From 73badee4280ce30a927b82eedc919fb23ee549ae Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Tue, 12 Sep 2023 01:17:22 -0400 Subject: [PATCH] lib/generic-radix-tree.c: Add peek_prev() This patch adds genradix_peek_prev(), genradix_iter_rewind(), and genradix_for_each_reverse(), for iterating backwards over a generic radix tree. Signed-off-by: Kent Overstreet --- include/linux/generic-radix-tree.h | 61 +++++++++++++++++++++++++++++- lib/generic-radix-tree.c | 59 +++++++++++++++++++++++++++++ 2 files changed, 119 insertions(+), 1 deletion(-) diff --git a/include/linux/generic-radix-tree.h b/include/linux/generic-radix-tree.h index f6cd0f909d9f..847413164738 100644 --- a/include/linux/generic-radix-tree.h +++ b/include/linux/generic-radix-tree.h @@ -117,6 +117,11 @@ static inline size_t __idx_to_offset(size_t idx, size_t obj_size) #define __genradix_cast(_radix) (typeof((_radix)->type[0]) *) #define __genradix_obj_size(_radix) sizeof((_radix)->type[0]) +#define __genradix_objs_per_page(_radix) \ + (PAGE_SIZE / sizeof((_radix)->type[0])) +#define __genradix_page_remainder(_radix) \ + (PAGE_SIZE % sizeof((_radix)->type[0])) + #define __genradix_idx_to_offset(_radix, _idx) \ __idx_to_offset(_idx, __genradix_obj_size(_radix)) @@ -180,7 +185,25 @@ void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t); #define genradix_iter_peek(_iter, _radix) \ (__genradix_cast(_radix) \ __genradix_iter_peek(_iter, &(_radix)->tree, \ - PAGE_SIZE / __genradix_obj_size(_radix))) + __genradix_objs_per_page(_radix))) + +void *__genradix_iter_peek_prev(struct genradix_iter *, struct __genradix *, + size_t, size_t); + +/** + * genradix_iter_peek_prev - get first entry at or below iterator's current + * position + * @_iter: a genradix_iter + * @_radix: genradix being iterated over + * + * If no more entries exist at or below @_iter's current position, returns NULL + */ +#define genradix_iter_peek_prev(_iter, _radix) \ + (__genradix_cast(_radix) \ + __genradix_iter_peek_prev(_iter, &(_radix)->tree, \ + __genradix_objs_per_page(_radix), \ + __genradix_obj_size(_radix) + \ + __genradix_page_remainder(_radix))) static inline void __genradix_iter_advance(struct genradix_iter *iter, size_t obj_size) @@ -203,6 +226,25 @@ static inline void __genradix_iter_advance(struct genradix_iter *iter, #define genradix_iter_advance(_iter, _radix) \ __genradix_iter_advance(_iter, __genradix_obj_size(_radix)) +static inline void __genradix_iter_rewind(struct genradix_iter *iter, + size_t obj_size) +{ + if (iter->offset == 0 || + iter->offset == SIZE_MAX) { + iter->offset = SIZE_MAX; + return; + } + + if ((iter->offset & (PAGE_SIZE - 1)) == 0) + iter->offset -= PAGE_SIZE % obj_size; + + iter->offset -= obj_size; + iter->pos--; +} + +#define genradix_iter_rewind(_iter, _radix) \ + __genradix_iter_rewind(_iter, __genradix_obj_size(_radix)) + #define genradix_for_each_from(_radix, _iter, _p, _start) \ for (_iter = genradix_iter_init(_radix, _start); \ (_p = genradix_iter_peek(&_iter, _radix)) != NULL; \ @@ -220,6 +262,23 @@ static inline void __genradix_iter_advance(struct genradix_iter *iter, #define genradix_for_each(_radix, _iter, _p) \ genradix_for_each_from(_radix, _iter, _p, 0) +#define genradix_last_pos(_radix) \ + (SIZE_MAX / PAGE_SIZE * __genradix_objs_per_page(_radix) - 1) + +/** + * genradix_for_each_reverse - iterate over entry in a genradix, reverse order + * @_radix: genradix to iterate over + * @_iter: a genradix_iter to track current position + * @_p: pointer to genradix entry type + * + * On every iteration, @_p will point to the current entry, and @_iter.pos + * will be the current entry's index. + */ +#define genradix_for_each_reverse(_radix, _iter, _p) \ + for (_iter = genradix_iter_init(_radix, genradix_last_pos(_radix));\ + (_p = genradix_iter_peek_prev(&_iter, _radix)) != NULL;\ + genradix_iter_rewind(&_iter, _radix)) + int __genradix_prealloc(struct __genradix *, size_t, gfp_t); /** diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c index 7dfa88282b00..41f1bcdc4488 100644 --- a/lib/generic-radix-tree.c +++ b/lib/generic-radix-tree.c @@ -1,4 +1,5 @@ +#include #include #include #include @@ -212,6 +213,64 @@ void *__genradix_iter_peek(struct genradix_iter *iter, } EXPORT_SYMBOL(__genradix_iter_peek); +void *__genradix_iter_peek_prev(struct genradix_iter *iter, + struct __genradix *radix, + size_t objs_per_page, + size_t obj_size_plus_page_remainder) +{ + struct genradix_root *r; + struct genradix_node *n; + unsigned level, i; + + if (iter->offset == SIZE_MAX) + return NULL; + +restart: + r = READ_ONCE(radix->root); + if (!r) + return NULL; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (ilog2(iter->offset) >= genradix_depth_shift(level)) { + iter->offset = genradix_depth_size(level); + iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page; + + iter->offset -= obj_size_plus_page_remainder; + iter->pos--; + } + + while (level) { + level--; + + i = (iter->offset >> genradix_depth_shift(level)) & + (GENRADIX_ARY - 1); + + while (!n->children[i]) { + size_t objs_per_ptr = genradix_depth_size(level); + + iter->offset = round_down(iter->offset, objs_per_ptr); + iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page; + + if (!iter->offset) + return NULL; + + iter->offset -= obj_size_plus_page_remainder; + iter->pos--; + + if (!i) + goto restart; + --i; + } + + n = n->children[i]; + } + + return &n->data[iter->offset & (PAGE_SIZE - 1)]; +} +EXPORT_SYMBOL(__genradix_iter_peek_prev); + static void genradix_free_recurse(struct genradix_node *n, unsigned level) { if (level) {