Add a readonly flag open_ctree to force RO opens

[btrfs-progs-unstable.git] / radix-tree.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

/*
 * Copyright (C) 2001 Momchil Velikov
 * Portions Copyright (C) 2001 Christoph Hellwig
 * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
 *
 * 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 "kerncompat.h"
#include "radix-tree.h"
#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)

struct radix_tree_node {
        unsigned int    count;
        void            *slots[RADIX_TREE_MAP_SIZE];
        unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};

struct radix_tree_path {
        struct radix_tree_node *node;
        int offset;
};

#define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)

static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;

/*
 * Per-cpu pool of preloaded nodes
 */
struct radix_tree_preload {
        int nr;
        struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
};
struct radix_tree_preload radix_tree_preloads = { 0, };

static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
        return root->gfp_mask & __GFP_BITS_MASK;
}

static int internal_nodes = 0;
/*
 * 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;
        ret = malloc(sizeof(struct radix_tree_node));
        if (ret) {
                memset(ret, 0, sizeof(struct radix_tree_node));
                internal_nodes++;
        }
        return ret;
}

static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
        internal_nodes--;
        free(node);
}

/*
 * 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.
 */
int radix_tree_preload(gfp_t gfp_mask)
{
        struct radix_tree_preload *rtp;
        struct radix_tree_node *node;
        int ret = -ENOMEM;

        preempt_disable();
        rtp = &__get_cpu_var(radix_tree_preloads);
        while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
                preempt_enable();
                node = radix_tree_node_alloc(NULL);
                if (node == NULL)
                        goto out;
                preempt_disable();
                rtp = &__get_cpu_var(radix_tree_preloads);
                if (rtp->nr < ARRAY_SIZE(rtp->nodes))
                        rtp->nodes[rtp->nr++] = node;
                else
                        radix_tree_node_free(node);
        }
        ret = 0;
out:
        return ret;
}

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 int 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 unsigned)root->gfp_mask & (1 << (tag + __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)
{
        int idx;
        for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
                if (node->tags[tag][idx])
                        return 1;
        }
        return 0;
}

/*
 *      Return the maximum key which can be store into a
 *      radix tree with height HEIGHT.
 */
static inline unsigned long radix_tree_maxindex(unsigned int height)
{
        return height_to_maxindex[height];
}

/*
 *      Extend a radix tree so it can store key @index.
 */
static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
{
        struct radix_tree_node *node;
        unsigned int height;
        int tag;

        /* Figure out what the height should be.  */
        height = root->height + 1;
        while (index > radix_tree_maxindex(height))
                height++;

        if (root->rnode == NULL) {
                root->height = height;
                goto out;
        }

        do {
                if (!(node = radix_tree_node_alloc(root)))
                        return -ENOMEM;

                /* Increase the height.  */
                node->slots[0] = root->rnode;

                /* 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);
                }

                node->count = 1;
                root->rnode = node;
                root->height++;
        } while (height > root->height);
out:
        return 0;
}

/**
 *      radix_tree_insert    -    insert into a radix tree
 *      @root:          radix tree root
 *      @index:         index key
 *      @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, void *item)
{
        struct radix_tree_node *node = NULL, *slot;
        unsigned int height, shift;
        int offset;
        int error;

        /* Make sure the tree is high enough.  */
        if (index > radix_tree_maxindex(root->height)) {
                error = radix_tree_extend(root, index);
                if (error)
                        return error;
        }

        slot = root->rnode;
        height = root->height;
        shift = (height-1) * RADIX_TREE_MAP_SHIFT;

        offset = 0;                     /* uninitialised var warning */
        while (height > 0) {
                if (slot == NULL) {
                        /* Have to add a child node.  */
                        if (!(slot = radix_tree_node_alloc(root)))
                                return -ENOMEM;
                        if (node) {
                                node->slots[offset] = slot;
                                node->count++;
                        } else
                                root->rnode = slot;
                }

                /* Go a level down */
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                node = slot;
                slot = node->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }

        if (slot != NULL)
                return -EEXIST;

        if (node) {
                node->count++;
                node->slots[offset] = item;
                BUG_ON(tag_get(node, 0, offset));
                BUG_ON(tag_get(node, 1, offset));
        } else {
                root->rnode = item;
                BUG_ON(root_tag_get(root, 0));
                BUG_ON(root_tag_get(root, 1));
        }

        return 0;
}

static inline void **__lookup_slot(struct radix_tree_root *root,
                                   unsigned long index)
{
        unsigned int height, shift;
        struct radix_tree_node **slot;

        height = root->height;

        if (index > radix_tree_maxindex(height))
                return NULL;

        if (height == 0 && root->rnode)
                return (void *)&root->rnode;

        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
        slot = &root->rnode;

        while (height > 0) {
                if (*slot == NULL)
                        return NULL;

                slot = (struct radix_tree_node **)
                        ((*slot)->slots +
                                ((index >> shift) & RADIX_TREE_MAP_MASK));
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }

        return (void **)slot;
}

/**
 *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 *      @root:          radix tree root
 *      @index:         index key
 *
 *      Lookup the slot corresponding to the position @index in the radix tree
 *      @root. This is useful for update-if-exists operations.
 */
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
        return __lookup_slot(root, index);
}

/**
 *      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.
 */
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
        void **slot;

        slot = __lookup_slot(root, index);
        return slot != NULL ? *slot : NULL;
}

/**
 *      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)
{
        unsigned int height, shift;
        struct radix_tree_node *slot;

        height = root->height;
        BUG_ON(index > radix_tree_maxindex(height));

        slot = root->rnode;
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;

        while (height > 0) {
                int offset;

                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                if (!tag_get(slot, tag, offset))
                        tag_set(slot, tag, offset);
                slot = slot->slots[offset];
                BUG_ON(slot == NULL);
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }

        /* set the root's tag bit */
        if (slot && !root_tag_get(root, tag))
                root_tag_set(root, tag);

        return slot;
}

/**
 *      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_path path[RADIX_TREE_MAX_PATH], *pathp = path;
        struct radix_tree_node *slot = NULL;
        unsigned int height, shift;

        height = root->height;
        if (index > radix_tree_maxindex(height))
                goto out;

        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        pathp->node = NULL;
        slot = root->rnode;

        while (height > 0) {
                int offset;

                if (slot == NULL)
                        goto out;

                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                pathp[1].offset = offset;
                pathp[1].node = slot;
                slot = slot->slots[offset];
                pathp++;
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }

        if (slot == NULL)
                goto out;

        while (pathp->node) {
                if (!tag_get(pathp->node, tag, pathp->offset))
                        goto out;
                tag_clear(pathp->node, tag, pathp->offset);
                if (any_tag_set(pathp->node, tag))
                        goto out;
                pathp--;
        }

        /* clear the root's tag bit */
        if (root_tag_get(root, tag))
                root_tag_clear(root, tag);

out:
        return slot;
}

#ifndef __KERNEL__      /* Only the test harness uses this at present */
/**
 * 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
 */
int radix_tree_tag_get(struct radix_tree_root *root,
                        unsigned long index, unsigned int tag)
{
        unsigned int height, shift;
        struct radix_tree_node *slot;
        int saw_unset_tag = 0;

        height = root->height;
        if (index > radix_tree_maxindex(height))
                return 0;

        /* check the root's tag bit */
        if (!root_tag_get(root, tag))
                return 0;

        if (height == 0)
                return 1;

        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        slot = root->rnode;

        for ( ; ; ) {
                int offset;

                if (slot == NULL)
                        return 0;

                offset = (index >> shift) & RADIX_TREE_MAP_MASK;

                /*
                 * This is just a debug check.  Later, we can bale as soon as
                 * we see an unset tag.
                 */
                if (!tag_get(slot, tag, offset))
                        saw_unset_tag = 1;
                if (height == 1) {
                        int ret = tag_get(slot, tag, offset);

                        BUG_ON(ret && saw_unset_tag);
                        return !!ret;
                }
                slot = slot->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
}
#endif

static unsigned int
__lookup(struct radix_tree_root *root, void **results, unsigned long index,
        unsigned int max_items, unsigned long *next_index)
{
        unsigned int nr_found = 0;
        unsigned int shift, height;
        struct radix_tree_node *slot;
        unsigned long i;

        height = root->height;
        if (height == 0) {
                if (root->rnode && index == 0)
                        results[nr_found++] = root->rnode;
                goto out;
        }

        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
        slot = root->rnode;

        for ( ; height > 1; height--) {

                for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
                                i < RADIX_TREE_MAP_SIZE; i++) {
                        if (slot->slots[i] != NULL)
                                break;
                        index &= ~((1UL << shift) - 1);
                        index += 1UL << shift;
                        if (index == 0)
                                goto out;       /* 32-bit wraparound */
                }
                if (i == RADIX_TREE_MAP_SIZE)
                        goto out;

                shift -= RADIX_TREE_MAP_SHIFT;
                slot = slot->slots[i];
        }

        /* Bottom level: grab some items */
        for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
                index++;
                if (slot->slots[i]) {
                        results[nr_found++] = slot->slots[i];
                        if (nr_found == max_items)
                                goto out;
                }
        }
out:
        *next_index = index;
        return nr_found;
}

/**
 *      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.
 */
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
                        unsigned long first_index, unsigned int max_items)
{
        const unsigned long max_index = radix_tree_maxindex(root->height);
        unsigned long cur_index = first_index;
        unsigned int ret = 0;

        while (ret < max_items) {
                unsigned int nr_found;
                unsigned long next_index;       /* Index of next search */

                if (cur_index > max_index)
                        break;
                nr_found = __lookup(root, results + ret, cur_index,
                                        max_items - ret, &next_index);
                ret += nr_found;
                if (next_index == 0)
                        break;
                cur_index = next_index;
        }
        return ret;
}

/*
 * FIXME: the two tag_get()s here should use find_next_bit() instead of
 * open-coding the search.
 */
static unsigned int
__lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
        unsigned int max_items, unsigned long *next_index, unsigned int tag)
{
        unsigned int nr_found = 0;
        unsigned int shift;
        unsigned int height = root->height;
        struct radix_tree_node *slot;

        if (height == 0) {
                if (root->rnode && index == 0)
                        results[nr_found++] = root->rnode;
                goto out;
        }

        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        slot = root->rnode;

        do {
                unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;

                for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
                        if (tag_get(slot, tag, i)) {
                                BUG_ON(slot->slots[i] == NULL);
                                break;
                        }
                        index &= ~((1UL << shift) - 1);
                        index += 1UL << shift;
                        if (index == 0)
                                goto out;       /* 32-bit wraparound */
                }
                if (i == RADIX_TREE_MAP_SIZE)
                        goto out;
                height--;
                if (height == 0) {      /* Bottom level: grab some items */
                        unsigned long j = index & RADIX_TREE_MAP_MASK;

                        for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
                                index++;
                                if (tag_get(slot, tag, j)) {
                                        BUG_ON(slot->slots[j] == NULL);
                                        results[nr_found++] = slot->slots[j];
                                        if (nr_found == max_items)
                                                goto out;
                                }
                        }
                }
                shift -= RADIX_TREE_MAP_SHIFT;
                slot = slot->slots[i];
        } while (height > 0);
out:
        *next_index = index;
        return nr_found;
}

/**
 *      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)
{
        const unsigned long max_index = radix_tree_maxindex(root->height);
        unsigned long cur_index = first_index;
        unsigned int ret = 0;

        /* check the root's tag bit */
        if (!root_tag_get(root, tag))
                return 0;

        while (ret < max_items) {
                unsigned int nr_found;
                unsigned long next_index;       /* Index of next search */

                if (cur_index > max_index)
                        break;
                nr_found = __lookup_tag(root, results + ret, cur_index,
                                        max_items - ret, &next_index, tag);
                ret += nr_found;
                if (next_index == 0)
                        break;
                cur_index = next_index;
        }
        return ret;
}

/**
 *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 *      @root           radix tree root
 */
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
        /* try to shrink tree height */
        while (root->height > 0 &&
                        root->rnode->count == 1 &&
                        root->rnode->slots[0]) {
                struct radix_tree_node *to_free = root->rnode;

                root->rnode = to_free->slots[0];
                root->height--;
                /* must only free zeroed nodes into the slab */
                tag_clear(to_free, 0, 0);
                tag_clear(to_free, 1, 0);
                to_free->slots[0] = NULL;
                to_free->count = 0;
                radix_tree_node_free(to_free);
        }
}

/**
 *      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)
{
        struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
        struct radix_tree_node *slot = NULL;
        unsigned int height, shift;
        int tag;
        int offset;

        height = root->height;
        if (index > radix_tree_maxindex(height))
                goto out;

        slot = root->rnode;
        if (height == 0 && root->rnode) {
                root_tag_clear_all(root);
                root->rnode = NULL;
                goto out;
        }

        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        pathp->node = NULL;

        do {
                if (slot == NULL)
                        goto out;

                pathp++;
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                pathp->offset = offset;
                pathp->node = slot;
                slot = slot->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        } while (height > 0);

        if (slot == NULL)
                goto out;

        /*
         * Clear all tags associated with the just-deleted item
         */
        for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
                if (tag_get(pathp->node, tag, pathp->offset))
                        radix_tree_tag_clear(root, index, tag);
        }

        /* Now free the nodes we do not need anymore */
        while (pathp->node) {
                pathp->node->slots[pathp->offset] = NULL;
                pathp->node->count--;

                if (pathp->node->count) {
                        if (pathp->node == root->rnode)
                                radix_tree_shrink(root);
                        goto out;
                }

                /* Node with zero slots in use so free it */
                radix_tree_node_free(pathp->node);

                pathp--;
        }
        root_tag_clear_all(root);
        root->height = 0;
        root->rnode = NULL;

out:
        return slot;
}

/**
 *      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);
}

static unsigned long __maxindex(unsigned int height)
{
        unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
        unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;

        if (tmp >= RADIX_TREE_INDEX_BITS)
                index = ~0UL;
        return index;
}

static void radix_tree_init_maxindex(void)
{
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
                height_to_maxindex[i] = __maxindex(i);
}

void radix_tree_init(void)
{
        radix_tree_init_maxindex();
}