#define BLOCKS_PER_UNIT (1U << UNIT_SHIFT)
#define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1)
-#define firstfree_valid(b) ((b)->first_free != (uint64_t) -1)
-
static const unsigned long bit_masks[] = {
0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007,
0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f,
#endif
};
+/**
+ * struct axmap_level - a bitmap used to implement struct axmap
+ * @level: Level index. Each map has at least one level with index zero. The
+ * higher the level index, the fewer bits a struct axmap_level contains.
+ * @map_size: Number of elements of the @map array.
+ * @map: A bitmap with @map_size elements.
+ */
struct axmap_level {
int level;
unsigned long map_size;
unsigned long *map;
};
+/**
+ * struct axmap - a set that can store numbers 0 .. @nr_bits - 1
+ * @nr_level: Number of elements of the @levels array.
+ * @levels: struct axmap_level array in which lower levels contain more bits
+ * than higher levels.
+ * @nr_bits: One more than the highest value stored in the set.
+ */
struct axmap {
unsigned int nr_levels;
struct axmap_level *levels;
- uint64_t first_free;
uint64_t nr_bits;
};
return val;
}
+/* Remove all elements from the @axmap set */
void axmap_reset(struct axmap *axmap)
{
int i;
memset(al->map, 0, al->map_size * sizeof(unsigned long));
}
-
- axmap->first_free = 0;
}
void axmap_free(struct axmap *axmap)
free(axmap);
}
+/* Allocate memory for a set that can store the numbers 0 .. @nr_bits - 1. */
struct axmap *axmap_new(unsigned long nr_bits)
{
struct axmap *axmap;
return NULL;
}
+/*
+ * Call @func for each level, starting at level zero, until a level is found
+ * for which @func returns true. Return false if none of the @func calls
+ * returns true.
+ */
static bool axmap_handler(struct axmap *axmap, uint64_t bit_nr,
bool (*func)(struct axmap_level *, unsigned long, unsigned int,
void *), void *data)
return false;
}
+/*
+ * Call @func for each level, starting at the highest level, until a level is
+ * found for which @func returns true. Return false if none of the @func calls
+ * returns true.
+ */
static bool axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr,
bool (*func)(struct axmap_level *, unsigned long, unsigned int, void *))
{
return false;
}
-static bool axmap_clear_fn(struct axmap_level *al, unsigned long offset,
- unsigned int bit, void *unused)
-{
- if (!(al->map[offset] & (1UL << bit)))
- return true;
-
- al->map[offset] &= ~(1UL << bit);
- return false;
-}
-
-void axmap_clear(struct axmap *axmap, uint64_t bit_nr)
-{
- axmap_handler(axmap, bit_nr, axmap_clear_fn, NULL);
-
- if (bit_nr < axmap->first_free)
- axmap->first_free = bit_nr;
-}
-
struct axmap_set_data {
unsigned int nr_bits;
unsigned int set_bits;
};
+/*
+ * Set at most @__data->nr_bits bits in @al at offset @offset. Do not exceed
+ * the boundary of the element at offset @offset. Return the number of bits
+ * that have been set in @__data->set_bits if @al->level == 0.
+ */
static bool axmap_set_fn(struct axmap_level *al, unsigned long offset,
unsigned int bit, void *__data)
{
if (!al->level)
data->set_bits = nr_bits;
+ /* For the next level */
data->nr_bits = 1;
+
return al->map[offset] != -1UL;
}
+/*
+ * Set up to @data->nr_bits starting from @bit_nr in @axmap. Start at
+ * @bit_nr. If that bit has not yet been set then set it and continue until
+ * either @data->nr_bits have been set or a 1 bit is found. Store the number
+ * of bits that have been set in @data->set_bits. It is guaranteed that all
+ * bits that have been requested to set fit in the same unsigned long word of
+ * level 0 of @axmap.
+ */
static void __axmap_set(struct axmap *axmap, uint64_t bit_nr,
struct axmap_set_data *data)
{
unsigned int set_bits, nr_bits = data->nr_bits;
- if (axmap->first_free >= bit_nr &&
- axmap->first_free < bit_nr + data->nr_bits)
- axmap->first_free = -1ULL;
-
if (bit_nr > axmap->nr_bits)
return;
else if (bit_nr + nr_bits > axmap->nr_bits)
__axmap_set(axmap, bit_nr, &data);
}
+/*
+ * Set up to @nr_bits starting from @bit in @axmap. Start at @bit. If that
+ * bit has not yet been set then set it and continue until either @nr_bits
+ * have been set or a 1 bit is found. Return the number of bits that have been
+ * set.
+ */
unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr,
unsigned int nr_bits)
{
return false;
}
-static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
- uint64_t index)
+/*
+ * Find the first free bit that is at least as large as bit_nr. Return
+ * -1 if no free bit is found before the end of the map.
+ */
+static uint64_t axmap_find_first_free(struct axmap *axmap, uint64_t bit_nr)
{
- uint64_t ret = -1ULL;
- unsigned long j;
int i;
+ unsigned long temp;
+ unsigned int bit;
+ uint64_t offset, base_index, index;
+ struct axmap_level *al;
- /*
- * Start at the bottom, then converge towards first free bit at the top
- */
- for (i = level; i >= 0; i--) {
- struct axmap_level *al = &axmap->levels[i];
-
- if (index >= al->map_size)
- goto err;
-
- for (j = index; j < al->map_size; j++) {
- if (al->map[j] == -1UL)
- continue;
+ index = 0;
+ for (i = axmap->nr_levels - 1; i >= 0; i--) {
+ al = &axmap->levels[i];
- /*
- * First free bit here is our index into the first
- * free bit at the next higher level
- */
- ret = index = (j << UNIT_SHIFT) + ffz(al->map[j]);
- break;
+ /* Shift previously calculated index for next level */
+ index <<= UNIT_SHIFT;
+
+ /*
+ * Start from an index that's at least as large as the
+ * originally passed in bit number.
+ */
+ base_index = bit_nr >> (UNIT_SHIFT * i);
+ if (index < base_index)
+ index = base_index;
+
+ /* Get the offset and bit for this level */
+ offset = index >> UNIT_SHIFT;
+ bit = index & BLOCKS_PER_UNIT_MASK;
+
+ /*
+ * If the previous level had unused bits in its last
+ * word, the offset could be bigger than the map at
+ * this level. That means no free bits exist before the
+ * end of the map, so return -1.
+ */
+ if (offset >= al->map_size)
+ return -1ULL;
+
+ /* Check the first word starting with the specific bit */
+ temp = ~bit_masks[bit] & ~al->map[offset];
+ if (temp)
+ goto found;
+
+ /*
+ * No free bit in the first word, so iterate
+ * looking for a word with one or more free bits.
+ */
+ for (offset++; offset < al->map_size; offset++) {
+ temp = ~al->map[offset];
+ if (temp)
+ goto found;
}
- }
- if (ret < axmap->nr_bits)
- return ret;
+ /* Did not find a free bit */
+ return -1ULL;
-err:
- return (uint64_t) -1ULL;
-}
-
-static uint64_t axmap_first_free(struct axmap *axmap)
-{
- if (!firstfree_valid(axmap))
- axmap->first_free = axmap_find_first_free(axmap, axmap->nr_levels - 1, 0);
-
- return axmap->first_free;
-}
-
-struct axmap_next_free_data {
- unsigned int level;
- unsigned long offset;
- uint64_t bit;
-};
-
-static bool axmap_next_free_fn(struct axmap_level *al, unsigned long offset,
- unsigned int bit, void *__data)
-{
- struct axmap_next_free_data *data = __data;
- uint64_t mask = ~bit_masks[(data->bit + 1) & BLOCKS_PER_UNIT_MASK];
-
- if (!(mask & ~al->map[offset]))
- return false;
-
- if (al->map[offset] != -1UL) {
- data->level = al->level;
- data->offset = offset;
- return true;
+found:
+ /* Compute the index of the free bit just found */
+ index = (offset << UNIT_SHIFT) + ffz(~temp);
}
- data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
- return false;
+ /* If found an unused bit in the last word of level 0, return -1 */
+ if (index >= axmap->nr_bits)
+ return -1ULL;
+
+ return index;
}
/*
* 'bit_nr' is already set. Find the next free bit after this one.
+ * Return -1 if no free bits found.
*/
uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
{
- struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
uint64_t ret;
+ uint64_t next_bit = bit_nr + 1;
+ unsigned long temp;
+ uint64_t offset;
+ unsigned int bit;
- if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
- return axmap->first_free;
+ if (bit_nr >= axmap->nr_bits)
+ return -1ULL;
- if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
- return axmap_first_free(axmap);
+ /* If at the end of the map, wrap-around */
+ if (next_bit == axmap->nr_bits)
+ next_bit = 0;
- assert(data.level != -1U);
+ offset = next_bit >> UNIT_SHIFT;
+ bit = next_bit & BLOCKS_PER_UNIT_MASK;
/*
- * In the rare case that the map is unaligned, we might end up
- * finding an offset that's beyond the valid end. For that case,
- * find the first free one, the map is practically full.
+ * As an optimization, do a quick check for a free bit
+ * in the current word at level 0. If not found, do
+ * a topdown search.
*/
- ret = axmap_find_first_free(axmap, data.level, data.offset);
- if (ret != -1ULL)
- return ret;
+ temp = ~bit_masks[bit] & ~axmap->levels[0].map[offset];
+ if (temp) {
+ ret = (offset << UNIT_SHIFT) + ffz(~temp);
- return axmap_first_free(axmap);
+ /* Might have found an unused bit at level 0 */
+ if (ret >= axmap->nr_bits)
+ ret = -1ULL;
+ } else
+ ret = axmap_find_first_free(axmap, next_bit);
+
+ /*
+ * If there are no free bits starting at next_bit and going
+ * to the end of the map, wrap around by searching again
+ * starting at bit 0.
+ */
+ if (ret == -1ULL && next_bit != 0)
+ ret = axmap_find_first_free(axmap, 0);
+ return ret;
}
projects / fio.git / blobdiff