+/*
+ * Bitmap of bitmaps, where each layer is number-of-bits-per-word smaller than
+ * the previous. Hence an 'axmap', since we axe each previous layer into a
+ * much smaller piece. I swear, that is why it's named like that. It has
+ * nothing to do with anything remotely narcissistic.
+ *
+ * A set bit at layer N indicates a full word at layer N-1, and so forth. As
+ * the bitmap becomes progressively more full, checking for existance
+ * becomes cheaper (since fewer layers are walked, making it a lot more
+ * cache friendly) and locating the next free space likewise.
+ *
+ * Axmaps get pretty close to optimal (1 bit per block) space usage, since
+ * layers quickly diminish in size. Doing the size math is straight forward,
+ * since we have log64(blocks) layers of maps. For 20000 blocks, overhead
+ * is roughly 1.9%, or 1.019 bits per block. The number quickly converges
+ * towards 1.0158, or 1.58% of overhead.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "../arch/arch.h"
+#include "axmap.h"
+#include "../smalloc.h"
+#include "../minmax.h"
+
+#if BITS_PER_LONG == 64
+#define UNIT_SHIFT 6
+#elif BITS_PER_LONG == 32
+#define UNIT_SHIFT 5
+#else
+#error "Number of arch bits unknown"
+#endif
+
+#define BLOCKS_PER_UNIT (1UL << UNIT_SHIFT)
+#define BLOCKS_PER_UNIT_MASK (BLOCKS_PER_UNIT - 1)
+
+#define firstfree_valid(b) ((b)->first_free != (uint64_t) -1)
+
+struct axmap_level {
+ int level;
+ unsigned long map_size;
+ unsigned long *map;
+};
+
+struct axmap {
+ unsigned int nr_levels;
+ struct axmap_level *levels;
+ uint64_t first_free;
+};
+
+static unsigned long ulog64(unsigned long val, unsigned int log)
+{
+ while (log-- && val)
+ val >>= UNIT_SHIFT;
+
+ return val;
+}
+
+void axmap_reset(struct axmap *axmap)
+{
+ int i;
+
+ for (i = 0; i < axmap->nr_levels; i++) {
+ struct axmap_level *al = &axmap->levels[i];
+
+ memset(al->map, 0, al->map_size * sizeof(unsigned long));
+ }
+}
+
+void axmap_free(struct axmap *axmap)
+{
+ unsigned int i;
+
+ if (!axmap)
+ return;
+
+ for (i = 0; i < axmap->nr_levels; i++)
+ sfree(axmap->levels[i].map);
+
+ sfree(axmap->levels);
+ sfree(axmap);
+}
+
+struct axmap *axmap_new(unsigned long nr_bits)
+{
+ struct axmap *axmap;
+ unsigned int i, levels;
+
+ axmap = smalloc(sizeof(*axmap));
+ if (!axmap)
+ return NULL;
+
+ levels = 1;
+ i = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
+ while (i > 1) {
+ i = (i + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
+ levels++;
+ }
+
+ axmap->nr_levels = levels;
+ axmap->levels = smalloc(axmap->nr_levels * sizeof(struct axmap_level));
+ axmap->first_free = 0;
+
+ for (i = 0; i < axmap->nr_levels; i++) {
+ struct axmap_level *al = &axmap->levels[i];
+
+ al->level = i;
+ al->map_size = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
+ al->map = smalloc(al->map_size * sizeof(unsigned long));
+ if (!al->map)
+ goto err;
+
+ nr_bits = (nr_bits + BLOCKS_PER_UNIT - 1) >> UNIT_SHIFT;
+ }
+
+ axmap_reset(axmap);
+ return axmap;
+err:
+ for (i = 0; i < axmap->nr_levels; i++)
+ if (axmap->levels[i].map)
+ sfree(axmap->levels[i].map);
+
+ sfree(axmap->levels);
+ return NULL;
+}
+
+static int axmap_handler(struct axmap *axmap, uint64_t bit_nr,
+ int (*func)(struct axmap_level *, unsigned long, unsigned int,
+ void *), void *data)
+{
+ struct axmap_level *al;
+ int i;
+
+ for (i = 0; i < axmap->nr_levels; i++) {
+ unsigned long index = ulog64(bit_nr, i);
+ unsigned long offset = index >> UNIT_SHIFT;
+ unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
+
+ al = &axmap->levels[i];
+
+ if (func(al, offset, bit, data))
+ return 1;
+ }
+
+ return 0;
+}
+
+static int axmap_handler_topdown(struct axmap *axmap, uint64_t bit_nr,
+ int (*func)(struct axmap_level *, unsigned long, unsigned int, void *),
+ void *data)
+{
+ struct axmap_level *al;
+ int i, level = axmap->nr_levels;
+
+ for (i = axmap->nr_levels - 1; i >= 0; i--) {
+ unsigned long index = ulog64(bit_nr, --level);
+ unsigned long offset = index >> UNIT_SHIFT;
+ unsigned int bit = index & BLOCKS_PER_UNIT_MASK;
+
+ al = &axmap->levels[i];
+
+ if (func(al, offset, bit, data))
+ return 1;
+ }
+
+ return 0;
+}
+
+static int axmap_clear_fn(struct axmap_level *al, unsigned long offset,
+ unsigned int bit, void *unused)
+{
+ if (!(al->map[offset] & (1UL << bit)))
+ return 1;
+
+ al->map[offset] &= ~(1UL << bit);
+ return 0;
+}
+
+void axmap_clear(struct axmap *axmap, uint64_t bit_nr)
+{
+ axmap_handler(axmap, bit_nr, axmap_clear_fn, NULL);
+}
+
+struct axmap_set_data {
+ unsigned int nr_bits;
+ unsigned int set_bits;
+ unsigned int fail_ok;
+};
+
+static unsigned long bit_masks[] = {
+ 0x0000000000000000, 0x0000000000000001, 0x0000000000000003, 0x0000000000000007,
+ 0x000000000000000f, 0x000000000000001f, 0x000000000000003f, 0x000000000000007f,
+ 0x00000000000000ff, 0x00000000000001ff, 0x00000000000003ff, 0x00000000000007ff,
+ 0x0000000000000fff, 0x0000000000001fff, 0x0000000000003fff, 0x0000000000007fff,
+ 0x000000000000ffff, 0x000000000001ffff, 0x000000000003ffff, 0x000000000007ffff,
+ 0x00000000000fffff, 0x00000000001fffff, 0x00000000003fffff, 0x00000000007fffff,
+ 0x0000000000ffffff, 0x0000000001ffffff, 0x0000000003ffffff, 0x0000000007ffffff,
+ 0x000000000fffffff, 0x000000001fffffff, 0x000000003fffffff, 0x000000007fffffff,
+ 0x00000000ffffffff,
+#if BITS_PER_LONG == 64
+ 0x00000001ffffffff, 0x00000003ffffffff, 0x00000007ffffffff, 0x0000000fffffffff,
+ 0x0000001fffffffff, 0x0000003fffffffff, 0x0000007fffffffff, 0x000000ffffffffff,
+ 0x000001ffffffffff, 0x000003ffffffffff, 0x000007ffffffffff, 0x00000fffffffffff,
+ 0x00001fffffffffff, 0x00003fffffffffff, 0x00007fffffffffff, 0x0000ffffffffffff,
+ 0x0001ffffffffffff, 0x0003ffffffffffff, 0x0007ffffffffffff, 0x000fffffffffffff,
+ 0x001fffffffffffff, 0x003fffffffffffff, 0x007fffffffffffff, 0x00ffffffffffffff,
+ 0x01ffffffffffffff, 0x03ffffffffffffff, 0x07ffffffffffffff, 0x0fffffffffffffff,
+ 0x1fffffffffffffff, 0x3fffffffffffffff, 0x7fffffffffffffff, 0xffffffffffffffff
+#endif
+};
+
+static int axmap_set_fn(struct axmap_level *al, unsigned long offset,
+ unsigned int bit, void *__data)
+{
+ struct axmap_set_data *data = __data;
+ unsigned long mask, overlap;
+ unsigned int nr_bits;
+
+ nr_bits = min(data->nr_bits, BLOCKS_PER_UNIT - bit);
+
+ mask = bit_masks[nr_bits] << bit;
+
+ /*
+ * Mask off any potential overlap, only sets contig regions
+ */
+ overlap = al->map[offset] & mask;
+ if (overlap == mask) {
+ assert(data->fail_ok);
+ return 1;
+ }
+
+ while (overlap) {
+ unsigned long clear_mask = ~(1UL << ffz(~overlap));
+
+ mask &= clear_mask;
+ overlap &= clear_mask;
+ nr_bits--;
+ }
+
+ assert(mask);
+ assert(!(al->map[offset] & mask));
+
+ al->map[offset] |= mask;
+
+ if (!al->level)
+ data->set_bits = nr_bits;
+
+ data->nr_bits = 1;
+ return al->map[offset] != -1UL;
+}
+
+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;
+
+ set_bits = 0;
+ while (nr_bits) {
+ axmap_handler(axmap, bit_nr, axmap_set_fn, data);
+ set_bits += data->set_bits;
+
+ if (data->set_bits != (BLOCKS_PER_UNIT - nr_bits))
+ break;
+
+ nr_bits -= data->set_bits;
+ bit_nr += data->set_bits;
+
+ data->nr_bits = nr_bits;
+ data->fail_ok = 1;
+ }
+
+ data->set_bits = set_bits;
+}
+
+void axmap_set(struct axmap *axmap, uint64_t bit_nr)
+{
+ struct axmap_set_data data = { .nr_bits = 1, };
+
+ __axmap_set(axmap, bit_nr, &data);
+}
+
+unsigned int axmap_set_nr(struct axmap *axmap, uint64_t bit_nr, unsigned int nr_bits)
+{
+ struct axmap_set_data data = { .nr_bits = nr_bits, };
+
+ __axmap_set(axmap, bit_nr, &data);
+ return data.set_bits;
+}
+
+static int axmap_isset_fn(struct axmap_level *al, unsigned long offset,
+ unsigned int bit, void *unused)
+{
+ return (al->map[offset] & (1UL << bit)) != 0;
+}
+
+int axmap_isset(struct axmap *axmap, uint64_t bit_nr)
+{
+ return axmap_handler_topdown(axmap, bit_nr, axmap_isset_fn, NULL);
+}
+
+static uint64_t axmap_find_first_free(struct axmap *axmap, unsigned int level,
+ uint64_t index)
+{
+ unsigned long j;
+ int i;
+
+ /*
+ * 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) {
+ index = -1ULL;
+ break;
+ }
+
+ for (j = index; j < al->map_size; j++) {
+ if (al->map[j] == -1UL)
+ continue;
+
+ /*
+ * First free bit here is our index into the first
+ * free bit at the next higher level
+ */
+ index = (j << UNIT_SHIFT) + ffz(al->map[j]);
+ break;
+ }
+ }
+
+ return index;
+}
+
+uint64_t axmap_first_free(struct axmap *axmap)
+{
+ if (firstfree_valid(axmap))
+ return axmap->first_free;
+
+ 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 int 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 = ~((1UL << ((data->bit & BLOCKS_PER_UNIT_MASK) + 1)) - 1);
+
+ if (!(mask & al->map[offset]))
+ return 0;
+
+ if (al->map[offset] != -1UL) {
+ data->level = al->level;
+ data->offset = offset;
+ return 1;
+ }
+
+ data->bit = (data->bit + BLOCKS_PER_UNIT - 1) / BLOCKS_PER_UNIT;
+ return 0;
+}
+
+/*
+ * 'bit_nr' is already set. Find the next free bit after this one.
+ */
+uint64_t axmap_next_free(struct axmap *axmap, uint64_t bit_nr)
+{
+ struct axmap_next_free_data data = { .level = -1U, .bit = bit_nr, };
+
+ if (firstfree_valid(axmap) && bit_nr < axmap->first_free)
+ return axmap->first_free;
+
+ if (!axmap_handler(axmap, bit_nr, axmap_next_free_fn, &data))
+ return axmap_first_free(axmap);
+
+ assert(data.level != -1U);
+
+ return axmap_find_first_free(axmap, data.level, data.offset);
+}