1 files changed, 142 insertions, 0 deletions
diff --git a/block/qed-cluster.c b/block/qed-cluster.c
new file mode 100644
index 000000000..672e2e654
--- /dev/null
+++ b/block/qed-cluster.c
@@ -0,0 +1,142 @@
+/*
+ * QEMU Enhanced Disk Format Cluster functions
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qed.h"
+
+/**
+ * Count the number of contiguous data clusters
+ *
+ * @s:              QED state
+ * @table:          L2 table
+ * @index:          First cluster index
+ * @n:              Maximum number of clusters
+ * @offset:         Set to first cluster offset
+ *
+ * This function scans tables for contiguous clusters.  A contiguous run of
+ * clusters may be allocated, unallocated, or zero.
+ */
+static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,
+                                                  QEDTable *table,
+                                                  unsigned int index,
+                                                  unsigned int n,
+                                                  uint64_t *offset)
+{
+    unsigned int end = MIN(index + n, s->table_nelems);
+    uint64_t last = table->offsets[index];
+    unsigned int i;
+
+    *offset = last;
+
+    for (i = index + 1; i < end; i++) {
+        if (qed_offset_is_unalloc_cluster(last)) {
+            /* Counting unallocated clusters */
+            if (!qed_offset_is_unalloc_cluster(table->offsets[i])) {
+                break;
+            }
+        } else if (qed_offset_is_zero_cluster(last)) {
+            /* Counting zero clusters */
+            if (!qed_offset_is_zero_cluster(table->offsets[i])) {
+                break;
+            }
+        } else {
+            /* Counting allocated clusters */
+            if (table->offsets[i] != last + s->header.cluster_size) {
+                break;
+            }
+            last = table->offsets[i];
+        }
+    }
+    return i - index;
+}
+
+/**
+ * Find the offset of a data cluster
+ *
+ * @s:          QED state
+ * @request:    L2 cache entry
+ * @pos:        Byte position in device
+ * @len:        Number of bytes (may be shortened on return)
+ * @img_offset: Contains offset in the image file on success
+ *
+ * This function translates a position in the block device to an offset in the
+ * image file. The translated offset or unallocated range in the image file is
+ * reported back in *img_offset and *len.
+ *
+ * If the L2 table exists, request->l2_table points to the L2 table cache entry
+ * and the caller must free the reference when they are finished.  The cache
+ * entry is exposed in this way to avoid callers having to read the L2 table
+ * again later during request processing.  If request->l2_table is non-NULL it
+ * will be unreferenced before taking on the new cache entry.
+ *
+ * On success QED_CLUSTER_FOUND is returned and img_offset/len are a contiguous
+ * range in the image file.
+ *
+ * On failure QED_CLUSTER_L2 or QED_CLUSTER_L1 is returned for missing L2 or L1
+ * table offset, respectively. len is number of contiguous unallocated bytes.
+ *
+ * Called with table_lock held.
+ */
+int coroutine_fn qed_find_cluster(BDRVQEDState *s, QEDRequest *request,
+                                  uint64_t pos, size_t *len,
+                                  uint64_t *img_offset)
+{
+    uint64_t l2_offset;
+    uint64_t offset = 0;
+    unsigned int index;
+    unsigned int n;
+    int ret;
+
+    /* Limit length to L2 boundary.  Requests are broken up at the L2 boundary
+     * so that a request acts on one L2 table at a time.
+     */
+    *len = MIN(*len, (((pos >> s->l1_shift) + 1) << s->l1_shift) - pos);
+
+    l2_offset = s->l1_table->offsets[qed_l1_index(s, pos)];
+    if (qed_offset_is_unalloc_cluster(l2_offset)) {
+        *img_offset = 0;
+        return QED_CLUSTER_L1;
+    }
+    if (!qed_check_table_offset(s, l2_offset)) {
+        *img_offset = *len = 0;
+        return -EINVAL;
+    }
+
+    ret = qed_read_l2_table(s, request, l2_offset);
+    if (ret) {
+        goto out;
+    }
+
+    index = qed_l2_index(s, pos);
+    n = qed_bytes_to_clusters(s, qed_offset_into_cluster(s, pos) + *len);
+    n = qed_count_contiguous_clusters(s, request->l2_table->table,
+                                      index, n, &offset);
+
+    if (qed_offset_is_unalloc_cluster(offset)) {
+        ret = QED_CLUSTER_L2;
+    } else if (qed_offset_is_zero_cluster(offset)) {
+        ret = QED_CLUSTER_ZERO;
+    } else if (qed_check_cluster_offset(s, offset)) {
+        ret = QED_CLUSTER_FOUND;
+    } else {
+        ret = -EINVAL;
+    }
+
+    *len = MIN(*len,
+               n * s->header.cluster_size - qed_offset_into_cluster(s, pos));
+
+out:
+    *img_offset = offset;
+    return ret;
+}