qcow2: Add function for refcount order amendment

Add a function qcow2_change_refcount_order() which allows changing the
refcount order of a qcow2 image.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2015-07-27 17:51:37 +02:00 committed by Kevin Wolf
parent c293a80927
commit 791c9a004e
2 changed files with 451 additions and 0 deletions

View File

@ -2467,3 +2467,450 @@ int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset,
return 0; return 0;
} }
/* A pointer to a function of this type is given to walk_over_reftable(). That
* function will create refblocks and pass them to a RefblockFinishOp once they
* are completed (@refblock). @refblock_empty is set if the refblock is
* completely empty.
*
* Along with the refblock, a corresponding reftable entry is passed, in the
* reftable @reftable (which may be reallocated) at @reftable_index.
*
* @allocated should be set to true if a new cluster has been allocated.
*/
typedef int (RefblockFinishOp)(BlockDriverState *bs, uint64_t **reftable,
uint64_t reftable_index, uint64_t *reftable_size,
void *refblock, bool refblock_empty,
bool *allocated, Error **errp);
/**
* This "operation" for walk_over_reftable() allocates the refblock on disk (if
* it is not empty) and inserts its offset into the new reftable. The size of
* this new reftable is increased as required.
*/
static int alloc_refblock(BlockDriverState *bs, uint64_t **reftable,
uint64_t reftable_index, uint64_t *reftable_size,
void *refblock, bool refblock_empty, bool *allocated,
Error **errp)
{
BDRVQcow2State *s = bs->opaque;
int64_t offset;
if (!refblock_empty && reftable_index >= *reftable_size) {
uint64_t *new_reftable;
uint64_t new_reftable_size;
new_reftable_size = ROUND_UP(reftable_index + 1,
s->cluster_size / sizeof(uint64_t));
if (new_reftable_size > QCOW_MAX_REFTABLE_SIZE / sizeof(uint64_t)) {
error_setg(errp,
"This operation would make the refcount table grow "
"beyond the maximum size supported by QEMU, aborting");
return -ENOTSUP;
}
new_reftable = g_try_realloc(*reftable, new_reftable_size *
sizeof(uint64_t));
if (!new_reftable) {
error_setg(errp, "Failed to increase reftable buffer size");
return -ENOMEM;
}
memset(new_reftable + *reftable_size, 0,
(new_reftable_size - *reftable_size) * sizeof(uint64_t));
*reftable = new_reftable;
*reftable_size = new_reftable_size;
}
if (!refblock_empty && !(*reftable)[reftable_index]) {
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
error_setg_errno(errp, -offset, "Failed to allocate refblock");
return offset;
}
(*reftable)[reftable_index] = offset;
*allocated = true;
}
return 0;
}
/**
* This "operation" for walk_over_reftable() writes the refblock to disk at the
* offset specified by the new reftable's entry. It does not modify the new
* reftable or change any refcounts.
*/
static int flush_refblock(BlockDriverState *bs, uint64_t **reftable,
uint64_t reftable_index, uint64_t *reftable_size,
void *refblock, bool refblock_empty, bool *allocated,
Error **errp)
{
BDRVQcow2State *s = bs->opaque;
int64_t offset;
int ret;
if (reftable_index < *reftable_size && (*reftable)[reftable_index]) {
offset = (*reftable)[reftable_index];
ret = qcow2_pre_write_overlap_check(bs, 0, offset, s->cluster_size);
if (ret < 0) {
error_setg_errno(errp, -ret, "Overlap check failed");
return ret;
}
ret = bdrv_pwrite(bs->file->bs, offset, refblock, s->cluster_size);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to write refblock");
return ret;
}
} else {
assert(refblock_empty);
}
return 0;
}
/**
* This function walks over the existing reftable and every referenced refblock;
* if @new_set_refcount is non-NULL, it is called for every refcount entry to
* create an equal new entry in the passed @new_refblock. Once that
* @new_refblock is completely filled, @operation will be called.
*
* @status_cb and @cb_opaque are used for the amend operation's status callback.
* @index is the index of the walk_over_reftable() calls and @total is the total
* number of walk_over_reftable() calls per amend operation. Both are used for
* calculating the parameters for the status callback.
*
* @allocated is set to true if a new cluster has been allocated.
*/
static int walk_over_reftable(BlockDriverState *bs, uint64_t **new_reftable,
uint64_t *new_reftable_index,
uint64_t *new_reftable_size,
void *new_refblock, int new_refblock_size,
int new_refcount_bits,
RefblockFinishOp *operation, bool *allocated,
Qcow2SetRefcountFunc *new_set_refcount,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque, int index, int total,
Error **errp)
{
BDRVQcow2State *s = bs->opaque;
uint64_t reftable_index;
bool new_refblock_empty = true;
int refblock_index;
int new_refblock_index = 0;
int ret;
for (reftable_index = 0; reftable_index < s->refcount_table_size;
reftable_index++)
{
uint64_t refblock_offset = s->refcount_table[reftable_index]
& REFT_OFFSET_MASK;
status_cb(bs, (uint64_t)index * s->refcount_table_size + reftable_index,
(uint64_t)total * s->refcount_table_size, cb_opaque);
if (refblock_offset) {
void *refblock;
if (offset_into_cluster(s, refblock_offset)) {
qcow2_signal_corruption(bs, true, -1, -1, "Refblock offset %#"
PRIx64 " unaligned (reftable index: %#"
PRIx64 ")", refblock_offset,
reftable_index);
error_setg(errp,
"Image is corrupt (unaligned refblock offset)");
return -EIO;
}
ret = qcow2_cache_get(bs, s->refcount_block_cache, refblock_offset,
&refblock);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to retrieve refblock");
return ret;
}
for (refblock_index = 0; refblock_index < s->refcount_block_size;
refblock_index++)
{
uint64_t refcount;
if (new_refblock_index >= new_refblock_size) {
/* new_refblock is now complete */
ret = operation(bs, new_reftable, *new_reftable_index,
new_reftable_size, new_refblock,
new_refblock_empty, allocated, errp);
if (ret < 0) {
qcow2_cache_put(bs, s->refcount_block_cache, &refblock);
return ret;
}
(*new_reftable_index)++;
new_refblock_index = 0;
new_refblock_empty = true;
}
refcount = s->get_refcount(refblock, refblock_index);
if (new_refcount_bits < 64 && refcount >> new_refcount_bits) {
uint64_t offset;
qcow2_cache_put(bs, s->refcount_block_cache, &refblock);
offset = ((reftable_index << s->refcount_block_bits)
+ refblock_index) << s->cluster_bits;
error_setg(errp, "Cannot decrease refcount entry width to "
"%i bits: Cluster at offset %#" PRIx64 " has a "
"refcount of %" PRIu64, new_refcount_bits,
offset, refcount);
return -EINVAL;
}
if (new_set_refcount) {
new_set_refcount(new_refblock, new_refblock_index++,
refcount);
} else {
new_refblock_index++;
}
new_refblock_empty = new_refblock_empty && refcount == 0;
}
qcow2_cache_put(bs, s->refcount_block_cache, &refblock);
} else {
/* No refblock means every refcount is 0 */
for (refblock_index = 0; refblock_index < s->refcount_block_size;
refblock_index++)
{
if (new_refblock_index >= new_refblock_size) {
/* new_refblock is now complete */
ret = operation(bs, new_reftable, *new_reftable_index,
new_reftable_size, new_refblock,
new_refblock_empty, allocated, errp);
if (ret < 0) {
return ret;
}
(*new_reftable_index)++;
new_refblock_index = 0;
new_refblock_empty = true;
}
if (new_set_refcount) {
new_set_refcount(new_refblock, new_refblock_index++, 0);
} else {
new_refblock_index++;
}
}
}
}
if (new_refblock_index > 0) {
/* Complete the potentially existing partially filled final refblock */
if (new_set_refcount) {
for (; new_refblock_index < new_refblock_size;
new_refblock_index++)
{
new_set_refcount(new_refblock, new_refblock_index, 0);
}
}
ret = operation(bs, new_reftable, *new_reftable_index,
new_reftable_size, new_refblock, new_refblock_empty,
allocated, errp);
if (ret < 0) {
return ret;
}
(*new_reftable_index)++;
}
status_cb(bs, (uint64_t)(index + 1) * s->refcount_table_size,
(uint64_t)total * s->refcount_table_size, cb_opaque);
return 0;
}
int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque, Error **errp)
{
BDRVQcow2State *s = bs->opaque;
Qcow2GetRefcountFunc *new_get_refcount;
Qcow2SetRefcountFunc *new_set_refcount;
void *new_refblock = qemu_blockalign(bs->file->bs, s->cluster_size);
uint64_t *new_reftable = NULL, new_reftable_size = 0;
uint64_t *old_reftable, old_reftable_size, old_reftable_offset;
uint64_t new_reftable_index = 0;
uint64_t i;
int64_t new_reftable_offset = 0, allocated_reftable_size = 0;
int new_refblock_size, new_refcount_bits = 1 << refcount_order;
int old_refcount_order;
int walk_index = 0;
int ret;
bool new_allocation;
assert(s->qcow_version >= 3);
assert(refcount_order >= 0 && refcount_order <= 6);
/* see qcow2_open() */
new_refblock_size = 1 << (s->cluster_bits - (refcount_order - 3));
new_get_refcount = get_refcount_funcs[refcount_order];
new_set_refcount = set_refcount_funcs[refcount_order];
do {
int total_walks;
new_allocation = false;
/* At least we have to do this walk and the one which writes the
* refblocks; also, at least we have to do this loop here at least
* twice (normally), first to do the allocations, and second to
* determine that everything is correctly allocated, this then makes
* three walks in total */
total_walks = MAX(walk_index + 2, 3);
/* First, allocate the structures so they are present in the refcount
* structures */
ret = walk_over_reftable(bs, &new_reftable, &new_reftable_index,
&new_reftable_size, NULL, new_refblock_size,
new_refcount_bits, &alloc_refblock,
&new_allocation, NULL, status_cb, cb_opaque,
walk_index++, total_walks, errp);
if (ret < 0) {
goto done;
}
new_reftable_index = 0;
if (new_allocation) {
if (new_reftable_offset) {
qcow2_free_clusters(bs, new_reftable_offset,
allocated_reftable_size * sizeof(uint64_t),
QCOW2_DISCARD_NEVER);
}
new_reftable_offset = qcow2_alloc_clusters(bs, new_reftable_size *
sizeof(uint64_t));
if (new_reftable_offset < 0) {
error_setg_errno(errp, -new_reftable_offset,
"Failed to allocate the new reftable");
ret = new_reftable_offset;
goto done;
}
allocated_reftable_size = new_reftable_size;
}
} while (new_allocation);
/* Second, write the new refblocks */
ret = walk_over_reftable(bs, &new_reftable, &new_reftable_index,
&new_reftable_size, new_refblock,
new_refblock_size, new_refcount_bits,
&flush_refblock, &new_allocation, new_set_refcount,
status_cb, cb_opaque, walk_index, walk_index + 1,
errp);
if (ret < 0) {
goto done;
}
assert(!new_allocation);
/* Write the new reftable */
ret = qcow2_pre_write_overlap_check(bs, 0, new_reftable_offset,
new_reftable_size * sizeof(uint64_t));
if (ret < 0) {
error_setg_errno(errp, -ret, "Overlap check failed");
goto done;
}
for (i = 0; i < new_reftable_size; i++) {
cpu_to_be64s(&new_reftable[i]);
}
ret = bdrv_pwrite(bs->file->bs, new_reftable_offset, new_reftable,
new_reftable_size * sizeof(uint64_t));
for (i = 0; i < new_reftable_size; i++) {
be64_to_cpus(&new_reftable[i]);
}
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to write the new reftable");
goto done;
}
/* Empty the refcount cache */
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to flush the refblock cache");
goto done;
}
/* Update the image header to point to the new reftable; this only updates
* the fields which are relevant to qcow2_update_header(); other fields
* such as s->refcount_table or s->refcount_bits stay stale for now
* (because we have to restore everything if qcow2_update_header() fails) */
old_refcount_order = s->refcount_order;
old_reftable_size = s->refcount_table_size;
old_reftable_offset = s->refcount_table_offset;
s->refcount_order = refcount_order;
s->refcount_table_size = new_reftable_size;
s->refcount_table_offset = new_reftable_offset;
ret = qcow2_update_header(bs);
if (ret < 0) {
s->refcount_order = old_refcount_order;
s->refcount_table_size = old_reftable_size;
s->refcount_table_offset = old_reftable_offset;
error_setg_errno(errp, -ret, "Failed to update the qcow2 header");
goto done;
}
/* Now update the rest of the in-memory information */
old_reftable = s->refcount_table;
s->refcount_table = new_reftable;
s->refcount_bits = 1 << refcount_order;
s->refcount_max = UINT64_C(1) << (s->refcount_bits - 1);
s->refcount_max += s->refcount_max - 1;
s->refcount_block_bits = s->cluster_bits - (refcount_order - 3);
s->refcount_block_size = 1 << s->refcount_block_bits;
s->get_refcount = new_get_refcount;
s->set_refcount = new_set_refcount;
/* For cleaning up all old refblocks and the old reftable below the "done"
* label */
new_reftable = old_reftable;
new_reftable_size = old_reftable_size;
new_reftable_offset = old_reftable_offset;
done:
if (new_reftable) {
/* On success, new_reftable actually points to the old reftable (and
* new_reftable_size is the old reftable's size); but that is just
* fine */
for (i = 0; i < new_reftable_size; i++) {
uint64_t offset = new_reftable[i] & REFT_OFFSET_MASK;
if (offset) {
qcow2_free_clusters(bs, offset, s->cluster_size,
QCOW2_DISCARD_OTHER);
}
}
g_free(new_reftable);
if (new_reftable_offset > 0) {
qcow2_free_clusters(bs, new_reftable_offset,
new_reftable_size * sizeof(uint64_t),
QCOW2_DISCARD_OTHER);
}
}
qemu_vfree(new_refblock);
return ret;
}

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@ -529,6 +529,10 @@ int qcow2_check_metadata_overlap(BlockDriverState *bs, int ign, int64_t offset,
int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset, int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset,
int64_t size); int64_t size);
int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque, Error **errp);
/* qcow2-cluster.c functions */ /* qcow2-cluster.c functions */
int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
bool exact_size); bool exact_size);