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qcow2: Add calculate_l2_meta()

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handle_alloc() creates a QCowL2Meta structure in order to update the
image metadata and perform the necessary copy-on-write operations.

This patch moves that code to a separate function so it can be used
from other places.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <e5bc4a648dac31972bfa7a0e554be8064be78799.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2020-07-10 18:12:45 +02:00 committed by Max Reitz
parent 388e581615
commit 8f91d6906c
1 changed files with 53 additions and 24 deletions
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77
block/qcow2-cluster.c
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@ -1038,6 +1038,56 @@ void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m)
}
}
/*
* For a given write request, create a new QCowL2Meta structure, add
* it to @m and the BDRVQcow2State.cluster_allocs list.
*
* @host_cluster_offset points to the beginning of the first cluster.
*
* @guest_offset and @bytes indicate the offset and length of the
* request.
*
* 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.
*/
static void calculate_l2_meta(BlockDriverState *bs,
uint64_t host_cluster_offset,
uint64_t guest_offset, unsigned bytes,
QCowL2Meta **m, bool keep_old)
{
BDRVQcow2State *s = bs->opaque;
unsigned cow_start_from = 0;
unsigned cow_start_to = offset_into_cluster(s, guest_offset);
unsigned cow_end_from = cow_start_to + bytes;
unsigned cow_end_to = ROUND_UP(cow_end_from, s->cluster_size);
unsigned nb_clusters = size_to_clusters(s, cow_end_from);
QCowL2Meta *old_m = *m;
*m = g_malloc0(sizeof(**m));
**m = (QCowL2Meta) {
.next = old_m,
.alloc_offset = host_cluster_offset,
.offset = start_of_cluster(s, guest_offset),
.nb_clusters = nb_clusters,
.keep_old_clusters = keep_old,
.cow_start = {
.offset = cow_start_from,
.nb_bytes = cow_start_to - cow_start_from,
},
.cow_end = {
.offset = cow_end_from,
.nb_bytes = cow_end_to - cow_end_from,
},
};
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
}
/*
* 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,
@ -1436,35 +1486,14 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset);
int avail_bytes = nb_clusters << s->cluster_bits;
int nb_bytes = MIN(requested_bytes, avail_bytes);
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,
.keep_old_clusters = keep_old_clusters,
.cow_start = {
.offset = 0,
.nb_bytes = offset_into_cluster(s, guest_offset),
},
.cow_end = {
.offset = nb_bytes,
.nb_bytes = avail_bytes - nb_bytes,
},
};
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_bytes - offset_into_cluster(s, guest_offset));
assert(*bytes != 0);
calculate_l2_meta(bs, alloc_cluster_offset, guest_offset, *bytes,
m, keep_old_clusters);
return 1;
fail: