L2 slice is handled by its own loop iteration */
while (nb_clusters > 0) {
cleared = discard_in_l2_slice(bs, offset, nb_clusters, type,
full_discard);
if (cleared < 0) {
ret = cleared;
goto fail;
}
nb_clusters -= cleared;
offset += (cleared * s->cluster_size);
}
ret = 0;
fail:
s->cache_discards = false;
qcow2_process_discards(bs, ret);
return ret;
}
/*
* This zeroes as many clusters of nb_clusters as possible at once (i.e.
* all clusters in the same L2 slice) and returns the number of zeroed
* clusters.
*/
static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset,
uint64_t nb_clusters, int flags)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l2_slice;
int l2_index;
int ret;
int i;
ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
/* Limit nb_clusters to one L2 slice */
nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index);
assert(nb_clusters <= INT_MAX);
for (i = 0; i < nb_clusters; i++) {
uint64_t old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
uint64_t old_l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
QCow2ClusterType type = qcow2_get_cluster_type(bs, old_l2_entry);
bool unmap = (type == QCOW2_CLUSTER_COMPRESSED) ||
((flags & BDRV_REQ_MAY_UNMAP) && qcow2_cluster_is_allocated(type));
uint64_t new_l2_entry = unmap ? 0 : old_l2_entry;
uint64_t new_l2_bitmap = old_l2_bitmap;
if (has_subclusters(s)) {
new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES;
} else {
new_l2_entry |= QCOW_OFLAG_ZERO;
}
if (old_l2_entry == new_l2_entry && old_l2_bitmap == new_l2_bitmap) {
continue;
}
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
if (unmap) {
qcow2_free_any_cluster(bs, old_l2_entry, QCOW2_DISCARD_REQUEST);
}
set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry);
if (has_subclusters(s)) {
set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap);
}
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return nb_clusters;
}
static int zero_l2_subclusters(BlockDriverState *bs, uint64_t offset,
unsigned nb_subclusters)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l2_slice;
uint64_t old_l2_bitmap, l2_bitmap;
int l2_index, ret, sc = offset_to_sc_index(s, offset);
/* For full clusters use zero_in_l2_slice() instead */
assert(nb_subclusters > 0 && nb_subclusters < s->subclusters_per_cluster);
assert(sc + nb_subclusters <= s->subclusters_per_cluster);
assert(offset_into_subcluster(s, offset) == 0);
ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
if (ret < 0) {
return ret;
}
switch (qcow2_get_cluster_type(bs, get_l2_entry(s, l2_slice, l2_index))) {
case QCOW2_CLUSTER_COMPRESSED:
ret = -ENOTSUP; /* We cannot partially zeroize compressed clusters */
goto out;
case QCOW2_CLUSTER_NORMAL:
case QCOW2_CLUSTER_UNALLOCATED:
break;
default:
g_assert_not_reached();
}
old_l2_bitmap = l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
l2_bitmap |= QCOW_OFLAG_SUB_ZERO_RANGE(sc, sc + nb_subclusters);
l2_bitmap &= ~QCOW_OFLAG_SUB_ALLOC_RANGE(sc, sc + nb_subclusters);
if (old_l2_bitmap != l2_bitmap) {
set_l2_bitmap(s, l2_slice, l2_index, l2_bitmap);
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
}
ret = 0;
out:
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
return ret;
}
int qcow2_subcluster_zeroize(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, int flags)
{
BDRVQcow2State *s = bs->opaque;
uint64_t end_offset = offset + bytes;
uint64_t nb_clusters;
unsigned head, tail;
int64_t cleared;
int ret;
/* If we have to stay in sync with an external data file, zero out
* s->data_file first. */
if (data_file_is_raw(bs)) {
assert(has_data_file(bs));
ret = bdrv_co_pwrite_zeroes(s->data_file, offset, bytes, flags);
if (ret < 0) {
return ret;
}
}
/* Caller must pass aligned values, except at image end */
assert(offset_into_subcluster(s, offset) == 0);
assert(offset_into_subcluster(s, end_offset) == 0 ||
end_offset >= bs->total_sectors << BDRV_SECTOR_BITS);
/*
* The zero flag is only supported by version 3 and newer. However, if we
* have no backing file, we can resort to discard in version 2.
*/
if (s->qcow_version < 3) {
if (!bs->backing) {
return qcow2_cluster_discard(bs, offset, bytes,
QCOW2_DISCARD_REQUEST, false);
}
return -ENOTSUP;
}
head = MIN(end_offset, ROUND_UP(offset, s->cluster_size)) - offset;
offset += head;
tail = (end_offset >= bs->total_sectors << BDRV_SECTOR_BITS) ? 0 :
end_offset - MAX(offset, start_of_cluster(s, end_offset));
end_offset -= tail;
s->cache_discards = true;
if (head) {
ret = zero_l2_subclusters(bs, offset - head,
size_to_subclusters(s, head));
if (ret < 0) {
goto fail;
}
}
/* Each L2 slice is handled by its own loop iteration */
nb_clusters = size_to_clusters(s, end_offset - offset);
while (nb_clusters > 0) {
cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags);
if (cleared < 0) {
ret = cleared;
goto fail;
}
nb_clusters -= cleared;
offset += (cleared * s->cluster_size);
}
if (tail) {
ret = zero_l2_subclusters(bs, end_offset, size_to_subclusters(s, tail));
if (ret < 0) {
goto fail;
}
}
ret = 0;
fail:
s->cache_discards = false;
qcow2_process_discards(bs, ret);
return ret;
}
/*
* Expands all zero clusters in a specific L1 table (or deallocates them, for
* non-backed non-pre-allocated zero clusters).
*
* l1_entries and *visited_l1_entries are used to keep track of progress for
* status_cb(). l1_entries contains the total number of L1 entries and
* *visited_l1_entries counts all visited L1 entries.
*/
static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
int l1_size, int64_t *visited_l1_entries,
int64_t l1_entries,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque)
{
BDRVQcow2State *s = bs->opaque;
bool is_active_l1 = (l1_table == s->l1_table);
uint64_t *l2_slice = NULL;
unsigned slice, slice_size2, n_slices;
int ret;
int i, j;
/* qcow2_downgrade() is not allowed in images with subclusters */
assert(!has_subclusters(s));
slice_size2 = s->l2_slice_size * l2_entry_size(s);
n_slices = s->cluster_size / slice_size2;
if (!is_active_l1) {
/* inactive L2 tables require a buffer to be stored in when loading
* them from disk */
l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2);
if (l2_slice == NULL) {
return -ENOMEM;
}
}
for (i = 0; i < l1_size; i++) {
uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
uint64_t l2_refcount;
if (!l2_offset) {
/* unallocated */
(*visited_l1_entries)++;
if (status_cb) {
status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque);
}
continue;
}
if (offset_into_cluster(s, l2_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#"
PRIx64 " unaligned (L1 index: %#x)",
l2_offset, i);
ret = -EIO;
goto fail;
}
ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
&l2_refcount);
if (ret < 0) {
goto fail;
}
for (slice = 0; slice < n_slices; slice++) {
uint64_t slice_offset = l2_offset + slice * slice_size2;
bool l2_dirty = false;
if (is_active_l1) {
/* get active L2 tables from cache */
ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset,
(void **)&l2_slice);
} else {
/* load inactive L2 tables from disk */
ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2);
}
if (ret < 0) {
goto fail;
}
for (j = 0; j < s->l2_slice_size; j++) {
uint64_t l2_entry = get_l2_entry(s, l2_slice, j);
int64_t offset = l2_entry & L2E_OFFSET_MASK;
QCow2ClusterType cluster_type =
qcow2_get_cluster_type(bs, l2_entry);
if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN &&
cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) {
continue;
}
if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) {
if (!bs->backing) {
/*
* not backed; therefore we can simply deallocate the
* cluster. No need to call set_l2_bitmap(), this
* function doesn't support images with subclusters.
*/
set_l2_entry(s, l2_slice, j, 0);
l2_dirty = true;
continue;
}
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
ret = offset;
goto fail;
}
/* The offset must fit in the offset field */
assert((offset & L2E_OFFSET_MASK) == offset);
if (l2_refcount > 1) {
/* For shared L2 tables, set the refcount accordingly
* (it is already 1 and needs to be l2_refcount) */
ret = qcow2_update_cluster_refcount(
bs, offset >> s->cluster_bits,
refcount_diff(1, l2_refcount), false,
QCOW2_DISCARD_OTHER);
if (ret < 0) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_OTHER);
goto fail;
}
}
}
if (offset_into_cluster(s, offset)) {
int l2_index = slice * s->l2_slice_size + j;
qcow2_signal_corruption(
bs, true, -1, -1,
"Cluster allocation offset "
"%#" PRIx64 " unaligned (L2 offset: %#"
PRIx64 ", L2 index: %#x)", offset,
l2_offset, l2_index);
if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
ret = -EIO;
goto fail;
}
ret = qcow2_pre_write_overlap_check(bs, 0, offset,
s->cluster_size, true);
if (ret < 0) {
if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
goto fail;
}
ret = bdrv_pwrite_zeroes(s->data_file, offset,
s->cluster_size, 0);
if (ret < 0) {
if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
goto fail;
}
if (l2_refcount == 1) {
set_l2_entry(s, l2_slice, j, offset | QCOW_OFLAG_COPIED);
} else {
set_l2_entry(s, l2_slice, j, offset);
}
/*
* No need to call set_l2_bitmap() after set_l2_entry() because
* this function doesn't support images with subclusters.
*/
l2_dirty = true;
}
if (is_active_l1) {
if (l2_dirty) {
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
qcow2_cache_depends_on_flush(s->l2_table_cache);
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
} else {
if (l2_dirty) {
ret = qcow2_pre_write_overlap_check(
bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2,
slice_offset, slice_size2, false);
if (ret < 0) {
goto fail;
}
ret = bdrv_pwrite(bs->file, slice_offset,
l2_slice, slice_size2);
if (ret < 0) {
goto fail;
}
}
}
}
(*visited_l1_entries)++;
if (status_cb) {
status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque);
}
}
ret = 0;
fail:
if (l2_slice) {
if (!is_active_l1) {
qemu_vfree(l2_slice);
} else {
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
}
}
return ret;
}
/*
* For backed images, expands all zero clusters on the image. For non-backed
* images, deallocates all non-pre-allocated zero clusters (and claims the
* allocation for pre-allocated ones). This is important for downgrading to a
* qcow2 version which doesn't yet support metadata zero clusters.
*/
int qcow2_expand_zero_clusters(BlockDriverState *bs,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l1_table = NULL;
int64_t l1_entries = 0, visited_l1_entries = 0;
int ret;
int i, j;
if (status_cb) {
l1_entries = s->l1_size;
for (i = 0; i < s->nb_snapshots; i++) {
l1_entries += s->snapshots[i].l1_size;
}
}
ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size,
&visited_l1_entries, l1_entries,
status_cb, cb_opaque);
if (ret < 0) {
goto fail;
}
/* Inactive L1 tables may point to active L2 tables - therefore it is
* necessary to flush the L2 table cache before trying to access the L2
* tables pointed to by inactive L1 entries (else we might try to expand
* zero clusters that have already been expanded); furthermore, it is also
* necessary to empty the L2 table cache, since it may contain tables which
* are now going to be modified directly on disk, bypassing the cache.
* qcow2_cache_empty() does both for us. */
ret = qcow2_cache_empty(bs, s->l2_table_cache);
if (ret < 0) {
goto fail;
}
for (i = 0; i < s->nb_snapshots; i++) {
int l1_size2;
uint64_t *new_l1_table;
Error *local_err = NULL;
ret = qcow2_validate_table(bs, s->snapshots[i].l1_table_offset,
s->snapshots[i].l1_size, L1E_SIZE,
QCOW_MAX_L1_SIZE, "Snapshot L1 table",
&local_err);
if (ret < 0) {
error_report_err(local_err);
goto fail;
}
l1_size2 = s->snapshots[i].l1_size * L1E_SIZE;
new_l1_table = g_try_realloc(l1_table, l1_size2);
if (!new_l1_table) {
ret = -ENOMEM;
goto fail;
}
l1_table = new_l1_table;
ret = bdrv_pread(bs->file, s->snapshots[i].l1_table_offset,
l1_table, l1_size2);
if (ret < 0) {
goto fail;
}
for (j = 0; j < s->snapshots[i].l1_size; j++) {
be64_to_cpus(&l1_table[j]);
}
ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size,
&visited_l1_entries, l1_entries,
status_cb, cb_opaque);
if (ret < 0) {
goto fail;
}
}
ret = 0;
fail:
g_free(l1_table);
return ret;
}
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