lib/bitmap.c: conversion routines to/from u32 array

Aimed at transferring bitmaps to/from user-space in a 32/64-bit agnostic
way.

Tested:
  unit tests (next patch) on qemu i386, x86_64, ppc, ppc64 BE and LE,
  ARM.

Signed-off-by: David Decotigny <decot@googlers.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 9653fdb..e9b0b9a 100644 (file)
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -59,6 +59,8 @@
  * bitmap_find_free_region(bitmap, bits, order)        Find and allocate bit region
  * bitmap_release_region(bitmap, pos, order)   Free specified bit region
  * bitmap_allocate_region(bitmap, pos, order)  Allocate specified bit region
+ * bitmap_from_u32array(dst, nbits, buf, nwords) *dst = *buf (nwords 32b words)
+ * bitmap_to_u32array(buf, nwords, src, nbits) *buf = *dst (nwords 32b words)
  */
 
 /*
@@ -163,6 +165,14 @@ extern void bitmap_fold(unsigned long *dst, const unsigned long *orig,
 extern int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int order);
 extern void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order);
 extern int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order);
+extern unsigned int bitmap_from_u32array(unsigned long *bitmap,
+                                        unsigned int nbits,
+                                        const u32 *buf,
+                                        unsigned int nwords);
+extern unsigned int bitmap_to_u32array(u32 *buf,
+                                      unsigned int nwords,
+                                      const unsigned long *bitmap,
+                                      unsigned int nbits);
 #ifdef __BIG_ENDIAN
 extern void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int nbits);
 #else

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 8148143..c66da50 100644 (file)
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -12,6 +12,8 @@
 #include <linux/bitmap.h>
 #include <linux/bitops.h>
 #include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1059,6 +1061,93 @@ int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order)
 }
 EXPORT_SYMBOL(bitmap_allocate_region);
 
+/**
+ * bitmap_from_u32array - copy the contents of a u32 array of bits to bitmap
+ *     @bitmap: array of unsigned longs, the destination bitmap, non NULL
+ *     @nbits: number of bits in @bitmap
+ *     @buf: array of u32 (in host byte order), the source bitmap, non NULL
+ *     @nwords: number of u32 words in @buf
+ *
+ * copy min(nbits, 32*nwords) bits from @buf to @bitmap, remaining
+ * bits between nword and nbits in @bitmap (if any) are cleared. In
+ * last word of @bitmap, the bits beyond nbits (if any) are kept
+ * unchanged.
+ *
+ * Return the number of bits effectively copied.
+ */
+unsigned int
+bitmap_from_u32array(unsigned long *bitmap, unsigned int nbits,
+                    const u32 *buf, unsigned int nwords)
+{
+       unsigned int dst_idx, src_idx;
+
+       for (src_idx = dst_idx = 0; dst_idx < BITS_TO_LONGS(nbits); ++dst_idx) {
+               unsigned long part = 0;
+
+               if (src_idx < nwords)
+                       part = buf[src_idx++];
+
+#if BITS_PER_LONG == 64
+               if (src_idx < nwords)
+                       part |= ((unsigned long) buf[src_idx++]) << 32;
+#endif
+
+               if (dst_idx < nbits/BITS_PER_LONG)
+                       bitmap[dst_idx] = part;
+               else {
+                       unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
+
+                       bitmap[dst_idx] = (bitmap[dst_idx] & ~mask)
+                               | (part & mask);
+               }
+       }
+
+       return min_t(unsigned int, nbits, 32*nwords);
+}
+EXPORT_SYMBOL(bitmap_from_u32array);
+
+/**
+ * bitmap_to_u32array - copy the contents of bitmap to a u32 array of bits
+ *     @buf: array of u32 (in host byte order), the dest bitmap, non NULL
+ *     @nwords: number of u32 words in @buf
+ *     @bitmap: array of unsigned longs, the source bitmap, non NULL
+ *     @nbits: number of bits in @bitmap
+ *
+ * copy min(nbits, 32*nwords) bits from @bitmap to @buf. Remaining
+ * bits after nbits in @buf (if any) are cleared.
+ *
+ * Return the number of bits effectively copied.
+ */
+unsigned int
+bitmap_to_u32array(u32 *buf, unsigned int nwords,
+                  const unsigned long *bitmap, unsigned int nbits)
+{
+       unsigned int dst_idx = 0, src_idx = 0;
+
+       while (dst_idx < nwords) {
+               unsigned long part = 0;
+
+               if (src_idx < BITS_TO_LONGS(nbits)) {
+                       part = bitmap[src_idx];
+                       if (src_idx >= nbits/BITS_PER_LONG)
+                               part &= BITMAP_LAST_WORD_MASK(nbits);
+                       src_idx++;
+               }
+
+               buf[dst_idx++] = part & 0xffffffffUL;
+
+#if BITS_PER_LONG == 64
+               if (dst_idx < nwords) {
+                       part >>= 32;
+                       buf[dst_idx++] = part & 0xffffffffUL;
+               }
+#endif
+       }
+
+       return min_t(unsigned int, nbits, 32*nwords);
+}
+EXPORT_SYMBOL(bitmap_to_u32array);
+
 /**
  * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
  * @dst:   destination buffer