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qemu/block/qcow2-cluster.c
Kevin Wolf ecdd5333ab qcow2: Gather clusters in a looping loop 
Instead of just checking once in exactly this order if there are
dependendies, non-COW clusters and new allocation, this starts looping
around these. This way we can, for example, gather non-COW clusters after
new allocations as long as the host cluster offsets stay contiguous.

Once handle_dependencies() is extended so that COW areas of in-flight
allocations can be overwritten, this allows to continue with gathering
other clusters (we wouldn't be able to do that without this change
because we would have missed a possible second dependency in one of the
next clusters).

This means that in the typical sequential write case, we can combine the
COW overwrite of one cluster with the allocation of the next cluster as
soon as something like Delayed COW gets actually implemented. It is only
by avoiding splitting requests this way that Delayed COW actually starts
improving performance noticably.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:44 +01:00

1450 lines
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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 <zlib.h>
#include "qemu-common.h"
#include "block/block_int.h"
#include "block/qcow2.h"
#include "trace.h"
int qcow2_grow_l1_table(BlockDriverState *bs, int min_size, bool exact_size)
{
BDRVQcowState *s = bs->opaque;
int new_l1_size, new_l1_size2, ret, i;
uint64_t *new_l1_table;
int64_t new_l1_table_offset;
uint8_t data[12];
if (min_size <= s->l1_size)
return 0;
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;
}
}
#ifdef DEBUG_ALLOC2
fprintf(stderr, "grow l1_table from %d to %d\n", s->l1_size, new_l1_size);
#endif
new_l1_size2 = sizeof(uint64_t) * new_l1_size;
new_l1_table = g_malloc0(align_offset(new_l1_size2, 512));
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) {
g_free(new_l1_table);
return new_l1_table_offset;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
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);
cpu_to_be32w((uint32_t*)data, new_l1_size);
cpu_to_be64wu((uint64_t*)(data + 4), new_l1_table_offset);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), data,sizeof(data));
if (ret < 0) {
goto fail;
}
g_free(s->l1_table);
qcow2_free_clusters(bs, s->l1_table_offset, s->l1_size * sizeof(uint64_t));
s->l1_table_offset = new_l1_table_offset;
s->l1_table = new_l1_table;
s->l1_size = new_l1_size;
return 0;
fail:
g_free(new_l1_table);
qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2);
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)
{
BDRVQcowState *s = bs->opaque;
int ret;
ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, (void**) l2_table);
return ret;
}
/*
* 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)
static int write_l1_entry(BlockDriverState *bs, int l1_index)
{
BDRVQcowState *s = bs->opaque;
uint64_t buf[L1_ENTRIES_PER_SECTOR];
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; i++) {
buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
}
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)
{
BDRVQcowState *s = bs->opaque;
uint64_t old_l2_offset;
uint64_t *l2_table;
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) {
return l2_offset;
}
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) {
return ret;
}
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);
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &old_table);
if (ret < 0) {
goto fail;
}
}
/* 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(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 = 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);
qcow2_cache_put(bs, s->l2_table_cache, (void**) table);
s->l1_table[l1_index] = old_l2_offset;
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(uint64_t nb_clusters, int cluster_size,
uint64_t *l2_table, uint64_t start, uint64_t stop_flags)
{
int i;
uint64_t mask = stop_flags | L2E_OFFSET_MASK;
uint64_t offset = be64_to_cpu(l2_table[0]) & mask;
if (!offset)
return 0;
for (i = start; i < start + 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 - start);
}
static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_table)
{
int i;
for (i = 0; i < nb_clusters; i++) {
int type = qcow2_get_cluster_type(be64_to_cpu(l2_table[i]));
if (type != QCOW2_CLUSTER_UNALLOCATED) {
break;
}
}
return i;
}
/* The crypt function is compatible with the linux cryptoloop
algorithm for < 4 GB images. NOTE: out_buf == in_buf is
supported */
void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
uint8_t *out_buf, const uint8_t *in_buf,
int nb_sectors, int enc,
const AES_KEY *key)
{
union {
uint64_t ll[2];
uint8_t b[16];
} ivec;
int i;
for(i = 0; i < nb_sectors; i++) {
ivec.ll[0] = cpu_to_le64(sector_num);
ivec.ll[1] = 0;
AES_cbc_encrypt(in_buf, out_buf, 512, key,
ivec.b, enc);
sector_num++;
in_buf += 512;
out_buf += 512;
}
}
static int coroutine_fn copy_sectors(BlockDriverState *bs,
uint64_t start_sect,
uint64_t cluster_offset,
int n_start, int n_end)
{
BDRVQcowState *s = bs->opaque;
QEMUIOVector qiov;
struct iovec iov;
int n, ret;
/*
* If this is the last cluster and it is only partially used, we must only
* copy until the end of the image, or bdrv_check_request will fail for the
* bdrv_read/write calls below.
*/
if (start_sect + n_end > bs->total_sectors) {
n_end = bs->total_sectors - start_sect;
}
n = n_end - n_start;
if (n <= 0) {
return 0;
}
iov.iov_len = n * BDRV_SECTOR_SIZE;
iov.iov_base = qemu_blockalign(bs, iov.iov_len);
qemu_iovec_init_external(&qiov, &iov, 1);
BLKDBG_EVENT(bs->file, BLKDBG_COW_READ);
/* 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_readv(bs, start_sect + n_start, n, &qiov);
if (ret < 0) {
goto out;
}
if (s->crypt_method) {
qcow2_encrypt_sectors(s, start_sect + n_start,
iov.iov_base, iov.iov_base, n, 1,
&s->aes_encrypt_key);
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
ret = bdrv_co_writev(bs->file, (cluster_offset >> 9) + n_start, n, &qiov);
if (ret < 0) {
goto out;
}
ret = 0;
out:
qemu_vfree(iov.iov_base);
return ret;
}
/*
* get_cluster_offset
*
* For a given offset of the disk image, find the cluster offset in
* qcow2 file. The offset is stored in *cluster_offset.
*
* on entry, *num is the number of contiguous sectors we'd like to
* access following offset.
*
* on exit, *num is the number of contiguous sectors we can read.
*
* Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error
* cases.
*/
int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
int *num, uint64_t *cluster_offset)
{
BDRVQcowState *s = bs->opaque;
unsigned int l1_index, l2_index;
uint64_t l2_offset, *l2_table;
int l1_bits, c;
unsigned int index_in_cluster, nb_clusters;
uint64_t nb_available, nb_needed;
int ret;
index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1);
nb_needed = *num + index_in_cluster;
l1_bits = s->l2_bits + s->cluster_bits;
/* compute how many bytes there are between the offset and
* the end of the l1 entry
*/
nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1));
/* compute the number of available sectors */
nb_available = (nb_available >> 9) + index_in_cluster;
if (nb_needed > nb_available) {
nb_needed = nb_available;
}
*cluster_offset = 0;
/* seek the 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;
}
/* 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, nb_needed << 9);
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) {
return -EIO;
}
c = count_contiguous_clusters(nb_clusters, s->cluster_size,
&l2_table[l2_index], 0,
QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
*cluster_offset = 0;
break;
case QCOW2_CLUSTER_UNALLOCATED:
/* how many empty clusters ? */
c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]);
*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], 0,
QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
*cluster_offset &= L2E_OFFSET_MASK;
break;
default:
abort();
}
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
nb_available = (c * s->cluster_sectors);
out:
if (nb_available > nb_needed)
nb_available = nb_needed;
*num = nb_available - index_in_cluster;
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)
{
BDRVQcowState *s = bs->opaque;
unsigned int l1_index, l2_index;
uint64_t l2_offset;
uint64_t *l2_table = NULL;
int ret;
/* seek the 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;
}
}
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
/* 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));
}
}
/* 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)
{
BDRVQcowState *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(s->l2_table_cache, l2_table);
l2_table[l2_index] = cpu_to_be64(cluster_offset);
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return 0;
}
return cluster_offset;
}
static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r)
{
BDRVQcowState *s = bs->opaque;
int ret;
if (r->nb_sectors == 0) {
return 0;
}
qemu_co_mutex_unlock(&s->lock);
ret = copy_sectors(bs, m->offset / BDRV_SECTOR_SIZE, m->alloc_offset,
r->offset / BDRV_SECTOR_SIZE,
r->offset / BDRV_SECTOR_SIZE + r->nb_sectors);
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)
{
BDRVQcowState *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_malloc(m->nb_clusters * sizeof(uint64_t));
/* 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(s->l2_table_cache, l2_table);
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
* copy_sectors()), 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);
}
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
goto err;
}
/*
* If this was a COW, we need to decrease the refcount of the old cluster.
* Also flush bs->file to get the right order for L2 and refcount update.
*/
if (j != 0) {
for (i = 0; i < j; i++) {
qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1);
}
}
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(BDRVQcowState *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)
{
BDRVQcowState *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_mutex_unlock(&s->lock);
qemu_co_queue_wait(&old_alloc->dependent_requests);
qemu_co_mutex_lock(&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)
{
BDRVQcowState *s = bs->opaque;
int l2_index;
uint64_t cluster_offset;
uint64_t *l2_table;
unsigned int nb_clusters;
unsigned int keep_clusters;
int ret, pret;
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);
/* 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 (*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], 0,
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:
pret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (pret < 0) {
return pret;
}
/* 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) {
*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, unsigned int *nb_clusters)
{
BDRVQcowState *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 {
int 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)
{
BDRVQcowState *s = bs->opaque;
int l2_index;
uint64_t *l2_table;
uint64_t entry;
unsigned int 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);
/* 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);
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return ret;
}
/* 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;
}
/*
* Save info needed for meta data update.
*
* requested_sectors: Number of sectors from the start of the first
* newly allocated cluster to the end of the (possibly shortened
* before) write request.
*
* avail_sectors: Number of sectors from the start of the first
* newly allocated to the end of the last newly allocated cluster.
*
* nb_sectors: The number of sectors 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)
*/
int requested_sectors =
(*bytes + offset_into_cluster(s, guest_offset))
>> BDRV_SECTOR_BITS;
int avail_sectors = nb_clusters
<< (s->cluster_bits - BDRV_SECTOR_BITS);
int alloc_n_start = offset_into_cluster(s, guest_offset)
>> BDRV_SECTOR_BITS;
int nb_sectors = MIN(requested_sectors, avail_sectors);
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,
.nb_available = nb_sectors,
.cow_start = {
.offset = 0,
.nb_sectors = alloc_n_start,
},
.cow_end = {
.offset = nb_sectors * BDRV_SECTOR_SIZE,
.nb_sectors = avail_sectors - nb_sectors,
},
};
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_sectors * BDRV_SECTOR_SIZE)
- 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,
int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta **m)
{
BDRVQcowState *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,
n_start, n_end);
assert(n_start * BDRV_SECTOR_SIZE == offset_into_cluster(s, offset));
offset = start_of_cluster(s, offset);
again:
start = offset + (n_start << BDRV_SECTOR_BITS);
remaining = (n_end - n_start) << BDRV_SECTOR_BITS;
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;
}
}
*num = (n_end - n_start) - (remaining >> BDRV_SECTOR_BITS);
assert(*num > 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)
{
BDRVQcowState *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,
unsigned int nb_clusters)
{
BDRVQcowState *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);
for (i = 0; i < nb_clusters; i++) {
uint64_t old_offset;
old_offset = be64_to_cpu(l2_table[l2_index + i]);
if ((old_offset & L2E_OFFSET_MASK) == 0) {
continue;
}
/* First remove L2 entries */
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
l2_table[l2_index + i] = cpu_to_be64(0);
/* Then decrease the refcount */
qcow2_free_any_clusters(bs, old_offset, 1);
}
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return ret;
}
return nb_clusters;
}
int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
uint64_t end_offset;
unsigned int nb_clusters;
int ret;
end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
/* Round start up and end down */
offset = align_offset(offset, s->cluster_size);
end_offset &= ~(s->cluster_size - 1);
if (offset > end_offset) {
return 0;
}
nb_clusters = size_to_clusters(s, end_offset - offset);
/* Each L2 table is handled by its own loop iteration */
while (nb_clusters > 0) {
ret = discard_single_l2(bs, offset, nb_clusters);
if (ret < 0) {
return ret;
}
nb_clusters -= ret;
offset += (ret * s->cluster_size);
}
return 0;
}
/*
* 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,
unsigned int nb_clusters)
{
BDRVQcowState *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);
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(s->l2_table_cache, l2_table);
if (old_offset & QCOW_OFLAG_COMPRESSED) {
l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO);
qcow2_free_any_clusters(bs, old_offset, 1);
} else {
l2_table[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO);
}
}
ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return ret;
}
return nb_clusters;
}
int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
unsigned int 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);
while (nb_clusters > 0) {
ret = zero_single_l2(bs, offset, nb_clusters);
if (ret < 0) {
return ret;
}
nb_clusters -= ret;
offset += (ret * s->cluster_size);
}
return 0;
}
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