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author | Alberto Garcia <berto@igalia.com> | 2020-07-10 18:12:57 +0200 |
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committer | Max Reitz <mreitz@redhat.com> | 2020-08-25 08:33:20 +0200 |
commit | 70d1cbae03b54995fdc99f9934c847a87125e4f5 (patch) | |
tree | 9276c1d9dd5519569ee3f4331610665d90e983c0 /block | |
parent | 34905d8eb1ef788a41a490cb1602582ff78cb6f4 (diff) | |
download | qemu-70d1cbae03b54995fdc99f9934c847a87125e4f5.zip qemu-70d1cbae03b54995fdc99f9934c847a87125e4f5.tar.gz qemu-70d1cbae03b54995fdc99f9934c847a87125e4f5.tar.bz2 |
qcow2: Add qcow2_get_subcluster_range_type()
There are situations in which we want to know how many contiguous
subclusters of the same type there are in a given cluster. This can be
done by simply iterating over the subclusters and repeatedly calling
qcow2_get_subcluster_type() for each one of them.
However once we determined the type of a subcluster we can check the
rest efficiently by counting the number of adjacent ones (or zeroes)
in the bitmap. This is what this function does.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <db917263d568ec6ffb4a41cac3c9100f96bf6c18.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/qcow2-cluster.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 0b76250..2fe7a0f 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -376,6 +376,57 @@ fail: } /* + * For a given L2 entry, count the number of contiguous subclusters of + * the same type starting from @sc_from. Compressed clusters are + * treated as if they were divided into subclusters of size + * s->subcluster_size. + * + * Return the number of contiguous subclusters and set @type to the + * subcluster type. + * + * 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, + unsigned sc_from, + QCow2SubclusterType *type) +{ + BDRVQcow2State *s = bs->opaque; + uint32_t val; + + *type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_from); + + if (*type == QCOW2_SUBCLUSTER_INVALID) { + return -EINVAL; + } else if (!has_subclusters(s) || *type == QCOW2_SUBCLUSTER_COMPRESSED) { + return s->subclusters_per_cluster - sc_from; + } + + switch (*type) { + case QCOW2_SUBCLUSTER_NORMAL: + val = l2_bitmap | QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from); + return cto32(val) - sc_from; + + case QCOW2_SUBCLUSTER_ZERO_PLAIN: + case QCOW2_SUBCLUSTER_ZERO_ALLOC: + val = (l2_bitmap | QCOW_OFLAG_SUB_ZERO_RANGE(0, sc_from)) >> 32; + return cto32(val) - sc_from; + + case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN: + case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC: + val = ((l2_bitmap >> 32) | l2_bitmap) + & ~QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from); + return ctz32(val) - sc_from; + + default: + g_assert_not_reached(); + } +} + +/* * 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 |