linux/lib/radix-tree.c
Vladimir Davydov 05eb6e7263 radix-tree: account nodes to memcg only if explicitly requested
Radix trees may be used not only for storing page cache pages, so
unconditionally accounting radix tree nodes to the current memory cgroup
is bad: if a radix tree node is used for storing data shared among
different cgroups we risk pinning dead memory cgroups forever.

So let's only account radix tree nodes if it was explicitly requested by
passing __GFP_ACCOUNT to INIT_RADIX_TREE.  Currently, we only want to
account page cache entries, so mark mapping->page_tree so.

Fixes: 58e698af4c ("radix-tree: account radix_tree_node to memory cgroup")
Link: http://lkml.kernel.org/r/1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>	[4.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02 17:31:41 -04:00

1682 lines
44 KiB
C

/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2005 SGI, Christoph Lameter
* Copyright (C) 2006 Nick Piggin
* Copyright (C) 2012 Konstantin Khlebnikov
* Copyright (C) 2016 Intel, Matthew Wilcox
* Copyright (C) 2016 Intel, Ross Zwisler
*
* 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.
*/
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/radix-tree.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/kmemleak.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/string.h>
#include <linux/bitops.h>
#include <linux/rcupdate.h>
#include <linux/preempt.h> /* in_interrupt() */
/* Number of nodes in fully populated tree of given height */
static unsigned long height_to_maxnodes[RADIX_TREE_MAX_PATH + 1] __read_mostly;
/*
* Radix tree node cache.
*/
static struct kmem_cache *radix_tree_node_cachep;
/*
* The radix tree is variable-height, so an insert operation not only has
* to build the branch to its corresponding item, it also has to build the
* branch to existing items if the size has to be increased (by
* radix_tree_extend).
*
* The worst case is a zero height tree with just a single item at index 0,
* and then inserting an item at index ULONG_MAX. This requires 2 new branches
* of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
* Hence:
*/
#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
/*
* Per-cpu pool of preloaded nodes
*/
struct radix_tree_preload {
unsigned nr;
/* nodes->private_data points to next preallocated node */
struct radix_tree_node *nodes;
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
static inline void *node_to_entry(void *ptr)
{
return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
}
#define RADIX_TREE_RETRY node_to_entry(NULL)
#ifdef CONFIG_RADIX_TREE_MULTIORDER
/* Sibling slots point directly to another slot in the same node */
static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
{
void **ptr = node;
return (parent->slots <= ptr) &&
(ptr < parent->slots + RADIX_TREE_MAP_SIZE);
}
#else
static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
{
return false;
}
#endif
static inline unsigned long get_slot_offset(struct radix_tree_node *parent,
void **slot)
{
return slot - parent->slots;
}
static unsigned int radix_tree_descend(struct radix_tree_node *parent,
struct radix_tree_node **nodep, unsigned long index)
{
unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
void **entry = rcu_dereference_raw(parent->slots[offset]);
#ifdef CONFIG_RADIX_TREE_MULTIORDER
if (radix_tree_is_internal_node(entry)) {
unsigned long siboff = get_slot_offset(parent, entry);
if (siboff < RADIX_TREE_MAP_SIZE) {
offset = siboff;
entry = rcu_dereference_raw(parent->slots[offset]);
}
}
#endif
*nodep = (void *)entry;
return offset;
}
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
}
static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__set_bit(offset, node->tags[tag]);
}
static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__clear_bit(offset, node->tags[tag]);
}
static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
int offset)
{
return test_bit(offset, node->tags[tag]);
}
static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
{
root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
{
root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear_all(struct radix_tree_root *root)
{
root->gfp_mask &= __GFP_BITS_MASK;
}
static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
{
return (__force int)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
}
static inline unsigned root_tags_get(struct radix_tree_root *root)
{
return (__force unsigned)root->gfp_mask >> __GFP_BITS_SHIFT;
}
/*
* Returns 1 if any slot in the node has this tag set.
* Otherwise returns 0.
*/
static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
{
unsigned idx;
for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
if (node->tags[tag][idx])
return 1;
}
return 0;
}
/**
* radix_tree_find_next_bit - find the next set bit in a memory region
*
* @addr: The address to base the search on
* @size: The bitmap size in bits
* @offset: The bitnumber to start searching at
*
* Unrollable variant of find_next_bit() for constant size arrays.
* Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
* Returns next bit offset, or size if nothing found.
*/
static __always_inline unsigned long
radix_tree_find_next_bit(const unsigned long *addr,
unsigned long size, unsigned long offset)
{
if (!__builtin_constant_p(size))
return find_next_bit(addr, size, offset);
if (offset < size) {
unsigned long tmp;
addr += offset / BITS_PER_LONG;
tmp = *addr >> (offset % BITS_PER_LONG);
if (tmp)
return __ffs(tmp) + offset;
offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
while (offset < size) {
tmp = *++addr;
if (tmp)
return __ffs(tmp) + offset;
offset += BITS_PER_LONG;
}
}
return size;
}
#ifndef __KERNEL__
static void dump_node(struct radix_tree_node *node, unsigned long index)
{
unsigned long i;
pr_debug("radix node: %p offset %d tags %lx %lx %lx shift %d count %d parent %p\n",
node, node->offset,
node->tags[0][0], node->tags[1][0], node->tags[2][0],
node->shift, node->count, node->parent);
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
unsigned long first = index | (i << node->shift);
unsigned long last = first | ((1UL << node->shift) - 1);
void *entry = node->slots[i];
if (!entry)
continue;
if (is_sibling_entry(node, entry)) {
pr_debug("radix sblng %p offset %ld val %p indices %ld-%ld\n",
entry, i,
*(void **)entry_to_node(entry),
first, last);
} else if (!radix_tree_is_internal_node(entry)) {
pr_debug("radix entry %p offset %ld indices %ld-%ld\n",
entry, i, first, last);
} else {
dump_node(entry_to_node(entry), first);
}
}
}
/* For debug */
static void radix_tree_dump(struct radix_tree_root *root)
{
pr_debug("radix root: %p rnode %p tags %x\n",
root, root->rnode,
root->gfp_mask >> __GFP_BITS_SHIFT);
if (!radix_tree_is_internal_node(root->rnode))
return;
dump_node(entry_to_node(root->rnode), 0);
}
#endif
/*
* This assumes that the caller has performed appropriate preallocation, and
* that the caller has pinned this thread of control to the current CPU.
*/
static struct radix_tree_node *
radix_tree_node_alloc(struct radix_tree_root *root)
{
struct radix_tree_node *ret = NULL;
gfp_t gfp_mask = root_gfp_mask(root);
/*
* Preload code isn't irq safe and it doesn't make sense to use
* preloading during an interrupt anyway as all the allocations have
* to be atomic. So just do normal allocation when in interrupt.
*/
if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
struct radix_tree_preload *rtp;
/*
* Even if the caller has preloaded, try to allocate from the
* cache first for the new node to get accounted to the memory
* cgroup.
*/
ret = kmem_cache_alloc(radix_tree_node_cachep,
gfp_mask | __GFP_NOWARN);
if (ret)
goto out;
/*
* Provided the caller has preloaded here, we will always
* succeed in getting a node here (and never reach
* kmem_cache_alloc)
*/
rtp = this_cpu_ptr(&radix_tree_preloads);
if (rtp->nr) {
ret = rtp->nodes;
rtp->nodes = ret->private_data;
ret->private_data = NULL;
rtp->nr--;
}
/*
* Update the allocation stack trace as this is more useful
* for debugging.
*/
kmemleak_update_trace(ret);
goto out;
}
ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
out:
BUG_ON(radix_tree_is_internal_node(ret));
return ret;
}
static void radix_tree_node_rcu_free(struct rcu_head *head)
{
struct radix_tree_node *node =
container_of(head, struct radix_tree_node, rcu_head);
int i;
/*
* must only free zeroed nodes into the slab. radix_tree_shrink
* can leave us with a non-NULL entry in the first slot, so clear
* that here to make sure.
*/
for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
tag_clear(node, i, 0);
node->slots[0] = NULL;
node->count = 0;
kmem_cache_free(radix_tree_node_cachep, node);
}
static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
}
/*
* Load up this CPU's radix_tree_node buffer with sufficient objects to
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
*
* To make use of this facility, the radix tree must be initialised without
* __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
*/
static int __radix_tree_preload(gfp_t gfp_mask, int nr)
{
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
int ret = -ENOMEM;
/*
* Nodes preloaded by one cgroup can be be used by another cgroup, so
* they should never be accounted to any particular memory cgroup.
*/
gfp_mask &= ~__GFP_ACCOUNT;
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
while (rtp->nr < nr) {
preempt_enable();
node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
if (node == NULL)
goto out;
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
if (rtp->nr < nr) {
node->private_data = rtp->nodes;
rtp->nodes = node;
rtp->nr++;
} else {
kmem_cache_free(radix_tree_node_cachep, node);
}
}
ret = 0;
out:
return ret;
}
/*
* Load up this CPU's radix_tree_node buffer with sufficient objects to
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
*
* To make use of this facility, the radix tree must be initialised without
* __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
*/
int radix_tree_preload(gfp_t gfp_mask)
{
/* Warn on non-sensical use... */
WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
}
EXPORT_SYMBOL(radix_tree_preload);
/*
* The same as above function, except we don't guarantee preloading happens.
* We do it, if we decide it helps. On success, return zero with preemption
* disabled. On error, return -ENOMEM with preemption not disabled.
*/
int radix_tree_maybe_preload(gfp_t gfp_mask)
{
if (gfpflags_allow_blocking(gfp_mask))
return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
/* Preloading doesn't help anything with this gfp mask, skip it */
preempt_disable();
return 0;
}
EXPORT_SYMBOL(radix_tree_maybe_preload);
/*
* The same as function above, but preload number of nodes required to insert
* (1 << order) continuous naturally-aligned elements.
*/
int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order)
{
unsigned long nr_subtrees;
int nr_nodes, subtree_height;
/* Preloading doesn't help anything with this gfp mask, skip it */
if (!gfpflags_allow_blocking(gfp_mask)) {
preempt_disable();
return 0;
}
/*
* Calculate number and height of fully populated subtrees it takes to
* store (1 << order) elements.
*/
nr_subtrees = 1 << order;
for (subtree_height = 0; nr_subtrees > RADIX_TREE_MAP_SIZE;
subtree_height++)
nr_subtrees >>= RADIX_TREE_MAP_SHIFT;
/*
* The worst case is zero height tree with a single item at index 0 and
* then inserting items starting at ULONG_MAX - (1 << order).
*
* This requires RADIX_TREE_MAX_PATH nodes to build branch from root to
* 0-index item.
*/
nr_nodes = RADIX_TREE_MAX_PATH;
/* Plus branch to fully populated subtrees. */
nr_nodes += RADIX_TREE_MAX_PATH - subtree_height;
/* Root node is shared. */
nr_nodes--;
/* Plus nodes required to build subtrees. */
nr_nodes += nr_subtrees * height_to_maxnodes[subtree_height];
return __radix_tree_preload(gfp_mask, nr_nodes);
}
/*
* The maximum index which can be stored in a radix tree
*/
static inline unsigned long shift_maxindex(unsigned int shift)
{
return (RADIX_TREE_MAP_SIZE << shift) - 1;
}
static inline unsigned long node_maxindex(struct radix_tree_node *node)
{
return shift_maxindex(node->shift);
}
static unsigned radix_tree_load_root(struct radix_tree_root *root,
struct radix_tree_node **nodep, unsigned long *maxindex)
{
struct radix_tree_node *node = rcu_dereference_raw(root->rnode);
*nodep = node;
if (likely(radix_tree_is_internal_node(node))) {
node = entry_to_node(node);
*maxindex = node_maxindex(node);
return node->shift + RADIX_TREE_MAP_SHIFT;
}
*maxindex = 0;
return 0;
}
/*
* Extend a radix tree so it can store key @index.
*/
static int radix_tree_extend(struct radix_tree_root *root,
unsigned long index, unsigned int shift)
{
struct radix_tree_node *slot;
unsigned int maxshift;
int tag;
/* Figure out what the shift should be. */
maxshift = shift;
while (index > shift_maxindex(maxshift))
maxshift += RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
if (!slot)
goto out;
do {
struct radix_tree_node *node = radix_tree_node_alloc(root);
if (!node)
return -ENOMEM;
/* Propagate the aggregated tag info into the new root */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (root_tag_get(root, tag))
tag_set(node, tag, 0);
}
BUG_ON(shift > BITS_PER_LONG);
node->shift = shift;
node->offset = 0;
node->count = 1;
node->parent = NULL;
if (radix_tree_is_internal_node(slot))
entry_to_node(slot)->parent = node;
node->slots[0] = slot;
slot = node_to_entry(node);
rcu_assign_pointer(root->rnode, slot);
shift += RADIX_TREE_MAP_SHIFT;
} while (shift <= maxshift);
out:
return maxshift + RADIX_TREE_MAP_SHIFT;
}
/**
* __radix_tree_create - create a slot in a radix tree
* @root: radix tree root
* @index: index key
* @order: index occupies 2^order aligned slots
* @nodep: returns node
* @slotp: returns slot
*
* Create, if necessary, and return the node and slot for an item
* at position @index in the radix tree @root.
*
* Until there is more than one item in the tree, no nodes are
* allocated and @root->rnode is used as a direct slot instead of
* pointing to a node, in which case *@nodep will be NULL.
*
* Returns -ENOMEM, or 0 for success.
*/
int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
unsigned order, struct radix_tree_node **nodep,
void ***slotp)
{
struct radix_tree_node *node = NULL, *child;
void **slot = (void **)&root->rnode;
unsigned long maxindex;
unsigned int shift, offset = 0;
unsigned long max = index | ((1UL << order) - 1);
shift = radix_tree_load_root(root, &child, &maxindex);
/* Make sure the tree is high enough. */
if (max > maxindex) {
int error = radix_tree_extend(root, max, shift);
if (error < 0)
return error;
shift = error;
child = root->rnode;
if (order == shift)
shift += RADIX_TREE_MAP_SHIFT;
}
while (shift > order) {
shift -= RADIX_TREE_MAP_SHIFT;
if (child == NULL) {
/* Have to add a child node. */
child = radix_tree_node_alloc(root);
if (!child)
return -ENOMEM;
child->shift = shift;
child->offset = offset;
child->parent = node;
rcu_assign_pointer(*slot, node_to_entry(child));
if (node)
node->count++;
} else if (!radix_tree_is_internal_node(child))
break;
/* Go a level down */
node = entry_to_node(child);
offset = radix_tree_descend(node, &child, index);
slot = &node->slots[offset];
}
#ifdef CONFIG_RADIX_TREE_MULTIORDER
/* Insert pointers to the canonical entry */
if (order > shift) {
unsigned i, n = 1 << (order - shift);
offset = offset & ~(n - 1);
slot = &node->slots[offset];
child = node_to_entry(slot);
for (i = 0; i < n; i++) {
if (slot[i])
return -EEXIST;
}
for (i = 1; i < n; i++) {
rcu_assign_pointer(slot[i], child);
node->count++;
}
}
#endif
if (nodep)
*nodep = node;
if (slotp)
*slotp = slot;
return 0;
}
/**
* __radix_tree_insert - insert into a radix tree
* @root: radix tree root
* @index: index key
* @order: key covers the 2^order indices around index
* @item: item to insert
*
* Insert an item into the radix tree at position @index.
*/
int __radix_tree_insert(struct radix_tree_root *root, unsigned long index,
unsigned order, void *item)
{
struct radix_tree_node *node;
void **slot;
int error;
BUG_ON(radix_tree_is_internal_node(item));
error = __radix_tree_create(root, index, order, &node, &slot);
if (error)
return error;
if (*slot != NULL)
return -EEXIST;
rcu_assign_pointer(*slot, item);
if (node) {
unsigned offset = get_slot_offset(node, slot);
node->count++;
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
BUG_ON(tag_get(node, 2, offset));
} else {
BUG_ON(root_tags_get(root));
}
return 0;
}
EXPORT_SYMBOL(__radix_tree_insert);
/**
* __radix_tree_lookup - lookup an item in a radix tree
* @root: radix tree root
* @index: index key
* @nodep: returns node
* @slotp: returns slot
*
* Lookup and return the item at position @index in the radix
* tree @root.
*
* Until there is more than one item in the tree, no nodes are
* allocated and @root->rnode is used as a direct slot instead of
* pointing to a node, in which case *@nodep will be NULL.
*/
void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
struct radix_tree_node **nodep, void ***slotp)
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
void **slot;
restart:
parent = NULL;
slot = (void **)&root->rnode;
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return NULL;
while (radix_tree_is_internal_node(node)) {
unsigned offset;
if (node == RADIX_TREE_RETRY)
goto restart;
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);
slot = parent->slots + offset;
}
if (nodep)
*nodep = parent;
if (slotp)
*slotp = slot;
return node;
}
/**
* radix_tree_lookup_slot - lookup a slot in a radix tree
* @root: radix tree root
* @index: index key
*
* Returns: the slot corresponding to the position @index in the
* radix tree @root. This is useful for update-if-exists operations.
*
* This function can be called under rcu_read_lock iff the slot is not
* modified by radix_tree_replace_slot, otherwise it must be called
* exclusive from other writers. Any dereference of the slot must be done
* using radix_tree_deref_slot.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
void **slot;
if (!__radix_tree_lookup(root, index, NULL, &slot))
return NULL;
return slot;
}
EXPORT_SYMBOL(radix_tree_lookup_slot);
/**
* radix_tree_lookup - perform lookup operation on a radix tree
* @root: radix tree root
* @index: index key
*
* Lookup the item at the position @index in the radix tree @root.
*
* This function can be called under rcu_read_lock, however the caller
* must manage lifetimes of leaf nodes (eg. RCU may also be used to free
* them safely). No RCU barriers are required to access or modify the
* returned item, however.
*/
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
return __radix_tree_lookup(root, index, NULL, NULL);
}
EXPORT_SYMBOL(radix_tree_lookup);
/**
* radix_tree_tag_set - set a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. From
* the root all the way down to the leaf node.
*
* Returns the address of the tagged item. Setting a tag on a not-present
* item is a bug.
*/
void *radix_tree_tag_set(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
radix_tree_load_root(root, &node, &maxindex);
BUG_ON(index > maxindex);
while (radix_tree_is_internal_node(node)) {
unsigned offset;
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);
BUG_ON(!node);
if (!tag_get(parent, tag, offset))
tag_set(parent, tag, offset);
}
/* set the root's tag bit */
if (!root_tag_get(root, tag))
root_tag_set(root, tag);
return node;
}
EXPORT_SYMBOL(radix_tree_tag_set);
static void node_tag_clear(struct radix_tree_root *root,
struct radix_tree_node *node,
unsigned int tag, unsigned int offset)
{
while (node) {
if (!tag_get(node, tag, offset))
return;
tag_clear(node, tag, offset);
if (any_tag_set(node, tag))
return;
offset = node->offset;
node = node->parent;
}
/* clear the root's tag bit */
if (root_tag_get(root, tag))
root_tag_clear(root, tag);
}
/**
* radix_tree_tag_clear - clear a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. If this causes
* the leaf node to have no tags set then clear the tag in the
* next-to-leaf node, etc.
*
* Returns the address of the tagged item on success, else NULL. ie:
* has the same return value and semantics as radix_tree_lookup().
*/
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
int uninitialized_var(offset);
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return NULL;
parent = NULL;
while (radix_tree_is_internal_node(node)) {
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);
}
if (node)
node_tag_clear(root, parent, tag, offset);
return node;
}
EXPORT_SYMBOL(radix_tree_tag_clear);
/**
* radix_tree_tag_get - get a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index (< RADIX_TREE_MAX_TAGS)
*
* Return values:
*
* 0: tag not present or not set
* 1: tag set
*
* Note that the return value of this function may not be relied on, even if
* the RCU lock is held, unless tag modification and node deletion are excluded
* from concurrency.
*/
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
if (!root_tag_get(root, tag))
return 0;
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return 0;
if (node == NULL)
return 0;
while (radix_tree_is_internal_node(node)) {
unsigned offset;
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);
if (!node)
return 0;
if (!tag_get(parent, tag, offset))
return 0;
if (node == RADIX_TREE_RETRY)
break;
}
return 1;
}
EXPORT_SYMBOL(radix_tree_tag_get);
static inline void __set_iter_shift(struct radix_tree_iter *iter,
unsigned int shift)
{
#ifdef CONFIG_RADIX_TREE_MULTIORDER
iter->shift = shift;
#endif
}
/**
* 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 iteration is over
*/
void **radix_tree_next_chunk(struct radix_tree_root *root,
struct radix_tree_iter *iter, unsigned flags)
{
unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
struct radix_tree_node *node, *child;
unsigned long index, offset, maxindex;
if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
return NULL;
/*
* Catch next_index overflow after ~0UL. iter->index never overflows
* during iterating; it can be zero only at the beginning.
* And we cannot overflow iter->next_index in a single step,
* because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
*
* This condition also used by radix_tree_next_slot() to stop
* contiguous iterating, and forbid swithing to the next chunk.
*/
index = iter->next_index;
if (!index && iter->index)
return NULL;
restart:
radix_tree_load_root(root, &child, &maxindex);
if (index > maxindex)
return NULL;
if (!child)
return NULL;
if (!radix_tree_is_internal_node(child)) {
/* Single-slot tree */
iter->index = index;
iter->next_index = maxindex + 1;
iter->tags = 1;
__set_iter_shift(iter, 0);
return (void **)&root->rnode;
}
do {
node = entry_to_node(child);
offset = radix_tree_descend(node, &child, index);
if ((flags & RADIX_TREE_ITER_TAGGED) ?
!tag_get(node, tag, offset) : !child) {
/* Hole detected */
if (flags & RADIX_TREE_ITER_CONTIG)
return NULL;
if (flags & RADIX_TREE_ITER_TAGGED)
offset = radix_tree_find_next_bit(
node->tags[tag],
RADIX_TREE_MAP_SIZE,
offset + 1);
else
while (++offset < RADIX_TREE_MAP_SIZE) {
void *slot = node->slots[offset];
if (is_sibling_entry(node, slot))
continue;
if (slot)
break;
}
index &= ~node_maxindex(node);
index += offset << node->shift;
/* Overflow after ~0UL */
if (!index)
return NULL;
if (offset == RADIX_TREE_MAP_SIZE)
goto restart;
child = rcu_dereference_raw(node->slots[offset]);
}
if ((child == NULL) || (child == RADIX_TREE_RETRY))
goto restart;
} while (radix_tree_is_internal_node(child));
/* Update the iterator state */
iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
iter->next_index = (index | node_maxindex(node)) + 1;
__set_iter_shift(iter, node->shift);
/* Construct iter->tags bit-mask from node->tags[tag] array */
if (flags & RADIX_TREE_ITER_TAGGED) {
unsigned tag_long, tag_bit;
tag_long = offset / BITS_PER_LONG;
tag_bit = offset % BITS_PER_LONG;
iter->tags = node->tags[tag][tag_long] >> tag_bit;
/* This never happens if RADIX_TREE_TAG_LONGS == 1 */
if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
/* Pick tags from next element */
if (tag_bit)
iter->tags |= node->tags[tag][tag_long + 1] <<
(BITS_PER_LONG - tag_bit);
/* Clip chunk size, here only BITS_PER_LONG tags */
iter->next_index = index + BITS_PER_LONG;
}
}
return node->slots + offset;
}
EXPORT_SYMBOL(radix_tree_next_chunk);
/**
* radix_tree_range_tag_if_tagged - for each item in given range set given
* tag if item has another tag set
* @root: radix tree root
* @first_indexp: pointer to a starting index of a range to scan
* @last_index: last index of a range to scan
* @nr_to_tag: maximum number items to tag
* @iftag: tag index to test
* @settag: tag index to set if tested tag is set
*
* This function scans range of radix tree from first_index to last_index
* (inclusive). For each item in the range if iftag is set, the function sets
* also settag. The function stops either after tagging nr_to_tag items or
* after reaching last_index.
*
* The tags must be set from the leaf level only and propagated back up the
* path to the root. We must do this so that we resolve the full path before
* setting any tags on intermediate nodes. If we set tags as we descend, then
* we can get to the leaf node and find that the index that has the iftag
* set is outside the range we are scanning. This reults in dangling tags and
* can lead to problems with later tag operations (e.g. livelocks on lookups).
*
* The function returns the number of leaves where the tag was set and sets
* *first_indexp to the first unscanned index.
* WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
* be prepared to handle that.
*/
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 iftag, unsigned int settag)
{
struct radix_tree_node *parent, *node, *child;
unsigned long maxindex;
unsigned long tagged = 0;
unsigned long index = *first_indexp;
radix_tree_load_root(root, &child, &maxindex);
last_index = min(last_index, maxindex);
if (index > last_index)
return 0;
if (!nr_to_tag)
return 0;
if (!root_tag_get(root, iftag)) {
*first_indexp = last_index + 1;
return 0;
}
if (!radix_tree_is_internal_node(child)) {
*first_indexp = last_index + 1;
root_tag_set(root, settag);
return 1;
}
node = entry_to_node(child);
for (;;) {
unsigned offset = radix_tree_descend(node, &child, index);
if (!child)
goto next;
if (!tag_get(node, iftag, offset))
goto next;
/* Sibling slots never have tags set on them */
if (radix_tree_is_internal_node(child)) {
node = entry_to_node(child);
continue;
}
/* tag the leaf */
tagged++;
tag_set(node, settag, offset);
/* walk back up the path tagging interior nodes */
parent = node;
for (;;) {
offset = parent->offset;
parent = parent->parent;
if (!parent)
break;
/* stop if we find a node with the tag already set */
if (tag_get(parent, settag, offset))
break;
tag_set(parent, settag, offset);
}
next:
/* Go to next entry in node */
index = ((index >> node->shift) + 1) << node->shift;
/* Overflow can happen when last_index is ~0UL... */
if (index > last_index || !index)
break;
offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
while (offset == 0) {
/*
* We've fully scanned this node. Go up. Because
* last_index is guaranteed to be in the tree, what
* we do below cannot wander astray.
*/
node = node->parent;
offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
}
if (is_sibling_entry(node, node->slots[offset]))
goto next;
if (tagged >= nr_to_tag)
break;
}
/*
* We need not to tag the root tag if there is no tag which is set with
* settag within the range from *first_indexp to last_index.
*/
if (tagged > 0)
root_tag_set(root, settag);
*first_indexp = index;
return tagged;
}
EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
/**
* radix_tree_gang_lookup - perform multiple lookup on a radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
*
* Performs an index-ascending scan of the tree for present items. Places
* them at *@results and returns the number of items which were placed at
* *@results.
*
* The implementation is naive.
*
* Like radix_tree_lookup, radix_tree_gang_lookup may be called under
* rcu_read_lock. In this case, rather than the returned results being
* an atomic snapshot of the tree at a single point in time, the
* semantics of an RCU protected gang lookup are as though multiple
* radix_tree_lookups have been issued in individual locks, and results
* stored in 'results'.
*/
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_slot(slot, root, &iter, first_index) {
results[ret] = rcu_dereference_raw(*slot);
if (!results[ret])
continue;
if (radix_tree_is_internal_node(results[ret])) {
slot = radix_tree_iter_retry(&iter);
continue;
}
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup);
/**
* radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed
* @indices: where their indices should be placed (but usually NULL)
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
*
* Performs an index-ascending scan of the tree for present items. Places
* their slots at *@results and returns the number of items which were
* placed at *@results.
*
* The implementation is naive.
*
* Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
* be dereferenced with radix_tree_deref_slot, and if using only RCU
* protection, radix_tree_deref_slot may fail requiring a retry.
*/
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)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_slot(slot, root, &iter, first_index) {
results[ret] = slot;
if (indices)
indices[ret] = iter.index;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
/**
* radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
* based on a tag
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
* @tag: the tag index (< RADIX_TREE_MAX_TAGS)
*
* Performs an index-ascending scan of the tree for present items which
* have the tag indexed by @tag set. Places the items at *@results and
* returns the number of items which were placed at *@results.
*/
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)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
results[ret] = rcu_dereference_raw(*slot);
if (!results[ret])
continue;
if (radix_tree_is_internal_node(results[ret])) {
slot = radix_tree_iter_retry(&iter);
continue;
}
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
/**
* radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
* radix tree based on a tag
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
* @tag: the tag index (< RADIX_TREE_MAX_TAGS)
*
* Performs an index-ascending scan of the tree for present items which
* have the tag indexed by @tag set. Places the slots at *@results and
* returns the number of slots which were placed at *@results.
*/
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)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
results[ret] = slot;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
#include <linux/sched.h> /* for cond_resched() */
struct locate_info {
unsigned long found_index;
bool stop;
};
/*
* This linear search is at present only useful to shmem_unuse_inode().
*/
static unsigned long __locate(struct radix_tree_node *slot, void *item,
unsigned long index, struct locate_info *info)
{
unsigned long i;
do {
unsigned int shift = slot->shift;
for (i = (index >> shift) & RADIX_TREE_MAP_MASK;
i < RADIX_TREE_MAP_SIZE;
i++, index += (1UL << shift)) {
struct radix_tree_node *node =
rcu_dereference_raw(slot->slots[i]);
if (node == RADIX_TREE_RETRY)
goto out;
if (!radix_tree_is_internal_node(node)) {
if (node == item) {
info->found_index = index;
info->stop = true;
goto out;
}
continue;
}
node = entry_to_node(node);
if (is_sibling_entry(slot, node))
continue;
slot = node;
break;
}
} while (i < RADIX_TREE_MAP_SIZE);
out:
if ((index == 0) && (i == RADIX_TREE_MAP_SIZE))
info->stop = true;
return index;
}
/**
* radix_tree_locate_item - search through radix tree for item
* @root: radix tree root
* @item: item to be found
*
* Returns index where item was found, or -1 if not found.
* Caller must hold no lock (since this time-consuming function needs
* to be preemptible), and must check afterwards if item is still there.
*/
unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
{
struct radix_tree_node *node;
unsigned long max_index;
unsigned long cur_index = 0;
struct locate_info info = {
.found_index = -1,
.stop = false,
};
do {
rcu_read_lock();
node = rcu_dereference_raw(root->rnode);
if (!radix_tree_is_internal_node(node)) {
rcu_read_unlock();
if (node == item)
info.found_index = 0;
break;
}
node = entry_to_node(node);
max_index = node_maxindex(node);
if (cur_index > max_index) {
rcu_read_unlock();
break;
}
cur_index = __locate(node, item, cur_index, &info);
rcu_read_unlock();
cond_resched();
} while (!info.stop && cur_index <= max_index);
return info.found_index;
}
#else
unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
{
return -1;
}
#endif /* CONFIG_SHMEM && CONFIG_SWAP */
/**
* radix_tree_shrink - shrink radix tree to minimum height
* @root radix tree root
*/
static inline bool radix_tree_shrink(struct radix_tree_root *root)
{
bool shrunk = false;
for (;;) {
struct radix_tree_node *node = root->rnode;
struct radix_tree_node *child;
if (!radix_tree_is_internal_node(node))
break;
node = entry_to_node(node);
/*
* The candidate node has more than one child, or its child
* is not at the leftmost slot, or the child is a multiorder
* entry, we cannot shrink.
*/
if (node->count != 1)
break;
child = node->slots[0];
if (!child)
break;
if (!radix_tree_is_internal_node(child) && node->shift)
break;
if (radix_tree_is_internal_node(child))
entry_to_node(child)->parent = NULL;
/*
* We don't need rcu_assign_pointer(), since we are simply
* moving the node from one part of the tree to another: if it
* was safe to dereference the old pointer to it
* (node->slots[0]), it will be safe to dereference the new
* one (root->rnode) as far as dependent read barriers go.
*/
root->rnode = child;
/*
* We have a dilemma here. The node's slot[0] must not be
* NULLed in case there are concurrent lookups expecting to
* find the item. However if this was a bottom-level node,
* then it may be subject to the slot pointer being visible
* to callers dereferencing it. If item corresponding to
* slot[0] is subsequently deleted, these callers would expect
* their slot to become empty sooner or later.
*
* For example, lockless pagecache will look up a slot, deref
* the page pointer, and if the page has 0 refcount it means it
* was concurrently deleted from pagecache so try the deref
* again. Fortunately there is already a requirement for logic
* to retry the entire slot lookup -- the indirect pointer
* problem (replacing direct root node with an indirect pointer
* also results in a stale slot). So tag the slot as indirect
* to force callers to retry.
*/
if (!radix_tree_is_internal_node(child))
node->slots[0] = RADIX_TREE_RETRY;
radix_tree_node_free(node);
shrunk = true;
}
return shrunk;
}
/**
* __radix_tree_delete_node - try to free node after clearing a slot
* @root: radix tree root
* @node: node containing @index
*
* After clearing the slot at @index in @node from radix tree
* rooted at @root, call this function to attempt freeing the
* node and shrinking the tree.
*
* Returns %true if @node was freed, %false otherwise.
*/
bool __radix_tree_delete_node(struct radix_tree_root *root,
struct radix_tree_node *node)
{
bool deleted = false;
do {
struct radix_tree_node *parent;
if (node->count) {
if (node == entry_to_node(root->rnode))
deleted |= radix_tree_shrink(root);
return deleted;
}
parent = node->parent;
if (parent) {
parent->slots[node->offset] = NULL;
parent->count--;
} else {
root_tag_clear_all(root);
root->rnode = NULL;
}
radix_tree_node_free(node);
deleted = true;
node = parent;
} while (node);
return deleted;
}
static inline void delete_sibling_entries(struct radix_tree_node *node,
void *ptr, unsigned offset)
{
#ifdef CONFIG_RADIX_TREE_MULTIORDER
int i;
for (i = 1; offset + i < RADIX_TREE_MAP_SIZE; i++) {
if (node->slots[offset + i] != ptr)
break;
node->slots[offset + i] = NULL;
node->count--;
}
#endif
}
/**
* radix_tree_delete_item - delete an item from a radix tree
* @root: radix tree root
* @index: index key
* @item: expected item
*
* Remove @item at @index from the radix tree rooted at @root.
*
* Returns the address of the deleted item, or NULL if it was not present
* or the entry at the given @index was not @item.
*/
void *radix_tree_delete_item(struct radix_tree_root *root,
unsigned long index, void *item)
{
struct radix_tree_node *node;
unsigned int offset;
void **slot;
void *entry;
int tag;
entry = __radix_tree_lookup(root, index, &node, &slot);
if (!entry)
return NULL;
if (item && entry != item)
return NULL;
if (!node) {
root_tag_clear_all(root);
root->rnode = NULL;
return entry;
}
offset = get_slot_offset(node, slot);
/* Clear all tags associated with the item to be deleted. */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
node_tag_clear(root, node, tag, offset);
delete_sibling_entries(node, node_to_entry(slot), offset);
node->slots[offset] = NULL;
node->count--;
__radix_tree_delete_node(root, node);
return entry;
}
EXPORT_SYMBOL(radix_tree_delete_item);
/**
* radix_tree_delete - delete an item from a radix tree
* @root: radix tree root
* @index: index key
*
* Remove the item at @index from the radix tree rooted at @root.
*
* Returns the address of the deleted item, or NULL if it was not present.
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
return radix_tree_delete_item(root, index, NULL);
}
EXPORT_SYMBOL(radix_tree_delete);
struct radix_tree_node *radix_tree_replace_clear_tags(
struct radix_tree_root *root,
unsigned long index, void *entry)
{
struct radix_tree_node *node;
void **slot;
__radix_tree_lookup(root, index, &node, &slot);
if (node) {
unsigned int tag, offset = get_slot_offset(node, slot);
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
node_tag_clear(root, node, tag, offset);
} else {
/* Clear root node tags */
root->gfp_mask &= __GFP_BITS_MASK;
}
radix_tree_replace_slot(slot, entry);
return node;
}
/**
* radix_tree_tagged - test whether any items in the tree are tagged
* @root: radix tree root
* @tag: tag to test
*/
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
{
return root_tag_get(root, tag);
}
EXPORT_SYMBOL(radix_tree_tagged);
static void
radix_tree_node_ctor(void *arg)
{
struct radix_tree_node *node = arg;
memset(node, 0, sizeof(*node));
INIT_LIST_HEAD(&node->private_list);
}
static __init unsigned long __maxindex(unsigned int height)
{
unsigned int width = height * RADIX_TREE_MAP_SHIFT;
int shift = RADIX_TREE_INDEX_BITS - width;
if (shift < 0)
return ~0UL;
if (shift >= BITS_PER_LONG)
return 0UL;
return ~0UL >> shift;
}
static __init void radix_tree_init_maxnodes(void)
{
unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1];
unsigned int i, j;
for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
height_to_maxindex[i] = __maxindex(i);
for (i = 0; i < ARRAY_SIZE(height_to_maxnodes); i++) {
for (j = i; j > 0; j--)
height_to_maxnodes[i] += height_to_maxindex[j - 1] + 1;
}
}
static int radix_tree_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
/* Free per-cpu pool of preloaded nodes */
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
rtp = &per_cpu(radix_tree_preloads, cpu);
while (rtp->nr) {
node = rtp->nodes;
rtp->nodes = node->private_data;
kmem_cache_free(radix_tree_node_cachep, node);
rtp->nr--;
}
}
return NOTIFY_OK;
}
void __init radix_tree_init(void)
{
radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
sizeof(struct radix_tree_node), 0,
SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
radix_tree_node_ctor);
radix_tree_init_maxnodes();
hotcpu_notifier(radix_tree_callback, 0);
}