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qcow2: Add subcluster support to qcow2_get_host_offset()

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The logic of this function remains pretty much the same, except that
it uses count_contiguous_subclusters(), which combines the logic of
count_contiguous_clusters() / count_contiguous_clusters_unallocated()
and checks individual subclusters.

qcow2_cluster_to_subcluster_type() is not necessary as a separate
function anymore so it's inlined into its caller.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <d2193fd48653a350d80f0eca1c67b1d9053fb2f3.1594396418.git.berto@igalia.com>
[mreitz: Initialize expected_type to anything]
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2020-07-10 18:13:03 +02:00 committed by Max Reitz
parent d53ec3d8d8
commit 3f9c6b3b1f
2 changed files with 94 additions and 98 deletions
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154
block/qcow2-cluster.c
View file

@ -426,66 +426,66 @@ static int qcow2_get_subcluster_range_type(BlockDriverState *bs,
}
/*
* Checks how many clusters in a given L2 slice 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)
* Return the number of contiguous subclusters of the exact same type
* in a given L2 slice, starting from cluster @l2_index, subcluster
* @sc_index. Allocated subclusters are required to be contiguous in
* the image file.
* At most @nb_clusters are checked (note that this means clusters,
* not subclusters).
* Compressed clusters are always processed one by one but for the
* purpose of this count they are treated as if they were divided into
* subclusters of size s->subcluster_size.
* On failure return -errno and update @l2_index to point to the
* invalid entry.
*/
static int count_contiguous_clusters(BlockDriverState *bs, int nb_clusters,
int cluster_size, uint64_t *l2_slice, int l2_index, uint64_t stop_flags)
static int count_contiguous_subclusters(BlockDriverState *bs, int nb_clusters,
unsigned sc_index, uint64_t *l2_slice,
unsigned *l2_index)
{
BDRVQcow2State *s = bs->opaque;
int i;
QCow2ClusterType first_cluster_type;
uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED;
uint64_t first_entry = get_l2_entry(s, l2_slice, l2_index);
uint64_t offset = first_entry & mask;
int i, count = 0;
bool check_offset = false;
uint64_t expected_offset = 0;
QCow2SubclusterType expected_type = QCOW2_SUBCLUSTER_NORMAL, type;
first_cluster_type = qcow2_get_cluster_type(bs, first_entry);
if (first_cluster_type == QCOW2_CLUSTER_UNALLOCATED) {
return 0;
}
/* must be allocated */
assert(first_cluster_type == QCOW2_CLUSTER_NORMAL ||
first_cluster_type == QCOW2_CLUSTER_ZERO_ALLOC);
assert(*l2_index + nb_clusters <= s->l2_slice_size);
for (i = 0; i < nb_clusters; i++) {
uint64_t l2_entry = get_l2_entry(s, l2_slice, l2_index + i) & mask;
if (offset + (uint64_t) i * cluster_size != l2_entry) {
unsigned first_sc = (i == 0) ? sc_index : 0;
uint64_t l2_entry = get_l2_entry(s, l2_slice, *l2_index + i);
uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, *l2_index + i);
int ret = qcow2_get_subcluster_range_type(bs, l2_entry, l2_bitmap,
first_sc, &type);
if (ret < 0) {
*l2_index += i; /* Point to the invalid entry */
return -EIO;
}
if (i == 0) {
if (type == QCOW2_SUBCLUSTER_COMPRESSED) {
/* Compressed clusters are always processed one by one */
return ret;
}
expected_type = type;
expected_offset = l2_entry & L2E_OFFSET_MASK;
check_offset = (type == QCOW2_SUBCLUSTER_NORMAL ||
type == QCOW2_SUBCLUSTER_ZERO_ALLOC ||
type == QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC);
} else if (type != expected_type) {
break;
} else if (check_offset) {
expected_offset += s->cluster_size;
if (expected_offset != (l2_entry & L2E_OFFSET_MASK)) {
break;
}
}
count += ret;
/* Stop if there are type changes before the end of the cluster */
if (first_sc + ret < s->subclusters_per_cluster) {
break;
}
}
return i;
}
/*
* Checks how many consecutive unallocated clusters in a given L2
* slice have the same cluster type.
*/
static int count_contiguous_clusters_unallocated(BlockDriverState *bs,
int nb_clusters,
uint64_t *l2_slice,
int l2_index,
QCow2ClusterType wanted_type)
{
BDRVQcow2State *s = bs->opaque;
int i;
assert(wanted_type == QCOW2_CLUSTER_ZERO_PLAIN ||
wanted_type == QCOW2_CLUSTER_UNALLOCATED);
for (i = 0; i < nb_clusters; i++) {
uint64_t entry = get_l2_entry(s, l2_slice, l2_index + i);
QCow2ClusterType type = qcow2_get_cluster_type(bs, entry);
if (type != wanted_type) {
break;
}
}
return i;
return count;
}
static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
@ -574,12 +574,12 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
QCow2SubclusterType *subcluster_type)
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index;
uint64_t l1_index, l2_offset, *l2_slice, l2_entry;
int c;
unsigned int l2_index, sc_index;
uint64_t l1_index, l2_offset, *l2_slice, l2_entry, l2_bitmap;
int sc;
unsigned int offset_in_cluster;
uint64_t bytes_available, bytes_needed, nb_clusters;
QCow2ClusterType type;
QCow2SubclusterType type;
int ret;
offset_in_cluster = offset_into_cluster(s, offset);
@ -602,13 +602,13 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
l1_index = offset_to_l1_index(s, offset);
if (l1_index >= s->l1_size) {
type = QCOW2_CLUSTER_UNALLOCATED;
type = QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
if (!l2_offset) {
type = QCOW2_CLUSTER_UNALLOCATED;
type = QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
@ -629,7 +629,9 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
/* find the cluster offset for the given disk offset */
l2_index = offset_to_l2_slice_index(s, offset);
sc_index = offset_to_sc_index(s, offset);
l2_entry = get_l2_entry(s, l2_slice, l2_index);
l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
nb_clusters = size_to_clusters(s, bytes_needed);
/* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned
@ -637,9 +639,9 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
* true */
assert(nb_clusters <= INT_MAX);
type = qcow2_get_cluster_type(bs, l2_entry);
if (s->qcow_version < 3 && (type == QCOW2_CLUSTER_ZERO_PLAIN ||
type == QCOW2_CLUSTER_ZERO_ALLOC)) {
type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
if (s->qcow_version < 3 && (type == QCOW2_SUBCLUSTER_ZERO_PLAIN ||
type == QCOW2_SUBCLUSTER_ZERO_ALLOC)) {
qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found"
" in pre-v3 image (L2 offset: %#" PRIx64
", L2 index: %#x)", l2_offset, l2_index);
@ -647,7 +649,9 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
goto fail;
}
switch (type) {
case QCOW2_CLUSTER_COMPRESSED:
case QCOW2_SUBCLUSTER_INVALID:
break; /* This is handled by count_contiguous_subclusters() below */
case QCOW2_SUBCLUSTER_COMPRESSED:
if (has_data_file(bs)) {
qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluster "
"entry found in image with external data "
@ -656,23 +660,16 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
ret = -EIO;
goto fail;
}
/* Compressed clusters can only be processed one by one */
c = 1;
*host_offset = l2_entry & L2E_COMPRESSED_OFFSET_SIZE_MASK;
break;
case QCOW2_CLUSTER_ZERO_PLAIN:
case QCOW2_CLUSTER_UNALLOCATED:
/* how many empty clusters ? */
c = count_contiguous_clusters_unallocated(bs, nb_clusters,
l2_slice, l2_index, type);
case QCOW2_SUBCLUSTER_ZERO_PLAIN:
case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
break;
case QCOW2_CLUSTER_ZERO_ALLOC:
case QCOW2_CLUSTER_NORMAL: {
case QCOW2_SUBCLUSTER_ZERO_ALLOC:
case QCOW2_SUBCLUSTER_NORMAL:
case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC: {
uint64_t host_cluster_offset = l2_entry & L2E_OFFSET_MASK;
*host_offset = host_cluster_offset + offset_in_cluster;
/* how many allocated clusters ? */
c = count_contiguous_clusters(bs, nb_clusters, s->cluster_size,
l2_slice, l2_index, QCOW_OFLAG_ZERO);
if (offset_into_cluster(s, host_cluster_offset)) {
qcow2_signal_corruption(bs, true, -1, -1,
"Cluster allocation offset %#"
@ -698,9 +695,18 @@ int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
abort();
}
sc = count_contiguous_subclusters(bs, nb_clusters, sc_index,
l2_slice, &l2_index);
if (sc < 0) {
qcow2_signal_corruption(bs, true, -1, -1, "Invalid cluster entry found "
" (L2 offset: %#" PRIx64 ", L2 index: %#x)",
l2_offset, l2_index);
ret = -EIO;
goto fail;
}
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
bytes_available = (int64_t)c * s->cluster_size;
bytes_available = ((int64_t)sc + sc_index) << s->subcluster_bits;
out:
if (bytes_available > bytes_needed) {
@ -713,7 +719,7 @@ out:
assert(bytes_available - offset_in_cluster <= UINT_MAX);
*bytes = bytes_available - offset_in_cluster;
*subcluster_type = qcow2_cluster_to_subcluster_type(type);
*subcluster_type = type;
return 0;

38
block/qcow2.h
View file

@ -710,29 +710,6 @@ static inline QCow2ClusterType qcow2_get_cluster_type(BlockDriverState *bs,
}
}
/*
* For an image without extended L2 entries, return the
* QCow2SubclusterType equivalent of a given QCow2ClusterType.
*/
static inline
QCow2SubclusterType qcow2_cluster_to_subcluster_type(QCow2ClusterType type)
{
switch (type) {
case QCOW2_CLUSTER_COMPRESSED:
return QCOW2_SUBCLUSTER_COMPRESSED;
case QCOW2_CLUSTER_ZERO_PLAIN:
return QCOW2_SUBCLUSTER_ZERO_PLAIN;
case QCOW2_CLUSTER_ZERO_ALLOC:
return QCOW2_SUBCLUSTER_ZERO_ALLOC;
case QCOW2_CLUSTER_NORMAL:
return QCOW2_SUBCLUSTER_NORMAL;
case QCOW2_CLUSTER_UNALLOCATED:
return QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
default:
g_assert_not_reached();
}
}
/*
* In an image without subsclusters @l2_bitmap is ignored and
* @sc_index must be 0.
@ -776,7 +753,20 @@ QCow2SubclusterType qcow2_get_subcluster_type(BlockDriverState *bs,
g_assert_not_reached();
}
} else {
return qcow2_cluster_to_subcluster_type(type);
switch (type) {
case QCOW2_CLUSTER_COMPRESSED:
return QCOW2_SUBCLUSTER_COMPRESSED;
case QCOW2_CLUSTER_ZERO_PLAIN:
return QCOW2_SUBCLUSTER_ZERO_PLAIN;
case QCOW2_CLUSTER_ZERO_ALLOC:
return QCOW2_SUBCLUSTER_ZERO_ALLOC;
case QCOW2_CLUSTER_NORMAL:
return QCOW2_SUBCLUSTER_NORMAL;
case QCOW2_CLUSTER_UNALLOCATED:
return QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
default:
g_assert_not_reached();
}
}
}