Re: [PATCH 1/6] genalloc: track beginning of allocations
From: Mike Rapoport
Date: Sun Feb 11 2018 - 07:25:09 EST
On Sun, Feb 11, 2018 at 05:19:15AM +0200, 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.
> Examples:
> * 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,
> to track their beginning.
>
> For details, see the documentation inside lib/genalloc.c
>
> Signed-off-by: Igor Stoppa <igor.stoppa@xxxxxxxxxx>
> ---
> include/linux/genalloc.h | 4 +-
> lib/genalloc.c | 527 ++++++++++++++++++++++++++++++++++-------------
> 2 files changed, 390 insertions(+), 141 deletions(-)
>
> diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
> index 872f930f1b06..dcaa33e74b1c 100644
> --- a/include/linux/genalloc.h
> +++ b/include/linux/genalloc.h
> @@ -32,7 +32,7 @@
>
> #include <linux/types.h>
> #include <linux/spinlock_types.h>
> -#include <linux/atomic.h>
> +#include <linux/slab.h>
>
> struct device;
> struct device_node;
> @@ -76,7 +76,7 @@ struct gen_pool_chunk {
> phys_addr_t phys_addr; /* physical starting address of memory chunk */
> unsigned long start_addr; /* start address of memory chunk */
> unsigned long end_addr; /* end address of memory chunk (inclusive) */
> - unsigned long bits[0]; /* bitmap for allocating memory chunk */
> + unsigned long entries[0]; /* bitmap for allocating memory chunk */
> };
>
> /*
> diff --git a/lib/genalloc.c b/lib/genalloc.c
> index ca06adc4f445..044347163acb 100644
> --- a/lib/genalloc.c
> +++ b/lib/genalloc.c
> @@ -26,6 +26,74 @@
> *
> * This source code is licensed under the GNU General Public License,
> * Version 2. See the file COPYING for more details.
> + *
> + *
> + *
> + * Encoding of the bitmap tracking the allocations
> + * -----------------------------------------------
> + *
> + * The bitmap is composed of units of allocations.
> + *
> + * Each unit of allocation is represented using 2 consecutive bits.
> + *
> + * This makes it possible to encode, for each unit of allocation,
> + * information about:
> + * - allocation status (busy/free)
> + * - beginning of a sequennce of allocation units (first / successive)
> + *
> + *
> + * Dictionary of allocation units (msb to the left, lsb to the right):
> + *
> + * 11: first allocation unit in the allocation
> + * 10: any subsequent allocation unit (if any) in the allocation
> + * 00: available allocation unit
> + * 01: invalid
> + *
> + * Example, using 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
> + *
> + * The encoding allows for lockless operations, such as:
> + * - search for a sufficiently large range of allocation units
> + * - reservation of a selected range of allocation units
> + * - release of a specific allocation
> + *
> + * The alignment at which to perform the research for sequence of empty
> + * allocation units (marked as zeros in the bitmap) is 2^1.
> + *
> + * This means that an allocation can start only at even places
> + * (bit 0, bit 2, etc.) in the bitmap.
> + *
> + * Therefore, the number of zeroes to look for must be twice the number
> + * of desired allocation units.
> + *
> + * 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 can be either set to 0, for automated
> + * assessment, or it can be specified explicitly.
> + *
> + * In case it is specified explicitly, the value is verified agaisnt what
> + * the library is tracking internally.
> + *
> + * If ever needed, the bitmap could be extended, assigning larger amounts
> + * of bits to each allocation unit (the increase must follow powers of 2),
> + * to track other properties of the allocations.
> */
>
> #include <linux/slab.h>
> @@ -36,118 +104,230 @@
> #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
> + *
> + * Return: 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
Documentation/doc-guide/kernel-doc.rst recommends to to include brackets
for function comments. I haven't noticed any difference in the resulting
html, so I'm not sure if the brackets are actually required.
> + * @size: amount in bytes
> + * @order: power of 2 represented by each entry in the bitmap
> + *
> + * Returns the number of units representing the size.
Please s/Return/Return:/
> + */
> +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, in bytes
> + * @chunk: pointer to the struct describing the chunk
> + *
> + * Return: The size of the chunk, in bytes.
> + */
> 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
> + *
> + * Return: 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)
> +
> +/**
> + * clear_bits_ll - according to the mask, clears 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 clear
> + *
> + * Return: 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 users
> - * 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.
> + * Return: 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 with an allocation
> + * @alteration: indicates if the bits selected should be set or cleared
> * @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
> + *
> + * The modification happens lock-lessly.
> + * Several users can write to the same map simultaneously, without lock.
> *
> - * 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.
> + * Return: If two users alter the same bit, to one it will return
> + * remaining entries, to the other it will return 0.
And what if there are three or four concurrent users? ;-)
I believe that a more elaborate description about what happens with
concurrent attempts to alter the bitmap would be really helpful.
> */
> -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.
> + */
> + 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);
> +
> + /*
> + * 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.
> + */
> + 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
> * memory not managed by the regular kmalloc/kfree interface.
> + *
> + * Return: pointer to the pool, if successful, NULL otherwise
> */
> struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
> {
> @@ -177,16 +357,18 @@ EXPORT_SYMBOL(gen_pool_create);
> *
> * Add a new chunk of special memory to the specified pool.
> *
> - * Returns 0 on success or a -ve errno on failure.
> + * Return: 0 on success or a -ve errno on failure.
> */
> int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
> 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;
> @@ -209,7 +391,7 @@ EXPORT_SYMBOL(gen_pool_add_virt);
> * @pool: pool to allocate from
> * @addr: starting address of memory
> *
> - * Returns the physical address on success, or -1 on error.
> + * Return: the physical address on success, or -1 on error.
> */
> phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
> {
> @@ -248,7 +430,7 @@ 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);
> @@ -267,6 +449,8 @@ EXPORT_SYMBOL(gen_pool_destroy);
> * Uses the pool allocation function (with first-fit algorithm by default).
> * Can not be used in NMI handler on architectures without
> * NMI-safe cmpxchg implementation.
> + *
> + * Return: address of the memory allocated, otherwise NULL
> */
> unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
> {
> @@ -285,6 +469,8 @@ EXPORT_SYMBOL(gen_pool_alloc);
> * Uses the pool allocation function (with first-fit algorithm by default).
> * Can not be used in NMI handler on architectures without
> * NMI-safe cmpxchg implementation.
> + *
> + * Return: address of the memory allocated, otherwise NULL
> */
> unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
> genpool_algo_t algo, void *data)
> @@ -292,7 +478,7 @@ 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 +487,32 @@ 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;
> }
> @@ -342,6 +531,8 @@ EXPORT_SYMBOL(gen_pool_alloc_algo);
> * Uses the pool allocation function (with first-fit algorithm by default).
> * Can not be used in NMI handler on architectures without
> * NMI-safe cmpxchg implementation.
> + *
> + * Return: address of the memory allocated, otherwise NULL
> */
> void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size, dma_addr_t *dma)
> {
> @@ -365,7 +556,7 @@ 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 +566,29 @@ 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;
> }
> @@ -428,8 +626,9 @@ EXPORT_SYMBOL(gen_pool_for_each_chunk);
> * @start: start address
> * @size: size of the region
> *
> - * Check if the range of addresses falls within the specified pool. Returns
> - * true if the entire range is contained in the pool and false otherwise.
> + * Check if the range of addresses falls within the specified pool.
> + *
> + * Return: true if the entire range is contained in the pool, false otherwise.
> */
> bool addr_in_gen_pool(struct gen_pool *pool, unsigned long start,
> size_t size)
> @@ -455,7 +654,7 @@ bool addr_in_gen_pool(struct gen_pool *pool, unsigned long start,
> * gen_pool_avail - get available free space of the pool
> * @pool: pool to get available free space
> *
> - * Return available free space of the specified pool.
> + * Return: available free space of the specified pool.
> */
> size_t gen_pool_avail(struct gen_pool *pool)
> {
> @@ -474,7 +673,7 @@ EXPORT_SYMBOL_GPL(gen_pool_avail);
> * gen_pool_size - get size in bytes of memory managed by the pool
> * @pool: pool to get size
> *
> - * Return size in bytes of memory managed by the pool.
> + * Return: size in bytes of memory managed by the pool.
> */
> size_t gen_pool_size(struct gen_pool *pool)
> {
> @@ -517,17 +716,27 @@ 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
> + *
> + * Return: index of the memory allocated, otherwise the end of the range
> */
> 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);
>
> @@ -535,11 +744,13 @@ 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
> + *
> + * Return: index of the memory allocated, otherwise the end of the range
> */
> unsigned long gen_pool_first_fit_align(unsigned long *map, unsigned long size,
> unsigned long start, unsigned int nr, void *data,
> @@ -547,23 +758,32 @@ 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
> + *
> + * Return: index of the memory allocated, otherwise the end of the range
> */
> unsigned long gen_pool_fixed_alloc(unsigned long *map, unsigned long size,
> unsigned long start, unsigned int nr, void *data,
> @@ -571,20 +791,23 @@ 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);
>
> @@ -593,60 +816,84 @@ 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
> + *
> + * Return: index of the memory allocated, otherwise the end of the range
> */
> 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);
>
> /**
> * gen_pool_best_fit - find the best fitting region of memory
> - * macthing the size requirement (no alignment constraint)
> + * 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
> *
> * Iterate over the bitmap to find the smallest free region
> * which we can allocate the memory.
> + *
> + * Return: index of the memory allocated, otherwise the end of the range
> */
> unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
> unsigned long start, unsigned int nr, void *data,
> struct gen_pool *pool)
> {
> - unsigned long start_bit = size;
> + unsigned long start_bit = ENTRIES_TO_BITS(size);
> unsigned long len = size + 1;
> unsigned long index;
> + unsigned long align_mask;
> + unsigned long bit_index;
>
> - index = bitmap_find_next_zero_area(map, size, start, nr, 0);
> + 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);
> + index = BITS_DIV_ENTRIES(bit_index);
>
> while (index < size) {
> - int next_bit = find_next_bit(map, size, index + nr);
> - if ((next_bit - index) < len) {
> - len = next_bit - index;
> - start_bit = index;
> + int next_bit;
> +
> + next_bit = find_next_bit(map, ENTRIES_TO_BITS(size),
> + ENTRIES_TO_BITS(index + nr));
> + if ((BITS_DIV_ENTRIES(next_bit) - index) < len) {
> + len = BITS_DIV_ENTRIES(next_bit) - index;
> + start_bit = ENTRIES_TO_BITS(index);
> if (len == nr)
> - return start_bit;
> + return BITS_DIV_ENTRIES(start_bit);
> }
> - index = bitmap_find_next_zero_area(map, size,
> - next_bit + 1, nr, 0);
> + bit_index =
> + bitmap_find_next_zero_area(map,
> + ENTRIES_TO_BITS(size),
> + next_bit + 1,
> + ENTRIES_TO_BITS(nr),
> + align_mask);
> + index = BITS_DIV_ENTRIES(bit_index);
> }
>
> - return start_bit;
> + return BITS_DIV_ENTRIES(start_bit);
> }
> -EXPORT_SYMBOL(gen_pool_best_fit);
>
> static void devm_gen_pool_release(struct device *dev, void *res)
> {
> @@ -672,7 +919,7 @@ static int devm_gen_pool_match(struct device *dev, void *res, void *data)
> * @dev: device to retrieve the gen_pool from
> * @name: name of a gen_pool or NULL, identifies a particular gen_pool on device
> *
> - * Returns the gen_pool for the device if one is present, or NULL.
> + * Return: the gen_pool for the device if one is present, or NULL.
> */
> struct gen_pool *gen_pool_get(struct device *dev, const char *name)
> {
> @@ -696,6 +943,8 @@ EXPORT_SYMBOL_GPL(gen_pool_get);
> * Create a new special memory pool that can be used to manage special purpose
> * memory not managed by the regular kmalloc/kfree interface. The pool will be
> * automatically destroyed by the device management code.
> + *
> + * Return: the address of the pool, if successful, otherwise NULL
> */
> struct gen_pool *devm_gen_pool_create(struct device *dev, int min_alloc_order,
> int nid, const char *name)
> @@ -743,7 +992,7 @@ EXPORT_SYMBOL(devm_gen_pool_create);
> * @propname: property name containing phandle(s)
> * @index: index into the phandle array
> *
> - * Returns the pool that contains the chunk starting at the physical
> + * Return: the pool that contains the chunk starting at the physical
> * address of the device tree node pointed at by the phandle property,
> * or NULL if not found.
> */
> --
> 2.14.1
>
> --
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>
>
--
Sincerely yours,
Mike.