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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /include/linux/radix-tree.h
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+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#ifndef _LINUX_RADIX_TREE_H
+#define _LINUX_RADIX_TREE_H
+
+#include <linux/preempt.h>
+#include <linux/types.h>
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/rcupdate.h>
+
+/*
+ * An indirect pointer (root->rnode pointing to a radix_tree_node, rather
+ * than a data item) is signalled by the low bit set in the root->rnode
+ * pointer.
+ *
+ * In this case root->height is > 0, but the indirect pointer tests are
+ * needed for RCU lookups (because root->height is unreliable). The only
+ * time callers need worry about this is when doing a lookup_slot under
+ * RCU.
+ *
+ * Indirect pointer in fact is also used to tag the last pointer of a node
+ * when it is shrunk, before we rcu free the node. See shrink code for
+ * details.
+ */
+#define RADIX_TREE_INDIRECT_PTR 1
+/*
+ * A common use of the radix tree is to store pointers to struct pages;
+ * but shmem/tmpfs needs also to store swap entries in the same tree:
+ * those are marked as exceptional entries to distinguish them.
+ * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
+ */
+#define RADIX_TREE_EXCEPTIONAL_ENTRY 2
+#define RADIX_TREE_EXCEPTIONAL_SHIFT 2
+
+static inline int radix_tree_is_indirect_ptr(void *ptr)
+{
+ return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
+}
+
+/*** radix-tree API starts here ***/
+
+#define RADIX_TREE_MAX_TAGS 3
+
+#ifdef __KERNEL__
+#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
+#else
+#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */
+#endif
+
+#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
+#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
+
+#define RADIX_TREE_TAG_LONGS \
+ ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
+
+#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
+#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
+ RADIX_TREE_MAP_SHIFT))
+
+/* Height component in node->path */
+#define RADIX_TREE_HEIGHT_SHIFT (RADIX_TREE_MAX_PATH + 1)
+#define RADIX_TREE_HEIGHT_MASK ((1UL << RADIX_TREE_HEIGHT_SHIFT) - 1)
+
+/* Internally used bits of node->count */
+#define RADIX_TREE_COUNT_SHIFT (RADIX_TREE_MAP_SHIFT + 1)
+#define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)
+
+struct radix_tree_node {
+ unsigned int path; /* Offset in parent & height from the bottom */
+ unsigned int count;
+ union {
+ struct {
+ /* Used when ascending tree */
+ struct radix_tree_node *parent;
+ /* For tree user */
+ void *private_data;
+ };
+ /* Used when freeing node */
+ struct rcu_head rcu_head;
+ };
+ /* For tree user */
+ struct list_head private_list;
+ void __rcu *slots[RADIX_TREE_MAP_SIZE];
+ unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
+};
+
+/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
+struct radix_tree_root {
+ unsigned int height;
+ gfp_t gfp_mask;
+ struct radix_tree_node __rcu *rnode;
+};
+
+#define RADIX_TREE_INIT(mask) { \
+ .height = 0, \
+ .gfp_mask = (mask), \
+ .rnode = NULL, \
+}
+
+#define RADIX_TREE(name, mask) \
+ struct radix_tree_root name = RADIX_TREE_INIT(mask)
+
+#define INIT_RADIX_TREE(root, mask) \
+do { \
+ (root)->height = 0; \
+ (root)->gfp_mask = (mask); \
+ (root)->rnode = NULL; \
+} while (0)
+
+/**
+ * Radix-tree synchronization
+ *
+ * The radix-tree API requires that users provide all synchronisation (with
+ * specific exceptions, noted below).
+ *
+ * Synchronization of access to the data items being stored in the tree, and
+ * management of their lifetimes must be completely managed by API users.
+ *
+ * For API usage, in general,
+ * - any function _modifying_ the tree or tags (inserting or deleting
+ * items, setting or clearing tags) must exclude other modifications, and
+ * exclude any functions reading the tree.
+ * - any function _reading_ the tree or tags (looking up items or tags,
+ * gang lookups) must exclude modifications to the tree, but may occur
+ * concurrently with other readers.
+ *
+ * The notable exceptions to this rule are the following functions:
+ * __radix_tree_lookup
+ * radix_tree_lookup
+ * radix_tree_lookup_slot
+ * radix_tree_tag_get
+ * radix_tree_gang_lookup
+ * radix_tree_gang_lookup_slot
+ * radix_tree_gang_lookup_tag
+ * radix_tree_gang_lookup_tag_slot
+ * radix_tree_tagged
+ *
+ * The first 7 functions are able to be called locklessly, using RCU. The
+ * caller must ensure calls to these functions are made within rcu_read_lock()
+ * regions. Other readers (lock-free or otherwise) and modifications may be
+ * running concurrently.
+ *
+ * It is still required that the caller manage the synchronization and lifetimes
+ * of the items. So if RCU lock-free lookups are used, typically this would mean
+ * that the items have their own locks, or are amenable to lock-free access; and
+ * that the items are freed by RCU (or only freed after having been deleted from
+ * the radix tree *and* a synchronize_rcu() grace period).
+ *
+ * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
+ * access to data items when inserting into or looking up from the radix tree)
+ *
+ * Note that the value returned by radix_tree_tag_get() may not be relied upon
+ * if only the RCU read lock is held. Functions to set/clear tags and to
+ * delete nodes running concurrently with it may affect its result such that
+ * two consecutive reads in the same locked section may return different
+ * values. If reliability is required, modification functions must also be
+ * excluded from concurrency.
+ *
+ * radix_tree_tagged is able to be called without locking or RCU.
+ */
+
+/**
+ * radix_tree_deref_slot - dereference a slot
+ * @pslot: pointer to slot, returned by radix_tree_lookup_slot
+ * Returns: item that was stored in that slot with any direct pointer flag
+ * removed.
+ *
+ * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
+ * locked across slot lookup and dereference. Not required if write lock is
+ * held (ie. items cannot be concurrently inserted).
+ *
+ * radix_tree_deref_retry must be used to confirm validity of the pointer if
+ * only the read lock is held.
+ */
+static inline void *radix_tree_deref_slot(void **pslot)
+{
+ return rcu_dereference(*pslot);
+}
+
+/**
+ * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
+ * @pslot: pointer to slot, returned by radix_tree_lookup_slot
+ * Returns: item that was stored in that slot with any direct pointer flag
+ * removed.
+ *
+ * Similar to radix_tree_deref_slot but only used during migration when a pages
+ * mapping is being moved. The caller does not hold the RCU read lock but it
+ * must hold the tree lock to prevent parallel updates.
+ */
+static inline void *radix_tree_deref_slot_protected(void **pslot,
+ spinlock_t *treelock)
+{
+ return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
+}
+
+/**
+ * radix_tree_deref_retry - check radix_tree_deref_slot
+ * @arg: pointer returned by radix_tree_deref_slot
+ * Returns: 0 if retry is not required, otherwise retry is required
+ *
+ * radix_tree_deref_retry must be used with radix_tree_deref_slot.
+ */
+static inline int radix_tree_deref_retry(void *arg)
+{
+ return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
+}
+
+/**
+ * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
+ * @arg: value returned by radix_tree_deref_slot
+ * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
+ */
+static inline int radix_tree_exceptional_entry(void *arg)
+{
+ /* Not unlikely because radix_tree_exception often tested first */
+ return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
+}
+
+/**
+ * radix_tree_exception - radix_tree_deref_slot returned either exception?
+ * @arg: value returned by radix_tree_deref_slot
+ * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
+ */
+static inline int radix_tree_exception(void *arg)
+{
+ return unlikely((unsigned long)arg &
+ (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
+}
+
+/**
+ * radix_tree_replace_slot - replace item in a slot
+ * @pslot: pointer to slot, returned by radix_tree_lookup_slot
+ * @item: new item to store in the slot.
+ *
+ * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
+ * across slot lookup and replacement.
+ */
+static inline void radix_tree_replace_slot(void **pslot, void *item)
+{
+ BUG_ON(radix_tree_is_indirect_ptr(item));
+ rcu_assign_pointer(*pslot, item);
+}
+
+int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
+ struct radix_tree_node **nodep, void ***slotp);
+int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
+void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
+ struct radix_tree_node **nodep, void ***slotp);
+void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
+void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
+bool __radix_tree_delete_node(struct radix_tree_root *root,
+ struct radix_tree_node *node);
+void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
+void *radix_tree_delete(struct radix_tree_root *, unsigned long);
+unsigned int
+radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
+ unsigned long first_index, unsigned int max_items);
+unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
+ void ***results, unsigned long *indices,
+ unsigned long first_index, unsigned int max_items);
+int radix_tree_preload(gfp_t gfp_mask);
+int radix_tree_maybe_preload(gfp_t gfp_mask);
+void radix_tree_init(void);
+void *radix_tree_tag_set(struct radix_tree_root *root,
+ unsigned long index, unsigned int tag);
+void *radix_tree_tag_clear(struct radix_tree_root *root,
+ unsigned long index, unsigned int tag);
+int radix_tree_tag_get(struct radix_tree_root *root,
+ unsigned long index, unsigned int tag);
+unsigned int
+radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
+ unsigned long first_index, unsigned int max_items,
+ unsigned int tag);
+unsigned int
+radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
+ unsigned long first_index, unsigned int max_items,
+ unsigned int tag);
+unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
+ unsigned long *first_indexp, unsigned long last_index,
+ unsigned long nr_to_tag,
+ unsigned int fromtag, unsigned int totag);
+int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);
+
+static inline void radix_tree_preload_end(void)
+{
+ preempt_enable();
+}
+
+/**
+ * struct radix_tree_iter - radix tree iterator state
+ *
+ * @index: index of current slot
+ * @next_index: next-to-last index for this chunk
+ * @tags: bit-mask for tag-iterating
+ *
+ * This radix tree iterator works in terms of "chunks" of slots. A chunk is a
+ * subinterval of slots contained within one radix tree leaf node. It is
+ * described by a pointer to its first slot and a struct radix_tree_iter
+ * which holds the chunk's position in the tree and its size. For tagged
+ * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
+ * radix tree tag.
+ */
+struct radix_tree_iter {
+ unsigned long index;
+ unsigned long next_index;
+ unsigned long tags;
+};
+
+#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */
+#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */
+#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */
+
+/**
+ * radix_tree_iter_init - initialize radix tree iterator
+ *
+ * @iter: pointer to iterator state
+ * @start: iteration starting index
+ * Returns: NULL
+ */
+static __always_inline void **
+radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
+{
+ /*
+ * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
+ * in the case of a successful tagged chunk lookup. If the lookup was
+ * unsuccessful or non-tagged then nobody cares about ->tags.
+ *
+ * Set index to zero to bypass next_index overflow protection.
+ * See the comment in radix_tree_next_chunk() for details.
+ */
+ iter->index = 0;
+ iter->next_index = start;
+ return NULL;
+}
+
+/**
+ * radix_tree_next_chunk - find next chunk of slots for iteration
+ *
+ * @root: radix tree root
+ * @iter: iterator state
+ * @flags: RADIX_TREE_ITER_* flags and tag index
+ * Returns: pointer to chunk first slot, or NULL if there no more left
+ *
+ * This function looks up the next chunk in the radix tree starting from
+ * @iter->next_index. It returns a pointer to the chunk's first slot.
+ * Also it fills @iter with data about chunk: position in the tree (index),
+ * its end (next_index), and constructs a bit mask for tagged iterating (tags).
+ */
+void **radix_tree_next_chunk(struct radix_tree_root *root,
+ struct radix_tree_iter *iter, unsigned flags);
+
+/**
+ * radix_tree_chunk_size - get current chunk size
+ *
+ * @iter: pointer to radix tree iterator
+ * Returns: current chunk size
+ */
+static __always_inline unsigned
+radix_tree_chunk_size(struct radix_tree_iter *iter)
+{
+ return iter->next_index - iter->index;
+}
+
+/**
+ * radix_tree_next_slot - find next slot in chunk
+ *
+ * @slot: pointer to current slot
+ * @iter: pointer to interator state
+ * @flags: RADIX_TREE_ITER_*, should be constant
+ * Returns: pointer to next slot, or NULL if there no more left
+ *
+ * This function updates @iter->index in the case of a successful lookup.
+ * For tagged lookup it also eats @iter->tags.
+ */
+static __always_inline void **
+radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
+{
+ if (flags & RADIX_TREE_ITER_TAGGED) {
+ iter->tags >>= 1;
+ if (likely(iter->tags & 1ul)) {
+ iter->index++;
+ return slot + 1;
+ }
+ if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) {
+ unsigned offset = __ffs(iter->tags);
+
+ iter->tags >>= offset;
+ iter->index += offset + 1;
+ return slot + offset + 1;
+ }
+ } else {
+ unsigned size = radix_tree_chunk_size(iter) - 1;
+
+ while (size--) {
+ slot++;
+ iter->index++;
+ if (likely(*slot))
+ return slot;
+ if (flags & RADIX_TREE_ITER_CONTIG) {
+ /* forbid switching to the next chunk */
+ iter->next_index = 0;
+ break;
+ }
+ }
+ }
+ return NULL;
+}
+
+/**
+ * radix_tree_for_each_chunk - iterate over chunks
+ *
+ * @slot: the void** variable for pointer to chunk first slot
+ * @root: the struct radix_tree_root pointer
+ * @iter: the struct radix_tree_iter pointer
+ * @start: iteration starting index
+ * @flags: RADIX_TREE_ITER_* and tag index
+ *
+ * Locks can be released and reacquired between iterations.
+ */
+#define radix_tree_for_each_chunk(slot, root, iter, start, flags) \
+ for (slot = radix_tree_iter_init(iter, start) ; \
+ (slot = radix_tree_next_chunk(root, iter, flags)) ;)
+
+/**
+ * radix_tree_for_each_chunk_slot - iterate over slots in one chunk
+ *
+ * @slot: the void** variable, at the beginning points to chunk first slot
+ * @iter: the struct radix_tree_iter pointer
+ * @flags: RADIX_TREE_ITER_*, should be constant
+ *
+ * This macro is designed to be nested inside radix_tree_for_each_chunk().
+ * @slot points to the radix tree slot, @iter->index contains its index.
+ */
+#define radix_tree_for_each_chunk_slot(slot, iter, flags) \
+ for (; slot ; slot = radix_tree_next_slot(slot, iter, flags))
+
+/**
+ * radix_tree_for_each_slot - iterate over non-empty slots
+ *
+ * @slot: the void** variable for pointer to slot
+ * @root: the struct radix_tree_root pointer
+ * @iter: the struct radix_tree_iter pointer
+ * @start: iteration starting index
+ *
+ * @slot points to radix tree slot, @iter->index contains its index.
+ */
+#define radix_tree_for_each_slot(slot, root, iter, start) \
+ for (slot = radix_tree_iter_init(iter, start) ; \
+ slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
+ slot = radix_tree_next_slot(slot, iter, 0))
+
+/**
+ * radix_tree_for_each_contig - iterate over contiguous slots
+ *
+ * @slot: the void** variable for pointer to slot
+ * @root: the struct radix_tree_root pointer
+ * @iter: the struct radix_tree_iter pointer
+ * @start: iteration starting index
+ *
+ * @slot points to radix tree slot, @iter->index contains its index.
+ */
+#define radix_tree_for_each_contig(slot, root, iter, start) \
+ for (slot = radix_tree_iter_init(iter, start) ; \
+ slot || (slot = radix_tree_next_chunk(root, iter, \
+ RADIX_TREE_ITER_CONTIG)) ; \
+ slot = radix_tree_next_slot(slot, iter, \
+ RADIX_TREE_ITER_CONTIG))
+
+/**
+ * radix_tree_for_each_tagged - iterate over tagged slots
+ *
+ * @slot: the void** variable for pointer to slot
+ * @root: the struct radix_tree_root pointer
+ * @iter: the struct radix_tree_iter pointer
+ * @start: iteration starting index
+ * @tag: tag index
+ *
+ * @slot points to radix tree slot, @iter->index contains its index.
+ */
+#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
+ for (slot = radix_tree_iter_init(iter, start) ; \
+ slot || (slot = radix_tree_next_chunk(root, iter, \
+ RADIX_TREE_ITER_TAGGED | tag)) ; \
+ slot = radix_tree_next_slot(slot, iter, \
+ RADIX_TREE_ITER_TAGGED))
+
+#endif /* _LINUX_RADIX_TREE_H */