libdm: add extent table helpers

Add a pair of helper functions for searching tables of _extent
objects:

  /* test whether an extent matching start/len exists */
  _extent_in_extents(nr_extents, extents, start, len)

  /* return the extent matching star/len or NULL */
  _find_extent(nr_extents, extents, start, len)

The filemap remapping support will use these when filtering the
set of extents that need to be updated in order to reflect the
current state of a mapped file.

1 files changed, 19 insertions, 0 deletions

diff --git a/libdm/libdm-stats.c b/libdm/libdm-stats.c
index 8d202d21c..038312a50 100644
--- a/libdm/libdm-stats.c
+++ b/libdm/libdm-stats.c
@@ -4390,6 +4390,25 @@ bad:
 	return NULL;
 }
 
+#define MATCH_EXTENT(e, s, l) \
+(((e).start == (s)) && ((e).len == (l)))
+
+static struct _extent *_find_extent(size_t nr_extents, struct _extent *extents,
+				    uint64_t start, uint64_t len)
+{
+	size_t i;
+	for (i = 0; i < nr_extents; i++)
+		if (MATCH_EXTENT(extents[i], start, len))
+			return extents + i;
+	return NULL;
+}
+
+static int _extent_in_extents(size_t nr_extents, struct _extent *extents,
+		       uint64_t start, uint64_t len)
+{
+	return (_find_extent(nr_extents, extents, start, len) != NULL);
+}
+
 /*
  * Create a set of regions representing the extents of a file and
  * return a table of uint64_t region_id values. The number of regions