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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Code for working with individual keys, and sorted sets of keys with in a
  * btree node
  *
  * Copyright 2012 Google, Inc.
  */
 
 #define pr_fmt(fmt) "bcache: %s() " fmt, __func__
 
 #include "util.h"
 #include "bset.h"
 
 #include <linux/console.h>
 #include <linux/sched/clock.h>
 #include <linux/random.h>
 #include <linux/prefetch.h>
 
 #ifdef CONFIG_BCACHE_DEBUG
 
 void bch_dump_bset(struct btree_keys *b, struct bset *i, unsigned int set)
 {
     struct bkey *k, *next;
 
     for (k = i->start; k < bset_bkey_last(i); k = next) {
         next = bkey_next(k);
 
         pr_err("block %u key %u/%u: ", set,
                (unsigned int) ((u64 *) k - i->d), i->keys);
 
         if (b->ops->key_dump)
             b->ops->key_dump(b, k);
         else
             pr_cont("%llu:%llu\n", KEY_INODE(k), KEY_OFFSET(k));
 
         if (next < bset_bkey_last(i) &&
             bkey_cmp(k, b->ops->is_extents ?
                  &START_KEY(next) : next) > 0)
             pr_err("Key skipped backwards\n");
     }
 }
 
 void bch_dump_bucket(struct btree_keys *b)
 {
     unsigned int i;
 
     console_lock();
     for (i = 0; i <= b->nsets; i++)
         bch_dump_bset(b, b->set[i].data,
                   bset_sector_offset(b, b->set[i].data));
     console_unlock();
 }
 
 int __bch_count_data(struct btree_keys *b)
 {
     unsigned int ret = 0;
     struct btree_iter iter;
     struct bkey *k;
 
     if (b->ops->is_extents)
         for_each_key(b, k, &iter)
             ret += KEY_SIZE(k);
     return ret;
 }
 
 void __bch_check_keys(struct btree_keys *b, const char *fmt, ...)
 {
     va_list args;
     struct bkey *k, *p = NULL;
     struct btree_iter iter;
     const char *err;
 
     for_each_key(b, k, &iter) {
         if (b->ops->is_extents) {
             err = "Keys out of order";
             if (p && bkey_cmp(&START_KEY(p), &START_KEY(k)) > 0)
                 goto bug;
 
             if (bch_ptr_invalid(b, k))
                 continue;
 
             err =  "Overlapping keys";
             if (p && bkey_cmp(p, &START_KEY(k)) > 0)
                 goto bug;
         } else {
             if (bch_ptr_bad(b, k))
                 continue;
 
             err = "Duplicate keys";
             if (p && !bkey_cmp(p, k))
                 goto bug;
         }
         p = k;
     }
 #if 0
     err = "Key larger than btree node key";
     if (p && bkey_cmp(p, &b->key) > 0)
         goto bug;
 #endif
     return;
 bug:
     bch_dump_bucket(b);
 
     va_start(args, fmt);
     vprintk(fmt, args);
     va_end(args);
 
     panic("bch_check_keys error:  %s:\n", err);
 }
 
 static void bch_btree_iter_next_check(struct btree_iter *iter)
 {
     struct bkey *k = iter->data->k, *next = bkey_next(k);
 
     if (next < iter->data->end &&
         bkey_cmp(k, iter->b->ops->is_extents ?
              &START_KEY(next) : next) > 0) {
         bch_dump_bucket(iter->b);
         panic("Key skipped backwards\n");
     }
 }
 
 #else
 
 static inline void bch_btree_iter_next_check(struct btree_iter *iter) {}
 
 #endif
 
 /* Keylists */
 
 int __bch_keylist_realloc(struct keylist *l, unsigned int u64s)
 {
     size_t oldsize = bch_keylist_nkeys(l);
     size_t newsize = oldsize + u64s;
     uint64_t *old_keys = l->keys_p == l->inline_keys ? NULL : l->keys_p;
     uint64_t *new_keys;
 
     newsize = roundup_pow_of_two(newsize);
 
     if (newsize <= KEYLIST_INLINE ||
         roundup_pow_of_two(oldsize) == newsize)
         return 0;
 
     new_keys = krealloc(old_keys, sizeof(uint64_t) * newsize, GFP_NOIO);
 
     if (!new_keys)
         return -ENOMEM;
 
     if (!old_keys)
         memcpy(new_keys, l->inline_keys, sizeof(uint64_t) * oldsize);
 
     l->keys_p = new_keys;
     l->top_p = new_keys + oldsize;
 
     return 0;
 }
 
 /* Pop the top key of keylist by pointing l->top to its previous key */
 struct bkey *bch_keylist_pop(struct keylist *l)
 {
     struct bkey *k = l->keys;
 
     if (k == l->top)
         return NULL;
 
     while (bkey_next(k) != l->top)
         k = bkey_next(k);
 
     return l->top = k;
 }
 
 /* Pop the bottom key of keylist and update l->top_p */
 void bch_keylist_pop_front(struct keylist *l)
 {
     l->top_p -= bkey_u64s(l->keys);
 
     memmove(l->keys,
         bkey_next(l->keys),
         bch_keylist_bytes(l));
 }
 
 /* Key/pointer manipulation */
 
 void bch_bkey_copy_single_ptr(struct bkey *dest, const struct bkey *src,
                   unsigned int i)
 {
     BUG_ON(i > KEY_PTRS(src));
 
     /* Only copy the header, key, and one pointer. */
     memcpy(dest, src, 2 * sizeof(uint64_t));
     dest->ptr[0] = src->ptr[i];
     SET_KEY_PTRS(dest, 1);
     /* We didn't copy the checksum so clear that bit. */
     SET_KEY_CSUM(dest, 0);
 }
 
 bool __bch_cut_front(const struct bkey *where, struct bkey *k)
 {
     unsigned int i, len = 0;
 
     if (bkey_cmp(where, &START_KEY(k)) <= 0)
         return false;
 
     if (bkey_cmp(where, k) < 0)
         len = KEY_OFFSET(k) - KEY_OFFSET(where);
     else
         bkey_copy_key(k, where);
 
     for (i = 0; i < KEY_PTRS(k); i++)
         SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + KEY_SIZE(k) - len);
 
     BUG_ON(len > KEY_SIZE(k));
     SET_KEY_SIZE(k, len);
     return true;
 }
 
 bool __bch_cut_back(const struct bkey *where, struct bkey *k)
 {
     unsigned int len = 0;
 
     if (bkey_cmp(where, k) >= 0)
         return false;
 
     BUG_ON(KEY_INODE(where) != KEY_INODE(k));
 
     if (bkey_cmp(where, &START_KEY(k)) > 0)
         len = KEY_OFFSET(where) - KEY_START(k);
 
     bkey_copy_key(k, where);
 
     BUG_ON(len > KEY_SIZE(k));
     SET_KEY_SIZE(k, len);
     return true;
 }
 
 /* Auxiliary search trees */
 
 /* 32 bits total: */
 #define BKEY_MID_BITS       3
 #define BKEY_EXPONENT_BITS  7
 #define BKEY_MANTISSA_BITS  (32 - BKEY_MID_BITS - BKEY_EXPONENT_BITS)
 #define BKEY_MANTISSA_MASK  ((1 << BKEY_MANTISSA_BITS) - 1)
 
 struct bkey_float {
     unsigned int    exponent:BKEY_EXPONENT_BITS;
     unsigned int    m:BKEY_MID_BITS;
     unsigned int    mantissa:BKEY_MANTISSA_BITS;
 } __packed;
 
 /*
  * BSET_CACHELINE was originally intended to match the hardware cacheline size -
  * it used to be 64, but I realized the lookup code would touch slightly less
  * memory if it was 128.
  *
  * It definites the number of bytes (in struct bset) per struct bkey_float in
  * the auxiliar search tree - when we're done searching the bset_float tree we
  * have this many bytes left that we do a linear search over.
  *
  * Since (after level 5) every level of the bset_tree is on a new cacheline,
  * we're touching one fewer cacheline in the bset tree in exchange for one more
  * cacheline in the linear search - but the linear search might stop before it
  * gets to the second cacheline.
  */
 
 #define BSET_CACHELINE      128
 
 /* Space required for the btree node keys */
 static inline size_t btree_keys_bytes(struct btree_keys *b)
 {
     return PAGE_SIZE << b->page_order;
 }
 
 static inline size_t btree_keys_cachelines(struct btree_keys *b)
 {
     return btree_keys_bytes(b) / BSET_CACHELINE;
 }
 
 /* Space required for the auxiliary search trees */
 static inline size_t bset_tree_bytes(struct btree_keys *b)
 {
     return btree_keys_cachelines(b) * sizeof(struct bkey_float);
 }
 
 /* Space required for the prev pointers */
 static inline size_t bset_prev_bytes(struct btree_keys *b)
 {
     return btree_keys_cachelines(b) * sizeof(uint8_t);
 }
 
 /* Memory allocation */
 
 void bch_btree_keys_free(struct btree_keys *b)
 {
     struct bset_tree *t = b->set;
 
     if (bset_prev_bytes(b) < PAGE_SIZE)
         kfree(t->prev);
     else
         free_pages((unsigned long) t->prev,
                get_order(bset_prev_bytes(b)));
 
     if (bset_tree_bytes(b) < PAGE_SIZE)
         kfree(t->tree);
     else
         free_pages((unsigned long) t->tree,
                get_order(bset_tree_bytes(b)));
 
     free_pages((unsigned long) t->data, b->page_order);
 
     t->prev = NULL;
     t->tree = NULL;
     t->data = NULL;
 }
 
 int bch_btree_keys_alloc(struct btree_keys *b,
              unsigned int page_order,
              gfp_t gfp)
 {
     struct bset_tree *t = b->set;
 
     BUG_ON(t->data);
 
     b->page_order = page_order;
 
     t->data = (void *) __get_free_pages(__GFP_COMP|gfp, b->page_order);
     if (!t->data)
         goto err;
 
     t->tree = bset_tree_bytes(b) < PAGE_SIZE
         ? kmalloc(bset_tree_bytes(b), gfp)
         : (void *) __get_free_pages(gfp, get_order(bset_tree_bytes(b)));
     if (!t->tree)
         goto err;
 
     t->prev = bset_prev_bytes(b) < PAGE_SIZE
         ? kmalloc(bset_prev_bytes(b), gfp)
         : (void *) __get_free_pages(gfp, get_order(bset_prev_bytes(b)));
     if (!t->prev)
         goto err;
 
     return 0;
 err:
     bch_btree_keys_free(b);
     return -ENOMEM;
 }
 
 void bch_btree_keys_init(struct btree_keys *b, const struct btree_keys_ops *ops,
              bool *expensive_debug_checks)
 {
     b->ops = ops;
     b->expensive_debug_checks = expensive_debug_checks;
     b->nsets = 0;
     b->last_set_unwritten = 0;
 
     /*
      * struct btree_keys in embedded in struct btree, and struct
      * bset_tree is embedded into struct btree_keys. They are all
      * initialized as 0 by kzalloc() in mca_bucket_alloc(), and
      * b->set[0].data is allocated in bch_btree_keys_alloc(), so we
      * don't have to initiate b->set[].size and b->set[].data here
      * any more.
      */
 }
 
 /* Binary tree stuff for auxiliary search trees */
 
 /*
  * return array index next to j when does in-order traverse
  * of a binary tree which is stored in a linear array
  */
 static unsigned int inorder_next(unsigned int j, unsigned int size)
 {
     if (j * 2 + 1 < size) {
         j = j * 2 + 1;
 
         while (j * 2 < size)
             j *= 2;
     } else
         j >>= ffz(j) + 1;
 
     return j;
 }
 
 /*
  * return array index previous to j when does in-order traverse
  * of a binary tree which is stored in a linear array
  */
 static unsigned int inorder_prev(unsigned int j, unsigned int size)
 {
     if (j * 2 < size) {
         j = j * 2;
 
         while (j * 2 + 1 < size)
             j = j * 2 + 1;
     } else
         j >>= ffs(j);
 
     return j;
 }
 
 /*
  * I have no idea why this code works... and I'm the one who wrote it
  *
  * However, I do know what it does:
  * Given a binary tree constructed in an array (i.e. how you normally implement
  * a heap), it converts a node in the tree - referenced by array index - to the
  * index it would have if you did an inorder traversal.
  *
  * Also tested for every j, size up to size somewhere around 6 million.
  *
  * The binary tree starts at array index 1, not 0
  * extra is a function of size:
  *   extra = (size - rounddown_pow_of_two(size - 1)) << 1;
  */
 static unsigned int __to_inorder(unsigned int j,
                   unsigned int size,
                   unsigned int extra)
 {
     unsigned int b = fls(j);
     unsigned int shift = fls(size - 1) - b;
 
     j  ^= 1U << (b - 1);
     j <<= 1;
     j  |= 1;
     j <<= shift;
 
     if (j > extra)
         j -= (j - extra) >> 1;
 
     return j;
 }
 
 /*
  * Return the cacheline index in bset_tree->data, where j is index
  * from a linear array which stores the auxiliar binary tree
  */
 static unsigned int to_inorder(unsigned int j, struct bset_tree *t)
 {
     return __to_inorder(j, t->size, t->extra);
 }
 
 static unsigned int __inorder_to_tree(unsigned int j,
                       unsigned int size,
                       unsigned int extra)
 {
     unsigned int shift;
 
     if (j > extra)
         j += j - extra;
 
     shift = ffs(j);
 
     j >>= shift;
     j  |= roundup_pow_of_two(size) >> shift;
 
     return j;
 }
 
 /*
  * Return an index from a linear array which stores the auxiliar binary
  * tree, j is the cacheline index of t->data.
  */
 static unsigned int inorder_to_tree(unsigned int j, struct bset_tree *t)
 {
     return __inorder_to_tree(j, t->size, t->extra);
 }
 
 #if 0
 void inorder_test(void)
 {
     unsigned long done = 0;
     ktime_t start = ktime_get();
 
     for (unsigned int size = 2;
          size < 65536000;
          size++) {
         unsigned int extra =
             (size - rounddown_pow_of_two(size - 1)) << 1;
         unsigned int i = 1, j = rounddown_pow_of_two(size - 1);
 
         if (!(size % 4096))
             pr_notice("loop %u, %llu per us\n", size,
                    done / ktime_us_delta(ktime_get(), start));
 
         while (1) {
             if (__inorder_to_tree(i, size, extra) != j)
                 panic("size %10u j %10u i %10u", size, j, i);
 
             if (__to_inorder(j, size, extra) != i)
                 panic("size %10u j %10u i %10u", size, j, i);
 
             if (j == rounddown_pow_of_two(size) - 1)
                 break;
 
             BUG_ON(inorder_prev(inorder_next(j, size), size) != j);
 
             j = inorder_next(j, size);
             i++;
         }
 
         done += size - 1;
     }
 }
 #endif
 
 /*
  * Cacheline/offset <-> bkey pointer arithmetic:
  *
  * t->tree is a binary search tree in an array; each node corresponds to a key
  * in one cacheline in t->set (BSET_CACHELINE bytes).
  *
  * This means we don't have to store the full index of the key that a node in
  * the binary tree points to; to_inorder() gives us the cacheline, and then
  * bkey_float->m gives us the offset within that cacheline, in units of 8 bytes.
  *
  * cacheline_to_bkey() and friends abstract out all the pointer arithmetic to
  * make this work.
  *
  * To construct the bfloat for an arbitrary key we need to know what the key
  * immediately preceding it is: we have to check if the two keys differ in the
  * bits we're going to store in bkey_float->mantissa. t->prev[j] stores the size
  * of the previous key so we can walk backwards to it from t->tree[j]'s key.
  */
 
 static struct bkey *cacheline_to_bkey(struct bset_tree *t,
                       unsigned int cacheline,
                       unsigned int offset)
 {
     return ((void *) t->data) + cacheline * BSET_CACHELINE + offset * 8;
 }
 
 static unsigned int bkey_to_cacheline(struct bset_tree *t, struct bkey *k)
 {
     return ((void *) k - (void *) t->data) / BSET_CACHELINE;
 }
 
 static unsigned int bkey_to_cacheline_offset(struct bset_tree *t,
                      unsigned int cacheline,
                      struct bkey *k)
 {
     return (u64 *) k - (u64 *) cacheline_to_bkey(t, cacheline, 0);
 }
 
 static struct bkey *tree_to_bkey(struct bset_tree *t, unsigned int j)
 {
     return cacheline_to_bkey(t, to_inorder(j, t), t->tree[j].m);
 }
 
 static struct bkey *tree_to_prev_bkey(struct bset_tree *t, unsigned int j)
 {
     return (void *) (((uint64_t *) tree_to_bkey(t, j)) - t->prev[j]);
 }
 
 /*
  * For the write set - the one we're currently inserting keys into - we don't
  * maintain a full search tree, we just keep a simple lookup table in t->prev.
  */
 static struct bkey *table_to_bkey(struct bset_tree *t, unsigned int cacheline)
 {
     return cacheline_to_bkey(t, cacheline, t->prev[cacheline]);
 }
 
 static inline uint64_t shrd128(uint64_t high, uint64_t low, uint8_t shift)
 {
     low >>= shift;
     low  |= (high << 1) << (63U - shift);
     return low;
 }
 
 /*
  * Calculate mantissa value for struct bkey_float.
  * If most significant bit of f->exponent is not set, then
  *  - f->exponent >> 6 is 0
  *  - p[0] points to bkey->low
  *  - p[-1] borrows bits from KEY_INODE() of bkey->high
  * if most isgnificant bits of f->exponent is set, then
  *  - f->exponent >> 6 is 1
  *  - p[0] points to bits from KEY_INODE() of bkey->high
  *  - p[-1] points to other bits from KEY_INODE() of
  *    bkey->high too.
  * See make_bfloat() to check when most significant bit of f->exponent
  * is set or not.
  */
 static inline unsigned int bfloat_mantissa(const struct bkey *k,
                        struct bkey_float *f)
 {
     const uint64_t *p = &k->low - (f->exponent >> 6);
 
     return shrd128(p[-1], p[0], f->exponent & 63) & BKEY_MANTISSA_MASK;
 }
 
 static void make_bfloat(struct bset_tree *t, unsigned int j)
 {
     struct bkey_float *f = &t->tree[j];
     struct bkey *m = tree_to_bkey(t, j);
     struct bkey *p = tree_to_prev_bkey(t, j);
 
     struct bkey *l = is_power_of_2(j)
         ? t->data->start
         : tree_to_prev_bkey(t, j >> ffs(j));
 
     struct bkey *r = is_power_of_2(j + 1)
         ? bset_bkey_idx(t->data, t->data->keys - bkey_u64s(&t->end))
         : tree_to_bkey(t, j >> (ffz(j) + 1));
 
     BUG_ON(m < l || m > r);
     BUG_ON(bkey_next(p) != m);
 
     /*
      * If l and r have different KEY_INODE values (different backing
      * device), f->exponent records how many least significant bits
      * are different in KEY_INODE values and sets most significant
      * bits to 1 (by +64).
      * If l and r have same KEY_INODE value, f->exponent records
      * how many different bits in least significant bits of bkey->low.
      * See bfloat_mantiss() how the most significant bit of
      * f->exponent is used to calculate bfloat mantissa value.
      */
     if (KEY_INODE(l) != KEY_INODE(r))
         f->exponent = fls64(KEY_INODE(r) ^ KEY_INODE(l)) + 64;
     else
         f->exponent = fls64(r->low ^ l->low);
 
     f->exponent = max_t(int, f->exponent - BKEY_MANTISSA_BITS, 0);
 
     /*
      * Setting f->exponent = 127 flags this node as failed, and causes the
      * lookup code to fall back to comparing against the original key.
      */
 
     if (bfloat_mantissa(m, f) != bfloat_mantissa(p, f))
         f->mantissa = bfloat_mantissa(m, f) - 1;
     else
         f->exponent = 127;
 }
 
 static void bset_alloc_tree(struct btree_keys *b, struct bset_tree *t)
 {
     if (t != b->set) {
         unsigned int j = roundup(t[-1].size,
                      64 / sizeof(struct bkey_float));
 
         t->tree = t[-1].tree + j;
         t->prev = t[-1].prev + j;
     }
 
     while (t < b->set + MAX_BSETS)
         t++->size = 0;
 }
 
 static void bch_bset_build_unwritten_tree(struct btree_keys *b)
 {
     struct bset_tree *t = bset_tree_last(b);
 
     BUG_ON(b->last_set_unwritten);
     b->last_set_unwritten = 1;
 
     bset_alloc_tree(b, t);
 
     if (t->tree != b->set->tree + btree_keys_cachelines(b)) {
         t->prev[0] = bkey_to_cacheline_offset(t, 0, t->data->start);
         t->size = 1;
     }
 }
 
 void bch_bset_init_next(struct btree_keys *b, struct bset *i, uint64_t magic)
 {
     if (i != b->set->data) {
         b->set[++b->nsets].data = i;
         i->seq = b->set->data->seq;
     } else
         get_random_bytes(&i->seq, sizeof(uint64_t));
 
     i->magic    = magic;
     i->version  = 0;
     i->keys     = 0;
 
     bch_bset_build_unwritten_tree(b);
 }
 
 /*
  * Build auxiliary binary tree 'struct bset_tree *t', this tree is used to
  * accelerate bkey search in a btree node (pointed by bset_tree->data in
  * memory). After search in the auxiliar tree by calling bset_search_tree(),
  * a struct bset_search_iter is returned which indicates range [l, r] from
  * bset_tree->data where the searching bkey might be inside. Then a followed
  * linear comparison does the exact search, see __bch_bset_search() for how
  * the auxiliary tree is used.
  */
 void bch_bset_build_written_tree(struct btree_keys *b)
 {
     struct bset_tree *t = bset_tree_last(b);
     struct bkey *prev = NULL, *k = t->data->start;
     unsigned int j, cacheline = 1;
 
     b->last_set_unwritten = 0;
 
     bset_alloc_tree(b, t);
 
     t->size = min_t(unsigned int,
             bkey_to_cacheline(t, bset_bkey_last(t->data)),
             b->set->tree + btree_keys_cachelines(b) - t->tree);
 
     if (t->size < 2) {
         t->size = 0;
         return;
     }
 
     t->extra = (t->size - rounddown_pow_of_two(t->size - 1)) << 1;
 
     /* First we figure out where the first key in each cacheline is */
     for (j = inorder_next(0, t->size);
          j;
          j = inorder_next(j, t->size)) {
         while (bkey_to_cacheline(t, k) < cacheline) {
             prev = k;
             k = bkey_next(k);
         }
 
         t->prev[j] = bkey_u64s(prev);
         t->tree[j].m = bkey_to_cacheline_offset(t, cacheline++, k);
     }
 
     while (bkey_next(k) != bset_bkey_last(t->data))
         k = bkey_next(k);
 
     t->end = *k;
 
     /* Then we build the tree */
     for (j = inorder_next(0, t->size);
          j;
          j = inorder_next(j, t->size))
         make_bfloat(t, j);
 }
 
 /* Insert */
 
 void bch_bset_fix_invalidated_key(struct btree_keys *b, struct bkey *k)
 {
     struct bset_tree *t;
     unsigned int inorder, j = 1;
 
     for (t = b->set; t <= bset_tree_last(b); t++)
         if (k < bset_bkey_last(t->data))
             goto found_set;
 
     BUG();
 found_set:
     if (!t->size || !bset_written(b, t))
         return;
 
     inorder = bkey_to_cacheline(t, k);
 
     if (k == t->data->start)
         goto fix_left;
 
     if (bkey_next(k) == bset_bkey_last(t->data)) {
         t->end = *k;
         goto fix_right;
     }
 
     j = inorder_to_tree(inorder, t);
 
     if (j &&
         j < t->size &&
         k == tree_to_bkey(t, j))
 fix_left:   do {
             make_bfloat(t, j);
             j = j * 2;
         } while (j < t->size);
 
     j = inorder_to_tree(inorder + 1, t);
 
     if (j &&
         j < t->size &&
         k == tree_to_prev_bkey(t, j))
 fix_right:  do {
             make_bfloat(t, j);
             j = j * 2 + 1;
         } while (j < t->size);
 }
 
 static void bch_bset_fix_lookup_table(struct btree_keys *b,
                       struct bset_tree *t,
                       struct bkey *k)
 {
     unsigned int shift = bkey_u64s(k);
     unsigned int j = bkey_to_cacheline(t, k);
 
     /* We're getting called from btree_split() or btree_gc, just bail out */
     if (!t->size)
         return;
 
     /*
      * k is the key we just inserted; we need to find the entry in the
      * lookup table for the first key that is strictly greater than k:
      * it's either k's cacheline or the next one
      */
     while (j < t->size &&
            table_to_bkey(t, j) <= k)
         j++;
 
     /*
      * Adjust all the lookup table entries, and find a new key for any that
      * have gotten too big
      */
     for (; j < t->size; j++) {
         t->prev[j] += shift;
 
         if (t->prev[j] > 7) {
             k = table_to_bkey(t, j - 1);
 
             while (k < cacheline_to_bkey(t, j, 0))
                 k = bkey_next(k);
 
             t->prev[j] = bkey_to_cacheline_offset(t, j, k);
         }
     }
 
     if (t->size == b->set->tree + btree_keys_cachelines(b) - t->tree)
         return;
 
     /* Possibly add a new entry to the end of the lookup table */
 
     for (k = table_to_bkey(t, t->size - 1);
          k != bset_bkey_last(t->data);
          k = bkey_next(k))
         if (t->size == bkey_to_cacheline(t, k)) {
             t->prev[t->size] =
                 bkey_to_cacheline_offset(t, t->size, k);
             t->size++;
         }
 }
 
 /*
  * Tries to merge l and r: l should be lower than r
  * Returns true if we were able to merge. If we did merge, l will be the merged
  * key, r will be untouched.
  */
 bool bch_bkey_try_merge(struct btree_keys *b, struct bkey *l, struct bkey *r)
 {
     if (!b->ops->key_merge)
         return false;
 
     /*
      * Generic header checks
      * Assumes left and right are in order
      * Left and right must be exactly aligned
      */
     if (!bch_bkey_equal_header(l, r) ||
          bkey_cmp(l, &START_KEY(r)))
         return false;
 
     return b->ops->key_merge(b, l, r);
 }
 
 void bch_bset_insert(struct btree_keys *b, struct bkey *where,
              struct bkey *insert)
 {
     struct bset_tree *t = bset_tree_last(b);
 
     BUG_ON(!b->last_set_unwritten);
     BUG_ON(bset_byte_offset(b, t->data) +
            __set_bytes(t->data, t->data->keys + bkey_u64s(insert)) >
            PAGE_SIZE << b->page_order);
 
     memmove((uint64_t *) where + bkey_u64s(insert),
         where,
         (void *) bset_bkey_last(t->data) - (void *) where);
 
     t->data->keys += bkey_u64s(insert);
     bkey_copy(where, insert);
     bch_bset_fix_lookup_table(b, t, where);
 }
 
 unsigned int bch_btree_insert_key(struct btree_keys *b, struct bkey *k,
                   struct bkey *replace_key)
 {
     unsigned int status = BTREE_INSERT_STATUS_NO_INSERT;
     struct bset *i = bset_tree_last(b)->data;
     struct bkey *m, *prev = NULL;
     struct btree_iter iter;
     struct bkey preceding_key_on_stack = ZERO_KEY;
     struct bkey *preceding_key_p = &preceding_key_on_stack;
 
     BUG_ON(b->ops->is_extents && !KEY_SIZE(k));
 
     /*
      * If k has preceding key, preceding_key_p will be set to address
      *  of k's preceding key; otherwise preceding_key_p will be set
      * to NULL inside preceding_key().
      */
     if (b->ops->is_extents)
         preceding_key(&START_KEY(k), &preceding_key_p);
     else
         preceding_key(k, &preceding_key_p);
 
     m = bch_btree_iter_init(b, &iter, preceding_key_p);
 
     if (b->ops->insert_fixup(b, k, &iter, replace_key))
         return status;
 
     status = BTREE_INSERT_STATUS_INSERT;
 
     while (m != bset_bkey_last(i) &&
            bkey_cmp(k, b->ops->is_extents ? &START_KEY(m) : m) > 0) {
         prev = m;
         m = bkey_next(m);
     }
 
     /* prev is in the tree, if we merge we're done */
     status = BTREE_INSERT_STATUS_BACK_MERGE;
     if (prev &&
         bch_bkey_try_merge(b, prev, k))
         goto merged;
 #if 0
     status = BTREE_INSERT_STATUS_OVERWROTE;
     if (m != bset_bkey_last(i) &&
         KEY_PTRS(m) == KEY_PTRS(k) && !KEY_SIZE(m))
         goto copy;
 #endif
     status = BTREE_INSERT_STATUS_FRONT_MERGE;
     if (m != bset_bkey_last(i) &&
         bch_bkey_try_merge(b, k, m))
         goto copy;
 
     bch_bset_insert(b, m, k);
 copy:   bkey_copy(m, k);
 merged:
     return status;
 }
 
 /* Lookup */
 
 struct bset_search_iter {
     struct bkey *l, *r;
 };
 
 static struct bset_search_iter bset_search_write_set(struct bset_tree *t,
                              const struct bkey *search)
 {
     unsigned int li = 0, ri = t->size;
 
     while (li + 1 != ri) {
         unsigned int m = (li + ri) >> 1;
 
         if (bkey_cmp(table_to_bkey(t, m), search) > 0)
             ri = m;
         else
             li = m;
     }
 
     return (struct bset_search_iter) {
         table_to_bkey(t, li),
         ri < t->size ? table_to_bkey(t, ri) : bset_bkey_last(t->data)
     };
 }
 
 static struct bset_search_iter bset_search_tree(struct bset_tree *t,
                         const struct bkey *search)
 {
     struct bkey *l, *r;
     struct bkey_float *f;
     unsigned int inorder, j, n = 1;
 
     do {
         unsigned int p = n << 4;
 
         if (p < t->size)
             prefetch(&t->tree[p]);
 
         j = n;
         f = &t->tree[j];
 
         if (likely(f->exponent != 127)) {
             if (f->mantissa >= bfloat_mantissa(search, f))
                 n = j * 2;
             else
                 n = j * 2 + 1;
         } else {
             if (bkey_cmp(tree_to_bkey(t, j), search) > 0)
                 n = j * 2;
             else
                 n = j * 2 + 1;
         }
     } while (n < t->size);
 
     inorder = to_inorder(j, t);
 
     /*
      * n would have been the node we recursed to - the low bit tells us if
      * we recursed left or recursed right.
      */
     if (n & 1) {
         l = cacheline_to_bkey(t, inorder, f->m);
 
         if (++inorder != t->size) {
             f = &t->tree[inorder_next(j, t->size)];
             r = cacheline_to_bkey(t, inorder, f->m);
         } else
             r = bset_bkey_last(t->data);
     } else {
         r = cacheline_to_bkey(t, inorder, f->m);
 
         if (--inorder) {
             f = &t->tree[inorder_prev(j, t->size)];
             l = cacheline_to_bkey(t, inorder, f->m);
         } else
             l = t->data->start;
     }
 
     return (struct bset_search_iter) {l, r};
 }
 
 struct bkey *__bch_bset_search(struct btree_keys *b, struct bset_tree *t,
                    const struct bkey *search)
 {
     struct bset_search_iter i;
 
     /*
      * First, we search for a cacheline, then lastly we do a linear search
      * within that cacheline.
      *
      * To search for the cacheline, there's three different possibilities:
      *  * The set is too small to have a search tree, so we just do a linear
      *    search over the whole set.
      *  * The set is the one we're currently inserting into; keeping a full
      *    auxiliary search tree up to date would be too expensive, so we
      *    use a much simpler lookup table to do a binary search -
      *    bset_search_write_set().
      *  * Or we use the auxiliary search tree we constructed earlier -
      *    bset_search_tree()
      */
 
     if (unlikely(!t->size)) {
         i.l = t->data->start;
         i.r = bset_bkey_last(t->data);
     } else if (bset_written(b, t)) {
         /*
          * Each node in the auxiliary search tree covers a certain range
          * of bits, and keys above and below the set it covers might
          * differ outside those bits - so we have to special case the
          * start and end - handle that here:
          */
 
         if (unlikely(bkey_cmp(search, &t->end) >= 0))
             return bset_bkey_last(t->data);
 
         if (unlikely(bkey_cmp(search, t->data->start) < 0))
             return t->data->start;
 
         i = bset_search_tree(t, search);
     } else {
         BUG_ON(!b->nsets &&
                t->size < bkey_to_cacheline(t, bset_bkey_last(t->data)));
 
         i = bset_search_write_set(t, search);
     }
 
     if (btree_keys_expensive_checks(b)) {
         BUG_ON(bset_written(b, t) &&
                i.l != t->data->start &&
                bkey_cmp(tree_to_prev_bkey(t,
               inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
                 search) > 0);
 
         BUG_ON(i.r != bset_bkey_last(t->data) &&
                bkey_cmp(i.r, search) <= 0);
     }
 
     while (likely(i.l != i.r) &&
            bkey_cmp(i.l, search) <= 0)
         i.l = bkey_next(i.l);
 
     return i.l;
 }
 
 /* Btree iterator */
 
 typedef bool (btree_iter_cmp_fn)(struct btree_iter_set,
                  struct btree_iter_set);
 
 static inline bool btree_iter_cmp(struct btree_iter_set l,
                   struct btree_iter_set r)
 {
     return bkey_cmp(l.k, r.k) > 0;
 }
 
 static inline bool btree_iter_end(struct btree_iter *iter)
 {
     return !iter->used;
 }
 
 void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
              struct bkey *end)
 {
     if (k != end)
         BUG_ON(!heap_add(iter,
                  ((struct btree_iter_set) { k, end }),
                  btree_iter_cmp));
 }
 
 static struct bkey *__bch_btree_iter_init(struct btree_keys *b,
                       struct btree_iter *iter,
                       struct bkey *search,
                       struct bset_tree *start)
 {
     struct bkey *ret = NULL;
 
     iter->size = ARRAY_SIZE(iter->data);
     iter->used = 0;
 
 #ifdef CONFIG_BCACHE_DEBUG
     iter->b = b;
 #endif
 
     for (; start <= bset_tree_last(b); start++) {
         ret = bch_bset_search(b, start, search);
         bch_btree_iter_push(iter, ret, bset_bkey_last(start->data));
     }
 
     return ret;
 }
 
 struct bkey *bch_btree_iter_init(struct btree_keys *b,
                  struct btree_iter *iter,
                  struct bkey *search)
 {
     return __bch_btree_iter_init(b, iter, search, b->set);
 }
 
 static inline struct bkey *__bch_btree_iter_next(struct btree_iter *iter,
                          btree_iter_cmp_fn *cmp)
 {
     struct btree_iter_set b __maybe_unused;
     struct bkey *ret = NULL;
 
     if (!btree_iter_end(iter)) {
         bch_btree_iter_next_check(iter);
 
         ret = iter->data->k;
         iter->data->k = bkey_next(iter->data->k);
 
         if (iter->data->k > iter->data->end) {
             WARN_ONCE(1, "bset was corrupt!\n");
             iter->data->k = iter->data->end;
         }
 
         if (iter->data->k == iter->data->end)
             heap_pop(iter, b, cmp);
         else
             heap_sift(iter, 0, cmp);
     }
 
     return ret;
 }
 
 struct bkey *bch_btree_iter_next(struct btree_iter *iter)
 {
     return __bch_btree_iter_next(iter, btree_iter_cmp);
 
 }
 
 struct bkey *bch_btree_iter_next_filter(struct btree_iter *iter,
                     struct btree_keys *b, ptr_filter_fn fn)
 {
     struct bkey *ret;
 
     do {
         ret = bch_btree_iter_next(iter);
     } while (ret && fn(b, ret));
 
     return ret;
 }
 
 /* Mergesort */
 
 void bch_bset_sort_state_free(struct bset_sort_state *state)
 {
     mempool_exit(&state->pool);
 }
 
 int bch_bset_sort_state_init(struct bset_sort_state *state,
                  unsigned int page_order)
 {
     spin_lock_init(&state->time.lock);
 
     state->page_order = page_order;
     state->crit_factor = int_sqrt(1 << page_order);
 
     return mempool_init_page_pool(&state->pool, 1, page_order);
 }
 
 static void btree_mergesort(struct btree_keys *b, struct bset *out,
                 struct btree_iter *iter,
                 bool fixup, bool remove_stale)
 {
     int i;
     struct bkey *k, *last = NULL;
     BKEY_PADDED(k) tmp;
     bool (*bad)(struct btree_keys *, const struct bkey *) = remove_stale
         ? bch_ptr_bad
         : bch_ptr_invalid;
 
     /* Heapify the iterator, using our comparison function */
     for (i = iter->used / 2 - 1; i >= 0; --i)
         heap_sift(iter, i, b->ops->sort_cmp);
 
     while (!btree_iter_end(iter)) {
         if (b->ops->sort_fixup && fixup)
             k = b->ops->sort_fixup(iter, &tmp.k);
         else
             k = NULL;
 
         if (!k)
             k = __bch_btree_iter_next(iter, b->ops->sort_cmp);
 
         if (bad(b, k))
             continue;
 
         if (!last) {
             last = out->start;
             bkey_copy(last, k);
         } else if (!bch_bkey_try_merge(b, last, k)) {
             last = bkey_next(last);
             bkey_copy(last, k);
         }
     }
 
     out->keys = last ? (uint64_t *) bkey_next(last) - out->d : 0;
 
     pr_debug("sorted %i keys\n", out->keys);
 }
 
 static void __btree_sort(struct btree_keys *b, struct btree_iter *iter,
              unsigned int start, unsigned int order, bool fixup,
              struct bset_sort_state *state)
 {
     uint64_t start_time;
     bool used_mempool = false;
     struct bset *out = (void *) __get_free_pages(__GFP_NOWARN|GFP_NOWAIT,
                              order);
     if (!out) {
         struct page *outp;
 
         BUG_ON(order > state->page_order);
 
         outp = mempool_alloc(&state->pool, GFP_NOIO);
         out = page_address(outp);
         used_mempool = true;
         order = state->page_order;
     }
 
     start_time = local_clock();
 
     btree_mergesort(b, out, iter, fixup, false);
     b->nsets = start;
 
     if (!start && order == b->page_order) {
         /*
          * Our temporary buffer is the same size as the btree node's
          * buffer, we can just swap buffers instead of doing a big
          * memcpy()
          *
          * Don't worry event 'out' is allocated from mempool, it can
          * still be swapped here. Because state->pool is a page mempool
          * creaated by by mempool_init_page_pool(), which allocates
          * pages by alloc_pages() indeed.
          */
 
         out->magic  = b->set->data->magic;
         out->seq    = b->set->data->seq;
         out->version    = b->set->data->version;
         swap(out, b->set->data);
     } else {
         b->set[start].data->keys = out->keys;
         memcpy(b->set[start].data->start, out->start,
                (void *) bset_bkey_last(out) - (void *) out->start);
     }
 
     if (used_mempool)
         mempool_free(virt_to_page(out), &state->pool);
     else
         free_pages((unsigned long) out, order);
 
     bch_bset_build_written_tree(b);
 
     if (!start)
         bch_time_stats_update(&state->time, start_time);
 }
 
 void bch_btree_sort_partial(struct btree_keys *b, unsigned int start,
                 struct bset_sort_state *state)
 {
     size_t order = b->page_order, keys = 0;
     struct btree_iter iter;
     int oldsize = bch_count_data(b);
 
     __bch_btree_iter_init(b, &iter, NULL, &b->set[start]);
 
     if (start) {
         unsigned int i;
 
         for (i = start; i <= b->nsets; i++)
             keys += b->set[i].data->keys;
 
         order = get_order(__set_bytes(b->set->data, keys));
     }
 
     __btree_sort(b, &iter, start, order, false, state);
 
     EBUG_ON(oldsize >= 0 && bch_count_data(b) != oldsize);
 }
 
 void bch_btree_sort_and_fix_extents(struct btree_keys *b,
                     struct btree_iter *iter,
                     struct bset_sort_state *state)
 {
     __btree_sort(b, iter, 0, b->page_order, true, state);
 }
 
 void bch_btree_sort_into(struct btree_keys *b, struct btree_keys *new,
              struct bset_sort_state *state)
 {
     uint64_t start_time = local_clock();
     struct btree_iter iter;
 
     bch_btree_iter_init(b, &iter, NULL);
 
     btree_mergesort(b, new->set->data, &iter, false, true);
 
     bch_time_stats_update(&state->time, start_time);
 
     new->set->size = 0; // XXX: why?
 }
 
 #define SORT_CRIT   (4096 / sizeof(uint64_t))
 
 void bch_btree_sort_lazy(struct btree_keys *b, struct bset_sort_state *state)
 {
     unsigned int crit = SORT_CRIT;
     int i;
 
     /* Don't sort if nothing to do */
     if (!b->nsets)
         goto out;
 
     for (i = b->nsets - 1; i >= 0; --i) {
         crit *= state->crit_factor;
 
         if (b->set[i].data->keys < crit) {
             bch_btree_sort_partial(b, i, state);
             return;
         }
     }
 
     /* Sort if we'd overflow */
     if (b->nsets + 1 == MAX_BSETS) {
         bch_btree_sort(b, state);
         return;
     }
 
 out:
     bch_bset_build_written_tree(b);
 }
 
 void bch_btree_keys_stats(struct btree_keys *b, struct bset_stats *stats)
 {
     unsigned int i;
 
     for (i = 0; i <= b->nsets; i++) {
         struct bset_tree *t = &b->set[i];
         size_t bytes = t->data->keys * sizeof(uint64_t);
         size_t j;
 
         if (bset_written(b, t)) {
             stats->sets_written++;
             stats->bytes_written += bytes;
 
             stats->floats += t->size - 1;
 
             for (j = 1; j < t->size; j++)
                 if (t->tree[j].exponent == 127)
                     stats->failed++;
         } else {
             stats->sets_unwritten++;
             stats->bytes_unwritten += bytes;
         }
     }
 }

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