mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
24dfa9fa2f
qemu/block/qcow2-cluster.c
Eric Blake 0c1bd4692f qcow2: Discard unaligned tail when wiping image 
There is a subtle difference between the fast (qcow2v3 with no
extra data) and slow path (qcow2v2 format [aka 0.10], or when a
snapshot is present) of qcow2_make_empty().  The slow path fails
to discard the final (partial) cluster of an unaligned image.

The problem stems from the fact that qcow2_discard_clusters() was
silently ignoring sub-cluster head and tail on unaligned requests.
A quick audit of all callers shows that qcow2_snapshot_create() has
always passed a cluster-aligned request since the call was added
in commit 1ebf561; qcow2_co_pdiscard() has passed a cluster-aligned
request since commit ecdbead taught the block layer about preferred
discard alignment; and qcow2_make_empty() was fixed to pass an
aligned start (but not necessarily end) in commit a3e1505.

Asserting that the start is always aligned also points out that we
now have a dead check: rounding the end offset down can never result
in a value less than the aligned start offset (the check was rendered
dead with commit ecdbead).  Meanwhile, we do not want to round the
end cluster down in the one case of the end offset matching the
(unaligned) file size - that final partial cluster should still be
discarded.

With those fixes in place, the fast and slow paths are back in sync
at discarding an entire image; the next patch will update
qemu-iotests to ensure we don't regress.

Note that bdrv_co_pdiscard ignores ALL partial cluster requests,
including the partial cluster at the end of an image; it can be
argued that the partial cluster at the end should be special-cased
so that a guest issuing discard requests at proper alignments
everywhere else can likewise empty the entire image.  But that
optimization is left for another day.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-id: 20170331185356.2479-3-eblake@redhat.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-03 17:11:40 +02:00

1893 lines
60 KiB
C
Raw Blame History

/*
* 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 "qemu-common.h"
#include "block/block_int.h"
#include "block/qcow2.h"
#include "qemu/bswap.h"
#include "trace.h"
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 / sizeof(uint64_t)) {
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 = (new_l1_size * 3 + 1) / 2;
}
}
QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE > INT_MAX);
if (new_l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) {
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 = sizeof(uint64_t) * new_l1_size;
new_l1_table = qemu_try_blockalign(bs->file->bs,
align_offset(new_l1_size2, 512));
if (new_l1_table == NULL) {
return -ENOMEM;
}
memset(new_l1_table, 0, align_offset(new_l1_size2, 512));
if (s->l1_size) {
memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t));
}
/* 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);
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 * sizeof(uint64_t),
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
*
* Loads a L2 table into memory. If the table is in the cache, the cache
* is used; otherwise the L2 table is loaded from the image file.
*
* Returns a pointer to the L2 table on success, or NULL if the read from
* the image file failed.
*/
static int l2_load(BlockDriverState *bs, uint64_t l2_offset,
uint64_t **l2_table)
{
BDRVQcow2State *s = bs->opaque;
return qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
(void **)l2_table);
}
/*
* Writes one sector of the L1 table to the disk (can't update single entries
* and we really don't want bdrv_pread to perform a read-modify-write)
*/
#define L1_ENTRIES_PER_SECTOR (512 / 8)
int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
{
BDRVQcow2State *s = bs->opaque;
uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 };
int l1_start_index;
int i, ret;
l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1);
for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size;
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 + 8 * l1_start_index, sizeof(buf));
if (ret < 0) {
return ret;
}
BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
ret = bdrv_pwrite_sync(bs->file,
s->l1_table_offset + 8 * l1_start_index,
buf, sizeof(buf));
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, uint64_t **table)
{
BDRVQcow2State *s = bs->opaque;
uint64_t old_l2_offset;
uint64_t *l2_table = NULL;
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 * sizeof(uint64_t));
if (l2_offset < 0) {
ret = l2_offset;
goto fail;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
goto fail;
}
/* allocate a new entry in the l2 cache */
trace_qcow2_l2_allocate_get_empty(bs, l1_index);
ret = qcow2_cache_get_empty(bs, s->l2_table_cache, l2_offset, (void**) table);
if (ret < 0) {
goto fail;
}
l2_table = *table;
if ((old_l2_offset & L1E_OFFSET_MASK) == 0) {
/* if there was no old l2 table, clear the new table */
memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
} else {
uint64_t* old_table;
/* if there was an old l2 table, read it from the disk */
BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ);
ret = qcow2_cache_get(bs, s->l2_table_cache,
old_l2_offset & L1E_OFFSET_MASK,
(void**) &old_table);
if (ret < 0) {
goto fail;
}
memcpy(l2_table, old_table, s->cluster_size);
qcow2_cache_put(bs, s->l2_table_cache, (void **) &old_table);
}
/* write the l2 table 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(bs, s->l2_table_cache, l2_table);
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;
}
*table = l2_table;
trace_qcow2_l2_allocate_done(bs, l1_index, 0);
return 0;
fail:
trace_qcow2_l2_allocate_done(bs, l1_index, ret);
if (l2_table != NULL) {
qcow2_cache_put(bs, s->l2_table_cache, (void**) table);
}
s->l1_table[l1_index] = old_l2_offset;
if (l2_offset > 0) {
qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t),
QCOW2_DISCARD_ALWAYS);
}
return ret;
}
/*
* Checks how many clusters in a given L2 table are contiguous in the image
* file. As soon as one of the flags in the bitmask stop_flags changes compared
* to the first cluster, the search is stopped and the cluster is not counted
* as contiguous. (This allows it, for example, to stop at the first compressed
* cluster which may require a different handling)
*/
static int count_contiguous_clusters(int nb_clusters, int cluster_size,
uint64_t *l2_table, uint64_t stop_flags)
{
int i;
uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED;
uint64_t first_entry = be64_to_cpu(l2_table[0]);
uint64_t offset = first_entry & mask;
if (!offset)
return 0;
assert(qcow2_get_cluster_type(first_entry) == QCOW2_CLUSTER_NORMAL);
for (i = 0; i < nb_clusters; i++) {
uint64_t l2_entry = be64_to_cpu(l2_table[i]) & mask;
if (offset + (uint64_t) i * cluster_size != l2_entry) {
break;
}
}
return i;
}
static int count_contiguous_clusters_by_type(int nb_clusters,
uint64_t *l2_table,
int wanted_type)
{
int i;
for (i = 0; i < nb_clusters; i++) {
int type = qcow2_get_cluster_type(be64_to_cpu(l2_table[i]));
if (type != wanted_type) {
break;
}
}
return i;
}
/* The crypt function is compatible with the linux cryptoloop
algorithm for < 4 GB images. NOTE: out_buf == in_buf is
supported */
int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num,
uint8_t *out_buf, const uint8_t *in_buf,
int nb_sectors, bool enc,
Error **errp)
{
union {
uint64_t ll[2];
uint8_t b[16];
} ivec;
int i;
int ret;
for(i = 0; i < nb_sectors; i++) {
ivec.ll[0] = cpu_to_le64(sector_num);
ivec.ll[1] = 0;
if (qcrypto_cipher_setiv(s->cipher,
ivec.b, G_N_ELEMENTS(ivec.b),
errp) < 0) {
return -1;
}
if (enc) {
ret = qcrypto_cipher_encrypt(s->cipher,
in_buf,
out_buf,
512,
errp);
} else {
ret = qcrypto_cipher_decrypt(s->cipher,
in_buf,
out_buf,
512,
errp);
}
if (ret < 0) {
return -1;
}
sector_num++;
in_buf += 512;
out_buf += 512;
}
return 0;
}
static int coroutine_fn do_perform_cow(BlockDriverState *bs,
uint64_t src_cluster_offset,
uint64_t cluster_offset,
int offset_in_cluster,
int bytes)
{
BDRVQcow2State *s = bs->opaque;
QEMUIOVector qiov;
struct iovec iov;
int ret;
iov.iov_len = bytes;
iov.iov_base = qemu_try_blockalign(bs, iov.iov_len);
if (iov.iov_base == NULL) {
return -ENOMEM;
}
qemu_iovec_init_external(&qiov, &iov, 1);
BLKDBG_EVENT(bs->file, BLKDBG_COW_READ);
if (!bs->drv) {
ret = -ENOMEDIUM;
goto out;
}
/* 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(bs, src_cluster_offset + offset_in_cluster,
bytes, &qiov, 0);
if (ret < 0) {
goto out;
}
if (bs->encrypted) {
Error *err = NULL;
int64_t sector = (src_cluster_offset + offset_in_cluster)
>> BDRV_SECTOR_BITS;
assert(s->cipher);
assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
assert((bytes & ~BDRV_SECTOR_MASK) == 0);
if (qcow2_encrypt_sectors(s, sector, iov.iov_base, iov.iov_base,
bytes >> BDRV_SECTOR_BITS, true, &err) < 0) {
ret = -EIO;
error_free(err);
goto out;
}
}
ret = qcow2_pre_write_overlap_check(bs, 0,
cluster_offset + offset_in_cluster, bytes);
if (ret < 0) {
goto out;
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
ret = bdrv_co_pwritev(bs->file, cluster_offset + offset_in_cluster,
bytes, &qiov, 0);
if (ret < 0) {
goto out;
}
ret = 0;
out:
qemu_vfree(iov.iov_base);
return ret;
}
/*
* get_cluster_offset
*
* For a given offset of the virtual disk, find the cluster type and offset in
* the qcow2 file. The offset is stored in *cluster_offset.
*
* 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
* cluster type and (if applicable) are stored contiguously in the image file.
* Compressed clusters are always returned one by one.
*
* Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error
* cases.
*/
int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
unsigned int *bytes, uint64_t *cluster_offset)
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index;
uint64_t l1_index, l2_offset, *l2_table;
int l1_bits, c;
unsigned int offset_in_cluster;
uint64_t bytes_available, bytes_needed, nb_clusters;
int ret;
offset_in_cluster = offset_into_cluster(s, offset);
bytes_needed = (uint64_t) *bytes + offset_in_cluster;
l1_bits = s->l2_bits + s->cluster_bits;
/* compute how many bytes there are between the start of the cluster
* containing offset and the end of the l1 entry */
bytes_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1))
+ offset_in_cluster;
if (bytes_needed > bytes_available) {
bytes_needed = bytes_available;
}
*cluster_offset = 0;
/* seek to the l2 offset in the l1 table */
l1_index = offset >> l1_bits;
if (l1_index >= s->l1_size) {
ret = QCOW2_CLUSTER_UNALLOCATED;
goto out;
}
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
if (!l2_offset) {
ret = QCOW2_CLUSTER_UNALLOCATED;
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 table in memory */
ret = l2_load(bs, l2_offset, &l2_table);
if (ret < 0) {
return ret;
}
/* find the cluster offset for the given disk offset */
l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
*cluster_offset = be64_to_cpu(l2_table[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);
ret = qcow2_get_cluster_type(*cluster_offset);
switch (ret) {
case QCOW2_CLUSTER_COMPRESSED:
/* Compressed clusters can only be processed one by one */
c = 1;
*cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK;
break;
case QCOW2_CLUSTER_ZERO:
if (s->qcow_version < 3) {
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;
}
c = count_contiguous_clusters_by_type(nb_clusters, &l2_table[l2_index],
QCOW2_CLUSTER_ZERO);
*cluster_offset = 0;
break;
case QCOW2_CLUSTER_UNALLOCATED:
/* how many empty clusters ? */
c = count_contiguous_clusters_by_type(nb_clusters, &l2_table[l2_index],
QCOW2_CLUSTER_UNALLOCATED);
*cluster_offset = 0;
break;
case QCOW2_CLUSTER_NORMAL:
/* how many allocated clusters ? */
c = count_contiguous_clusters(nb_clusters, s->cluster_size,
&l2_table[l2_index], QCOW_OFLAG_ZERO);
*cluster_offset &= L2E_OFFSET_MASK;
if (offset_into_cluster(s, *cluster_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset %#"
PRIx64 " unaligned (L2 offset: %#" PRIx64
", L2 index: %#x)", *cluster_offset,
l2_offset, l2_index);
ret = -EIO;
goto fail;
}
break;
default:
abort();
}
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
bytes_available = (int64_t)c * s->cluster_size;
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;
return ret;
fail:
qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
return ret;
}
/*
* get_cluster_table
*
* for a given disk offset, load (and allocate if needed)
* the l2 table.
*
* the l2 table offset in the qcow2 file and the cluster index
* in the l2 table are 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_table,
int *new_l2_index)
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index;
uint64_t l1_index, l2_offset;
uint64_t *l2_table = NULL;
int ret;
/* seek to the l2 offset in the l1 table */
l1_index = offset >> (s->l2_bits + s->cluster_bits);
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;
}
/* seek the l2 table of the given l2 offset */
if (s->l1_table[l1_index] & QCOW_OFLAG_COPIED) {
/* load the l2 table in memory */
ret = l2_load(bs, l2_offset, &l2_table);
if (ret < 0) {
return ret;
}
} else {
/* First allocate a new L2 table (and do COW if needed) */
ret = l2_allocate(bs, l1_index, &l2_table);
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 * sizeof(uint64_t),
QCOW2_DISCARD_OTHER);
}
}
/* find the cluster offset for the given disk offset */
l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
*new_l2_table = l2_table;
*new_l2_index = l2_index;
return 0;
}
/*
* alloc_compressed_cluster_offset
*
* For a given offset of the disk image, return cluster offset in
* qcow2 file.
*
* If the offset is not found, allocate a new compressed cluster.
*
* Return the cluster offset if successful,
* Return 0, otherwise.
*
*/
uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
uint64_t offset,
int compressed_size)
{
BDRVQcow2State *s = bs->opaque;
int l2_index, ret;
uint64_t *l2_table;
int64_t cluster_offset;
int nb_csectors;
ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
if (ret < 0) {
return 0;
}
/* Compression can't overwrite anything. Fail if the cluster was already
* allocated. */
cluster_offset = be64_to_cpu(l2_table[l2_index]);
if (cluster_offset & L2E_OFFSET_MASK) {
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
return 0;
}
cluster_offset = qcow2_alloc_bytes(bs, compressed_size);
if (cluster_offset < 0) {
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
return 0;
}
nb_csectors = ((cluster_offset + compressed_size - 1) >> 9) -
(cluster_offset >> 9);
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(bs, s->l2_table_cache, l2_table);
l2_table[l2_index] = cpu_to_be64(cluster_offset);
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
return cluster_offset;
}
static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r)
{
BDRVQcow2State *s = bs->opaque;
int ret;
if (r->nb_bytes == 0) {
return 0;
}
qemu_co_mutex_unlock(&s->lock);
ret = do_perform_cow(bs, m->offset, m->alloc_offset, r->offset, r->nb_bytes);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
return ret;
}
/*
* 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.
*/
qcow2_cache_depends_on_flush(s->l2_table_cache);
return 0;
}
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_table;
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, &m->cow_start);
if (ret < 0) {
goto err;
}
ret = perform_cow(bs, m, &m->cow_end);
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_table, &l2_index);
if (ret < 0) {
goto err;
}
qcow2_cache_entry_mark_dirty(bs, s->l2_table_cache, l2_table);
assert(l2_index + m->nb_clusters <= s->l2_size);
for (i = 0; i < m->nb_clusters; i++) {
/* 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 (l2_table[l2_index + i] != 0) {
old_cluster[j++] = l2_table[l2_index + i];
}
l2_table[l2_index + i] = cpu_to_be64((cluster_offset +
(i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
}
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
/*
* 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 (j != 0) {
for (i = 0; i < j; i++) {
qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1,
QCOW2_DISCARD_NEVER);
}
}
ret = 0;
err:
g_free(old_cluster);
return ret;
}
/*
* Returns the number of contiguous clusters that can be used for an allocating
* write, but require COW to be performed (this includes yet unallocated space,
* which must copy from the backing file)
*/
static int count_cow_clusters(BDRVQcow2State *s, int nb_clusters,
uint64_t *l2_table, int l2_index)
{
int i;
for (i = 0; i < nb_clusters; i++) {
uint64_t l2_entry = be64_to_cpu(l2_table[l2_index + i]);
int cluster_type = qcow2_get_cluster_type(l2_entry);
switch(cluster_type) {
case QCOW2_CLUSTER_NORMAL:
if (l2_entry & QCOW_OFLAG_COPIED) {
goto out;
}
break;
case QCOW2_CLUSTER_UNALLOCATED:
case QCOW2_CLUSTER_COMPRESSED:
case QCOW2_CLUSTER_ZERO:
break;
default:
abort();
}
}
out:
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 = l2meta_cow_start(old_alloc);
uint64_t old_end = l2meta_cow_end(old_alloc);
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 copy on
* write there are at the given guest_offset (up to *bytes). If
* *host_offset is not zero, 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 doesn't need COW, but doesn't have the right
* physical offset.
*
* 1: if allocated clusters that don't require a COW 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 cluster_offset;
uint64_t *l2_table;
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 == 0 || offset_into_cluster(s, guest_offset)
== offset_into_cluster(s, *host_offset));
/*
* Calculate the number of clusters to look for. We stop at L2 table
* boundaries to keep things simple.
*/
nb_clusters =
size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes);
l2_index = offset_to_l2_index(s, guest_offset);
nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
assert(nb_clusters <= INT_MAX);
/* Find L2 entry for the first involved cluster */
ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}
cluster_offset = be64_to_cpu(l2_table[l2_index]);
/* Check how many clusters are already allocated and don't need COW */
if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL
&& (cluster_offset & QCOW_OFLAG_COPIED))
{
/* If a specific host_offset is required, check it */
bool offset_matches =
(cluster_offset & L2E_OFFSET_MASK) == *host_offset;
if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) {
qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset "
"%#llx unaligned (guest offset: %#" PRIx64
")", cluster_offset & L2E_OFFSET_MASK,
guest_offset);
ret = -EIO;
goto out;
}
if (*host_offset != 0 && !offset_matches) {
*bytes = 0;
ret = 0;
goto out;
}
/* We keep all QCOW_OFLAG_COPIED clusters */
keep_clusters =
count_contiguous_clusters(nb_clusters, s->cluster_size,
&l2_table[l2_index],
QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO);
assert(keep_clusters <= nb_clusters);
*bytes = MIN(*bytes,
keep_clusters * s->cluster_size
- offset_into_cluster(s, guest_offset));
ret = 1;
} else {
ret = 0;
}
/* Cleanup */
out:
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
/* 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 & L2E_OFFSET_MASK)
+ 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 non-zero, 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
* zero, 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);
/* Allocate new clusters */
trace_qcow2_cluster_alloc_phys(qemu_coroutine_self());
if (*host_offset == 0) {
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 either is yet unallocated or needs a
* copy on write. If *host_offset is non-zero, 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_table;
uint64_t entry;
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 table
* boundaries to keep things simple.
*/
nb_clusters =
size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes);
l2_index = offset_to_l2_index(s, guest_offset);
nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
assert(nb_clusters <= INT_MAX);
/* Find L2 entry for the first involved cluster */
ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}
entry = be64_to_cpu(l2_table[l2_index]);
/* For the moment, overwrite compressed clusters one by one */
if (entry & QCOW_OFLAG_COMPRESSED) {
nb_clusters = 1;
} else {
nb_clusters = count_cow_clusters(s, nb_clusters, l2_table, l2_index);
}
/* 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);
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
/* Allocate, if necessary at a given offset in the image file */
alloc_cluster_offset = start_of_cluster(s, *host_offset);
ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset,
&nb_clusters);
if (ret < 0) {
goto fail;
}
/* Can't extend contiguous allocation */
if (nb_clusters == 0) {
*bytes = 0;
return 0;
}
/* !*host_offset would overwrite the image header and is reserved for "no
* host offset preferred". If 0 was a valid host offset, it'd trigger the
* following overlap check; do that now to avoid having an invalid value in
* *host_offset. */
if (!alloc_cluster_offset) {
ret = qcow2_pre_write_overlap_check(bs, 0, alloc_cluster_offset,
nb_clusters * s->cluster_size);
assert(ret < 0);
goto fail;
}
/*
* 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 = MIN(INT_MAX, nb_clusters << s->cluster_bits);
int nb_bytes = MIN(requested_bytes, avail_bytes);
QCowL2Meta *old_m = *m;
*m = g_malloc0(sizeof(**m));
**m = (QCowL2Meta) {
.next = old_m,
.alloc_offset = alloc_cluster_offset,
.offset = start_of_cluster(s, guest_offset),
.nb_clusters = nb_clusters,
.cow_start = {
.offset = 0,
.nb_bytes = offset_into_cluster(s, guest_offset),
},
.cow_end = {
.offset = nb_bytes,
.nb_bytes = avail_bytes - nb_bytes,
},
};
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
*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);
return 1;
fail:
if (*m && (*m)->nb_clusters > 0) {
QLIST_REMOVE(*m, next_in_flight);
}
return ret;
}
/*
* alloc_cluster_offset
*
* For a given offset on the virtual disk, find the cluster offset in qcow2
* file. If the offset is not found, allocate a new cluster.
*
* If the cluster was already allocated, m->nb_clusters is set to 0 and
* other fields in m are meaningless.
*
* If the cluster is newly allocated, m->nb_clusters is set to the number of
* contiguous clusters that have been allocated. In this case, the other
* fields of m are valid and contain information about the first allocated
* cluster.
*
* 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_cluster_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 = 0;
*host_offset = 0;
cur_bytes = 0;
*m = NULL;
while (true) {
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
}
assert(remaining >= cur_bytes);
start += cur_bytes;
remaining -= cur_bytes;
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 != 0);
return 0;
}
static int decompress_buffer(uint8_t *out_buf, int out_buf_size,
const uint8_t *buf, int buf_size)
{
z_stream strm1, *strm = &strm1;
int ret, out_len;
memset(strm, 0, sizeof(*strm));
strm->next_in = (uint8_t *)buf;
strm->avail_in = buf_size;
strm->next_out = out_buf;
strm->avail_out = out_buf_size;
ret = inflateInit2(strm, -12);
if (ret != Z_OK)
return -1;
ret = inflate(strm, Z_FINISH);
out_len = strm->next_out - out_buf;
if ((ret != Z_STREAM_END && ret != Z_BUF_ERROR) ||
out_len != out_buf_size) {
inflateEnd(strm);
return -1;
}
inflateEnd(strm);
return 0;
}
int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
{
BDRVQcow2State *s = bs->opaque;
int ret, csize, nb_csectors, sector_offset;
uint64_t coffset;
coffset = cluster_offset & s->cluster_offset_mask;
if (s->cluster_cache_offset != coffset) {
nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1;
sector_offset = coffset & 511;
csize = nb_csectors * 512 - sector_offset;
BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data,
nb_csectors);
if (ret < 0) {
return ret;
}
if (decompress_buffer(s->cluster_cache, s->cluster_size,
s->cluster_data + sector_offset, csize) < 0) {
return -EIO;
}
s->cluster_cache_offset = coffset;
}
return 0;
}
/*
* This discards as many clusters of nb_clusters as possible at once (i.e.
* all clusters in the same L2 table) and returns the number of discarded
* clusters.
*/
static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
uint64_t nb_clusters, enum qcow2_discard_type type,
bool full_discard)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l2_table;
int l2_index;
int ret;
int i;
ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}
/* Limit nb_clusters to one L2 table */
nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
assert(nb_clusters <= INT_MAX);
for (i = 0; i < nb_clusters; i++) {
uint64_t old_l2_entry;
old_l2_entry = be64_to_cpu(l2_table[l2_index + i]);
/*
* 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_get_block_status(bs) here, but we're
* holding s->lock, so that doesn't work today.
*
* If full_discard is true, the sector should not read back as zeroes,
* but rather fall through to the backing file.
*/
switch (qcow2_get_cluster_type(old_l2_entry)) {
case QCOW2_CLUSTER_UNALLOCATED:
if (full_discard || !bs->backing) {
continue;
}
break;
case QCOW2_CLUSTER_ZERO:
if (!full_discard) {
continue;
}
break;
case QCOW2_CLUSTER_NORMAL:
case QCOW2_CLUSTER_COMPRESSED:
break;
default:
abort();
}
/* First remove L2 entries */
qcow2_cache_entry_mark_dirty(bs, s->l2_table_cache, l2_table);
if (!full_discard && s->qcow_version >= 3) {
l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO);
} else {
l2_table[l2_index + i] = cpu_to_be64(0);
}
/* Then decrease the refcount */
qcow2_free_any_clusters(bs, old_l2_entry, 1, type);
}
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
return nb_clusters;
}
int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
int nb_sectors, enum qcow2_discard_type type, bool full_discard)
{
BDRVQcow2State *s = bs->opaque;
uint64_t end_offset;
uint64_t nb_clusters;
int ret;
end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
/* The caller must cluster-align start; round end down except at EOF */
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
if (end_offset != bs->total_sectors * BDRV_SECTOR_SIZE) {
end_offset = start_of_cluster(s, end_offset);
}
nb_clusters = size_to_clusters(s, end_offset - offset);
s->cache_discards = true;
/* Each L2 table is handled by its own loop iteration */
while (nb_clusters > 0) {
ret = discard_single_l2(bs, offset, nb_clusters, type, full_discard);
if (ret < 0) {
goto fail;
}
nb_clusters -= ret;
offset += (ret * 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 table) and returns the number of zeroed
* clusters.
*/
static int zero_single_l2(BlockDriverState *bs, uint64_t offset,
uint64_t nb_clusters, int flags)
{
BDRVQcow2State *s = bs->opaque;
uint64_t *l2_table;
int l2_index;
int ret;
int i;
ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}
/* Limit nb_clusters to one L2 table */
nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
assert(nb_clusters <= INT_MAX);
for (i = 0; i < nb_clusters; i++) {
uint64_t old_offset;
old_offset = be64_to_cpu(l2_table[l2_index + i]);
/* Update L2 entries */
qcow2_cache_entry_mark_dirty(bs, s->l2_table_cache, l2_table);
if (old_offset & QCOW_OFLAG_COMPRESSED || flags & BDRV_REQ_MAY_UNMAP) {
l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO);
qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST);
} else {
l2_table[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO);
}
}
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
return nb_clusters;
}
int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors,
int flags)
{
BDRVQcow2State *s = bs->opaque;
uint64_t nb_clusters;
int ret;
/* The zero flag is only supported by version 3 and newer */
if (s->qcow_version < 3) {
return -ENOTSUP;
}
/* Each L2 table is handled by its own loop iteration */
nb_clusters = size_to_clusters(s, nb_sectors << BDRV_SECTOR_BITS);
s->cache_discards = true;
while (nb_clusters > 0) {
ret = zero_single_l2(bs, offset, nb_clusters, flags);
if (ret < 0) {
goto fail;
}
nb_clusters -= ret;
offset += (ret * s->cluster_size);
}
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_table = NULL;
int ret;
int i, j;
if (!is_active_l1) {
/* inactive L2 tables require a buffer to be stored in when loading
* them from disk */
l2_table = qemu_try_blockalign(bs->file->bs, s->cluster_size);
if (l2_table == NULL) {
return -ENOMEM;
}
}
for (i = 0; i < l1_size; i++) {
uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
bool l2_dirty = false;
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;
}
if (is_active_l1) {
/* get active L2 tables from cache */
ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
(void **)&l2_table);
} else {
/* load inactive L2 tables from disk */
ret = bdrv_read(bs->file, l2_offset / BDRV_SECTOR_SIZE,
(void *)l2_table, s->cluster_sectors);
}
if (ret < 0) {
goto fail;
}
ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
&l2_refcount);
if (ret < 0) {
goto fail;
}
for (j = 0; j < s->l2_size; j++) {
uint64_t l2_entry = be64_to_cpu(l2_table[j]);
int64_t offset = l2_entry & L2E_OFFSET_MASK;
int cluster_type = qcow2_get_cluster_type(l2_entry);
bool preallocated = offset != 0;
if (cluster_type != QCOW2_CLUSTER_ZERO) {
continue;
}
if (!preallocated) {
if (!bs->backing) {
/* not backed; therefore we can simply deallocate the
* cluster */
l2_table[j] = 0;
l2_dirty = true;
continue;
}
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
ret = offset;
goto fail;
}
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)) {
qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset "
"%#" PRIx64 " unaligned (L2 offset: %#"
PRIx64 ", L2 index: %#x)", offset,
l2_offset, j);
if (!preallocated) {
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);
if (ret < 0) {
if (!preallocated) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
goto fail;
}
ret = bdrv_pwrite_zeroes(bs->file, offset, s->cluster_size, 0);
if (ret < 0) {
if (!preallocated) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_ALWAYS);
}
goto fail;
}
if (l2_refcount == 1) {
l2_table[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED);
} else {
l2_table[j] = cpu_to_be64(offset);
}
l2_dirty = true;
}
if (is_active_l1) {
if (l2_dirty) {
qcow2_cache_entry_mark_dirty(bs, s->l2_table_cache, l2_table);
qcow2_cache_depends_on_flush(s->l2_table_cache);
}
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
} else {
if (l2_dirty) {
ret = qcow2_pre_write_overlap_check(bs,
QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, l2_offset,
s->cluster_size);
if (ret < 0) {
goto fail;
}
ret = bdrv_write(bs->file, l2_offset / BDRV_SECTOR_SIZE,
(void *)l2_table, s->cluster_sectors);
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_table) {
if (!is_active_l1) {
qemu_vfree(l2_table);
} else {
qcow2_cache_put(bs, s->l2_table_cache, (void **) &l2_table);
}
}
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_sectors = DIV_ROUND_UP(s->snapshots[i].l1_size *
sizeof(uint64_t), BDRV_SECTOR_SIZE);
l1_table = g_realloc(l1_table, l1_sectors * BDRV_SECTOR_SIZE);
ret = bdrv_read(bs->file,
s->snapshots[i].l1_table_offset / BDRV_SECTOR_SIZE,
(void *)l1_table, l1_sectors);
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;
}
Reference in New Issue View Git Blame Copy Permalink