1 files changed, 46 insertions, 4 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index eca88087fa8a..0b66f0e5eb6b 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -496,6 +496,11 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
  * ranges.  Consecutively set bits are shown as two hyphen-separated
  * decimal numbers, the smallest and largest bit numbers set in
  * the range.
+ * Optionally each range can be postfixed to denote that only parts of it
+ * should be set. The range will divided to groups of specific size.
+ * From each group will be used only defined amount of bits.
+ * Syntax: range:used_size/group_size
+ * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769
  *
  * Returns 0 on success, -errno on invalid input strings.
  * Error values:
@@ -507,16 +512,20 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
                 int is_user, unsigned long *maskp,
                 int nmaskbits)
 {
-        unsigned a, b;
+        unsigned int a, b, old_a, old_b;
+        unsigned int group_size, used_size;
         int c, old_c, totaldigits, ndigits;
         const char __user __force *ubuf = (const char __user __force *)buf;
-        int at_start, in_range;
+        int at_start, in_range, in_partial_range;
 
         totaldigits = c = 0;
+        old_a = old_b = 0;
+        group_size = used_size = 0;
         bitmap_zero(maskp, nmaskbits);
         do {
                 at_start = 1;
                 in_range = 0;
+                in_partial_range = 0;
                 a = b = 0;
                 ndigits = totaldigits;
 
@@ -547,6 +556,24 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
                         if ((totaldigits != ndigits) && isspace(old_c))
                                 return -EINVAL;
 
+                        if (c == '/') {
+                                used_size = a;
+                                at_start = 1;
+                                in_range = 0;
+                                a = b = 0;
+                                continue;
+                        }
+
+                        if (c == ':') {
+                                old_a = a;
+                                old_b = b;
+                                at_start = 1;
+                                in_range = 0;
+                                in_partial_range = 1;
+                                a = b = 0;
+                                continue;
+                        }
+
                         if (c == '-') {
                                 if (at_start || in_range)
                                         return -EINVAL;
@@ -567,15 +594,30 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
                 }
                 if (ndigits == totaldigits)
                         continue;
+                if (in_partial_range) {
+                        group_size = a;
+                        a = old_a;
+                        b = old_b;
+                        old_a = old_b = 0;
+                }
                 /* if no digit is after '-', it's wrong*/
                 if (at_start && in_range)
                         return -EINVAL;
-                if (!(a <= b))
+                if (!(a <= b) || !(used_size <= group_size))
                         return -EINVAL;
                 if (b >= nmaskbits)
                         return -ERANGE;
                 while (a <= b) {
-                        set_bit(a, maskp);
+                        if (in_partial_range) {
+                                static int pos_in_group = 1;
+
+                                if (pos_in_group <= used_size)
+                                        set_bit(a, maskp);
+
+                                if (a == b || ++pos_in_group > group_size)
+                                        pos_in_group = 1;
+                        } else
+                                set_bit(a, maskp);
                         a++;
                 }
         } while (buflen && c == ',');