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authorKent Overstreet <kent.overstreet@gmail.com>2019-03-11 23:31:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-12 10:04:02 -0700
commitba20ba2e3743bac786dff777954c11930256075e (patch)
treecd2f3f1282893d80183d12d6b49ab2b084122b88 /lib
parentacdf52d97f824019888422842757013b37441dd1 (diff)
downloadlinux-stericsson-ba20ba2e3743bac786dff777954c11930256075e.tar.gz
generic radix trees
Very simple radix tree implementation that supports storing arbitrary size entries, up to PAGE_SIZE - upcoming patches will convert existing flex_array users to genradixes. The new genradix code has a much simpler API and implementation, and doesn't have a hard limit on the number of elements like flex_array does. Link: http://lkml.kernel.org/r/20181217131929.11727-5-kent.overstreet@gmail.com Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Eric Paris <eparis@parisplace.org> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Paul Moore <paul@paul-moore.com> Cc: Pravin B Shelar <pshelar@ovn.org> Cc: Shaohua Li <shli@kernel.org> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Vlad Yasevich <vyasevich@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile3
-rw-r--r--lib/generic-radix-tree.c217
2 files changed, 219 insertions, 1 deletions
diff --git a/lib/Makefile b/lib/Makefile
index 647517940b29..b798b41d01ae 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -38,7 +38,8 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
bsearch.o find_bit.o llist.o memweight.o kfifo.o \
percpu-refcount.o rhashtable.o reciprocal_div.o \
- once.o refcount.o usercopy.o errseq.o bucket_locks.o
+ once.o refcount.o usercopy.o errseq.o bucket_locks.o \
+ generic-radix-tree.o
obj-$(CONFIG_STRING_SELFTEST) += test_string.o
obj-y += string_helpers.o
obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
new file mode 100644
index 000000000000..a7bafc413730
--- /dev/null
+++ b/lib/generic-radix-tree.c
@@ -0,0 +1,217 @@
+
+#include <linux/export.h>
+#include <linux/generic-radix-tree.h>
+#include <linux/gfp.h>
+
+#define GENRADIX_ARY (PAGE_SIZE / sizeof(struct genradix_node *))
+#define GENRADIX_ARY_SHIFT ilog2(GENRADIX_ARY)
+
+struct genradix_node {
+ union {
+ /* Interior node: */
+ struct genradix_node *children[GENRADIX_ARY];
+
+ /* Leaf: */
+ u8 data[PAGE_SIZE];
+ };
+};
+
+static inline int genradix_depth_shift(unsigned depth)
+{
+ return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth;
+}
+
+/*
+ * Returns size (of data, in bytes) that a tree of a given depth holds:
+ */
+static inline size_t genradix_depth_size(unsigned depth)
+{
+ return 1UL << genradix_depth_shift(depth);
+}
+
+/* depth that's needed for a genradix that can address up to ULONG_MAX: */
+#define GENRADIX_MAX_DEPTH \
+ DIV_ROUND_UP(BITS_PER_LONG - PAGE_SHIFT, GENRADIX_ARY_SHIFT)
+
+#define GENRADIX_DEPTH_MASK \
+ ((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
+
+unsigned genradix_root_to_depth(struct genradix_root *r)
+{
+ return (unsigned long) r & GENRADIX_DEPTH_MASK;
+}
+
+struct genradix_node *genradix_root_to_node(struct genradix_root *r)
+{
+ return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
+}
+
+/*
+ * Returns pointer to the specified byte @offset within @radix, or NULL if not
+ * allocated
+ */
+void *__genradix_ptr(struct __genradix *radix, size_t offset)
+{
+ struct genradix_root *r = READ_ONCE(radix->root);
+ struct genradix_node *n = genradix_root_to_node(r);
+ unsigned level = genradix_root_to_depth(r);
+
+ if (ilog2(offset) >= genradix_depth_shift(level))
+ return NULL;
+
+ while (1) {
+ if (!n)
+ return NULL;
+ if (!level)
+ break;
+
+ level--;
+
+ n = n->children[offset >> genradix_depth_shift(level)];
+ offset &= genradix_depth_size(level) - 1;
+ }
+
+ return &n->data[offset];
+}
+EXPORT_SYMBOL(__genradix_ptr);
+
+/*
+ * Returns pointer to the specified byte @offset within @radix, allocating it if
+ * necessary - newly allocated slots are always zeroed out:
+ */
+void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
+ gfp_t gfp_mask)
+{
+ struct genradix_root *v = READ_ONCE(radix->root);
+ struct genradix_node *n, *new_node = NULL;
+ unsigned level;
+
+ /* Increase tree depth if necessary: */
+ while (1) {
+ struct genradix_root *r = v, *new_root;
+
+ n = genradix_root_to_node(r);
+ level = genradix_root_to_depth(r);
+
+ if (n && ilog2(offset) < genradix_depth_shift(level))
+ break;
+
+ if (!new_node) {
+ new_node = (void *)
+ __get_free_page(gfp_mask|__GFP_ZERO);
+ if (!new_node)
+ return NULL;
+ }
+
+ new_node->children[0] = n;
+ new_root = ((struct genradix_root *)
+ ((unsigned long) new_node | (n ? level + 1 : 0)));
+
+ if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
+ v = new_root;
+ new_node = NULL;
+ }
+ }
+
+ while (level--) {
+ struct genradix_node **p =
+ &n->children[offset >> genradix_depth_shift(level)];
+ offset &= genradix_depth_size(level) - 1;
+
+ n = READ_ONCE(*p);
+ if (!n) {
+ if (!new_node) {
+ new_node = (void *)
+ __get_free_page(gfp_mask|__GFP_ZERO);
+ if (!new_node)
+ return NULL;
+ }
+
+ if (!(n = cmpxchg_release(p, NULL, new_node)))
+ swap(n, new_node);
+ }
+ }
+
+ if (new_node)
+ free_page((unsigned long) new_node);
+
+ return &n->data[offset];
+}
+EXPORT_SYMBOL(__genradix_ptr_alloc);
+
+void *__genradix_iter_peek(struct genradix_iter *iter,
+ struct __genradix *radix,
+ size_t objs_per_page)
+{
+ struct genradix_root *r;
+ struct genradix_node *n;
+ unsigned level, i;
+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))
+ return NULL;
+
+ while (level) {
+ level--;
+
+ i = (iter->offset >> genradix_depth_shift(level)) &
+ (GENRADIX_ARY - 1);
+
+ while (!n->children[i]) {
+ i++;
+ iter->offset = round_down(iter->offset +
+ genradix_depth_size(level),
+ genradix_depth_size(level));
+ iter->pos = (iter->offset >> PAGE_SHIFT) *
+ objs_per_page;
+ if (i == GENRADIX_ARY)
+ goto restart;
+ }
+
+ n = n->children[i];
+ }
+
+ return &n->data[iter->offset & (PAGE_SIZE - 1)];
+}
+EXPORT_SYMBOL(__genradix_iter_peek);
+
+static void genradix_free_recurse(struct genradix_node *n, unsigned level)
+{
+ if (level) {
+ unsigned i;
+
+ for (i = 0; i < GENRADIX_ARY; i++)
+ if (n->children[i])
+ genradix_free_recurse(n->children[i], level - 1);
+ }
+
+ free_page((unsigned long) n);
+}
+
+int __genradix_prealloc(struct __genradix *radix, size_t size,
+ gfp_t gfp_mask)
+{
+ size_t offset;
+
+ for (offset = 0; offset < size; offset += PAGE_SIZE)
+ if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
+ return -ENOMEM;
+
+ return 0;
+}
+EXPORT_SYMBOL(__genradix_prealloc);
+
+void __genradix_free(struct __genradix *radix)
+{
+ struct genradix_root *r = xchg(&radix->root, NULL);
+
+ genradix_free_recurse(genradix_root_to_node(r),
+ genradix_root_to_depth(r));
+}
+EXPORT_SYMBOL(__genradix_free);