// SPDX-License-Identifier: GPL-2.0

#include <linux/slab.h>
#include <trace/events/btrfs.h>
#include "messages.h"
#include "ctree.h"
#include "extent_io.h"
#include "extent-io-tree.h"
#include "btrfs_inode.h"

static struct kmem_cache *extent_state_cache;

static inline bool extent_state_in_tree(const struct extent_state *state)
{
        return !RB_EMPTY_NODE(&state->rb_node);
}

#ifdef CONFIG_BTRFS_DEBUG
static LIST_HEAD(states);
static DEFINE_SPINLOCK(leak_lock);

static inline void btrfs_leak_debug_add_state(struct extent_state *state)
{
        unsigned long flags;

        spin_lock_irqsave(&leak_lock, flags);
        list_add(&state->leak_list, &states);
        spin_unlock_irqrestore(&leak_lock, flags);
}

static inline void btrfs_leak_debug_del_state(struct extent_state *state)
{
        unsigned long flags;

        spin_lock_irqsave(&leak_lock, flags);
        list_del(&state->leak_list);
        spin_unlock_irqrestore(&leak_lock, flags);
}

static inline void btrfs_extent_state_leak_debug_check(void)
{
        struct extent_state *state;

        while (!list_empty(&states)) {
                state = list_first_entry(&states, struct extent_state, leak_list);
                btrfs_err(NULL,
                       "state leak: start %llu end %llu state %u in tree %d refs %d",
                       state->start, state->end, state->state,
                       extent_state_in_tree(state),
                       refcount_read(&state->refs));
                list_del(&state->leak_list);
                WARN_ON_ONCE(1);
                kmem_cache_free(extent_state_cache, state);
        }
}

#define btrfs_debug_check_extent_io_range(tree, start, end)             \
        __btrfs_debug_check_extent_io_range(__func__, (tree), (start), (end))
static inline void __btrfs_debug_check_extent_io_range(const char *caller,
                                                       struct extent_io_tree *tree,
                                                       u64 start, u64 end)
{
        const struct btrfs_inode *inode = tree->inode;
        u64 isize;

        if (tree->owner != IO_TREE_INODE_IO)
                return;

        isize = i_size_read(&inode->vfs_inode);
        if (end >= PAGE_SIZE && (end % 2) == 0 && end != isize - 1) {
                btrfs_debug_rl(inode->root->fs_info,
                    "%s: ino %llu isize %llu odd range [%llu,%llu]",
                        caller, btrfs_ino(inode), isize, start, end);
        }
}
#else
#define btrfs_leak_debug_add_state(state)               do {} while (0)
#define btrfs_leak_debug_del_state(state)               do {} while (0)
#define btrfs_extent_state_leak_debug_check()           do {} while (0)
#define btrfs_debug_check_extent_io_range(c, s, e)      do {} while (0)
#endif

/* Read-only access to the inode. */
const struct btrfs_inode *btrfs_extent_io_tree_to_inode(const struct extent_io_tree *tree)
{
        if (tree->owner == IO_TREE_INODE_IO)
                return tree->inode;
        return NULL;
}

/* For read-only access to fs_info. */
const struct btrfs_fs_info *btrfs_extent_io_tree_to_fs_info(const struct extent_io_tree *tree)
{
        if (tree->owner == IO_TREE_INODE_IO)
                return tree->inode->root->fs_info;
        return tree->fs_info;
}

void btrfs_extent_io_tree_init(struct btrfs_fs_info *fs_info,
                               struct extent_io_tree *tree, unsigned int owner)
{
        tree->state = RB_ROOT;
        spin_lock_init(&tree->lock);
        tree->fs_info = fs_info;
        tree->owner = owner;
}

/*
 * Empty an io tree, removing and freeing every extent state record from the
 * tree. This should be called once we are sure no other task can access the
 * tree anymore, so no tree updates happen after we empty the tree and there
 * aren't any waiters on any extent state record (EXTENT_LOCK_BITS are never
 * set on any extent state when calling this function).
 */
void btrfs_extent_io_tree_release(struct extent_io_tree *tree)
{
        struct rb_root root;
        struct extent_state *state;
        struct extent_state *tmp;

        spin_lock(&tree->lock);
        root = tree->state;
        tree->state = RB_ROOT;
        rbtree_postorder_for_each_entry_safe(state, tmp, &root, rb_node) {
                /* Clear node to keep free_extent_state() happy. */
                RB_CLEAR_NODE(&state->rb_node);
                ASSERT(!(state->state & EXTENT_LOCK_BITS));
                /*
                 * No need for a memory barrier here, as we are holding the tree
                 * lock and we only change the waitqueue while holding that lock
                 * (see wait_extent_bit()).
                 */
                ASSERT(!waitqueue_active(&state->wq));
                btrfs_free_extent_state(state);
                cond_resched_lock(&tree->lock);
        }
        /*
         * Should still be empty even after a reschedule, no other task should
         * be accessing the tree anymore.
         */
        ASSERT(RB_EMPTY_ROOT(&tree->state));
        spin_unlock(&tree->lock);
}

static struct extent_state *alloc_extent_state(gfp_t mask)
{
        struct extent_state *state;

        /*
         * The given mask might be not appropriate for the slab allocator,
         * drop the unsupported bits
         */
        mask &= ~(__GFP_DMA32|__GFP_HIGHMEM);
        state = kmem_cache_alloc(extent_state_cache, mask);
        if (!state)
                return state;
        state->state = 0;
        RB_CLEAR_NODE(&state->rb_node);
        btrfs_leak_debug_add_state(state);
        refcount_set(&state->refs, 1);
        init_waitqueue_head(&state->wq);
        trace_btrfs_alloc_extent_state(state, mask, _RET_IP_);
        return state;
}

static struct extent_state *alloc_extent_state_atomic(struct extent_state *prealloc)
{
        if (!prealloc)
                prealloc = alloc_extent_state(GFP_ATOMIC);

        return prealloc;
}

void btrfs_free_extent_state(struct extent_state *state)
{
        if (!state)
                return;
        if (refcount_dec_and_test(&state->refs)) {
                WARN_ON(extent_state_in_tree(state));
                btrfs_leak_debug_del_state(state);
                trace_btrfs_free_extent_state(state, _RET_IP_);
                kmem_cache_free(extent_state_cache, state);
        }
}

static int add_extent_changeset(struct extent_state *state, u32 bits,
                                 struct extent_changeset *changeset,
                                 int set)
{
        if (!changeset)
                return 0;
        if (set && (state->state & bits) == bits)
                return 0;
        if (!set && (state->state & bits) == 0)
                return 0;
        changeset->bytes_changed += state->end - state->start + 1;

        return ulist_add(&changeset->range_changed, state->start, state->end, GFP_ATOMIC);
}

static inline struct extent_state *next_state(struct extent_state *state)
{
        struct rb_node *next = rb_next(&state->rb_node);

        return rb_entry_safe(next, struct extent_state, rb_node);
}

static inline struct extent_state *prev_state(struct extent_state *state)
{
        struct rb_node *next = rb_prev(&state->rb_node);

        return rb_entry_safe(next, struct extent_state, rb_node);
}

/*
 * Search @tree for an entry that contains @offset or if none exists for the
 * first entry that starts and ends after that offset.
 *
 * @tree:       the tree to search
 * @offset:     search offset
 * @node_ret:   pointer where new node should be anchored (used when inserting an
 *              entry in the tree)
 * @parent_ret: points to entry which would have been the parent of the entry,
 *               containing @offset
 *
 * Return a pointer to the entry that contains @offset byte address.
 *
 * If no such entry exists, return the first entry that starts and ends after
 * @offset if one exists, otherwise NULL.
 *
 * If the returned entry starts at @offset, then @node_ret and @parent_ret
 * aren't changed.
 */
static inline struct extent_state *tree_search_for_insert(struct extent_io_tree *tree,
                                                          u64 offset,
                                                          struct rb_node ***node_ret,
                                                          struct rb_node **parent_ret)
{
        struct rb_root *root = &tree->state;
        struct rb_node **node = &root->rb_node;
        struct rb_node *prev = NULL;
        struct extent_state *entry = NULL;

        while (*node) {
                prev = *node;
                entry = rb_entry(prev, struct extent_state, rb_node);

                if (offset < entry->start)
                        node = &(*node)->rb_left;
                else if (offset > entry->end)
                        node = &(*node)->rb_right;
                else
                        return entry;
        }

        if (node_ret)
                *node_ret = node;
        if (parent_ret)
                *parent_ret = prev;

        /*
         * Return either the current entry if it contains offset (it ends after
         * or at offset) or the first entry that starts and ends after offset if
         * one exists, or NULL.
         */
        while (entry && offset > entry->end)
                entry = next_state(entry);

        return entry;
}

/*
 * Search offset in the tree or fill neighbor rbtree node pointers.
 *
 * @tree:      the tree to search
 * @offset:    offset that should fall within an entry in @tree
 * @next_ret:  pointer to the first entry whose range ends after @offset
 * @prev_ret:  pointer to the first entry whose range begins before @offset
 *
 * Return a pointer to the entry that contains @offset byte address. If no
 * such entry exists, then return NULL and fill @prev_ret and @next_ret.
 * Otherwise return the found entry and other pointers are left untouched.
 */
static struct extent_state *tree_search_prev_next(struct extent_io_tree *tree,
                                                  u64 offset,
                                                  struct extent_state **prev_ret,
                                                  struct extent_state **next_ret)
{
        struct rb_root *root = &tree->state;
        struct rb_node **node = &root->rb_node;
        struct extent_state *orig_prev;
        struct extent_state *entry = NULL;

        ASSERT(prev_ret);
        ASSERT(next_ret);

        while (*node) {
                entry = rb_entry(*node, struct extent_state, rb_node);

                if (offset < entry->start)
                        node = &(*node)->rb_left;
                else if (offset > entry->end)
                        node = &(*node)->rb_right;
                else
                        return entry;
        }

        orig_prev = entry;
        while (entry && offset > entry->end)
                entry = next_state(entry);
        *next_ret = entry;
        entry = orig_prev;

        while (entry && offset < entry->start)
                entry = prev_state(entry);
        *prev_ret = entry;

        return NULL;
}

/*
 * Inexact rb-tree search, return the next entry if @offset is not found
 */
static inline struct extent_state *tree_search(struct extent_io_tree *tree, u64 offset)
{
        return tree_search_for_insert(tree, offset, NULL, NULL);
}

static void __cold extent_io_tree_panic(const struct extent_io_tree *tree,
                                        const struct extent_state *state,
                                        const char *opname,
                                        int err)
{
        btrfs_panic(btrfs_extent_io_tree_to_fs_info(tree), err,
                    "extent io tree error on %s state start %llu end %llu",
                    opname, state->start, state->end);
}

static void merge_prev_state(struct extent_io_tree *tree, struct extent_state *state)
{
        struct extent_state *prev;

        prev = prev_state(state);
        if (prev && prev->end == state->start - 1 && prev->state == state->state) {
                if (tree->owner == IO_TREE_INODE_IO)
                        btrfs_merge_delalloc_extent(tree->inode, state, prev);
                state->start = prev->start;
                rb_erase(&prev->rb_node, &tree->state);
                RB_CLEAR_NODE(&prev->rb_node);
                btrfs_free_extent_state(prev);
        }
}

static void merge_next_state(struct extent_io_tree *tree, struct extent_state *state)
{
        struct extent_state *next;

        next = next_state(state);
        if (next && next->start == state->end + 1 && next->state == state->state) {
                if (tree->owner == IO_TREE_INODE_IO)
                        btrfs_merge_delalloc_extent(tree->inode, state, next);
                state->end = next->end;
                rb_erase(&next->rb_node, &tree->state);
                RB_CLEAR_NODE(&next->rb_node);
                btrfs_free_extent_state(next);
        }
}

/*
 * Utility function to look for merge candidates inside a given range.  Any
 * extents with matching state are merged together into a single extent in the
 * tree.  Extents with EXTENT_IO in their state field are not merged because
 * the end_io handlers need to be able to do operations on them without
 * sleeping (or doing allocations/splits).
 *
 * This should be called with the tree lock held.
 */
static void merge_state(struct extent_io_tree *tree, struct extent_state *state)
{
        if (state->state & (EXTENT_LOCK_BITS | EXTENT_BOUNDARY))
                return;

        merge_prev_state(tree, state);
        merge_next_state(tree, state);
}

static void set_state_bits(struct extent_io_tree *tree,
                           struct extent_state *state,
                           u32 bits, struct extent_changeset *changeset)
{
        u32 bits_to_set = bits & ~EXTENT_CTLBITS;
        int ret;

        if (tree->owner == IO_TREE_INODE_IO)
                btrfs_set_delalloc_extent(tree->inode, state, bits);

        ret = add_extent_changeset(state, bits_to_set, changeset, 1);
        BUG_ON(ret < 0);
        state->state |= bits_to_set;
}

/*
 * Insert an extent_state struct into the tree.  'bits' are set on the
 * struct before it is inserted.
 *
 * Returns a pointer to the struct extent_state record containing the range
 * requested for insertion, which may be the same as the given struct or it
 * may be an existing record in the tree that was expanded to accommodate the
 * requested range. In case of an extent_state different from the one that was
 * given, the later can be freed or reused by the caller.
 *
 * On error it returns an error pointer.
 *
 * The tree lock is not taken internally.  This is a utility function and
 * probably isn't what you want to call (see set/clear_extent_bit).
 */
static struct extent_state *insert_state(struct extent_io_tree *tree,
                                         struct extent_state *state,
                                         u32 bits,
                                         struct extent_changeset *changeset)
{
        struct rb_node **node;
        struct rb_node *parent = NULL;
        const u64 start = state->start - 1;
        const u64 end = state->end + 1;
        const bool try_merge = !(bits & (EXTENT_LOCK_BITS | EXTENT_BOUNDARY));

        set_state_bits(tree, state, bits, changeset);

        node = &tree->state.rb_node;
        while (*node) {
                struct extent_state *entry;

                parent = *node;
                entry = rb_entry(parent, struct extent_state, rb_node);

                if (state->end < entry->start) {
                        if (try_merge && end == entry->start &&
                            state->state == entry->state) {
                                if (tree->owner == IO_TREE_INODE_IO)
                                        btrfs_merge_delalloc_extent(tree->inode,
                                                                    state, entry);
                                entry->start = state->start;
                                merge_prev_state(tree, entry);
                                state->state = 0;
                                return entry;
                        }
                        node = &(*node)->rb_left;
                } else if (state->end > entry->end) {
                        if (try_merge && entry->end == start &&
                            state->state == entry->state) {
                                if (tree->owner == IO_TREE_INODE_IO)
                                        btrfs_merge_delalloc_extent(tree->inode,
                                                                    state, entry);
                                entry->end = state->end;
                                merge_next_state(tree, entry);
                                state->state = 0;
                                return entry;
                        }
                        node = &(*node)->rb_right;
                } else {
                        return ERR_PTR(-EEXIST);
                }
        }

        rb_link_node(&state->rb_node, parent, node);
        rb_insert_color(&state->rb_node, &tree->state);

        return state;
}

/*
 * Insert state to @tree to the location given by @node and @parent.
 */
static void insert_state_fast(struct extent_io_tree *tree,
                              struct extent_state *state, struct rb_node **node,
                              struct rb_node *parent, unsigned bits,
                              struct extent_changeset *changeset)
{
        set_state_bits(tree, state, bits, changeset);
        rb_link_node(&state->rb_node, parent, node);
        rb_insert_color(&state->rb_node, &tree->state);
        merge_state(tree, state);
}

/*
 * Split a given extent state struct in two, inserting the preallocated
 * struct 'prealloc' as the newly created second half.  'split' indicates an
 * offset inside 'orig' where it should be split.
 *
 * Before calling,
 * the tree has 'orig' at [orig->start, orig->end].  After calling, there
 * are two extent state structs in the tree:
 * prealloc: [orig->start, split - 1]
 * orig: [ split, orig->end ]
 *
 * The tree locks are not taken by this function. They need to be held
 * by the caller.
 */
static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
                       struct extent_state *prealloc, u64 split)
{
        struct rb_node *parent = NULL;
        struct rb_node **node;

        if (tree->owner == IO_TREE_INODE_IO)
                btrfs_split_delalloc_extent(tree->inode, orig, split);

        prealloc->start = orig->start;
        prealloc->end = split - 1;
        prealloc->state = orig->state;
        orig->start = split;

        parent = &orig->rb_node;
        node = &parent;
        while (*node) {
                struct extent_state *entry;

                parent = *node;
                entry = rb_entry(parent, struct extent_state, rb_node);

                if (prealloc->end < entry->start) {
                        node = &(*node)->rb_left;
                } else if (prealloc->end > entry->end) {
                        node = &(*node)->rb_right;
                } else {
                        btrfs_free_extent_state(prealloc);
                        return -EEXIST;
                }
        }

        rb_link_node(&prealloc->rb_node, parent, node);
        rb_insert_color(&prealloc->rb_node, &tree->state);

        return 0;
}

/*
 * Use this during tree iteration to avoid doing next node searches when it's
 * not needed (the current record ends at or after the target range's end).
 */
static inline struct extent_state *next_search_state(struct extent_state *state, u64 end)
{
        if (state->end < end)
                return next_state(state);

        return NULL;
}

/*
 * Utility function to clear some bits in an extent state struct.  It will
 * optionally wake up anyone waiting on this state (wake == 1).
 *
 * If no bits are set on the state struct after clearing things, the
 * struct is freed and removed from the tree
 */
static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
                                            struct extent_state *state,
                                            u32 bits, int wake, u64 end,
                                            struct extent_changeset *changeset)
{
        struct extent_state *next;
        u32 bits_to_clear = bits & ~EXTENT_CTLBITS;
        int ret;

        if (tree->owner == IO_TREE_INODE_IO)
                btrfs_clear_delalloc_extent(tree->inode, state, bits);

        ret = add_extent_changeset(state, bits_to_clear, changeset, 0);
        BUG_ON(ret < 0);
        state->state &= ~bits_to_clear;
        if (wake)
                wake_up(&state->wq);
        if (state->state == 0) {
                next = next_search_state(state, end);
                if (extent_state_in_tree(state)) {
                        rb_erase(&state->rb_node, &tree->state);
                        RB_CLEAR_NODE(&state->rb_node);
                        btrfs_free_extent_state(state);
                } else {
                        WARN_ON(1);
                }
        } else {
                merge_state(tree, state);
                next = next_search_state(state, end);
        }
        return next;
}

/*
 * Detect if extent bits request NOWAIT semantics and set the gfp mask accordingly,
 * unset the EXTENT_NOWAIT bit.
 */
static void set_gfp_mask_from_bits(u32 *bits, gfp_t *mask)
{
        *mask = (*bits & EXTENT_NOWAIT ? GFP_NOWAIT : GFP_NOFS);
        *bits &= EXTENT_NOWAIT - 1;
}

/*
 * Clear some bits on a range in the tree.  This may require splitting or
 * inserting elements in the tree, so the gfp mask is used to indicate which
 * allocations or sleeping are allowed.
 *
 * The range [start, end] is inclusive.
 *
 * This takes the tree lock, and returns 0 on success and < 0 on error.
 */
int btrfs_clear_extent_bit_changeset(struct extent_io_tree *tree, u64 start, u64 end,
                                     u32 bits, struct extent_state **cached_state,
                                     struct extent_changeset *changeset)
{
        struct extent_state *state;
        struct extent_state *cached;
        struct extent_state *prealloc = NULL;
        u64 last_end;
        int ret = 0;
        bool clear;
        bool wake;
        const bool delete = (bits & EXTENT_CLEAR_ALL_BITS);
        gfp_t mask;

        set_gfp_mask_from_bits(&bits, &mask);
        btrfs_debug_check_extent_io_range(tree, start, end);
        trace_btrfs_clear_extent_bit(tree, start, end - start + 1, bits);

        if (delete)
                bits |= ~EXTENT_CTLBITS;

        if (bits & EXTENT_DELALLOC)
                bits |= EXTENT_NORESERVE;

        wake = (bits & EXTENT_LOCK_BITS);
        clear = (bits & (EXTENT_LOCK_BITS | EXTENT_BOUNDARY));
again:
        if (!prealloc) {
                /*
                 * Don't care for allocation failure here because we might end
                 * up not needing the pre-allocated extent state at all, which
                 * is the case if we only have in the tree extent states that
                 * cover our input range and don't cover too any other range.
                 * If we end up needing a new extent state we allocate it later.
                 */
                prealloc = alloc_extent_state(mask);
        }

        spin_lock(&tree->lock);
        if (cached_state) {
                cached = *cached_state;

                if (clear) {
                        *cached_state = NULL;
                        cached_state = NULL;
                }

                if (cached && extent_state_in_tree(cached) &&
                    cached->start <= start && cached->end > start) {
                        if (clear)
                                refcount_dec(&cached->refs);
                        state = cached;
                        goto hit_next;
                }
                if (clear)
                        btrfs_free_extent_state(cached);
        }

        /* This search will find the extents that end after our range starts. */
        state = tree_search(tree, start);
        if (!state)
                goto out;
hit_next:
        if (state->start > end)
                goto out;
        WARN_ON(state->end < start);
        last_end = state->end;

        /* The state doesn't have the wanted bits, go ahead. */
        if (!(state->state & bits)) {
                state = next_search_state(state, end);
                goto next;
        }

        /*
         *     | ---- desired range ---- |
         *  | state | or
         *  | ------------- state -------------- |
         *
         * We need to split the extent we found, and may flip bits on second
         * half.
         *
         * If the extent we found extends past our range, we just split and
         * search again.  It'll get split again the next time though.
         *
         * If the extent we found is inside our range, we clear the desired bit
         * on it.
         */

        if (state->start < start) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;
                ret = split_state(tree, state, prealloc, start);
                prealloc = NULL;
                if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
                        goto out;
                }
                if (state->end <= end) {
                        state = clear_state_bit(tree, state, bits, wake, end,
                                                changeset);
                        goto next;
                }
                if (need_resched())
                        goto search_again;
                /*
                 * Fallthrough and try atomic extent state allocation if needed.
                 * If it fails we'll jump to 'search_again' retry the allocation
                 * in non-atomic mode and start the search again.
                 */
        }
        /*
         * | ---- desired range ---- |
         *                        | state |
         * We need to split the extent, and clear the bit on the first half.
         */
        if (state->start <= end && state->end > end) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;
                ret = split_state(tree, state, prealloc, end + 1);
                if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
                        prealloc = NULL;
                        goto out;
                }

                if (wake)
                        wake_up(&state->wq);

                clear_state_bit(tree, prealloc, bits, wake, end, changeset);

                prealloc = NULL;
                goto out;
        }

        state = clear_state_bit(tree, state, bits, wake, end, changeset);
next:
        if (last_end >= end)
                goto out;
        start = last_end + 1;
        if (state && !need_resched())
                goto hit_next;

search_again:
        spin_unlock(&tree->lock);
        if (gfpflags_allow_blocking(mask))
                cond_resched();
        goto again;

out:
        spin_unlock(&tree->lock);
        btrfs_free_extent_state(prealloc);

        return ret;

}

/*
 * Wait for one or more bits to clear on a range in the state tree.
 * The range [start, end] is inclusive.
 * The tree lock is taken by this function
 */
static void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
                            u32 bits, struct extent_state **cached_state)
{
        struct extent_state *state;

        btrfs_debug_check_extent_io_range(tree, start, end);

        spin_lock(&tree->lock);
again:
        /*
         * Maintain cached_state, as we may not remove it from the tree if there
         * are more bits than the bits we're waiting on set on this state.
         */
        if (cached_state && *cached_state) {
                state = *cached_state;
                if (extent_state_in_tree(state) &&
                    state->start <= start && start < state->end)
                        goto process_node;
        }
        while (1) {
                /*
                 * This search will find all the extents that end after our
                 * range starts.
                 */
                state = tree_search(tree, start);
process_node:
                if (!state)
                        break;
                if (state->start > end)
                        goto out;

                if (state->state & bits) {
                        DEFINE_WAIT(wait);

                        start = state->start;
                        refcount_inc(&state->refs);
                        prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
                        spin_unlock(&tree->lock);
                        schedule();
                        spin_lock(&tree->lock);
                        finish_wait(&state->wq, &wait);
                        btrfs_free_extent_state(state);
                        goto again;
                }
                start = state->end + 1;

                if (start > end)
                        break;

                if (!cond_resched_lock(&tree->lock)) {
                        state = next_state(state);
                        goto process_node;
                }
        }
out:
        /* This state is no longer useful, clear it and free it up. */
        if (cached_state && *cached_state) {
                state = *cached_state;
                *cached_state = NULL;
                btrfs_free_extent_state(state);
        }
        spin_unlock(&tree->lock);
}

static void cache_state_if_flags(struct extent_state *state,
                                 struct extent_state **cached_ptr,
                                 unsigned flags)
{
        if (cached_ptr && !(*cached_ptr)) {
                if (!flags || (state->state & flags)) {
                        *cached_ptr = state;
                        refcount_inc(&state->refs);
                }
        }
}

static void cache_state(struct extent_state *state,
                        struct extent_state **cached_ptr)
{
        return cache_state_if_flags(state, cached_ptr, EXTENT_LOCK_BITS | EXTENT_BOUNDARY);
}

/*
 * Find the first state struct with 'bits' set after 'start', and return it.
 * tree->lock must be held.  NULL will returned if nothing was found after
 * 'start'.
 */
static struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
                                                        u64 start, u32 bits)
{
        struct extent_state *state;

        /*
         * This search will find all the extents that end after our range
         * starts.
         */
        state = tree_search(tree, start);
        while (state) {
                if (state->state & bits)
                        return state;
                state = next_state(state);
        }
        return NULL;
}

/*
 * Find the first offset in the io tree with one or more @bits set.
 *
 * Note: If there are multiple bits set in @bits, any of them will match.
 *
 * Return true if we find something, and update @start_ret and @end_ret.
 * Return false if we found nothing.
 */
bool btrfs_find_first_extent_bit(struct extent_io_tree *tree, u64 start,
                                 u64 *start_ret, u64 *end_ret, u32 bits,
                                 struct extent_state **cached_state)
{
        struct extent_state *state;
        bool ret = false;

        spin_lock(&tree->lock);
        if (cached_state && *cached_state) {
                state = *cached_state;
                if (state->end == start - 1 && extent_state_in_tree(state)) {
                        while ((state = next_state(state)) != NULL) {
                                if (state->state & bits)
                                        break;
                        }
                        /*
                         * If we found the next extent state, clear cached_state
                         * so that we can cache the next extent state below and
                         * avoid future calls going over the same extent state
                         * again. If we haven't found any, clear as well since
                         * it's now useless.
                         */
                        btrfs_free_extent_state(*cached_state);
                        *cached_state = NULL;
                        if (state)
                                goto got_it;
                        goto out;
                }
                btrfs_free_extent_state(*cached_state);
                *cached_state = NULL;
        }

        state = find_first_extent_bit_state(tree, start, bits);
got_it:
        if (state) {
                cache_state_if_flags(state, cached_state, 0);
                *start_ret = state->start;
                *end_ret = state->end;
                ret = true;
        }
out:
        spin_unlock(&tree->lock);
        return ret;
}

/*
 * Find a contiguous area of bits
 *
 * @tree:      io tree to check
 * @start:     offset to start the search from
 * @start_ret: the first offset we found with the bits set
 * @end_ret:   the final contiguous range of the bits that were set
 * @bits:      bits to look for
 *
 * set_extent_bit and clear_extent_bit can temporarily split contiguous ranges
 * to set bits appropriately, and then merge them again.  During this time it
 * will drop the tree->lock, so use this helper if you want to find the actual
 * contiguous area for given bits.  We will search to the first bit we find, and
 * then walk down the tree until we find a non-contiguous area.  The area
 * returned will be the full contiguous area with the bits set.
 *
 * Returns true if we found a range with the given bits set, in which case
 * @start_ret and @end_ret are updated, or false if no range was found.
 */
bool btrfs_find_contiguous_extent_bit(struct extent_io_tree *tree, u64 start,
                                      u64 *start_ret, u64 *end_ret, u32 bits)
{
        struct extent_state *state;
        bool ret = false;

        ASSERT(!btrfs_fs_incompat(btrfs_extent_io_tree_to_fs_info(tree), NO_HOLES));

        spin_lock(&tree->lock);
        state = find_first_extent_bit_state(tree, start, bits);
        if (state) {
                *start_ret = state->start;
                *end_ret = state->end;
                while ((state = next_state(state)) != NULL) {
                        if (state->start > (*end_ret + 1))
                                break;
                        *end_ret = state->end;
                }
                ret = true;
        }
        spin_unlock(&tree->lock);
        return ret;
}

/*
 * Find a contiguous range of bytes in the file marked as delalloc, not more
 * than 'max_bytes'.  start and end are used to return the range,
 *
 * True is returned if we find something, false if nothing was in the tree.
 */
bool btrfs_find_delalloc_range(struct extent_io_tree *tree, u64 *start,
                               u64 *end, u64 max_bytes,
                               struct extent_state **cached_state)
{
        struct extent_state *state;
        u64 cur_start = *start;
        bool found = false;
        u64 total_bytes = 0;

        spin_lock(&tree->lock);

        /*
         * This search will find all the extents that end after our range
         * starts.
         */
        state = tree_search(tree, cur_start);
        if (!state) {
                *end = (u64)-1;
                goto out;
        }

        while (state) {
                if (found && (state->start != cur_start ||
                              (state->state & EXTENT_BOUNDARY))) {
                        goto out;
                }
                if (!(state->state & EXTENT_DELALLOC)) {
                        if (!found)
                                *end = state->end;
                        goto out;
                }
                if (!found) {
                        *start = state->start;
                        *cached_state = state;
                        refcount_inc(&state->refs);
                }
                found = true;
                *end = state->end;
                cur_start = state->end + 1;
                total_bytes += state->end - state->start + 1;
                if (total_bytes >= max_bytes)
                        break;
                state = next_state(state);
        }
out:
        spin_unlock(&tree->lock);
        return found;
}

/*
 * Set some bits on a range in the tree.  This may require allocations or
 * sleeping. By default all allocations use GFP_NOFS, use EXTENT_NOWAIT for
 * GFP_NOWAIT.
 *
 * If any of the exclusive bits are set, this will fail with -EEXIST if some
 * part of the range already has the desired bits set.  The extent_state of the
 * existing range is returned in failed_state in this case, and the start of the
 * existing range is returned in failed_start.  failed_state is used as an
 * optimization for wait_extent_bit, failed_start must be used as the source of
 * truth as failed_state may have changed since we returned.
 *
 * [start, end] is inclusive This takes the tree lock.
 */
static int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
                          u32 bits, u64 *failed_start,
                          struct extent_state **failed_state,
                          struct extent_state **cached_state,
                          struct extent_changeset *changeset)
{
        struct extent_state *state;
        struct extent_state *prealloc = NULL;
        struct rb_node **p = NULL;
        struct rb_node *parent = NULL;
        int ret = 0;
        u64 last_start;
        u64 last_end;
        u32 exclusive_bits = (bits & EXTENT_LOCK_BITS);
        gfp_t mask;

        set_gfp_mask_from_bits(&bits, &mask);
        btrfs_debug_check_extent_io_range(tree, start, end);
        trace_btrfs_set_extent_bit(tree, start, end - start + 1, bits);

        if (exclusive_bits)
                ASSERT(failed_start);
        else
                ASSERT(failed_start == NULL && failed_state == NULL);
again:
        if (!prealloc) {
                /*
                 * Don't care for allocation failure here because we might end
                 * up not needing the pre-allocated extent state at all, which
                 * is the case if we only have in the tree extent states that
                 * cover our input range and don't cover too any other range.
                 * If we end up needing a new extent state we allocate it later.
                 */
                prealloc = alloc_extent_state(mask);
        }
        /* Optimistically preallocate the extent changeset ulist node. */
        if (changeset)
                extent_changeset_prealloc(changeset, mask);

        spin_lock(&tree->lock);
        if (cached_state && *cached_state) {
                state = *cached_state;
                if (state->start <= start && state->end > start &&
                    extent_state_in_tree(state))
                        goto hit_next;
        }
        /*
         * This search will find all the extents that end after our range
         * starts.
         */
        state = tree_search_for_insert(tree, start, &p, &parent);
        if (!state) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;
                prealloc->start = start;
                prealloc->end = end;
                insert_state_fast(tree, prealloc, p, parent, bits, changeset);
                cache_state(prealloc, cached_state);
                prealloc = NULL;
                goto out;
        }
hit_next:
        last_start = state->start;
        last_end = state->end;

        /*
         * | ---- desired range ---- |
         * | state |
         *
         * Just lock what we found and keep going
         */
        if (state->start == start && state->end <= end) {
                if (state->state & exclusive_bits) {
                        *failed_start = state->start;
                        cache_state(state, failed_state);
                        ret = -EEXIST;
                        goto out;
                }

                set_state_bits(tree, state, bits, changeset);
                cache_state(state, cached_state);
                merge_state(tree, state);
                if (last_end >= end)
                        goto out;
                start = last_end + 1;
                state = next_state(state);
                if (state && state->start == start && !need_resched())
                        goto hit_next;
                goto search_again;
        }

        /*
         *     | ---- desired range ---- |
         * | state |
         *   or
         * | ------------- state -------------- |
         *
         * We need to split the extent we found, and may flip bits on second
         * half.
         *
         * If the extent we found extends past our range, we just split and
         * search again.  It'll get split again the next time though.
         *
         * If the extent we found is inside our range, we set the desired bit
         * on it.
         */
        if (state->start < start) {
                if (state->state & exclusive_bits) {
                        *failed_start = start;
                        cache_state(state, failed_state);
                        ret = -EEXIST;
                        goto out;
                }

                /*
                 * If this extent already has all the bits we want set, then
                 * skip it, not necessary to split it or do anything with it.
                 */
                if ((state->state & bits) == bits) {
                        start = state->end + 1;
                        cache_state(state, cached_state);
                        goto search_again;
                }

                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;
                ret = split_state(tree, state, prealloc, start);
                if (ret)
                        extent_io_tree_panic(tree, state, "split", ret);

                prealloc = NULL;
                if (ret)
                        goto out;
                if (state->end <= end) {
                        set_state_bits(tree, state, bits, changeset);
                        cache_state(state, cached_state);
                        merge_state(tree, state);
                        if (last_end >= end)
                                goto out;
                        start = last_end + 1;
                        state = next_state(state);
                        if (state && state->start == start && !need_resched())
                                goto hit_next;
                }
                goto search_again;
        }
        /*
         * | ---- desired range ---- |
         *     | state | or               | state |
         *
         * There's a hole, we need to insert something in it and ignore the
         * extent we found.
         */
        if (state->start > start) {
                struct extent_state *inserted_state;

                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;

                /*
                 * Avoid to free 'prealloc' if it can be merged with the later
                 * extent.
                 */
                prealloc->start = start;
                if (end < last_start)
                        prealloc->end = end;
                else
                        prealloc->end = last_start - 1;

                inserted_state = insert_state(tree, prealloc, bits, changeset);
                if (IS_ERR(inserted_state)) {
                        ret = PTR_ERR(inserted_state);
                        extent_io_tree_panic(tree, prealloc, "insert", ret);
                        goto out;
                }

                cache_state(inserted_state, cached_state);
                if (inserted_state == prealloc)
                        prealloc = NULL;
                start = inserted_state->end + 1;

                /* Beyond target range, stop. */
                if (start > end)
                        goto out;

                if (need_resched())
                        goto search_again;

                state = next_search_state(inserted_state, end);
                /*
                 * If there's a next state, whether contiguous or not, we don't
                 * need to unlock and start search again. If it's not contiguous
                 * we will end up here and try to allocate a prealloc state and insert.
                 */
                if (state)
                        goto hit_next;
                goto search_again;
        }
        /*
         * | ---- desired range ---- |
         *                        | state |
         *
         * We need to split the extent, and set the bit on the first half
         */
        if (state->start <= end && state->end > end) {
                if (state->state & exclusive_bits) {
                        *failed_start = start;
                        cache_state(state, failed_state);
                        ret = -EEXIST;
                        goto out;
                }

                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc)
                        goto search_again;
                ret = split_state(tree, state, prealloc, end + 1);
                if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
                        prealloc = NULL;
                        goto out;
                }

                set_state_bits(tree, prealloc, bits, changeset);
                cache_state(prealloc, cached_state);
                merge_state(tree, prealloc);
                prealloc = NULL;
                goto out;
        }

search_again:
        if (start > end)
                goto out;
        spin_unlock(&tree->lock);
        if (gfpflags_allow_blocking(mask))
                cond_resched();
        goto again;

out:
        spin_unlock(&tree->lock);
        btrfs_free_extent_state(prealloc);

        return ret;

}

int btrfs_set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
                         u32 bits, struct extent_state **cached_state)
{
        return set_extent_bit(tree, start, end, bits, NULL, NULL, cached_state, NULL);
}

/*
 * Convert all bits in a given range from one bit to another
 *
 * @tree:       the io tree to search
 * @start:      the start offset in bytes
 * @end:        the end offset in bytes (inclusive)
 * @bits:       the bits to set in this range
 * @clear_bits: the bits to clear in this range
 * @cached_state:       state that we're going to cache
 *
 * This will go through and set bits for the given range.  If any states exist
 * already in this range they are set with the given bit and cleared of the
 * clear_bits.  This is only meant to be used by things that are mergeable, ie.
 * converting from say DELALLOC to DIRTY.  This is not meant to be used with
 * boundary bits like LOCK.
 *
 * All allocations are done with GFP_NOFS.
 */
int btrfs_convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
                             u32 bits, u32 clear_bits,
                             struct extent_state **cached_state)
{
        struct extent_state *state;
        struct extent_state *prealloc = NULL;
        struct rb_node **p = NULL;
        struct rb_node *parent = NULL;
        int ret = 0;
        u64 last_start;
        u64 last_end;
        bool first_iteration = true;

        btrfs_debug_check_extent_io_range(tree, start, end);
        trace_btrfs_convert_extent_bit(tree, start, end - start + 1, bits,
                                       clear_bits);

again:
        if (!prealloc) {
                /*
                 * Best effort, don't worry if extent state allocation fails
                 * here for the first iteration. We might have a cached state
                 * that matches exactly the target range, in which case no
                 * extent state allocations are needed. We'll only know this
                 * after locking the tree.
                 */
                prealloc = alloc_extent_state(GFP_NOFS);
                if (!prealloc && !first_iteration)
                        return -ENOMEM;
        }

        spin_lock(&tree->lock);
        if (cached_state && *cached_state) {
                state = *cached_state;
                if (state->start <= start && state->end > start &&
                    extent_state_in_tree(state))
                        goto hit_next;
        }

        /*
         * This search will find all the extents that end after our range
         * starts.
         */
        state = tree_search_for_insert(tree, start, &p, &parent);
        if (!state) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc) {
                        ret = -ENOMEM;
                        goto out;
                }
                prealloc->start = start;
                prealloc->end = end;
                insert_state_fast(tree, prealloc, p, parent, bits, NULL);
                cache_state(prealloc, cached_state);
                prealloc = NULL;
                goto out;
        }
hit_next:
        last_start = state->start;
        last_end = state->end;

        /*
         * | ---- desired range ---- |
         * | state |
         *
         * Just lock what we found and keep going.
         */
        if (state->start == start && state->end <= end) {
                set_state_bits(tree, state, bits, NULL);
                cache_state(state, cached_state);
                state = clear_state_bit(tree, state, clear_bits, 0, end, NULL);
                if (last_end >= end)
                        goto out;
                start = last_end + 1;
                if (state && state->start == start && !need_resched())
                        goto hit_next;
                goto search_again;
        }

        /*
         *     | ---- desired range ---- |
         * | state |
         *   or
         * | ------------- state -------------- |
         *
         * We need to split the extent we found, and may flip bits on second
         * half.
         *
         * If the extent we found extends past our range, we just split and
         * search again.  It'll get split again the next time though.
         *
         * If the extent we found is inside our range, we set the desired bit
         * on it.
         */
        if (state->start < start) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc) {
                        ret = -ENOMEM;
                        goto out;
                }
                ret = split_state(tree, state, prealloc, start);
                prealloc = NULL;
                if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
                        goto out;
                }
                if (state->end <= end) {
                        set_state_bits(tree, state, bits, NULL);
                        cache_state(state, cached_state);
                        state = clear_state_bit(tree, state, clear_bits, 0, end, NULL);
                        if (last_end >= end)
                                goto out;
                        start = last_end + 1;
                        if (state && state->start == start && !need_resched())
                                goto hit_next;
                }
                goto search_again;
        }
        /*
         * | ---- desired range ---- |
         *     | state | or               | state |
         *
         * There's a hole, we need to insert something in it and ignore the
         * extent we found.
         */
        if (state->start > start) {
                struct extent_state *inserted_state;

                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc) {
                        ret = -ENOMEM;
                        goto out;
                }

                /*
                 * Avoid to free 'prealloc' if it can be merged with the later
                 * extent.
                 */
                prealloc->start = start;
                if (end < last_start)
                        prealloc->end = end;
                else
                        prealloc->end = last_start - 1;

                inserted_state = insert_state(tree, prealloc, bits, NULL);
                if (IS_ERR(inserted_state)) {
                        ret = PTR_ERR(inserted_state);
                        extent_io_tree_panic(tree, prealloc, "insert", ret);
                        goto out;
                }
                cache_state(inserted_state, cached_state);
                if (inserted_state == prealloc)
                        prealloc = NULL;
                start = inserted_state->end + 1;

                /* Beyond target range, stop. */
                if (start > end)
                        goto out;

                if (need_resched())
                        goto search_again;

                state = next_search_state(inserted_state, end);
                /*
                 * If there's a next state, whether contiguous or not, we don't
                 * need to unlock and start search again. If it's not contiguous
                 * we will end up here and try to allocate a prealloc state and insert.
                 */
                if (state)
                        goto hit_next;
                goto search_again;
        }
        /*
         * | ---- desired range ---- |
         *                        | state |
         *
         * We need to split the extent, and set the bit on the first half.
         */
        if (state->start <= end && state->end > end) {
                prealloc = alloc_extent_state_atomic(prealloc);
                if (!prealloc) {
                        ret = -ENOMEM;
                        goto out;
                }

                ret = split_state(tree, state, prealloc, end + 1);
                if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
                        prealloc = NULL;
                        goto out;
                }

                set_state_bits(tree, prealloc, bits, NULL);
                cache_state(prealloc, cached_state);
                clear_state_bit(tree, prealloc, clear_bits, 0, end, NULL);
                prealloc = NULL;
                goto out;
        }

search_again:
        if (start > end)
                goto out;
        spin_unlock(&tree->lock);
        cond_resched();
        first_iteration = false;
        goto again;

out:
        spin_unlock(&tree->lock);
        btrfs_free_extent_state(prealloc);

        return ret;
}

/*
 * Find the first range that has @bits not set. This range could start before
 * @start.
 *
 * @tree:      the tree to search
 * @start:     offset at/after which the found extent should start
 * @start_ret: records the beginning of the range
 * @end_ret:   records the end of the range (inclusive)
 * @bits:      the set of bits which must be unset
 *
 * Since unallocated range is also considered one which doesn't have the bits
 * set it's possible that @end_ret contains -1, this happens in case the range
 * spans (last_range_end, end of device]. In this case it's up to the caller to
 * trim @end_ret to the appropriate size.
 */
void btrfs_find_first_clear_extent_bit(struct extent_io_tree *tree, u64 start,
                                       u64 *start_ret, u64 *end_ret, u32 bits)
{
        struct extent_state *state;
        struct extent_state *prev = NULL, *next = NULL;

        spin_lock(&tree->lock);

        /* Find first extent with bits cleared */
        while (1) {
                state = tree_search_prev_next(tree, start, &prev, &next);
                if (!state && !next && !prev) {
                        /*
                         * Tree is completely empty, send full range and let
                         * caller deal with it
                         */
                        *start_ret = 0;
                        *end_ret = -1;
                        goto out;
                } else if (!state && !next) {
                        /*
                         * We are past the last allocated chunk, set start at
                         * the end of the last extent.
                         */
                        *start_ret = prev->end + 1;
                        *end_ret = -1;
                        goto out;
                } else if (!state) {
                        state = next;
                }

                /*
                 * At this point 'state' either contains 'start' or start is
                 * before 'state'
                 */
                if (in_range(start, state->start, state->end - state->start + 1)) {
                        if (state->state & bits) {
                                /*
                                 * |--range with bits sets--|
                                 *    |
                                 *    start
                                 */
                                start = state->end + 1;
                        } else {
                                /*
                                 * 'start' falls within a range that doesn't
                                 * have the bits set, so take its start as the
                                 * beginning of the desired range
                                 *
                                 * |--range with bits cleared----|
                                 *      |
                                 *      start
                                 */
                                *start_ret = state->start;
                                break;
                        }
                } else {
                        /*
                         * |---prev range---|---hole/unset---|---node range---|
                         *                          |
                         *                        start
                         *
                         *                        or
                         *
                         * |---hole/unset--||--first node--|
                         * 0   |
                         *    start
                         */
                        if (prev)
                                *start_ret = prev->end + 1;
                        else
                                *start_ret = 0;
                        break;
                }
        }

        /*
         * Find the longest stretch from start until an entry which has the
         * bits set
         */
        while (state) {
                if (state->end >= start && !(state->state & bits)) {
                        *end_ret = state->end;
                } else {
                        *end_ret = state->start - 1;
                        break;
                }
                state = next_state(state);
        }
out:
        spin_unlock(&tree->lock);
}

/*
 * Count the number of bytes in the tree that have a given bit(s) set for a
 * given range.
 *
 * @tree:         The io tree to search.
 * @start:        The start offset of the range. This value is updated to the
 *                offset of the first byte found with the given bit(s), so it
 *                can end up being bigger than the initial value.
 * @search_end:   The end offset (inclusive value) of the search range.
 * @max_bytes:    The maximum byte count we are interested. The search stops
 *                once it reaches this count.
 * @bits:         The bits the range must have in order to be accounted for.
 *                If multiple bits are set, then only subranges that have all
 *                the bits set are accounted for.
 * @contig:       Indicate if we should ignore holes in the range or not. If
 *                this is true, then stop once we find a hole.
 * @cached_state: A cached state to be used across multiple calls to this
 *                function in order to speedup searches. Use NULL if this is
 *                called only once or if each call does not start where the
 *                previous one ended.
 *
 * Returns the total number of bytes found within the given range that have
 * all given bits set. If the returned number of bytes is greater than zero
 * then @start is updated with the offset of the first byte with the bits set.
 */
u64 btrfs_count_range_bits(struct extent_io_tree *tree,
                           u64 *start, u64 search_end, u64 max_bytes,
                           u32 bits, bool contig,
                           struct extent_state **cached_state)
{
        struct extent_state *state = NULL;
        struct extent_state *cached;
        u64 cur_start = *start;
        u64 total_bytes = 0;
        u64 last = 0;
        int found = 0;

        if (WARN_ON(search_end < cur_start))
                return 0;

        spin_lock(&tree->lock);

        if (!cached_state || !*cached_state)
                goto search;

        cached = *cached_state;

        if (!extent_state_in_tree(cached))
                goto search;

        if (cached->start <= cur_start && cur_start <= cached->end) {
                state = cached;
        } else if (cached->start > cur_start) {
                struct extent_state *prev;

                /*
                 * The cached state starts after our search range's start. Check
                 * if the previous state record starts at or before the range we
                 * are looking for, and if so, use it - this is a common case
                 * when there are holes between records in the tree. If there is
                 * no previous state record, we can start from our cached state.
                 */
                prev = prev_state(cached);
                if (!prev)
                        state = cached;
                else if (prev->start <= cur_start && cur_start <= prev->end)
                        state = prev;
        }

        /*
         * This search will find all the extents that end after our range
         * starts.
         */
search:
        if (!state)
                state = tree_search(tree, cur_start);

        while (state) {
                if (state->start > search_end)
                        break;
                if (contig && found && state->start > last + 1)
                        break;
                if (state->end >= cur_start && (state->state & bits) == bits) {
                        total_bytes += min(search_end, state->end) + 1 -
                                       max(cur_start, state->start);
                        if (total_bytes >= max_bytes)
                                break;
                        if (!found) {
                                *start = max(cur_start, state->start);
                                found = 1;
                        }
                        last = state->end;
                } else if (contig && found) {
                        break;
                }
                state = next_state(state);
        }

        if (cached_state) {
                btrfs_free_extent_state(*cached_state);
                *cached_state = state;
                if (state)
                        refcount_inc(&state->refs);
        }

        spin_unlock(&tree->lock);

        return total_bytes;
}

/*
 * Check if the single @bit exists in the given range.
 */
bool btrfs_test_range_bit_exists(struct extent_io_tree *tree, u64 start, u64 end, u32 bit)
{
        struct extent_state *state;
        bool bitset = false;

        ASSERT(is_power_of_2(bit));

        spin_lock(&tree->lock);
        state = tree_search(tree, start);
        while (state) {
                if (state->start > end)
                        break;

                if (state->state & bit) {
                        bitset = true;
                        break;
                }

                if (state->end >= end)
                        break;
                state = next_state(state);
        }
        spin_unlock(&tree->lock);
        return bitset;
}

void btrfs_get_range_bits(struct extent_io_tree *tree, u64 start, u64 end, u32 *bits,
                          struct extent_state **cached_state)
{
        struct extent_state *state;

        /*
         * The cached state is currently mandatory and not used to start the
         * search, only to cache the first state record found in the range.
         */
        ASSERT(cached_state != NULL);
        ASSERT(*cached_state == NULL);

        *bits = 0;

        spin_lock(&tree->lock);
        state = tree_search(tree, start);
        if (state && state->start < end) {
                *cached_state = state;
                refcount_inc(&state->refs);
        }
        while (state) {
                if (state->start > end)
                        break;

                *bits |= state->state;

                if (state->end >= end)
                        break;

                state = next_state(state);
        }
        spin_unlock(&tree->lock);
}

/*
 * Check if the whole range [@start,@end) contains the single @bit set.
 */
bool btrfs_test_range_bit(struct extent_io_tree *tree, u64 start, u64 end, u32 bit,
                          struct extent_state *cached)
{
        struct extent_state *state;
        bool bitset = true;

        ASSERT(is_power_of_2(bit));
        ASSERT(start < end);

        spin_lock(&tree->lock);
        if (cached && extent_state_in_tree(cached) && cached->start <= start &&
            cached->end > start)
                state = cached;
        else
                state = tree_search(tree, start);
        while (state) {
                if (state->start > start) {
                        bitset = false;
                        break;
                }

                if ((state->state & bit) == 0) {
                        bitset = false;
                        break;
                }

                if (state->end >= end)
                        break;

                /* Next state must start where this one ends. */
                start = state->end + 1;
                state = next_state(state);
        }

        /* We ran out of states and were still inside of our range. */
        if (!state)
                bitset = false;
        spin_unlock(&tree->lock);
        return bitset;
}

/* Wrappers around set/clear extent bit */
int btrfs_set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
                                 u32 bits, struct extent_changeset *changeset)
{
        /*
         * We don't support EXTENT_LOCK_BITS yet, as current changeset will
         * record any bits changed, so for EXTENT_LOCK_BITS case, it will either
         * fail with -EEXIST or changeset will record the whole range.
         */
        ASSERT(!(bits & EXTENT_LOCK_BITS));

        return set_extent_bit(tree, start, end, bits, NULL, NULL, NULL, changeset);
}

int btrfs_clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
                                   u32 bits, struct extent_changeset *changeset)
{
        /*
         * Don't support EXTENT_LOCK_BITS case, same reason as
         * set_record_extent_bits().
         */
        ASSERT(!(bits & EXTENT_LOCK_BITS));

        return btrfs_clear_extent_bit_changeset(tree, start, end, bits, NULL, changeset);
}

bool btrfs_try_lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
                                u32 bits, struct extent_state **cached)
{
        int ret;
        u64 failed_start;

        ret = set_extent_bit(tree, start, end, bits, &failed_start, NULL, cached, NULL);
        if (ret == -EEXIST) {
                if (failed_start > start)
                        btrfs_clear_extent_bit(tree, start, failed_start - 1,
                                               bits, cached);
                return 0;
        }
        return 1;
}

/*
 * Either insert or lock state struct between start and end use mask to tell
 * us if waiting is desired.
 */
int btrfs_lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end, u32 bits,
                           struct extent_state **cached_state)
{
        struct extent_state *failed_state = NULL;
        int ret;
        u64 failed_start;

        ret = set_extent_bit(tree, start, end, bits, &failed_start,
                             &failed_state, cached_state, NULL);
        while (ret == -EEXIST) {
                if (failed_start != start)
                        btrfs_clear_extent_bit(tree, start, failed_start - 1,
                                               bits, cached_state);

                wait_extent_bit(tree, failed_start, end, bits, &failed_state);
                ret = set_extent_bit(tree, start, end, bits, &failed_start,
                                     &failed_state, cached_state, NULL);
        }
        return ret;
}

/*
 * Get the extent state that follows the given extent state.
 * This is meant to be used in a context where we know no other tasks can
 * concurrently modify the tree.
 */
struct extent_state *btrfs_next_extent_state(struct extent_io_tree *tree,
                                             struct extent_state *state)
{
        struct extent_state *next;

        spin_lock(&tree->lock);
        ASSERT(extent_state_in_tree(state));
        next = next_state(state);
        if (next)
                refcount_inc(&next->refs);
        spin_unlock(&tree->lock);

        return next;
}

void __cold btrfs_extent_state_free_cachep(void)
{
        btrfs_extent_state_leak_debug_check();
        kmem_cache_destroy(extent_state_cache);
}

int __init btrfs_extent_state_init_cachep(void)
{
        extent_state_cache = kmem_cache_create("btrfs_extent_state",
                                               sizeof(struct extent_state), 0, 0,
                                               NULL);
        if (!extent_state_cache)
                return -ENOMEM;

        return 0;
}