1 files changed, 35 insertions, 0 deletions

diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
index 3f479f176610..396d767c2cab 100644
--- a/fs/ntfs/runlist.c
+++ b/fs/ntfs/runlist.c
@@ -980,6 +980,39 @@ LCN ntfs_rl_vcn_to_lcn(const runlist_element *rl, const VCN vcn)
         return LCN_ENOENT;
 }
 
+#ifdef NTFS_RW
+
+/**
+ * ntfs_rl_find_vcn_nolock - find a vcn in a runlist
+ * @rl:         runlist to search
+ * @vcn:        vcn to find
+ *
+ * Find the virtual cluster number @vcn in the runlist @rl and return the
+ * address of the runlist element containing the @vcn on success.
+ *
+ * Return NULL if @rl is NULL or @vcn is in an unmapped part/out of bounds of
+ * the runlist.
+ *
+ * Locking: The runlist must be locked on entry.
+ */
+runlist_element *ntfs_rl_find_vcn_nolock(runlist_element *rl, const VCN vcn)
+{
+        BUG_ON(vcn < 0);
+        if (unlikely(!rl || vcn < rl[0].vcn))
+                return NULL;
+        while (likely(rl->length)) {
+                if (unlikely(vcn < rl[1].vcn)) {
+                        if (likely(rl->lcn >= LCN_HOLE))
+                                return rl;
+                        return NULL;
+                }
+                rl++;
+        }
+        if (likely(rl->lcn == LCN_ENOENT))
+                return rl;
+        return NULL;
+}
+
 /**
  * ntfs_get_nr_significant_bytes - get number of bytes needed to store a number
  * @n:          number for which to get the number of bytes for
@@ -1452,3 +1485,5 @@ int ntfs_rl_truncate_nolock(const ntfs_volume *vol, runlist *const runlist,
         ntfs_debug("Done.");
         return 0;
 }
+
+#endif /* NTFS_RW */