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authorWu Fengguang <fengguang.wu@intel.com>2009-06-16 15:31:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:30 -0700
commitdc566127dd161b6c997466a2349ac179527ea89b (patch)
tree2973018dd4a89f0b20eaa0838eb654b6eff06f68 /lib
parentd30a11004e3411909f2448546f036a011978062e (diff)
downloadvexpress-lsk-dc566127dd161b6c997466a2349ac179527ea89b.tar.gz
radix-tree: add radix_tree_prev_hole()
The counterpart of radix_tree_next_hole(). To be used by context readahead. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Vladislav Bolkhovitin <vst@vlnb.net> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Ying Han <yinghan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/radix-tree.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 4bb42a0344e..5301a52cdb4 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -666,6 +666,43 @@ unsigned long radix_tree_next_hole(struct radix_tree_root *root,
}
EXPORT_SYMBOL(radix_tree_next_hole);
+/**
+ * radix_tree_prev_hole - find the prev hole (not-present entry)
+ * @root: tree root
+ * @index: index key
+ * @max_scan: maximum range to search
+ *
+ * Search backwards in the range [max(index-max_scan+1, 0), index]
+ * for the first hole.
+ *
+ * Returns: the index of the hole if found, otherwise returns an index
+ * outside of the set specified (in which case 'index - return >= max_scan'
+ * will be true). In rare cases of wrap-around, LONG_MAX will be returned.
+ *
+ * radix_tree_next_hole may be called under rcu_read_lock. However, like
+ * radix_tree_gang_lookup, this will not atomically search a snapshot of
+ * the tree at a single point in time. For example, if a hole is created
+ * at index 10, then subsequently a hole is created at index 5,
+ * radix_tree_prev_hole covering both indexes may return 5 if called under
+ * rcu_read_lock.
+ */
+unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
+ unsigned long index, unsigned long max_scan)
+{
+ unsigned long i;
+
+ for (i = 0; i < max_scan; i++) {
+ if (!radix_tree_lookup(root, index))
+ break;
+ index--;
+ if (index == LONG_MAX)
+ break;
+ }
+
+ return index;
+}
+EXPORT_SYMBOL(radix_tree_prev_hole);
+
static unsigned int
__lookup(struct radix_tree_node *slot, void ***results, unsigned long index,
unsigned int max_items, unsigned long *next_index)