// SPDX-License-Identifier: GPL-2.0

#include "ctree.h"
#include "space-info.h"
#include "sysfs.h"
#include "volumes.h"
#include "free-space-cache.h"
#include "ordered-data.h"
#include "transaction.h"
#include "math.h"

u64 btrfs_space_info_used(struct btrfs_space_info *s_info,
                          bool may_use_included)
{
        ASSERT(s_info);
        return s_info->bytes_used + s_info->bytes_reserved +
                s_info->bytes_pinned + s_info->bytes_readonly +
                (may_use_included ? s_info->bytes_may_use : 0);
}

/*
 * after adding space to the filesystem, we need to clear the full flags
 * on all the space infos.
 */
void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
{
        struct list_head *head = &info->space_info;
        struct btrfs_space_info *found;

        rcu_read_lock();
        list_for_each_entry_rcu(found, head, list)
                found->full = 0;
        rcu_read_unlock();
}

static const char *alloc_name(u64 flags)
{
        switch (flags) {
        case BTRFS_BLOCK_GROUP_METADATA|BTRFS_BLOCK_GROUP_DATA:
                return "mixed";
        case BTRFS_BLOCK_GROUP_METADATA:
                return "metadata";
        case BTRFS_BLOCK_GROUP_DATA:
                return "data";
        case BTRFS_BLOCK_GROUP_SYSTEM:
                return "system";
        default:
                WARN_ON(1);
                return "invalid-combination";
        };
}

static int create_space_info(struct btrfs_fs_info *info, u64 flags)
{

        struct btrfs_space_info *space_info;
        int i;
        int ret;

        space_info = kzalloc(sizeof(*space_info), GFP_NOFS);
        if (!space_info)
                return -ENOMEM;

        ret = percpu_counter_init(&space_info->total_bytes_pinned, 0,
                                 GFP_KERNEL);
        if (ret) {
                kfree(space_info);
                return ret;
        }

        for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
                INIT_LIST_HEAD(&space_info->block_groups[i]);
        init_rwsem(&space_info->groups_sem);
        spin_lock_init(&space_info->lock);
        space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
        space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
        init_waitqueue_head(&space_info->wait);
        INIT_LIST_HEAD(&space_info->ro_bgs);
        INIT_LIST_HEAD(&space_info->tickets);
        INIT_LIST_HEAD(&space_info->priority_tickets);

        ret = kobject_init_and_add(&space_info->kobj, &space_info_ktype,
                                    info->space_info_kobj, "%s",
                                    alloc_name(space_info->flags));
        if (ret) {
                kobject_put(&space_info->kobj);
                return ret;
        }

        list_add_rcu(&space_info->list, &info->space_info);
        if (flags & BTRFS_BLOCK_GROUP_DATA)
                info->data_sinfo = space_info;

        return ret;
}

int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
{
        struct btrfs_super_block *disk_super;
        u64 features;
        u64 flags;
        int mixed = 0;
        int ret;

        disk_super = fs_info->super_copy;
        if (!btrfs_super_root(disk_super))
                return -EINVAL;

        features = btrfs_super_incompat_flags(disk_super);
        if (features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
                mixed = 1;

        flags = BTRFS_BLOCK_GROUP_SYSTEM;
        ret = create_space_info(fs_info, flags);
        if (ret)
                goto out;

        if (mixed) {
                flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
                ret = create_space_info(fs_info, flags);
        } else {
                flags = BTRFS_BLOCK_GROUP_METADATA;
                ret = create_space_info(fs_info, flags);
                if (ret)
                        goto out;

                flags = BTRFS_BLOCK_GROUP_DATA;
                ret = create_space_info(fs_info, flags);
        }
out:
        return ret;
}

void btrfs_update_space_info(struct btrfs_fs_info *info, u64 flags,
                             u64 total_bytes, u64 bytes_used,
                             u64 bytes_readonly,
                             struct btrfs_space_info **space_info)
{
        struct btrfs_space_info *found;
        int factor;

        factor = btrfs_bg_type_to_factor(flags);

        found = btrfs_find_space_info(info, flags);
        ASSERT(found);
        spin_lock(&found->lock);
        found->total_bytes += total_bytes;
        found->disk_total += total_bytes * factor;
        found->bytes_used += bytes_used;
        found->disk_used += bytes_used * factor;
        found->bytes_readonly += bytes_readonly;
        if (total_bytes > 0)
                found->full = 0;
        btrfs_space_info_add_new_bytes(info, found,
                                       total_bytes - bytes_used -
                                       bytes_readonly);
        spin_unlock(&found->lock);
        *space_info = found;
}

struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
                                               u64 flags)
{
        struct list_head *head = &info->space_info;
        struct btrfs_space_info *found;

        flags &= BTRFS_BLOCK_GROUP_TYPE_MASK;

        rcu_read_lock();
        list_for_each_entry_rcu(found, head, list) {
                if (found->flags & flags) {
                        rcu_read_unlock();
                        return found;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static inline u64 calc_global_rsv_need_space(struct btrfs_block_rsv *global)
{
        return (global->size << 1);
}

static int can_overcommit(struct btrfs_fs_info *fs_info,
                          struct btrfs_space_info *space_info, u64 bytes,
                          enum btrfs_reserve_flush_enum flush,
                          bool system_chunk)
{
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        u64 profile;
        u64 space_size;
        u64 avail;
        u64 used;
        int factor;

        /* Don't overcommit when in mixed mode. */
        if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
                return 0;

        if (system_chunk)
                profile = btrfs_system_alloc_profile(fs_info);
        else
                profile = btrfs_metadata_alloc_profile(fs_info);

        used = btrfs_space_info_used(space_info, false);

        /*
         * We only want to allow over committing if we have lots of actual space
         * free, but if we don't have enough space to handle the global reserve
         * space then we could end up having a real enospc problem when trying
         * to allocate a chunk or some other such important allocation.
         */
        spin_lock(&global_rsv->lock);
        space_size = calc_global_rsv_need_space(global_rsv);
        spin_unlock(&global_rsv->lock);
        if (used + space_size >= space_info->total_bytes)
                return 0;

        used += space_info->bytes_may_use;

        avail = atomic64_read(&fs_info->free_chunk_space);

        /*
         * If we have dup, raid1 or raid10 then only half of the free
         * space is actually usable.  For raid56, the space info used
         * doesn't include the parity drive, so we don't have to
         * change the math
         */
        factor = btrfs_bg_type_to_factor(profile);
        avail = div_u64(avail, factor);

        /*
         * If we aren't flushing all things, let us overcommit up to
         * 1/2th of the space. If we can flush, don't let us overcommit
         * too much, let it overcommit up to 1/8 of the space.
         */
        if (flush == BTRFS_RESERVE_FLUSH_ALL)
                avail >>= 3;
        else
                avail >>= 1;

        if (used + bytes < space_info->total_bytes + avail)
                return 1;
        return 0;
}

/*
 * This is for space we already have accounted in space_info->bytes_may_use, so
 * basically when we're returning space from block_rsv's.
 */
void btrfs_space_info_add_old_bytes(struct btrfs_fs_info *fs_info,
                                    struct btrfs_space_info *space_info,
                                    u64 num_bytes)
{
        struct reserve_ticket *ticket;
        struct list_head *head;
        u64 used;
        enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;
        bool check_overcommit = false;

        spin_lock(&space_info->lock);
        head = &space_info->priority_tickets;

        /*
         * If we are over our limit then we need to check and see if we can
         * overcommit, and if we can't then we just need to free up our space
         * and not satisfy any requests.
         */
        used = btrfs_space_info_used(space_info, true);
        if (used - num_bytes >= space_info->total_bytes)
                check_overcommit = true;
again:
        while (!list_empty(head) && num_bytes) {
                ticket = list_first_entry(head, struct reserve_ticket,
                                          list);
                /*
                 * We use 0 bytes because this space is already reserved, so
                 * adding the ticket space would be a double count.
                 */
                if (check_overcommit &&
                    !can_overcommit(fs_info, space_info, 0, flush, false))
                        break;
                if (num_bytes >= ticket->bytes) {
                        list_del_init(&ticket->list);
                        num_bytes -= ticket->bytes;
                        ticket->bytes = 0;
                        space_info->tickets_id++;
                        wake_up(&ticket->wait);
                } else {
                        ticket->bytes -= num_bytes;
                        num_bytes = 0;
                }
        }

        if (num_bytes && head == &space_info->priority_tickets) {
                head = &space_info->tickets;
                flush = BTRFS_RESERVE_FLUSH_ALL;
                goto again;
        }
        btrfs_space_info_update_bytes_may_use(fs_info, space_info, -num_bytes);
        trace_btrfs_space_reservation(fs_info, "space_info",
                                      space_info->flags, num_bytes, 0);
        spin_unlock(&space_info->lock);
}

/*
 * This is for newly allocated space that isn't accounted in
 * space_info->bytes_may_use yet.  So if we allocate a chunk or unpin an extent
 * we use this helper.
 */
void btrfs_space_info_add_new_bytes(struct btrfs_fs_info *fs_info,
                                    struct btrfs_space_info *space_info,
                                    u64 num_bytes)
{
        struct reserve_ticket *ticket;
        struct list_head *head = &space_info->priority_tickets;

again:
        while (!list_empty(head) && num_bytes) {
                ticket = list_first_entry(head, struct reserve_ticket,
                                          list);
                if (num_bytes >= ticket->bytes) {
                        trace_btrfs_space_reservation(fs_info, "space_info",
                                                      space_info->flags,
                                                      ticket->bytes, 1);
                        list_del_init(&ticket->list);
                        num_bytes -= ticket->bytes;
                        btrfs_space_info_update_bytes_may_use(fs_info,
                                                              space_info,
                                                              ticket->bytes);
                        ticket->bytes = 0;
                        space_info->tickets_id++;
                        wake_up(&ticket->wait);
                } else {
                        trace_btrfs_space_reservation(fs_info, "space_info",
                                                      space_info->flags,
                                                      num_bytes, 1);
                        btrfs_space_info_update_bytes_may_use(fs_info,
                                                              space_info,
                                                              num_bytes);
                        ticket->bytes -= num_bytes;
                        num_bytes = 0;
                }
        }

        if (num_bytes && head == &space_info->priority_tickets) {
                head = &space_info->tickets;
                goto again;
        }
}

#define DUMP_BLOCK_RSV(fs_info, rsv_name)                               \
do {                                                                    \
        struct btrfs_block_rsv *__rsv = &(fs_info)->rsv_name;           \
        spin_lock(&__rsv->lock);                                        \
        btrfs_info(fs_info, #rsv_name ": size %llu reserved %llu",      \
                   __rsv->size, __rsv->reserved);                       \
        spin_unlock(&__rsv->lock);                                      \
} while (0)

void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
                           struct btrfs_space_info *info, u64 bytes,
                           int dump_block_groups)
{
        struct btrfs_block_group_cache *cache;
        int index = 0;

        spin_lock(&info->lock);
        btrfs_info(fs_info, "space_info %llu has %llu free, is %sfull",
                   info->flags,
                   info->total_bytes - btrfs_space_info_used(info, true),
                   info->full ? "" : "not ");
        btrfs_info(fs_info,
                "space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu",
                info->total_bytes, info->bytes_used, info->bytes_pinned,
                info->bytes_reserved, info->bytes_may_use,
                info->bytes_readonly);
        spin_unlock(&info->lock);

        DUMP_BLOCK_RSV(fs_info, global_block_rsv);
        DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
        DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
        DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
        DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);

        if (!dump_block_groups)
                return;

        down_read(&info->groups_sem);
again:
        list_for_each_entry(cache, &info->block_groups[index], list) {
                spin_lock(&cache->lock);
                btrfs_info(fs_info,
                        "block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %s",
                        cache->key.objectid, cache->key.offset,
                        btrfs_block_group_used(&cache->item), cache->pinned,
                        cache->reserved, cache->ro ? "[readonly]" : "");
                btrfs_dump_free_space(cache, bytes);
                spin_unlock(&cache->lock);
        }
        if (++index < BTRFS_NR_RAID_TYPES)
                goto again;
        up_read(&info->groups_sem);
}

static void btrfs_writeback_inodes_sb_nr(struct btrfs_fs_info *fs_info,
                                         unsigned long nr_pages, int nr_items)
{
        struct super_block *sb = fs_info->sb;

        if (down_read_trylock(&sb->s_umount)) {
                writeback_inodes_sb_nr(sb, nr_pages, WB_REASON_FS_FREE_SPACE);
                up_read(&sb->s_umount);
        } else {
                /*
                 * We needn't worry the filesystem going from r/w to r/o though
                 * we don't acquire ->s_umount mutex, because the filesystem
                 * should guarantee the delalloc inodes list be empty after
                 * the filesystem is readonly(all dirty pages are written to
                 * the disk).
                 */
                btrfs_start_delalloc_roots(fs_info, nr_items);
                if (!current->journal_info)
                        btrfs_wait_ordered_roots(fs_info, nr_items, 0, (u64)-1);
        }
}

static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
                                        u64 to_reclaim)
{
        u64 bytes;
        u64 nr;

        bytes = btrfs_calc_trans_metadata_size(fs_info, 1);
        nr = div64_u64(to_reclaim, bytes);
        if (!nr)
                nr = 1;
        return nr;
}

#define EXTENT_SIZE_PER_ITEM    SZ_256K

/*
 * shrink metadata reservation for delalloc
 */
static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
                            u64 orig, bool wait_ordered)
{
        struct btrfs_space_info *space_info;
        struct btrfs_trans_handle *trans;
        u64 delalloc_bytes;
        u64 dio_bytes;
        u64 async_pages;
        u64 items;
        long time_left;
        unsigned long nr_pages;
        int loops;

        /* Calc the number of the pages we need flush for space reservation */
        items = calc_reclaim_items_nr(fs_info, to_reclaim);
        to_reclaim = items * EXTENT_SIZE_PER_ITEM;

        trans = (struct btrfs_trans_handle *)current->journal_info;
        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);

        delalloc_bytes = percpu_counter_sum_positive(
                                                &fs_info->delalloc_bytes);
        dio_bytes = percpu_counter_sum_positive(&fs_info->dio_bytes);
        if (delalloc_bytes == 0 && dio_bytes == 0) {
                if (trans)
                        return;
                if (wait_ordered)
                        btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
                return;
        }

        /*
         * If we are doing more ordered than delalloc we need to just wait on
         * ordered extents, otherwise we'll waste time trying to flush delalloc
         * that likely won't give us the space back we need.
         */
        if (dio_bytes > delalloc_bytes)
                wait_ordered = true;

        loops = 0;
        while ((delalloc_bytes || dio_bytes) && loops < 3) {
                nr_pages = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;

                /*
                 * Triggers inode writeback for up to nr_pages. This will invoke
                 * ->writepages callback and trigger delalloc filling
                 *  (btrfs_run_delalloc_range()).
                 */
                btrfs_writeback_inodes_sb_nr(fs_info, nr_pages, items);

                /*
                 * We need to wait for the compressed pages to start before
                 * we continue.
                 */
                async_pages = atomic_read(&fs_info->async_delalloc_pages);
                if (!async_pages)
                        goto skip_async;

                /*
                 * Calculate how many compressed pages we want to be written
                 * before we continue. I.e if there are more async pages than we
                 * require wait_event will wait until nr_pages are written.
                 */
                if (async_pages <= nr_pages)
                        async_pages = 0;
                else
                        async_pages -= nr_pages;

                wait_event(fs_info->async_submit_wait,
                           atomic_read(&fs_info->async_delalloc_pages) <=
                           (int)async_pages);
skip_async:
                spin_lock(&space_info->lock);
                if (list_empty(&space_info->tickets) &&
                    list_empty(&space_info->priority_tickets)) {
                        spin_unlock(&space_info->lock);
                        break;
                }
                spin_unlock(&space_info->lock);

                loops++;
                if (wait_ordered && !trans) {
                        btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
                } else {
                        time_left = schedule_timeout_killable(1);
                        if (time_left)
                                break;
                }
                delalloc_bytes = percpu_counter_sum_positive(
                                                &fs_info->delalloc_bytes);
                dio_bytes = percpu_counter_sum_positive(&fs_info->dio_bytes);
        }
}

/**
 * maybe_commit_transaction - possibly commit the transaction if its ok to
 * @root - the root we're allocating for
 * @bytes - the number of bytes we want to reserve
 * @force - force the commit
 *
 * This will check to make sure that committing the transaction will actually
 * get us somewhere and then commit the transaction if it does.  Otherwise it
 * will return -ENOSPC.
 */
static int may_commit_transaction(struct btrfs_fs_info *fs_info,
                                  struct btrfs_space_info *space_info)
{
        struct reserve_ticket *ticket = NULL;
        struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_block_rsv;
        struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
        struct btrfs_trans_handle *trans;
        u64 bytes_needed;
        u64 reclaim_bytes = 0;

        trans = (struct btrfs_trans_handle *)current->journal_info;
        if (trans)
                return -EAGAIN;

        spin_lock(&space_info->lock);
        if (!list_empty(&space_info->priority_tickets))
                ticket = list_first_entry(&space_info->priority_tickets,
                                          struct reserve_ticket, list);
        else if (!list_empty(&space_info->tickets))
                ticket = list_first_entry(&space_info->tickets,
                                          struct reserve_ticket, list);
        bytes_needed = (ticket) ? ticket->bytes : 0;
        spin_unlock(&space_info->lock);

        if (!bytes_needed)
                return 0;

        trans = btrfs_join_transaction(fs_info->extent_root);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        /*
         * See if there is enough pinned space to make this reservation, or if
         * we have block groups that are going to be freed, allowing us to
         * possibly do a chunk allocation the next loop through.
         */
        if (test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags) ||
            __percpu_counter_compare(&space_info->total_bytes_pinned,
                                     bytes_needed,
                                     BTRFS_TOTAL_BYTES_PINNED_BATCH) >= 0)
                goto commit;

        /*
         * See if there is some space in the delayed insertion reservation for
         * this reservation.
         */
        if (space_info != delayed_rsv->space_info)
                goto enospc;

        spin_lock(&delayed_rsv->lock);
        reclaim_bytes += delayed_rsv->reserved;
        spin_unlock(&delayed_rsv->lock);

        spin_lock(&delayed_refs_rsv->lock);
        reclaim_bytes += delayed_refs_rsv->reserved;
        spin_unlock(&delayed_refs_rsv->lock);
        if (reclaim_bytes >= bytes_needed)
                goto commit;
        bytes_needed -= reclaim_bytes;

        if (__percpu_counter_compare(&space_info->total_bytes_pinned,
                                   bytes_needed,
                                   BTRFS_TOTAL_BYTES_PINNED_BATCH) < 0)
                goto enospc;

commit:
        return btrfs_commit_transaction(trans);
enospc:
        btrfs_end_transaction(trans);
        return -ENOSPC;
}

/*
 * Try to flush some data based on policy set by @state. This is only advisory
 * and may fail for various reasons. The caller is supposed to examine the
 * state of @space_info to detect the outcome.
 */
static void flush_space(struct btrfs_fs_info *fs_info,
                       struct btrfs_space_info *space_info, u64 num_bytes,
                       int state)
{
        struct btrfs_root *root = fs_info->extent_root;
        struct btrfs_trans_handle *trans;
        int nr;
        int ret = 0;

        switch (state) {
        case FLUSH_DELAYED_ITEMS_NR:
        case FLUSH_DELAYED_ITEMS:
                if (state == FLUSH_DELAYED_ITEMS_NR)
                        nr = calc_reclaim_items_nr(fs_info, num_bytes) * 2;
                else
                        nr = -1;

                trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        break;
                }
                ret = btrfs_run_delayed_items_nr(trans, nr);
                btrfs_end_transaction(trans);
                break;
        case FLUSH_DELALLOC:
        case FLUSH_DELALLOC_WAIT:
                shrink_delalloc(fs_info, num_bytes * 2, num_bytes,
                                state == FLUSH_DELALLOC_WAIT);
                break;
        case FLUSH_DELAYED_REFS_NR:
        case FLUSH_DELAYED_REFS:
                trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        break;
                }
                if (state == FLUSH_DELAYED_REFS_NR)
                        nr = calc_reclaim_items_nr(fs_info, num_bytes);
                else
                        nr = 0;
                btrfs_run_delayed_refs(trans, nr);
                btrfs_end_transaction(trans);
                break;
        case ALLOC_CHUNK:
        case ALLOC_CHUNK_FORCE:
                trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        break;
                }
                ret = btrfs_chunk_alloc(trans,
                                btrfs_metadata_alloc_profile(fs_info),
                                (state == ALLOC_CHUNK) ? CHUNK_ALLOC_NO_FORCE :
                                        CHUNK_ALLOC_FORCE);
                btrfs_end_transaction(trans);
                if (ret > 0 || ret == -ENOSPC)
                        ret = 0;
                break;
        case COMMIT_TRANS:
                /*
                 * If we have pending delayed iputs then we could free up a
                 * bunch of pinned space, so make sure we run the iputs before
                 * we do our pinned bytes check below.
                 */
                btrfs_run_delayed_iputs(fs_info);
                btrfs_wait_on_delayed_iputs(fs_info);

                ret = may_commit_transaction(fs_info, space_info);
                break;
        default:
                ret = -ENOSPC;
                break;
        }

        trace_btrfs_flush_space(fs_info, space_info->flags, num_bytes, state,
                                ret);
        return;
}

static inline u64
btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
                                 struct btrfs_space_info *space_info,
                                 bool system_chunk)
{
        struct reserve_ticket *ticket;
        u64 used;
        u64 expected;
        u64 to_reclaim = 0;

        list_for_each_entry(ticket, &space_info->tickets, list)
                to_reclaim += ticket->bytes;
        list_for_each_entry(ticket, &space_info->priority_tickets, list)
                to_reclaim += ticket->bytes;
        if (to_reclaim)
                return to_reclaim;

        to_reclaim = min_t(u64, num_online_cpus() * SZ_1M, SZ_16M);
        if (can_overcommit(fs_info, space_info, to_reclaim,
                           BTRFS_RESERVE_FLUSH_ALL, system_chunk))
                return 0;

        used = btrfs_space_info_used(space_info, true);

        if (can_overcommit(fs_info, space_info, SZ_1M,
                           BTRFS_RESERVE_FLUSH_ALL, system_chunk))
                expected = div_factor_fine(space_info->total_bytes, 95);
        else
                expected = div_factor_fine(space_info->total_bytes, 90);

        if (used > expected)
                to_reclaim = used - expected;
        else
                to_reclaim = 0;
        to_reclaim = min(to_reclaim, space_info->bytes_may_use +
                                     space_info->bytes_reserved);
        return to_reclaim;
}

static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
                                        struct btrfs_space_info *space_info,
                                        u64 used, bool system_chunk)
{
        u64 thresh = div_factor_fine(space_info->total_bytes, 98);

        /* If we're just plain full then async reclaim just slows us down. */
        if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh)
                return 0;

        if (!btrfs_calc_reclaim_metadata_size(fs_info, space_info,
                                              system_chunk))
                return 0;

        return (used >= thresh && !btrfs_fs_closing(fs_info) &&
                !test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
}

static bool wake_all_tickets(struct list_head *head)
{
        struct reserve_ticket *ticket;

        while (!list_empty(head)) {
                ticket = list_first_entry(head, struct reserve_ticket, list);
                list_del_init(&ticket->list);
                ticket->error = -ENOSPC;
                wake_up(&ticket->wait);
                if (ticket->bytes != ticket->orig_bytes)
                        return true;
        }
        return false;
}

/*
 * This is for normal flushers, we can wait all goddamned day if we want to.  We
 * will loop and continuously try to flush as long as we are making progress.
 * We count progress as clearing off tickets each time we have to loop.
 */
static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
{
        struct btrfs_fs_info *fs_info;
        struct btrfs_space_info *space_info;
        u64 to_reclaim;
        int flush_state;
        int commit_cycles = 0;
        u64 last_tickets_id;

        fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);

        spin_lock(&space_info->lock);
        to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
                                                      false);
        if (!to_reclaim) {
                space_info->flush = 0;
                spin_unlock(&space_info->lock);
                return;
        }
        last_tickets_id = space_info->tickets_id;
        spin_unlock(&space_info->lock);

        flush_state = FLUSH_DELAYED_ITEMS_NR;
        do {
                flush_space(fs_info, space_info, to_reclaim, flush_state);
                spin_lock(&space_info->lock);
                if (list_empty(&space_info->tickets)) {
                        space_info->flush = 0;
                        spin_unlock(&space_info->lock);
                        return;
                }
                to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
                                                              space_info,
                                                              false);
                if (last_tickets_id == space_info->tickets_id) {
                        flush_state++;
                } else {
                        last_tickets_id = space_info->tickets_id;
                        flush_state = FLUSH_DELAYED_ITEMS_NR;
                        if (commit_cycles)
                                commit_cycles--;
                }

                /*
                 * We don't want to force a chunk allocation until we've tried
                 * pretty hard to reclaim space.  Think of the case where we
                 * freed up a bunch of space and so have a lot of pinned space
                 * to reclaim.  We would rather use that than possibly create a
                 * underutilized metadata chunk.  So if this is our first run
                 * through the flushing state machine skip ALLOC_CHUNK_FORCE and
                 * commit the transaction.  If nothing has changed the next go
                 * around then we can force a chunk allocation.
                 */
                if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
                        flush_state++;

                if (flush_state > COMMIT_TRANS) {
                        commit_cycles++;
                        if (commit_cycles > 2) {
                                if (wake_all_tickets(&space_info->tickets)) {
                                        flush_state = FLUSH_DELAYED_ITEMS_NR;
                                        commit_cycles--;
                                } else {
                                        space_info->flush = 0;
                                }
                        } else {
                                flush_state = FLUSH_DELAYED_ITEMS_NR;
                        }
                }
                spin_unlock(&space_info->lock);
        } while (flush_state <= COMMIT_TRANS);
}

void btrfs_init_async_reclaim_work(struct work_struct *work)
{
        INIT_WORK(work, btrfs_async_reclaim_metadata_space);
}

static const enum btrfs_flush_state priority_flush_states[] = {
        FLUSH_DELAYED_ITEMS_NR,
        FLUSH_DELAYED_ITEMS,
        ALLOC_CHUNK,
};

static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
                                            struct btrfs_space_info *space_info,
                                            struct reserve_ticket *ticket)
{
        u64 to_reclaim;
        int flush_state;

        spin_lock(&space_info->lock);
        to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
                                                      false);
        if (!to_reclaim) {
                spin_unlock(&space_info->lock);
                return;
        }
        spin_unlock(&space_info->lock);

        flush_state = 0;
        do {
                flush_space(fs_info, space_info, to_reclaim,
                            priority_flush_states[flush_state]);
                flush_state++;
                spin_lock(&space_info->lock);
                if (ticket->bytes == 0) {
                        spin_unlock(&space_info->lock);
                        return;
                }
                spin_unlock(&space_info->lock);
        } while (flush_state < ARRAY_SIZE(priority_flush_states));
}

static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
                               struct btrfs_space_info *space_info,
                               struct reserve_ticket *ticket)

{
        DEFINE_WAIT(wait);
        u64 reclaim_bytes = 0;
        int ret = 0;

        spin_lock(&space_info->lock);
        while (ticket->bytes > 0 && ticket->error == 0) {
                ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
                if (ret) {
                        ret = -EINTR;
                        break;
                }
                spin_unlock(&space_info->lock);

                schedule();

                finish_wait(&ticket->wait, &wait);
                spin_lock(&space_info->lock);
        }
        if (!ret)
                ret = ticket->error;
        if (!list_empty(&ticket->list))
                list_del_init(&ticket->list);
        if (ticket->bytes && ticket->bytes < ticket->orig_bytes)
                reclaim_bytes = ticket->orig_bytes - ticket->bytes;
        spin_unlock(&space_info->lock);

        if (reclaim_bytes)
                btrfs_space_info_add_old_bytes(fs_info, space_info,
                                               reclaim_bytes);
        return ret;
}

/**
 * reserve_metadata_bytes - try to reserve bytes from the block_rsv's space
 * @root - the root we're allocating for
 * @space_info - the space info we want to allocate from
 * @orig_bytes - the number of bytes we want
 * @flush - whether or not we can flush to make our reservation
 *
 * This will reserve orig_bytes number of bytes from the space info associated
 * with the block_rsv.  If there is not enough space it will make an attempt to
 * flush out space to make room.  It will do this by flushing delalloc if
 * possible or committing the transaction.  If flush is 0 then no attempts to
 * regain reservations will be made and this will fail if there is not enough
 * space already.
 */
static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
                                    struct btrfs_space_info *space_info,
                                    u64 orig_bytes,
                                    enum btrfs_reserve_flush_enum flush,
                                    bool system_chunk)
{
        struct reserve_ticket ticket;
        u64 used;
        u64 reclaim_bytes = 0;
        int ret = 0;

        ASSERT(orig_bytes);
        ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);

        spin_lock(&space_info->lock);
        ret = -ENOSPC;
        used = btrfs_space_info_used(space_info, true);

        /*
         * Carry on if we have enough space (short-circuit) OR call
         * can_overcommit() to ensure we can overcommit to continue.
         */
        if ((used + orig_bytes <= space_info->total_bytes) ||
            can_overcommit(fs_info, space_info, orig_bytes, flush,
                           system_chunk)) {
                btrfs_space_info_update_bytes_may_use(fs_info, space_info,
                                                      orig_bytes);
                trace_btrfs_space_reservation(fs_info, "space_info",
                                              space_info->flags, orig_bytes, 1);
                ret = 0;
        }

        /*
         * If we couldn't make a reservation then setup our reservation ticket
         * and kick the async worker if it's not already running.
         *
         * If we are a priority flusher then we just need to add our ticket to
         * the list and we will do our own flushing further down.
         */
        if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
                ticket.orig_bytes = orig_bytes;
                ticket.bytes = orig_bytes;
                ticket.error = 0;
                init_waitqueue_head(&ticket.wait);
                if (flush == BTRFS_RESERVE_FLUSH_ALL) {
                        list_add_tail(&ticket.list, &space_info->tickets);
                        if (!space_info->flush) {
                                space_info->flush = 1;
                                trace_btrfs_trigger_flush(fs_info,
                                                          space_info->flags,

                                                          orig_bytes, flush,
                                                          "enospc");
                                queue_work(system_unbound_wq,
                                           &fs_info->async_reclaim_work);
                        }
                } else {
                        list_add_tail(&ticket.list,
                                      &space_info->priority_tickets);
                }
        } else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
                used += orig_bytes;
                /*
                 * We will do the space reservation dance during log replay,
                 * which means we won't have fs_info->fs_root set, so don't do
                 * the async reclaim as we will panic.
                 */
                if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
                    need_do_async_reclaim(fs_info, space_info,
                                          used, system_chunk) &&
                    !work_busy(&fs_info->async_reclaim_work)) {
                        trace_btrfs_trigger_flush(fs_info, space_info->flags,
                                                  orig_bytes, flush, "preempt");
                        queue_work(system_unbound_wq,
                                   &fs_info->async_reclaim_work);
                }
        }
        spin_unlock(&space_info->lock);
        if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
                return ret;

        if (flush == BTRFS_RESERVE_FLUSH_ALL)
                return wait_reserve_ticket(fs_info, space_info, &ticket);

        ret = 0;
        priority_reclaim_metadata_space(fs_info, space_info, &ticket);
        spin_lock(&space_info->lock);
        if (ticket.bytes) {
                if (ticket.bytes < orig_bytes)
                        reclaim_bytes = orig_bytes - ticket.bytes;
                list_del_init(&ticket.list);
                ret = -ENOSPC;
        }
        spin_unlock(&space_info->lock);

        if (reclaim_bytes)
                btrfs_space_info_add_old_bytes(fs_info, space_info,
                                               reclaim_bytes);
        ASSERT(list_empty(&ticket.list));
        return ret;
}

/**
 * reserve_metadata_bytes - try to reserve bytes from the block_rsv's space
 * @root - the root we're allocating for
 * @block_rsv - the block_rsv we're allocating for
 * @orig_bytes - the number of bytes we want
 * @flush - whether or not we can flush to make our reservation
 *
 * This will reserve orig_bytes number of bytes from the space info associated
 * with the block_rsv.  If there is not enough space it will make an attempt to
 * flush out space to make room.  It will do this by flushing delalloc if
 * possible or committing the transaction.  If flush is 0 then no attempts to
 * regain reservations will be made and this will fail if there is not enough
 * space already.
 */
int btrfs_reserve_metadata_bytes(struct btrfs_root *root,
                                 struct btrfs_block_rsv *block_rsv,
                                 u64 orig_bytes,
                                 enum btrfs_reserve_flush_enum flush)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        int ret;
        bool system_chunk = (root == fs_info->chunk_root);

        ret = __reserve_metadata_bytes(fs_info, block_rsv->space_info,
                                       orig_bytes, flush, system_chunk);
        if (ret == -ENOSPC &&
            unlikely(root->orphan_cleanup_state == ORPHAN_CLEANUP_STARTED)) {
                if (block_rsv != global_rsv &&
                    !btrfs_block_rsv_use_bytes(global_rsv, orig_bytes))
                        ret = 0;
        }
        if (ret == -ENOSPC) {
                trace_btrfs_space_reservation(fs_info, "space_info:enospc",
                                              block_rsv->space_info->flags,
                                              orig_bytes, 1);

                if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
                        btrfs_dump_space_info(fs_info, block_rsv->space_info,
                                              orig_bytes, 0);
        }
        return ret;
}