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[PATCH v6 15/32] qcow2: Add qcow2_get_subcluster_range_type()
From: |
Alberto Garcia |
Subject: |
[PATCH v6 15/32] qcow2: Add qcow2_get_subcluster_range_type() |
Date: |
Sun, 24 May 2020 16:51:35 +0200 |
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 <address@hidden>
---
block/qcow2-cluster.c | 51 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 8b2fc550b7..32dc6e75e3 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -375,6 +375,57 @@ fail:
return ret;
}
+/*
+ * 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
--
2.20.1
- [PATCH v6 02/32] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), (continued)
- [PATCH v6 02/32] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/05/24
- [PATCH v6 22/32] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2020/05/24
- [PATCH v6 17/32] qcow2: Add cluster type parameter to qcow2_get_host_offset(), Alberto Garcia, 2020/05/24
- [PATCH v6 24/32] qcow2: Add subcluster support to check_refcounts_l2(), Alberto Garcia, 2020/05/24
- [PATCH v6 26/32] qcow2: Clear the L2 bitmap when allocating a compressed cluster, Alberto Garcia, 2020/05/24
- [PATCH v6 28/32] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes(), Alberto Garcia, 2020/05/24
- [PATCH v6 27/32] qcow2: Add subcluster support to handle_alloc_space(), Alberto Garcia, 2020/05/24
- [PATCH v6 19/32] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/05/24
- [PATCH v6 25/32] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/05/24
- [PATCH v6 11/32] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/05/24
- [PATCH v6 15/32] qcow2: Add qcow2_get_subcluster_range_type(),
Alberto Garcia <=
- [PATCH v6 07/32] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/05/24
- [PATCH v6 13/32] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2020/05/24
- [PATCH v6 04/32] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/05/24
- [PATCH v6 31/32] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters, Alberto Garcia, 2020/05/24
- [PATCH v6 32/32] iotests: Add tests for qcow2 images with extended L2 entries, Alberto Garcia, 2020/05/24
- [PATCH v6 08/32] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2020/05/24
- [PATCH v6 18/32] qcow2: Replace QCOW2_CLUSTER_* with QCOW2_SUBCLUSTER_*, Alberto Garcia, 2020/05/24
- [PATCH v6 20/32] qcow2: Add subcluster support to calculate_l2_meta(), Alberto Garcia, 2020/05/24
- [PATCH v6 30/32] qcow2: Add the 'extended_l2' option and the QCOW2_INCOMPAT_EXTL2 bit, Alberto Garcia, 2020/05/24