the-tree/lib/generic-radix-tree.c

0001
0002 #include <linux/export.h>
0003 #include <linux/generic-radix-tree.h>
0004 #include <linux/gfp.h>
0005 #include <linux/kmemleak.h>
0006
0007 #define GENRADIX_ARY        (PAGE_SIZE / sizeof(struct genradix_node *))
0008 #define GENRADIX_ARY_SHIFT  ilog2(GENRADIX_ARY)
0009
0010 struct genradix_node {
0011     union {
0012         /* Interior node: */
0013         struct genradix_node    *children[GENRADIX_ARY];
0014
0015         /* Leaf: */
0016         u8          data[PAGE_SIZE];
0017     };
0018 };
0019
0020 static inline int genradix_depth_shift(unsigned depth)
0021 {
0022     return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth;
0023 }
0024
0025 /*
0026  * Returns size (of data, in bytes) that a tree of a given depth holds:
0027  */
0028 static inline size_t genradix_depth_size(unsigned depth)
0029 {
0030     return 1UL << genradix_depth_shift(depth);
0031 }
0032
0033 /* depth that's needed for a genradix that can address up to ULONG_MAX: */
0034 #define GENRADIX_MAX_DEPTH  \
0035     DIV_ROUND_UP(BITS_PER_LONG - PAGE_SHIFT, GENRADIX_ARY_SHIFT)
0036
0037 #define GENRADIX_DEPTH_MASK             \
0038     ((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
0039
0040 static inline unsigned genradix_root_to_depth(struct genradix_root *r)
0041 {
0042     return (unsigned long) r & GENRADIX_DEPTH_MASK;
0043 }
0044
0045 static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
0046 {
0047     return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
0048 }
0049
0050 /*
0051  * Returns pointer to the specified byte @offset within @radix, or NULL if not
0052  * allocated
0053  */
0054 void *__genradix_ptr(struct __genradix *radix, size_t offset)
0055 {
0056     struct genradix_root *r = READ_ONCE(radix->root);
0057     struct genradix_node *n = genradix_root_to_node(r);
0058     unsigned level      = genradix_root_to_depth(r);
0059
0060     if (ilog2(offset) >= genradix_depth_shift(level))
0061         return NULL;
0062
0063     while (1) {
0064         if (!n)
0065             return NULL;
0066         if (!level)
0067             break;
0068
0069         level--;
0070
0071         n = n->children[offset >> genradix_depth_shift(level)];
0072         offset &= genradix_depth_size(level) - 1;
0073     }
0074
0075     return &n->data[offset];
0076 }
0077 EXPORT_SYMBOL(__genradix_ptr);
0078
0079 static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
0080 {
0081     struct genradix_node *node;
0082
0083     node = (struct genradix_node *)__get_free_page(gfp_mask|__GFP_ZERO);
0084
0085     /*
0086      * We're using pages (not slab allocations) directly for kernel data
0087      * structures, so we need to explicitly inform kmemleak of them in order
0088      * to avoid false positive memory leak reports.
0089      */
0090     kmemleak_alloc(node, PAGE_SIZE, 1, gfp_mask);
0091     return node;
0092 }
0093
0094 static inline void genradix_free_node(struct genradix_node *node)
0095 {
0096     kmemleak_free(node);
0097     free_page((unsigned long)node);
0098 }
0099
0100 /*
0101  * Returns pointer to the specified byte @offset within @radix, allocating it if
0102  * necessary - newly allocated slots are always zeroed out:
0103  */
0104 void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
0105                gfp_t gfp_mask)
0106 {
0107     struct genradix_root *v = READ_ONCE(radix->root);
0108     struct genradix_node *n, *new_node = NULL;
0109     unsigned level;
0110
0111     /* Increase tree depth if necessary: */
0112     while (1) {
0113         struct genradix_root *r = v, *new_root;
0114
0115         n   = genradix_root_to_node(r);
0116         level   = genradix_root_to_depth(r);
0117
0118         if (n && ilog2(offset) < genradix_depth_shift(level))
0119             break;
0120
0121         if (!new_node) {
0122             new_node = genradix_alloc_node(gfp_mask);
0123             if (!new_node)
0124                 return NULL;
0125         }
0126
0127         new_node->children[0] = n;
0128         new_root = ((struct genradix_root *)
0129                 ((unsigned long) new_node | (n ? level + 1 : 0)));
0130
0131         if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
0132             v = new_root;
0133             new_node = NULL;
0134         }
0135     }
0136
0137     while (level--) {
0138         struct genradix_node **p =
0139             &n->children[offset >> genradix_depth_shift(level)];
0140         offset &= genradix_depth_size(level) - 1;
0141
0142         n = READ_ONCE(*p);
0143         if (!n) {
0144             if (!new_node) {
0145                 new_node = genradix_alloc_node(gfp_mask);
0146                 if (!new_node)
0147                     return NULL;
0148             }
0149
0150             if (!(n = cmpxchg_release(p, NULL, new_node)))
0151                 swap(n, new_node);
0152         }
0153     }
0154
0155     if (new_node)
0156         genradix_free_node(new_node);
0157
0158     return &n->data[offset];
0159 }
0160 EXPORT_SYMBOL(__genradix_ptr_alloc);
0161
0162 void *__genradix_iter_peek(struct genradix_iter *iter,
0163                struct __genradix *radix,
0164                size_t objs_per_page)
0165 {
0166     struct genradix_root *r;
0167     struct genradix_node *n;
0168     unsigned level, i;
0169 restart:
0170     r = READ_ONCE(radix->root);
0171     if (!r)
0172         return NULL;
0173
0174     n   = genradix_root_to_node(r);
0175     level   = genradix_root_to_depth(r);
0176
0177     if (ilog2(iter->offset) >= genradix_depth_shift(level))
0178         return NULL;
0179
0180     while (level) {
0181         level--;
0182
0183         i = (iter->offset >> genradix_depth_shift(level)) &
0184             (GENRADIX_ARY - 1);
0185
0186         while (!n->children[i]) {
0187             i++;
0188             iter->offset = round_down(iter->offset +
0189                        genradix_depth_size(level),
0190                        genradix_depth_size(level));
0191             iter->pos = (iter->offset >> PAGE_SHIFT) *
0192                 objs_per_page;
0193             if (i == GENRADIX_ARY)
0194                 goto restart;
0195         }
0196
0197         n = n->children[i];
0198     }
0199
0200     return &n->data[iter->offset & (PAGE_SIZE - 1)];
0201 }
0202 EXPORT_SYMBOL(__genradix_iter_peek);
0203
0204 static void genradix_free_recurse(struct genradix_node *n, unsigned level)
0205 {
0206     if (level) {
0207         unsigned i;
0208
0209         for (i = 0; i < GENRADIX_ARY; i++)
0210             if (n->children[i])
0211                 genradix_free_recurse(n->children[i], level - 1);
0212     }
0213
0214     genradix_free_node(n);
0215 }
0216
0217 int __genradix_prealloc(struct __genradix *radix, size_t size,
0218             gfp_t gfp_mask)
0219 {
0220     size_t offset;
0221
0222     for (offset = 0; offset < size; offset += PAGE_SIZE)
0223         if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
0224             return -ENOMEM;
0225
0226     return 0;
0227 }
0228 EXPORT_SYMBOL(__genradix_prealloc);
0229
0230 void __genradix_free(struct __genradix *radix)
0231 {
0232     struct genradix_root *r = xchg(&radix->root, NULL);
0233
0234     genradix_free_recurse(genradix_root_to_node(r),
0235                   genradix_root_to_depth(r));
0236 }
0237 EXPORT_SYMBOL(__genradix_free);