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[PATCH v4 17/30] qcow2: Add subcluster support to calculate_l2_meta()
From: |
Alberto Garcia |
Subject: |
[PATCH v4 17/30] qcow2: Add subcluster support to calculate_l2_meta() |
Date: |
Tue, 17 Mar 2020 19:16:14 +0100 |
If an image has subclusters then there are more copy-on-write
scenarios that we need to consider. Let's say we have a write request
from the middle of subcluster #3 until the end of the cluster:
- If the cluster is new, then subclusters #0 to #3 from the old
cluster must be copied into the new one.
- If the cluster is new but the old cluster was unallocated, then
only subcluster #3 needs copy-on-write. #0 to #2 are marked as
unallocated in the bitmap of the new L2 entry.
- If we are overwriting an old cluster and subcluster #3 is
unallocated or has the all-zeroes bit set then we need
copy-on-write on subcluster #3.
- If we are overwriting an old cluster and subcluster #3 was
allocated then there is no need to copy-on-write.
Signed-off-by: Alberto Garcia <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
block/qcow2-cluster.c | 140 +++++++++++++++++++++++++++++++++---------
1 file changed, 110 insertions(+), 30 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 8cdf8a23b6..c6f3cc9237 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1061,56 +1061,128 @@ void qcow2_alloc_cluster_abort(BlockDriverState *bs,
QCowL2Meta *m)
* If @keep_old is true it means that the clusters were already
* allocated and will be overwritten. If false then the clusters are
* new and we have to decrease the reference count of the old ones.
+ *
+ * Returns 1 on success, -errno on failure (in order to match the
+ * return value of handle_copied() and handle_alloc()).
*/
-static void calculate_l2_meta(BlockDriverState *bs,
- uint64_t host_cluster_offset,
- uint64_t guest_offset, unsigned bytes,
- uint64_t *l2_slice, QCowL2Meta **m, bool
keep_old)
+static int calculate_l2_meta(BlockDriverState *bs, uint64_t
host_cluster_offset,
+ uint64_t guest_offset, unsigned bytes,
+ uint64_t *l2_slice, QCowL2Meta **m, bool keep_old)
{
BDRVQcow2State *s = bs->opaque;
- int l2_index = offset_to_l2_slice_index(s, guest_offset);
- uint64_t l2_entry;
+ int sc_index, l2_index = offset_to_l2_slice_index(s, guest_offset);
+ uint64_t l2_entry, l2_bitmap;
unsigned cow_start_from, cow_end_to;
unsigned cow_start_to = offset_into_cluster(s, guest_offset);
unsigned cow_end_from = cow_start_to + bytes;
unsigned nb_clusters = size_to_clusters(s, cow_end_from);
QCowL2Meta *old_m = *m;
- QCow2ClusterType type;
+ QCow2SubclusterType type;
assert(nb_clusters <= s->l2_slice_size - l2_index);
- /* Return if there's no COW (all clusters are normal and we keep them) */
+ /* Return if there's no COW (all subclusters are normal and we are
+ * keeping the clusters) */
if (keep_old) {
+ unsigned first_sc = cow_start_to / s->subcluster_size;
+ unsigned last_sc = (cow_end_from - 1) / s->subcluster_size;
int i;
- for (i = 0; i < nb_clusters; i++) {
- l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
- if (qcow2_get_cluster_type(bs, l2_entry) != QCOW2_CLUSTER_NORMAL) {
+ for (i = first_sc; i <= last_sc; i++) {
+ unsigned c = i / s->subclusters_per_cluster;
+ unsigned sc = i % s->subclusters_per_cluster;
+ l2_entry = get_l2_entry(s, l2_slice, l2_index + c);
+ l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + c);
+ type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc);
+ if (type == QCOW2_SUBCLUSTER_INVALID) {
+ l2_index += c; /* Point to the invalid entry */
+ goto fail;
+ }
+ if (type != QCOW2_SUBCLUSTER_NORMAL) {
break;
}
}
- if (i == nb_clusters) {
- return;
+ if (i == last_sc + 1) {
+ return 1;
}
}
/* Get the L2 entry of the first cluster */
l2_entry = get_l2_entry(s, l2_slice, l2_index);
- type = qcow2_get_cluster_type(bs, l2_entry);
+ l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
+ sc_index = offset_to_sc_index(s, guest_offset);
+ type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
- if (type == QCOW2_CLUSTER_NORMAL && keep_old) {
- cow_start_from = cow_start_to;
+ if (type == QCOW2_SUBCLUSTER_INVALID) {
+ goto fail;
+ }
+
+ if (!keep_old) {
+ switch (type) {
+ case QCOW2_SUBCLUSTER_NORMAL:
+ case QCOW2_SUBCLUSTER_COMPRESSED:
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ cow_start_from = 0;
+ break;
+ case QCOW2_SUBCLUSTER_ZERO_PLAIN:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
+ cow_start_from = sc_index << s->subcluster_bits;
+ break;
+ default:
+ g_assert_not_reached();
+ }
} else {
- cow_start_from = 0;
+ switch (type) {
+ case QCOW2_SUBCLUSTER_NORMAL:
+ cow_start_from = cow_start_to;
+ break;
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ cow_start_from = sc_index << s->subcluster_bits;
+ break;
+ default:
+ g_assert_not_reached();
+ }
}
/* Get the L2 entry of the last cluster */
- l2_entry = get_l2_entry(s, l2_slice, l2_index + nb_clusters - 1);
- type = qcow2_get_cluster_type(bs, l2_entry);
+ l2_index += nb_clusters - 1;
+ l2_entry = get_l2_entry(s, l2_slice, l2_index);
+ l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
+ sc_index = offset_to_sc_index(s, guest_offset + bytes - 1);
+ type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index);
- if (type == QCOW2_CLUSTER_NORMAL && keep_old) {
- cow_end_to = cow_end_from;
+ if (type == QCOW2_SUBCLUSTER_INVALID) {
+ goto fail;
+ }
+
+ if (!keep_old) {
+ switch (type) {
+ case QCOW2_SUBCLUSTER_NORMAL:
+ case QCOW2_SUBCLUSTER_COMPRESSED:
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
+ break;
+ case QCOW2_SUBCLUSTER_ZERO_PLAIN:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
+ cow_end_to = ROUND_UP(cow_end_from, s->subcluster_size);
+ break;
+ default:
+ g_assert_not_reached();
+ }
} else {
- cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
+ switch (type) {
+ case QCOW2_SUBCLUSTER_NORMAL:
+ cow_end_to = cow_end_from;
+ break;
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ cow_end_to = ROUND_UP(cow_end_from, s->subcluster_size);
+ break;
+ default:
+ g_assert_not_reached();
+ }
}
*m = g_malloc0(sizeof(**m));
@@ -1135,6 +1207,18 @@ static void calculate_l2_meta(BlockDriverState *bs,
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
+
+fail:
+ if (type == QCOW2_SUBCLUSTER_INVALID) {
+ uint64_t l1_index = offset_to_l1_index(s, guest_offset);
+ uint64_t l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
+ qcow2_signal_corruption(bs, true, -1, -1, "Invalid cluster entry found
"
+ " (L2 offset: %#" PRIx64 ", L2 index: %#x)",
+ l2_offset, l2_index);
+ return -EIO;
+ }
+
+ return 1;
}
/*
@@ -1352,10 +1436,8 @@ static int handle_copied(BlockDriverState *bs, uint64_t
guest_offset,
- offset_into_cluster(s, guest_offset));
assert(*bytes != 0);
- calculate_l2_meta(bs, cluster_offset & L2E_OFFSET_MASK, guest_offset,
- *bytes, l2_slice, m, true);
-
- ret = 1;
+ ret = calculate_l2_meta(bs, cluster_offset & L2E_OFFSET_MASK,
+ guest_offset, *bytes, l2_slice, m, true);
} else {
ret = 0;
}
@@ -1530,10 +1612,8 @@ static int handle_alloc(BlockDriverState *bs, uint64_t
guest_offset,
*bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset));
assert(*bytes != 0);
- calculate_l2_meta(bs, alloc_cluster_offset, guest_offset, *bytes, l2_slice,
- m, false);
-
- ret = 1;
+ ret = calculate_l2_meta(bs, alloc_cluster_offset, guest_offset, *bytes,
+ l2_slice, m, false);
out:
qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
--
2.20.1
- [PATCH v4 23/30] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), (continued)
- [PATCH v4 23/30] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/03/17
- [PATCH v4 25/30] qcow2: Add subcluster support to handle_alloc_space(), Alberto Garcia, 2020/03/17
- [PATCH v4 09/30] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/03/17
- [PATCH v4 14/30] qcow2: Add cluster type parameter to qcow2_get_host_offset(), Alberto Garcia, 2020/03/17
- [PATCH v4 08/30] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2020/03/17
- [PATCH v4 20/30] qcow2: Add subcluster support to discard_in_l2_slice(), Alberto Garcia, 2020/03/17
- [PATCH v4 19/30] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2020/03/17
- [PATCH v4 24/30] qcow2: Clear the L2 bitmap when allocating a compressed cluster, Alberto Garcia, 2020/03/17
- [PATCH v4 03/30] qcow2: Add calculate_l2_meta(), Alberto Garcia, 2020/03/17
- [PATCH v4 13/30] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(), Alberto Garcia, 2020/03/17
- [PATCH v4 17/30] qcow2: Add subcluster support to calculate_l2_meta(),
Alberto Garcia <=
- [PATCH v4 01/30] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/03/17
- [PATCH v4 26/30] qcow2: Restrict qcow2_co_pwrite_zeroes() to full clusters only, Alberto Garcia, 2020/03/17
- [PATCH v4 27/30] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters, Alberto Garcia, 2020/03/17
- [PATCH v4 07/30] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/03/17
- [PATCH v4 30/30] iotests: Add tests for qcow2 images with extended L2 entries, Alberto Garcia, 2020/03/17
- [PATCH v4 28/30] qcow2: Add the 'extended_l2' option and the QCOW2_INCOMPAT_EXTL2 bit, Alberto Garcia, 2020/03/17