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-rw-r--r--lib/generic-radix-tree.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index 7dfa88282b..41f1bcdc44 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -1,4 +1,5 @@
+#include <linux/atomic.h>
#include <linux/export.h>
#include <linux/generic-radix-tree.h>
#include <linux/gfp.h>
@@ -212,6 +213,64 @@ restart:
}
EXPORT_SYMBOL(__genradix_iter_peek);
+void *__genradix_iter_peek_prev(struct genradix_iter *iter,
+ struct __genradix *radix,
+ size_t objs_per_page,
+ size_t obj_size_plus_page_remainder)
+{
+ struct genradix_root *r;
+ struct genradix_node *n;
+ unsigned level, i;
+
+ if (iter->offset == SIZE_MAX)
+ return NULL;
+
+restart:
+ r = READ_ONCE(radix->root);
+ if (!r)
+ return NULL;
+
+ n = genradix_root_to_node(r);
+ level = genradix_root_to_depth(r);
+
+ if (ilog2(iter->offset) >= genradix_depth_shift(level)) {
+ iter->offset = genradix_depth_size(level);
+ iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page;
+
+ iter->offset -= obj_size_plus_page_remainder;
+ iter->pos--;
+ }
+
+ while (level) {
+ level--;
+
+ i = (iter->offset >> genradix_depth_shift(level)) &
+ (GENRADIX_ARY - 1);
+
+ while (!n->children[i]) {
+ size_t objs_per_ptr = genradix_depth_size(level);
+
+ iter->offset = round_down(iter->offset, objs_per_ptr);
+ iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page;
+
+ if (!iter->offset)
+ return NULL;
+
+ iter->offset -= obj_size_plus_page_remainder;
+ iter->pos--;
+
+ if (!i)
+ goto restart;
+ --i;
+ }
+
+ n = n->children[i];
+ }
+
+ return &n->data[iter->offset & (PAGE_SIZE - 1)];
+}
+EXPORT_SYMBOL(__genradix_iter_peek_prev);
+
static void genradix_free_recurse(struct genradix_node *n, unsigned level)
{
if (level) {