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[PATCH v11 20/34] qcow2: Add subcluster support to calculate_l2_meta()
From: |
Alberto Garcia |
Subject: |
[PATCH v11 20/34] qcow2: Add subcluster support to calculate_l2_meta() |
Date: |
Fri, 10 Jul 2020 18:13:02 +0200 |
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:
1) If we are writing to a newly allocated cluster then we need
copy-on-write. The previous contents of subclusters #0 to #3 must
be copied to the new cluster. We can optimize this process by
skipping all leading unallocated or zero subclusters (the status of
those skipped subclusters will be reflected in the new L2 bitmap).
2) If we are overwriting an existing cluster:
2.1) If subcluster #3 is unallocated or has the all-zeroes bit set
then we need copy-on-write (on subcluster #3 only).
2.2) If subcluster #3 was already allocated then there is no need
for any copy-on-write. However we still need to update the L2
bitmap to reflect possible changes in the allocation status of
subclusters #4 to #31. Because of this, this function checks
if all the overwritten subclusters are already allocated and
in this case it returns without creating a new QCowL2Meta
structure.
After all these changes l2meta_cow_start() and l2meta_cow_end()
are not necessarily cluster-aligned anymore. We need to update the
calculation of old_start and old_end in handle_dependencies() to
guarantee that no two requests try to write on the same cluster.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
block/qcow2-cluster.c | 163 +++++++++++++++++++++++++++++++++---------
1 file changed, 131 insertions(+), 32 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index dd8a72381b..01495cb1c0 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -387,7 +387,6 @@ fail:
* If the L2 entry is invalid return -errno and set @type to
* QCOW2_SUBCLUSTER_INVALID.
*/
-G_GNUC_UNUSED
static int qcow2_get_subcluster_range_type(BlockDriverState *bs,
uint64_t l2_entry,
uint64_t l2_bitmap,
@@ -1111,56 +1110,148 @@ 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 0 on success, -errno on failure.
*/
-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;
+ int i;
+ bool skip_cow = keep_old;
assert(nb_clusters <= s->l2_slice_size - l2_index);
- /* Return if there's no COW (all clusters are normal and we keep them) */
- if (keep_old) {
- 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) {
- break;
+ /* Check the type of all affected subclusters */
+ for (i = 0; i < nb_clusters; i++) {
+ l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
+ l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
+ if (skip_cow) {
+ unsigned write_from = MAX(cow_start_to, i << s->cluster_bits);
+ unsigned write_to = MIN(cow_end_from, (i + 1) << s->cluster_bits);
+ int first_sc = offset_to_sc_index(s, write_from);
+ int last_sc = offset_to_sc_index(s, write_to - 1);
+ int cnt = qcow2_get_subcluster_range_type(bs, l2_entry, l2_bitmap,
+ first_sc, &type);
+ /* Is any of the subclusters of type != QCOW2_SUBCLUSTER_NORMAL ?
*/
+ if (type != QCOW2_SUBCLUSTER_NORMAL || first_sc + cnt <= last_sc) {
+ skip_cow = false;
}
+ } else {
+ /* If we can't skip the cow we can still look for invalid entries
*/
+ type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, 0);
}
- if (i == nb_clusters) {
- return;
+ if (type == QCOW2_SUBCLUSTER_INVALID) {
+ int 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 + i);
+ return -EIO;
}
}
+ if (skip_cow) {
+ return 0;
+ }
+
/* 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 (!keep_old) {
+ switch (type) {
+ case QCOW2_SUBCLUSTER_COMPRESSED:
+ cow_start_from = 0;
+ break;
+ case QCOW2_SUBCLUSTER_NORMAL:
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ if (has_subclusters(s)) {
+ /* Skip all leading zero and unallocated subclusters */
+ uint32_t alloc_bitmap = l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC;
+ cow_start_from =
+ MIN(sc_index, ctz32(alloc_bitmap)) << s->subcluster_bits;
+ } else {
+ 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 (!keep_old) {
+ switch (type) {
+ case QCOW2_SUBCLUSTER_COMPRESSED:
+ cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
+ break;
+ case QCOW2_SUBCLUSTER_NORMAL:
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
+ if (has_subclusters(s)) {
+ /* Skip all trailing zero and unallocated subclusters */
+ uint32_t alloc_bitmap = l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC;
+ cow_end_to -=
+ MIN(s->subclusters_per_cluster - sc_index - 1,
+ clz32(alloc_bitmap)) << s->subcluster_bits;
+ }
+ 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));
@@ -1185,6 +1276,8 @@ static void calculate_l2_meta(BlockDriverState *bs,
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
+
+ return 0;
}
/*
@@ -1273,8 +1366,8 @@ static int handle_dependencies(BlockDriverState *bs,
uint64_t guest_offset,
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);
+ uint64_t old_start = start_of_cluster(s, l2meta_cow_start(old_alloc));
+ uint64_t old_end = ROUND_UP(l2meta_cow_end(old_alloc),
s->cluster_size);
if (end <= old_start || start >= old_end) {
/* No intersection */
@@ -1399,8 +1492,11 @@ 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, guest_offset,
- *bytes, l2_slice, m, true);
+ ret = calculate_l2_meta(bs, cluster_offset, guest_offset,
+ *bytes, l2_slice, m, true);
+ if (ret < 0) {
+ goto out;
+ }
ret = 1;
} else {
@@ -1576,8 +1672,11 @@ 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 = calculate_l2_meta(bs, alloc_cluster_offset, guest_offset, *bytes,
+ l2_slice, m, false);
+ if (ret < 0) {
+ goto out;
+ }
ret = 1;
--
2.20.1
- [PATCH v11 01/34] qcow2: Make Qcow2AioTask store the full host offset, (continued)
- [PATCH v11 01/34] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/07/10
- [PATCH v11 02/34] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/07/10
- [PATCH v11 06/34] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/07/10
- [PATCH v11 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/07/10
- [PATCH v11 07/34] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/07/10
- [PATCH v11 05/34] qcow2: Process QCOW2_CLUSTER_ZERO_ALLOC clusters in handle_copied(), Alberto Garcia, 2020/07/10
- [PATCH v11 13/34] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2020/07/10
- [PATCH v11 15/34] qcow2: Add qcow2_get_subcluster_range_type(), Alberto Garcia, 2020/07/10
- [PATCH v11 19/34] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/07/10
- [PATCH v11 09/34] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/07/10
- [PATCH v11 20/34] qcow2: Add subcluster support to calculate_l2_meta(),
Alberto Garcia <=
- [PATCH v11 18/34] qcow2: Replace QCOW2_CLUSTER_* with QCOW2_SUBCLUSTER_*, Alberto Garcia, 2020/07/10
- [PATCH v11 22/34] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2020/07/10
- [PATCH v11 24/34] qcow2: Add subcluster support to check_refcounts_l2(), Alberto Garcia, 2020/07/10
- [PATCH v11 10/34] qcow2: Add offset_to_sc_index(), Alberto Garcia, 2020/07/10
- [PATCH v11 11/34] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/07/10
- [PATCH v11 12/34] qcow2: Add l2_entry_size(), Alberto Garcia, 2020/07/10
- [PATCH v11 32/34] qcow2: Allow preallocation and backing files if extended_l2 is set, Alberto Garcia, 2020/07/10
- [PATCH v11 25/34] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/07/10
- [PATCH v11 26/34] qcow2: Clear the L2 bitmap when allocating a compressed cluster, Alberto Garcia, 2020/07/10
- [PATCH v11 14/34] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(), Alberto Garcia, 2020/07/10