// SPDX-License-Identifier: GPL-2.0
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include "ctree.h"
#include "extent_map.h"
#include "compression.h"


static struct kmem_cache *extent_map_cache;

int __init extent_map_init(void)
{
        extent_map_cache = kmem_cache_create("btrfs_extent_map",
                        sizeof(struct extent_map), 0,
                        SLAB_MEM_SPREAD, NULL);
        if (!extent_map_cache)
                return -ENOMEM;
        return 0;
}

void extent_map_exit(void)
{
        kmem_cache_destroy(extent_map_cache);
}

/**
 * extent_map_tree_init - initialize extent map tree
 * @tree:               tree to initialize
 *
 * Initialize the extent tree @tree.  Should be called for each new inode
 * or other user of the extent_map interface.
 */
void extent_map_tree_init(struct extent_map_tree *tree)
{
        tree->map = RB_ROOT;
        INIT_LIST_HEAD(&tree->modified_extents);
        rwlock_init(&tree->lock);
}

/**
 * alloc_extent_map - allocate new extent map structure
 *
 * Allocate a new extent_map structure.  The new structure is
 * returned with a reference count of one and needs to be
 * freed using free_extent_map()
 */
struct extent_map *alloc_extent_map(void)
{
        struct extent_map *em;
        em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
        if (!em)
                return NULL;
        RB_CLEAR_NODE(&em->rb_node);
        em->flags = 0;
        em->compress_type = BTRFS_COMPRESS_NONE;
        em->generation = 0;
        refcount_set(&em->refs, 1);
        INIT_LIST_HEAD(&em->list);
        return em;
}

/**
 * free_extent_map - drop reference count of an extent_map
 * @em:         extent map being released
 *
 * Drops the reference out on @em by one and free the structure
 * if the reference count hits zero.
 */
void free_extent_map(struct extent_map *em)
{
        if (!em)
                return;
        WARN_ON(refcount_read(&em->refs) == 0);
        if (refcount_dec_and_test(&em->refs)) {
                WARN_ON(extent_map_in_tree(em));
                WARN_ON(!list_empty(&em->list));
                if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
                        kfree(em->map_lookup);
                kmem_cache_free(extent_map_cache, em);
        }
}

/* simple helper to do math around the end of an extent, handling wrap */
static u64 range_end(u64 start, u64 len)
{
        if (start + len < start)
                return (u64)-1;
        return start + len;
}

static int tree_insert(struct rb_root *root, struct extent_map *em)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent = NULL;
        struct extent_map *entry = NULL;
        struct rb_node *orig_parent = NULL;
        u64 end = range_end(em->start, em->len);

        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct extent_map, rb_node);

                if (em->start < entry->start)
                        p = &(*p)->rb_left;
                else if (em->start >= extent_map_end(entry))
                        p = &(*p)->rb_right;
                else
                        return -EEXIST;
        }

        orig_parent = parent;
        while (parent && em->start >= extent_map_end(entry)) {
                parent = rb_next(parent);
                entry = rb_entry(parent, struct extent_map, rb_node);
        }
        if (parent)
                if (end > entry->start && em->start < extent_map_end(entry))
                        return -EEXIST;

        parent = orig_parent;
        entry = rb_entry(parent, struct extent_map, rb_node);
        while (parent && em->start < entry->start) {
                parent = rb_prev(parent);
                entry = rb_entry(parent, struct extent_map, rb_node);
        }
        if (parent)
                if (end > entry->start && em->start < extent_map_end(entry))
                        return -EEXIST;

        rb_link_node(&em->rb_node, orig_parent, p);
        rb_insert_color(&em->rb_node, root);
        return 0;
}

/*
 * search through the tree for an extent_map with a given offset.  If
 * it can't be found, try to find some neighboring extents
 */
static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
                                     struct rb_node **prev_ret,
                                     struct rb_node **next_ret)
{
        struct rb_node *n = root->rb_node;
        struct rb_node *prev = NULL;
        struct rb_node *orig_prev = NULL;
        struct extent_map *entry;
        struct extent_map *prev_entry = NULL;

        while (n) {
                entry = rb_entry(n, struct extent_map, rb_node);
                prev = n;
                prev_entry = entry;

                if (offset < entry->start)
                        n = n->rb_left;
                else if (offset >= extent_map_end(entry))
                        n = n->rb_right;
                else
                        return n;
        }

        if (prev_ret) {
                orig_prev = prev;
                while (prev && offset >= extent_map_end(prev_entry)) {
                        prev = rb_next(prev);
                        prev_entry = rb_entry(prev, struct extent_map, rb_node);
                }
                *prev_ret = prev;
                prev = orig_prev;
        }

        if (next_ret) {
                prev_entry = rb_entry(prev, struct extent_map, rb_node);
                while (prev && offset < prev_entry->start) {
                        prev = rb_prev(prev);
                        prev_entry = rb_entry(prev, struct extent_map, rb_node);
                }
                *next_ret = prev;
        }
        return NULL;
}

/* check to see if two extent_map structs are adjacent and safe to merge */
static int mergable_maps(struct extent_map *prev, struct extent_map *next)
{
        if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
                return 0;

        /*
         * don't merge compressed extents, we need to know their
         * actual size
         */
        if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
                return 0;

        if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
            test_bit(EXTENT_FLAG_LOGGING, &next->flags))
                return 0;

        /*
         * We don't want to merge stuff that hasn't been written to the log yet
         * since it may not reflect exactly what is on disk, and that would be
         * bad.
         */
        if (!list_empty(&prev->list) || !list_empty(&next->list))
                return 0;

        if (extent_map_end(prev) == next->start &&
            prev->flags == next->flags &&
            prev->bdev == next->bdev &&
            ((next->block_start == EXTENT_MAP_HOLE &&
              prev->block_start == EXTENT_MAP_HOLE) ||
             (next->block_start == EXTENT_MAP_INLINE &&
              prev->block_start == EXTENT_MAP_INLINE) ||
             (next->block_start == EXTENT_MAP_DELALLOC &&
              prev->block_start == EXTENT_MAP_DELALLOC) ||
             (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
              next->block_start == extent_map_block_end(prev)))) {
                return 1;
        }
        return 0;
}

static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
{
        struct extent_map *merge = NULL;
        struct rb_node *rb;

        if (em->start != 0) {
                rb = rb_prev(&em->rb_node);
                if (rb)
                        merge = rb_entry(rb, struct extent_map, rb_node);
                if (rb && mergable_maps(merge, em)) {
                        em->start = merge->start;
                        em->orig_start = merge->orig_start;
                        em->len += merge->len;
                        em->block_len += merge->block_len;
                        em->block_start = merge->block_start;
                        em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
                        em->mod_start = merge->mod_start;
                        em->generation = max(em->generation, merge->generation);

                        rb_erase(&merge->rb_node, &tree->map);
                        RB_CLEAR_NODE(&merge->rb_node);
                        free_extent_map(merge);
                }
        }

        rb = rb_next(&em->rb_node);
        if (rb)
                merge = rb_entry(rb, struct extent_map, rb_node);
        if (rb && mergable_maps(em, merge)) {
                em->len += merge->len;
                em->block_len += merge->block_len;
                rb_erase(&merge->rb_node, &tree->map);
                RB_CLEAR_NODE(&merge->rb_node);
                em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
                em->generation = max(em->generation, merge->generation);
                free_extent_map(merge);
        }
}

/**
 * unpin_extent_cache - unpin an extent from the cache
 * @tree:       tree to unpin the extent in
 * @start:      logical offset in the file
 * @len:        length of the extent
 * @gen:        generation that this extent has been modified in
 *
 * Called after an extent has been written to disk properly.  Set the generation
 * to the generation that actually added the file item to the inode so we know
 * we need to sync this extent when we call fsync().
 */
int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
                       u64 gen)
{
        int ret = 0;
        struct extent_map *em;
        bool prealloc = false;

        write_lock(&tree->lock);
        em = lookup_extent_mapping(tree, start, len);

        WARN_ON(!em || em->start != start);

        if (!em)
                goto out;

        em->generation = gen;
        clear_bit(EXTENT_FLAG_PINNED, &em->flags);
        em->mod_start = em->start;
        em->mod_len = em->len;

        if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
                prealloc = true;
                clear_bit(EXTENT_FLAG_FILLING, &em->flags);
        }

        try_merge_map(tree, em);

        if (prealloc) {
                em->mod_start = em->start;
                em->mod_len = em->len;
        }

        free_extent_map(em);
out:
        write_unlock(&tree->lock);
        return ret;

}

void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
{
        clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
        if (extent_map_in_tree(em))
                try_merge_map(tree, em);
}

static inline void setup_extent_mapping(struct extent_map_tree *tree,
                                        struct extent_map *em,
                                        int modified)
{
        refcount_inc(&em->refs);
        em->mod_start = em->start;
        em->mod_len = em->len;

        if (modified)
                list_move(&em->list, &tree->modified_extents);
        else
                try_merge_map(tree, em);
}

/**
 * add_extent_mapping - add new extent map to the extent tree
 * @tree:       tree to insert new map in
 * @em:         map to insert
 *
 * Insert @em into @tree or perform a simple forward/backward merge with
 * existing mappings.  The extent_map struct passed in will be inserted
 * into the tree directly, with an additional reference taken, or a
 * reference dropped if the merge attempt was successful.
 */
int add_extent_mapping(struct extent_map_tree *tree,
                       struct extent_map *em, int modified)
{
        int ret = 0;

        ret = tree_insert(&tree->map, em);
        if (ret)
                goto out;

        setup_extent_mapping(tree, em, modified);
out:
        return ret;
}

static struct extent_map *
__lookup_extent_mapping(struct extent_map_tree *tree,
                        u64 start, u64 len, int strict)
{
        struct extent_map *em;
        struct rb_node *rb_node;
        struct rb_node *prev = NULL;
        struct rb_node *next = NULL;
        u64 end = range_end(start, len);

        rb_node = __tree_search(&tree->map, start, &prev, &next);
        if (!rb_node) {
                if (prev)
                        rb_node = prev;
                else if (next)
                        rb_node = next;
                else
                        return NULL;
        }

        em = rb_entry(rb_node, struct extent_map, rb_node);

        if (strict && !(end > em->start && start < extent_map_end(em)))
                return NULL;

        refcount_inc(&em->refs);
        return em;
}

/**
 * lookup_extent_mapping - lookup extent_map
 * @tree:       tree to lookup in
 * @start:      byte offset to start the search
 * @len:        length of the lookup range
 *
 * Find and return the first extent_map struct in @tree that intersects the
 * [start, len] range.  There may be additional objects in the tree that
 * intersect, so check the object returned carefully to make sure that no
 * additional lookups are needed.
 */
struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
                                         u64 start, u64 len)
{
        return __lookup_extent_mapping(tree, start, len, 1);
}

/**
 * search_extent_mapping - find a nearby extent map
 * @tree:       tree to lookup in
 * @start:      byte offset to start the search
 * @len:        length of the lookup range
 *
 * Find and return the first extent_map struct in @tree that intersects the
 * [start, len] range.
 *
 * If one can't be found, any nearby extent may be returned
 */
struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
                                         u64 start, u64 len)
{
        return __lookup_extent_mapping(tree, start, len, 0);
}

/**
 * remove_extent_mapping - removes an extent_map from the extent tree
 * @tree:       extent tree to remove from
 * @em:         extent map being removed
 *
 * Removes @em from @tree.  No reference counts are dropped, and no checks
 * are done to see if the range is in use
 */
int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
{
        int ret = 0;

        WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
        rb_erase(&em->rb_node, &tree->map);
        if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
                list_del_init(&em->list);
        RB_CLEAR_NODE(&em->rb_node);
        return ret;
}

void replace_extent_mapping(struct extent_map_tree *tree,
                            struct extent_map *cur,
                            struct extent_map *new,
                            int modified)
{
        WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
        ASSERT(extent_map_in_tree(cur));
        if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
                list_del_init(&cur->list);
        rb_replace_node(&cur->rb_node, &new->rb_node, &tree->map);
        RB_CLEAR_NODE(&cur->rb_node);

        setup_extent_mapping(tree, new, modified);
}