diff options
Diffstat (limited to 'lib/bitmap.c')
| -rw-r--r-- | lib/bitmap.c | 64 |
1 files changed, 38 insertions, 26 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c index 48e708381d44..3fab1ce9ac65 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -677,39 +677,38 @@ int bitmap_bitremap(int oldbit, const unsigned long *old, EXPORT_SYMBOL(bitmap_bitremap); /** - * bitmap_find_free_region - find a contiguous aligned mem region + * bitmap_find_free_region - find a contiguous aligned mem region * @bitmap: an array of unsigned longs corresponding to the bitmap * @bits: number of bits in the bitmap * @order: region size to find (size is actually 1<<order) * - * This is used to allocate a memory region from a bitmap. The idea is - * that the region has to be 1<<order sized and 1<<order aligned (this - * makes the search algorithm much faster). + * Find a sequence of free (zero) bits in a bitmap and allocate + * them (set them to one). Only consider sequences of length a + * power ('order') of two, aligned to that power of two, which + * makes the search algorithm much faster. * - * The region is marked as set bits in the bitmap if a free one is - * found. - * - * Returns either beginning of region or negative error + * Return the bit offset in bitmap of the allocated sequence, + * or -errno on failure. */ int bitmap_find_free_region(unsigned long *bitmap, int bits, int order) { unsigned long mask; - int pages = 1 << order; + int nbits = 1 << order; int i; - if(pages > BITS_PER_LONG) + if (nbits > BITS_PER_LONG) return -EINVAL; /* make a mask of the order */ - mask = (1ul << (pages - 1)); + mask = (1UL << (nbits - 1)); mask += mask - 1; - /* run up the bitmap pages bits at a time */ - for (i = 0; i < bits; i += pages) { - int index = i/BITS_PER_LONG; + /* run up the bitmap nbits at a time */ + for (i = 0; i < bits; i += nbits) { + int index = i / BITS_PER_LONG; int offset = i - (index * BITS_PER_LONG); - if((bitmap[index] & (mask << offset)) == 0) { - /* set region in bimap */ + if ((bitmap[index] & (mask << offset)) == 0) { + /* set region in bitmap */ bitmap[index] |= (mask << offset); return i; } @@ -719,7 +718,7 @@ int bitmap_find_free_region(unsigned long *bitmap, int bits, int order) EXPORT_SYMBOL(bitmap_find_free_region); /** - * bitmap_release_region - release allocated bitmap region + * bitmap_release_region - release allocated bitmap region * @bitmap: a pointer to the bitmap * @pos: the beginning of the region * @order: the order of the bits to release (number is 1<<order) @@ -729,27 +728,40 @@ EXPORT_SYMBOL(bitmap_find_free_region); */ void bitmap_release_region(unsigned long *bitmap, int pos, int order) { - int pages = 1 << order; - unsigned long mask = (1ul << (pages - 1)); - int index = pos/BITS_PER_LONG; + int nbits = 1 << order; + unsigned long mask = (1UL << (nbits - 1)); + int index = pos / BITS_PER_LONG; int offset = pos - (index * BITS_PER_LONG); + mask += mask - 1; bitmap[index] &= ~(mask << offset); } EXPORT_SYMBOL(bitmap_release_region); +/** + * bitmap_allocate_region - allocate bitmap region + * @bitmap: a pointer to the bitmap + * @pos: the beginning of the region + * @order: the order of the bits to allocate (number is 1<<order) + * + * Allocate (set bits in) a specified region of a bitmap. + * Return 0 on success, or -EBUSY if specified region wasn't + * free (not all bits were zero). + */ int bitmap_allocate_region(unsigned long *bitmap, int pos, int order) { - int pages = 1 << order; - unsigned long mask = (1ul << (pages - 1)); - int index = pos/BITS_PER_LONG; + int nbits = 1 << order; + unsigned long mask = (1UL << (nbits - 1)); + int index = pos / BITS_PER_LONG; int offset = pos - (index * BITS_PER_LONG); - /* We don't do regions of pages > BITS_PER_LONG. The + /* + * We don't do regions of nbits > BITS_PER_LONG. The * algorithm would be a simple look for multiple zeros in the * array, but there's no driver today that needs this. If you - * trip this BUG(), you get to code it... */ - BUG_ON(pages > BITS_PER_LONG); + * trip this BUG(), you get to code it... + */ + BUG_ON(nbits > BITS_PER_LONG); mask += mask - 1; if (bitmap[index] & (mask << offset)) return -EBUSY; |