Re: [PATCH 1/6] genalloc: track beginning of allocations

[Randy Dunlap]

On 02/04/2018 08:47 AM, Igor Stoppa wrote:
> The genalloc library is only capable of tracking if a certain unit of
> allocation is in use or not.
> 
> It is not capable of discerning where the memory associated to an
> allocation request begins and where it ends.
> 
> The reason is that units of allocations are tracked by using a bitmap,
> where each bit represents that the unit is either allocated (1) or
> available (0).
> 
> The user of the API must keep track of how much space was requested, if
> it ever needs to be freed.
> 
> This can cause errors being undetected.
> Ex:
> * Only a subset of the memory provided to an allocation request is freed
> * The memory from a subsequent allocation is freed
> * The memory being freed doesn't start at the beginning of an
>   allocation.
> 
> The bitmap is used because it allows to perform lockless read/write
> access, where this is supported by hw through cmpxchg.
> Similarly, it is possible to scan the bitmap for a sufficiently long
> sequence of zeros, to identify zones available for allocation.
> 
> --
> 
> This patch doubles the space reserved in the bitmap for each allocation.
> By using 2 bits per allocation, it is possible to encode also the
> information of where the allocation starts:
> (msb to the left, lsb to the right, in the following "dictionary")
> 
> 11: first allocation unit in the allocation
> 10: any subsequent allocation unit (if any) in the allocation
> 00: available allocation unit
> 01: invalid
> 
> Ex, with the same notation as above - MSb.......LSb:
> 
>  ...000010111100000010101011   <-- Read in this direction.
>     \__|\__|\|\____|\______|
>        |   | |     |       \___ 4 used allocation units
>        |   | |     \___________ 3 empty allocation units
>        |   | \_________________ 1 used allocation unit
>        |   \___________________ 2 used allocation units
>        \_______________________ 2 empty allocation units
> 
> Because of the encoding, the previous lockless operations are still
> possible. The only caveat is to change the parameter of the zero-finding
> function which establishes the alignment at which to perform the test
> for first zero.
> The original value of the parameter is 0, meaning that an allocation can
> start at any point in the bitmap, while the new value is 1, meaning that
> allocations can start only at even places (bit 0, bit 2, etc.)
> The number of zeroes to look for, must therefore be doubled.
> 
> When it's time to free the memory associated to an allocation request,
> it's a matter of checking if the corresponding allocation unit is really
> the beginning of an allocation (both bits are set to 1).
> Looking for the ending can also be performed locklessly.
> It's sufficient to identify the first mapped allocation unit
> that is represented either as free (00) or busy (11).
> Even if the allocation status should change in the meanwhile, it doesn't
> matter, since it can only transition between free (00) and
> first-allocated (11).
> 
> The parameter indicating to the *_free() function the size of the space
> that should be freed is not currently removed, to facilitate the
> transition, but it is verified, whenever it is not zero.
> If it is set to zero, then the free function will autonomously decide the
> size to be free, by scanning the bitmap.
> 
> About the implementation: the patch introduces the concept of "bitmap
> entry", which has a 1:1 mapping with allocation units, while the code
> being patched has a 1:1 mapping between allocation units and bits.
> 
> This means that, now, the bitmap can be extended (by following powers of
> 2), to track also other properties of the allocations, if ever needed.

It would be good for a lot of this to be in a source file or the
pmalloc.rst documentation file instead of living only in the git repository.

> 
> Signed-off-by: Igor Stoppa <igor.stoppa@xxxxxxxxxx>
> ---
>  include/linux/genalloc.h |   4 +-
>  lib/genalloc.c           | 417 ++++++++++++++++++++++++++++++++---------------
>  2 files changed, 289 insertions(+), 132 deletions(-)
> 

> diff --git a/lib/genalloc.c b/lib/genalloc.c
> index ca06adc4f445..dde78307b093 100644
> --- a/lib/genalloc.c
> +++ b/lib/genalloc.c
> @@ -36,114 +36,221 @@
>  #include <linux/genalloc.h>
>  #include <linux/of_device.h>
>  
> +#define ENTRY_ORDER 1UL
> +#define ENTRY_MASK ((1UL << ((ENTRY_ORDER) + 1UL)) - 1UL)
> +#define ENTRY_HEAD ENTRY_MASK
> +#define ENTRY_UNUSED 0UL
> +#define BITS_PER_ENTRY (1U << ENTRY_ORDER)
> +#define BITS_DIV_ENTRIES(x) ((x) >> ENTRY_ORDER)
> +#define ENTRIES_TO_BITS(x) ((x) << ENTRY_ORDER)
> +#define BITS_DIV_LONGS(x) ((x) / BITS_PER_LONG)
> +#define ENTRIES_DIV_LONGS(x) (BITS_DIV_LONGS(ENTRIES_TO_BITS(x)))
> +
> +#define ENTRIES_PER_LONG BITS_DIV_ENTRIES(BITS_PER_LONG)
> +
> +/* Binary pattern of 1010...1010 that spans one unsigned long. */
> +#define MASK (~0UL / 3 * 2)
> +
> +/**
> + * get_bitmap_entry - extracts the specified entry from the bitmap
> + * @map: pointer to a bitmap
> + * @entry_index: the index of the desired entry in the bitmap
> + *
> + * Returns the requested bitmap.
> + */
> +static inline unsigned long get_bitmap_entry(unsigned long *map,
> +					    int entry_index)
> +{
> +	return (map[ENTRIES_DIV_LONGS(entry_index)] >>
> +		ENTRIES_TO_BITS(entry_index % ENTRIES_PER_LONG)) &
> +		ENTRY_MASK;
> +}
> +
> +
> +/**
> + * mem_to_units - convert references to memory into orders of allocation
> + * @size: amount in bytes
> + * @order: pow of 2 represented by each entry in the bitmap

              power

> + *
> + * Returns the number of units representing the size.
> + */
> +static inline unsigned long mem_to_units(unsigned long size,
> +					 unsigned long order)
> +{
> +	return (size + (1UL << order) - 1) >> order;
> +}
> +
> +/**
> + * chunk_size - dimension of a chunk of memory

can this be more explicit about which dimension?

> + * @chunk: pointer to the struct describing the chunk
> + *
> + * Returns the size of the chunk.
> + */
>  static inline size_t chunk_size(const struct gen_pool_chunk *chunk)
>  {
>  	return chunk->end_addr - chunk->start_addr + 1;
>  }
>  
> -static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
> +
> +/**
> + * set_bits_ll - according to the mask, sets the bits specified by
> + * value, at the address specified.
> + * @addr: where to write
> + * @mask: filter to apply for the bits to alter
> + * @value: actual configuration of bits to store
> + *
> + * Returns 0 upon success, -EBUSY otherwise
> + */
> +static int set_bits_ll(unsigned long *addr,
> +		       unsigned long mask, unsigned long value)
>  {
> -	unsigned long val, nval;
> +	unsigned long nval;
> +	unsigned long present;
> +	unsigned long target;
>  
>  	nval = *addr;
>  	do {
> -		val = nval;
> -		if (val & mask_to_set)
> +		present = nval;
> +		if (present & mask)
>  			return -EBUSY;
> +		target =  present | value;
>  		cpu_relax();
> -	} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
> -
> +	} while ((nval = cmpxchg(addr, present, target)) != target);
>  	return 0;
>  }
>  
> -static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
> +
> +/**
> + * cleart_bits_ll - according to the mask, clears the bits specified by

      clear_bits_ll

> + * value, at the address specified.
> + * @addr: where to write
> + * @mask: filter to apply for the bits to alter
> + * @value: actual configuration of bits to clear
> + *
> + * Returns 0 upon success, -EBUSY otherwise
> + */
> +static int clear_bits_ll(unsigned long *addr,
> +			 unsigned long mask, unsigned long value)
>  {
> -	unsigned long val, nval;
> +	unsigned long nval;
> +	unsigned long present;
> +	unsigned long target;
>  
>  	nval = *addr;
> +	present = nval;
> +	if (unlikely((present & mask) ^ value))
> +		return -EBUSY;
>  	do {
> -		val = nval;
> -		if ((val & mask_to_clear) != mask_to_clear)
> +		present = nval;
> +		if (unlikely((present & mask) ^ value))
>  			return -EBUSY;
> +		target =  present & ~mask;
>  		cpu_relax();
> -	} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
> -
> +	} while ((nval = cmpxchg(addr, present, target)) != target);
>  	return 0;
>  }
>  
> -/*
> - * bitmap_set_ll - set the specified number of bits at the specified position
> +
> +/**
> + * get_boundary - verify that an allocation effectively
> + * starts at the given address, then measure its length.
>   * @map: pointer to a bitmap
> - * @start: a bit position in @map
> - * @nr: number of bits to set
> + * @start_entry: the index of the first entry in the bitmap
> + * @nentries: number of entries to alter
>   *
> - * Set @nr bits start from @start in @map lock-lessly. Several user> - * can set/clear the same bitmap simultaneously without lock. If two
> - * users set the same bit, one user will return remain bits, otherwise
> - * return 0.
> + * Returns the length of an allocation, otherwise -EINVAL if the
> + * parameters do not refer to a correct allocation.
>   */
> -static int bitmap_set_ll(unsigned long *map, int start, int nr)
> +static int get_boundary(unsigned long *map, int start_entry, int nentries)
>  {
> -	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) {
> -		if (set_bits_ll(p, mask_to_set))
> -			return nr;
> -		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);
> -		if (set_bits_ll(p, mask_to_set))
> -			return nr;
> -	}
> +	int i;
> +	unsigned long bitmap_entry;
>  
> -	return 0;
> +
> +	if (unlikely(get_bitmap_entry(map, start_entry) != ENTRY_HEAD))
> +		return -EINVAL;
> +	for (i = start_entry + 1; i < nentries; i++) {
> +		bitmap_entry = get_bitmap_entry(map, i);
> +		if (bitmap_entry == ENTRY_HEAD ||
> +		    bitmap_entry == ENTRY_UNUSED)
> +			return i;
> +	}
> +	return nentries - start_entry;
>  }
>  
> +
> +#define SET_BITS 1
> +#define CLEAR_BITS 0
> +
>  /*
> - * bitmap_clear_ll - clear the specified number of bits at the specified position
> + * alter_bitmap_ll - set or clear the entries associated to an allocation

                                                            with an allocation

> + * @alteration: selection if the bits selected should be set or cleared

                   indicates if

>   * @map: pointer to a bitmap
> - * @start: a bit position in @map
> - * @nr: number of bits to set
> + * @start: the index of the first entry in the bitmap
> + * @nentries: number of entries to alter
>   *
> - * Clear @nr bits start from @start in @map lock-lessly. Several users
> - * can set/clear the same bitmap simultaneously without lock. If two
> - * users clear the same bit, one user will return remain bits,
> - * otherwise return 0.
> + * The modification happens lock-lessly.
> + * Several users can write to the same map simultaneously, without lock.
> + * If two users alter the same bit, one user will return remaining
> + * entries, otherwise return 0.
>   */
> -static int bitmap_clear_ll(unsigned long *map, int start, int nr)
> +static int alter_bitmap_ll(bool alteration, unsigned long *map,
> +			   int start_entry, int nentries)
>  {
> -	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) {
> -		if (clear_bits_ll(p, mask_to_clear))
> -			return nr;
> -		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);
> -		if (clear_bits_ll(p, mask_to_clear))
> -			return nr;
> +	unsigned long start_bit;
> +	unsigned long end_bit;
> +	unsigned long mask;
> +	unsigned long value;
> +	int nbits;
> +	int bits_to_write;
> +	int index;
> +	int (*action)(unsigned long *addr,
> +		      unsigned long mask, unsigned long value);
> +
> +	action = (alteration == SET_BITS) ? set_bits_ll : clear_bits_ll;
> +
> +	/* Prepare for writing the initial part of the allocation, from
> +	 * starting entry, to the end of the UL bitmap element which
> +	 * contains it. It might be larger than the actual allocation.
> +	 */

Use kernel multi-line comment style.

> +	start_bit = ENTRIES_TO_BITS(start_entry);
> +	end_bit = ENTRIES_TO_BITS(start_entry + nentries);
> +	nbits = ENTRIES_TO_BITS(nentries);
> +	bits_to_write = BITS_PER_LONG - start_bit % BITS_PER_LONG;
> +	mask = BITMAP_FIRST_WORD_MASK(start_bit);
> +	/* Mark the beginning of the allocation. */
> +	value = MASK | (1UL << (start_bit % BITS_PER_LONG));
> +	index =  BITS_DIV_LONGS(start_bit);

	index = BITS_DIV_LONGS
(only 1 space after '=')

> +
> +	/* Writes entries to the bitmap, as long as the reminder is
> +	 * positive or zero.
> +	 * Might be skipped if the entries to write do not reach the end
> +	 * of a bitmap UL unit.
> +	 */

Fix comment style, please.

> +	while (nbits >= bits_to_write) {
> +		if (action(map + index, mask, value & mask))
> +			return BITS_DIV_ENTRIES(nbits);
> +		nbits -= bits_to_write;
> +		bits_to_write = BITS_PER_LONG;
> +		mask = ~0UL;
> +		value = MASK;
> +		index++;
>  	}
>  
> +	/* Takes care of the ending part of the entries to mark. */
> +	if (nbits > 0) {
> +		mask ^= BITMAP_FIRST_WORD_MASK((end_bit) % BITS_PER_LONG);
> +		bits_to_write = nbits;
> +		if (action(map + index, mask, value & mask))
> +			return BITS_DIV_ENTRIES(nbits);
> +	}
>  	return 0;
>  }
>  
> +
>  /**
>   * gen_pool_create - create a new special memory pool
> - * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
> + * @min_alloc_order: log base 2 of number of bytes each bitmap entry represents
>   * @nid: node id of the node the pool structure should be allocated on, or -1
>   *
>   * Create a new special memory pool that can be used to manage special purpose
> @@ -183,10 +290,12 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
>  		 size_t size, int nid)
>  {
>  	struct gen_pool_chunk *chunk;
> -	int nbits = size >> pool->min_alloc_order;
> -	int nbytes = sizeof(struct gen_pool_chunk) +
> -				BITS_TO_LONGS(nbits) * sizeof(long);
> +	int nentries;
> +	int nbytes;
>  
> +	nentries = size >> pool->min_alloc_order;
> +	nbytes = sizeof(struct gen_pool_chunk) +
> +		 ENTRIES_DIV_LONGS(nentries) * sizeof(long);
>  	chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);
>  	if (unlikely(chunk == NULL))
>  		return -ENOMEM;
> @@ -248,7 +357,7 @@ void gen_pool_destroy(struct gen_pool *pool)
>  		list_del(&chunk->next_chunk);
>  
>  		end_bit = chunk_size(chunk) >> order;
> -		bit = find_next_bit(chunk->bits, end_bit, 0);
> +		bit = find_next_bit(chunk->entries, end_bit, 0);
>  		BUG_ON(bit < end_bit);
>  
>  		kfree(chunk);
> @@ -292,7 +401,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
>  	struct gen_pool_chunk *chunk;
>  	unsigned long addr = 0;
>  	int order = pool->min_alloc_order;
> -	int nbits, start_bit, end_bit, remain;
> +	int nentries, start_entry, end_entry, remain;
>  
>  #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	BUG_ON(in_nmi());
> @@ -301,29 +410,32 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
>  	if (size == 0)
>  		return 0;
>  
> -	nbits = (size + (1UL << order) - 1) >> order;
> +	nentries = mem_to_units(size, order);
>  	rcu_read_lock();
>  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
>  		if (size > atomic_long_read(&chunk->avail))
>  			continue;
>  
> -		start_bit = 0;
> -		end_bit = chunk_size(chunk) >> order;
> +		start_entry = 0;
> +		end_entry = chunk_size(chunk) >> order;
>  retry:
> -		start_bit = algo(chunk->bits, end_bit, start_bit,
> -				 nbits, data, pool);
> -		if (start_bit >= end_bit)
> +		start_entry = algo(chunk->entries, end_entry, start_entry,
> +				  nentries, data, pool);
> +		if (start_entry >= end_entry)
>  			continue;
> -		remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
> +		remain = alter_bitmap_ll(SET_BITS, chunk->entries,
> +					 start_entry, nentries);
>  		if (remain) {
> -			remain = bitmap_clear_ll(chunk->bits, start_bit,
> -						 nbits - remain);
> -			BUG_ON(remain);
> +			remain = alter_bitmap_ll(CLEAR_BITS,
> +						 chunk->entries,
> +						 start_entry,
> +						 nentries - remain);
>  			goto retry;
>  		}
>  
> -		addr = chunk->start_addr + ((unsigned long)start_bit << order);
> -		size = nbits << order;
> +		addr = chunk->start_addr +
> +			((unsigned long)start_entry << order);
> +		size = nentries << order;
>  		atomic_long_sub(size, &chunk->avail);
>  		break;
>  	}
> @@ -365,7 +477,7 @@ EXPORT_SYMBOL(gen_pool_dma_alloc);
>   * gen_pool_free - free allocated special memory back to the pool
>   * @pool: pool to free to
>   * @addr: starting address of memory to free back to pool
> - * @size: size in bytes of memory to free
> + * @size: size in bytes of memory to free or 0, for auto-detection
>   *
>   * Free previously allocated special memory back to the specified
>   * pool.  Can not be used in NMI handler on architectures without
> @@ -375,22 +487,29 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
>  {
>  	struct gen_pool_chunk *chunk;
>  	int order = pool->min_alloc_order;
> -	int start_bit, nbits, remain;
> +	int start_entry, remaining_entries, nentries, remain;
> +	int boundary;
>  
>  #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	BUG_ON(in_nmi());
>  #endif
>  
> -	nbits = (size + (1UL << order) - 1) >> order;
>  	rcu_read_lock();
>  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
>  		if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
>  			BUG_ON(addr + size - 1 > chunk->end_addr);
> -			start_bit = (addr - chunk->start_addr) >> order;
> -			remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
> +			start_entry = (addr - chunk->start_addr) >> order;
> +			remaining_entries = (chunk->end_addr - addr) >> order;
> +			boundary = get_boundary(chunk->entries, start_entry,
> +						remaining_entries);
> +			BUG_ON(boundary < 0);
> +			nentries = boundary - start_entry;
> +			BUG_ON(size &&
> +			       (nentries != mem_to_units(size, order)));
> +			remain = alter_bitmap_ll(CLEAR_BITS, chunk->entries,
> +						 start_entry, nentries);
>  			BUG_ON(remain);
> -			size = nbits << order;
> -			atomic_long_add(size, &chunk->avail);
> +			atomic_long_add(nentries << order, &chunk->avail);
>  			rcu_read_unlock();
>  			return;
>  		}
> @@ -517,9 +636,9 @@ EXPORT_SYMBOL(gen_pool_set_algo);
>   * gen_pool_first_fit - find the first available region
>   * of memory matching the size requirement (no alignment constraint)
>   * @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
> + * @size: The number of allocation units in the bitmap
> + * @start: The allocation unit to start searching at
> + * @nr: The number of allocation units we're looking for
>   * @data: additional data - unused
>   * @pool: pool to find the fit region memory from
>   */
> @@ -527,7 +646,15 @@ unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
>  		unsigned long start, unsigned int nr, void *data,
>  		struct gen_pool *pool)
>  {
> -	return bitmap_find_next_zero_area(map, size, start, nr, 0);
> +	unsigned long align_mask;
> +	unsigned long bit_index;
> +
> +	align_mask = roundup_pow_of_two(BITS_PER_ENTRY) - 1;
> +	bit_index = bitmap_find_next_zero_area(map, ENTRIES_TO_BITS(size),
> +					       ENTRIES_TO_BITS(start),
> +					       ENTRIES_TO_BITS(nr),
> +					       align_mask);
> +	return BITS_DIV_ENTRIES(bit_index);
>  }
>  EXPORT_SYMBOL(gen_pool_first_fit);
>  
> @@ -535,9 +662,9 @@ EXPORT_SYMBOL(gen_pool_first_fit);
>   * gen_pool_first_fit_align - find the first available region
>   * of memory matching the size requirement (alignment constraint)
>   * @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
> + * @size: The number of allocation units in the bitmap
> + * @start: The allocation unit to start searching at
> + * @nr: The number of allocation units we're looking for
>   * @data: data for alignment
>   * @pool: pool to get order from
>   */
> @@ -547,21 +674,28 @@ unsigned long gen_pool_first_fit_align(unsigned long *map, unsigned long size,
>  {
>  	struct genpool_data_align *alignment;
>  	unsigned long align_mask;
> +	unsigned long bit_index;
>  	int order;
>  
>  	alignment = data;
>  	order = pool->min_alloc_order;
> -	align_mask = ((alignment->align + (1UL << order) - 1) >> order) - 1;
> -	return bitmap_find_next_zero_area(map, size, start, nr, align_mask);
> +	align_mask = roundup_pow_of_two(
> +			ENTRIES_TO_BITS(mem_to_units(alignment->align,
> +						     order))) - 1;
> +	bit_index = bitmap_find_next_zero_area(map, ENTRIES_TO_BITS(size),
> +					       ENTRIES_TO_BITS(start),
> +					       ENTRIES_TO_BITS(nr),
> +					       align_mask);
> +	return BITS_DIV_ENTRIES(bit_index);
>  }
>  EXPORT_SYMBOL(gen_pool_first_fit_align);
>  
>  /**
>   * gen_pool_fixed_alloc - reserve a specific region
>   * @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
> + * @size: The number of allocation units in the bitmap
> + * @start: The allocation unit to start searching at
> + * @nr: The number of allocation units we're looking for
>   * @data: data for alignment
>   * @pool: pool to get order from
>   */
> @@ -571,20 +705,23 @@ unsigned long gen_pool_fixed_alloc(unsigned long *map, unsigned long size,
>  {
>  	struct genpool_data_fixed *fixed_data;
>  	int order;
> -	unsigned long offset_bit;
> -	unsigned long start_bit;
> +	unsigned long offset;
> +	unsigned long align_mask;
> +	unsigned long bit_index;
>  
>  	fixed_data = data;
>  	order = pool->min_alloc_order;
> -	offset_bit = fixed_data->offset >> order;
>  	if (WARN_ON(fixed_data->offset & ((1UL << order) - 1)))
>  		return size;
> +	offset = fixed_data->offset >> order;
> +	align_mask = roundup_pow_of_two(BITS_PER_ENTRY) - 1;
> +	bit_index = bitmap_find_next_zero_area(map, ENTRIES_TO_BITS(size),
> +					       ENTRIES_TO_BITS(start + offset),
> +					       ENTRIES_TO_BITS(nr), align_mask);
> +	if (bit_index != ENTRIES_TO_BITS(offset))
> +		return size;
>  
> -	start_bit = bitmap_find_next_zero_area(map, size,
> -			start + offset_bit, nr, 0);
> -	if (start_bit != offset_bit)
> -		start_bit = size;
> -	return start_bit;
> +	return BITS_DIV_ENTRIES(bit_index);
>  }
>  EXPORT_SYMBOL(gen_pool_fixed_alloc);
>  
> @@ -593,9 +730,9 @@ EXPORT_SYMBOL(gen_pool_fixed_alloc);
>   * of memory matching the size requirement. The region will be aligned
>   * to the order of the size specified.
>   * @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
> + * @size: The number of allocation units in the bitmap
> + * @start: The allocation unit to start searching at
> + * @nr: The number of allocation units we're looking for
>   * @data: additional data - unused
>   * @pool: pool to find the fit region memory from
>   */
> @@ -603,9 +740,15 @@ unsigned long gen_pool_first_fit_order_align(unsigned long *map,
>  		unsigned long size, unsigned long start,
>  		unsigned int nr, void *data, struct gen_pool *pool)
>  {
> -	unsigned long align_mask = roundup_pow_of_two(nr) - 1;
> -
> -	return bitmap_find_next_zero_area(map, size, start, nr, align_mask);
> +	unsigned long align_mask;
> +	unsigned long bit_index;
> +
> +	align_mask = roundup_pow_of_two(ENTRIES_TO_BITS(nr)) - 1;
> +	bit_index = bitmap_find_next_zero_area(map, ENTRIES_TO_BITS(size),
> +					       ENTRIES_TO_BITS(start),
> +					       ENTRIES_TO_BITS(nr),
> +					       align_mask);
> +	return BITS_DIV_ENTRIES(bit_index);
>  }
>  EXPORT_SYMBOL(gen_pool_first_fit_order_align);
>  
> @@ -613,9 +756,9 @@ EXPORT_SYMBOL(gen_pool_first_fit_order_align);
>   * gen_pool_best_fit - find the best fitting region of memory
>   * macthing the size requirement (no alignment constraint)

    * matching
(if you don't mind fixing that also)

>   * @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
> + * @size: The number of allocation units in the bitmap
> + * @start: The allocation unit to start searching at
> + * @nr: The number of allocation units we're looking for
>   * @data: additional data - unused
>   * @pool: pool to find the fit region memory from
>   *



-- 
~Randy