bitmap: introduce bitmap_set, bitmap_clear, bitmap_find_next_zero_area

This introduces new bitmap functions:

bitmap_set: Set specified bit area
bitmap_clear: Clear specified bit area
bitmap_find_next_zero_area: Find free bit area

These are mostly stolen from iommu helper. The differences are:

- Use find_next_bit instead of doing test_bit for each bit

- Rewrite bitmap_set and bitmap_clear

  Instead of setting or clearing for each bit.

- Check the last bit of the limit

  iommu-helper doesn't want to find such area

- The return value if there is no zero area

  find_next_zero_area in iommu helper: returns -1
  bitmap_find_next_zero_area: return >= bitmap size

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Lothar Wassmann <LW@KARO-electronics.de>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 81 insertions, 0 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 702565821c99..11bf49750583 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -271,6 +271,87 @@ int __bitmap_weight(const unsigned long *bitmap, int bits)
 }
 EXPORT_SYMBOL(__bitmap_weight);
 
+#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
+
+void bitmap_set(unsigned long *map, int start, int nr)
+{
+        unsigned long *p = map + BIT_WORD(start);
+        const int size = start + nr;
+        int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+        unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+        while (nr - bits_to_set >= 0) {
+                *p |= mask_to_set;
+                nr -= bits_to_set;
+                bits_to_set = BITS_PER_LONG;
+                mask_to_set = ~0UL;
+                p++;
+        }
+        if (nr) {
+                mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+                *p |= mask_to_set;
+        }
+}
+EXPORT_SYMBOL(bitmap_set);
+
+void bitmap_clear(unsigned long *map, int start, int nr)
+{
+        unsigned long *p = map + BIT_WORD(start);
+        const int size = start + nr;
+        int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+        unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+        while (nr - bits_to_clear >= 0) {
+                *p &= ~mask_to_clear;
+                nr -= bits_to_clear;
+                bits_to_clear = BITS_PER_LONG;
+                mask_to_clear = ~0UL;
+                p++;
+        }
+        if (nr) {
+                mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+                *p &= ~mask_to_clear;
+        }
+}
+EXPORT_SYMBOL(bitmap_clear);
+
+/*
+ * bitmap_find_next_zero_area - find a contiguous aligned zero area
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @align_mask: Alignment mask for zero area
+ *
+ * The @align_mask should be one less than a power of 2; the effect is that
+ * the bit offset of all zero areas this function finds is multiples of that
+ * power of 2. A @align_mask of 0 means no alignment is required.
+ */
+unsigned long bitmap_find_next_zero_area(unsigned long *map,
+                                         unsigned long size,
+                                         unsigned long start,
+                                         unsigned int nr,
+                                         unsigned long align_mask)
+{
+        unsigned long index, end, i;
+again:
+        index = find_next_zero_bit(map, size, start);
+
+        /* Align allocation */
+        index = __ALIGN_MASK(index, align_mask);
+
+        end = index + nr;
+        if (end > size)
+                return end;
+        i = find_next_bit(map, end, index);
+        if (i < end) {
+                start = i + 1;
+                goto again;
+        }
+        return index;
+}
+EXPORT_SYMBOL(bitmap_find_next_zero_area);
+
 /*
  * Bitmap printing & parsing functions: first version by Bill Irwin,
  * second version by Paul Jackson, third by Joe Korty.