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[RFC PATCH v3 11/27] qcow2: Add QCow2SubclusterType and qcow2_get_subclu
From: |
Alberto Garcia |
Subject: |
[RFC PATCH v3 11/27] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type() |
Date: |
Sun, 22 Dec 2019 12:36:52 +0100 |
This patch adds QCow2SubclusterType, which is the subcluster-level
version of QCow2ClusterType. All QCOW2_SUBCLUSTER_* values have the
the same meaning as their QCOW2_CLUSTER_* equivalents (when they
exist). See below for details and caveats.
In images without extended L2 entries clusters are treated as having
exactly one subcluster so it is possible to replace one data type with
the other while keeping the exact same semantics.
With extended L2 entries there are new possible values, and every
subcluster in the same cluster can obviously have a different
QCow2SubclusterType so functions need to be adapted to work on the
subcluster level.
There are several things that have to be taken into account:
a) QCOW2_SUBCLUSTER_COMPRESSED means that the whole cluster is
compressed. We do not support compression at the subcluster
level.
b) There are two different values for unallocated subclusters:
QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN which means that the whole
cluster is unallocated, and QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC
which means that the cluster is allocated but the subcluster is
not. The latter can only happen in images with extended L2
entries.
c) QCOW2_SUBCLUSTER_INVALID is used to detect the cases where an L2
entry has a value that violates the specification. The caller is
responsible for handling these situations.
To prevent compatibility problems with images that have invalid
values but are currently being read by QEMU without causing side
effects, QCOW2_SUBCLUSTER_INVALID is only returned for images
with extended L2 entries.
qcow2_cluster_to_subcluster_type() is added as a separate function
from qcow2_get_subcluster_type(), but this is only temporary and both
will be merged in a subsequent patch.
Signed-off-by: Alberto Garcia <address@hidden>
---
block/qcow2.h | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 92 insertions(+)
diff --git a/block/qcow2.h b/block/qcow2.h
index 64b0a814f4..321ba9550f 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -80,6 +80,15 @@
#define QCOW_MAX_SUBCLUSTERS_PER_CLUSTER 32
+/* The subcluster X [0..31] reads as zeroes */
+#define QCOW_OFLAG_SUB_ZERO(X) ((1ULL << 63) >> (X))
+/* The subcluster X [0..31] is allocated */
+#define QCOW_OFLAG_SUB_ALLOC(X) ((1ULL << 31) >> (X))
+/* L2 entry bitmap with all "read as zeroes" bits set */
+#define QCOW_L2_BITMAP_ALL_ZEROES 0xFFFFFFFF00000000ULL
+/* L2 entry bitmap with all allocation bits set */
+#define QCOW_L2_BITMAP_ALL_ALLOC 0x00000000FFFFFFFFULL
+
/* Size of normal and extended L2 entries */
#define L2E_SIZE_NORMAL (sizeof(uint64_t))
#define L2E_SIZE_EXTENDED (sizeof(uint64_t) * 2)
@@ -455,6 +464,16 @@ typedef enum QCow2ClusterType {
QCOW2_CLUSTER_COMPRESSED,
} QCow2ClusterType;
+typedef enum QCow2SubclusterType {
+ QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN,
+ QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC,
+ QCOW2_SUBCLUSTER_ZERO_PLAIN,
+ QCOW2_SUBCLUSTER_ZERO_ALLOC,
+ QCOW2_SUBCLUSTER_NORMAL,
+ QCOW2_SUBCLUSTER_COMPRESSED,
+ QCOW2_SUBCLUSTER_INVALID,
+} QCow2SubclusterType;
+
typedef enum QCow2MetadataOverlap {
QCOW2_OL_MAIN_HEADER_BITNR = 0,
QCOW2_OL_ACTIVE_L1_BITNR = 1,
@@ -632,6 +651,79 @@ static inline QCow2ClusterType
qcow2_get_cluster_type(BlockDriverState *bs,
}
}
+/* For an image without extended L2 entries, return the
+ * QCow2SubclusterType equivalent of a given QCow2ClusterType */
+static inline
+QCow2SubclusterType qcow2_cluster_to_subcluster_type(QCow2ClusterType type)
+{
+ switch (type) {
+ case QCOW2_CLUSTER_COMPRESSED:
+ return QCOW2_SUBCLUSTER_COMPRESSED;
+ case QCOW2_CLUSTER_ZERO_PLAIN:
+ return QCOW2_SUBCLUSTER_ZERO_PLAIN;
+ case QCOW2_CLUSTER_ZERO_ALLOC:
+ return QCOW2_SUBCLUSTER_ZERO_ALLOC;
+ case QCOW2_CLUSTER_NORMAL:
+ return QCOW2_SUBCLUSTER_NORMAL;
+ case QCOW2_CLUSTER_UNALLOCATED:
+ return QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
+ default:
+ g_assert_not_reached();
+ }
+}
+
+/* In an image without subsclusters @l2_bitmap is ignored and
+ * @sc_index must be 0. */
+static inline
+QCow2SubclusterType qcow2_get_subcluster_type(BlockDriverState *bs,
+ uint64_t l2_entry,
+ uint64_t l2_bitmap,
+ unsigned sc_index)
+{
+ BDRVQcow2State *s = bs->opaque;
+ QCow2ClusterType type = qcow2_get_cluster_type(bs, l2_entry);
+ assert(sc_index < s->subclusters_per_cluster);
+
+ if (has_subclusters(s)) {
+ bool sc_zero = l2_bitmap & QCOW_OFLAG_SUB_ZERO(sc_index);
+ bool sc_alloc = l2_bitmap & QCOW_OFLAG_SUB_ALLOC(sc_index);
+ switch (type) {
+ case QCOW2_CLUSTER_COMPRESSED:
+ if (l2_bitmap != 0) {
+ return QCOW2_SUBCLUSTER_INVALID;
+ }
+ return QCOW2_SUBCLUSTER_COMPRESSED;
+ case QCOW2_CLUSTER_ZERO_PLAIN:
+ case QCOW2_CLUSTER_ZERO_ALLOC:
+ return QCOW2_SUBCLUSTER_INVALID;
+ case QCOW2_CLUSTER_NORMAL:
+ if (!sc_zero && !sc_alloc) {
+ return QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC;
+ } else if (!sc_zero && sc_alloc) {
+ return QCOW2_SUBCLUSTER_NORMAL;
+ } else if (sc_zero && !sc_alloc) {
+ return QCOW2_SUBCLUSTER_ZERO_ALLOC;
+ } else { /* sc_zero && sc_alloc */
+ return QCOW2_SUBCLUSTER_INVALID;
+ }
+ case QCOW2_CLUSTER_UNALLOCATED:
+ if (!sc_zero && !sc_alloc) {
+ return QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN;
+ } else if (!sc_zero && sc_alloc) {
+ return QCOW2_SUBCLUSTER_INVALID;
+ } else if (sc_zero && !sc_alloc) {
+ return QCOW2_SUBCLUSTER_ZERO_PLAIN;
+ } else { /* sc_zero && sc_alloc */
+ return QCOW2_SUBCLUSTER_INVALID;
+ }
+ default:
+ g_assert_not_reached();
+ }
+ } else {
+ return qcow2_cluster_to_subcluster_type(type);
+ }
+}
+
/* Check whether refcounts are eager or lazy */
static inline bool qcow2_need_accurate_refcounts(BDRVQcow2State *s)
{
--
2.20.1
- [RFC PATCH v3 00/27] Add subcluster allocation to qcow2, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 16/27] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 07/27] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 18/27] qcow2: Add subcluster support to check_refcounts_l2(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 17/27] qcow2: Add subcluster support to discard_in_l2_slice(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 10/27] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 01/27] qcow2: Add calculate_l2_meta(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 24/27] qcow2: Restrict qcow2_co_pwrite_zeroes() to full clusters only, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 11/27] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(),
Alberto Garcia <=
- [RFC PATCH v3 03/27] qcow2: Process QCOW2_CLUSTER_ZERO_ALLOC clusters in handle_copied(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 27/27] iotests: Add tests for qcow2 images with extended L2 entries, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 21/27] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 13/27] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 19/27] qcow2: Add subcluster support to expand_zero_clusters_in_l1(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 22/27] qcow2: Clear the L2 bitmap when allocating a compressed cluster, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 08/27] qcow2: Add offset_to_sc_index(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 06/27] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2019/12/22
- [RFC PATCH v3 02/27] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2019/12/22
- [RFC PATCH v3 23/27] qcow2: Add subcluster support to handle_alloc_space(), Alberto Garcia, 2019/12/22