// SPDX-License-Identifier: GPL-2.0

#include "misc.h"
#include "ctree.h"
#include "block-rsv.h"
#include "space-info.h"
#include "transaction.h"
#include "block-group.h"

/*
 * HOW DO BLOCK RESERVES WORK
 *
 *   Think of block_rsv's as buckets for logically grouped metadata
 *   reservations.  Each block_rsv has a ->size and a ->reserved.  ->size is
 *   how large we want our block rsv to be, ->reserved is how much space is
 *   currently reserved for this block reserve.
 *
 *   ->failfast exists for the truncate case, and is described below.
 *
 * NORMAL OPERATION
 *
 *   -> Reserve
 *     Entrance: btrfs_block_rsv_add, btrfs_block_rsv_refill
 *
 *     We call into btrfs_reserve_metadata_bytes() with our bytes, which is
 *     accounted for in space_info->bytes_may_use, and then add the bytes to
 *     ->reserved, and ->size in the case of btrfs_block_rsv_add.
 *
 *     ->size is an over-estimation of how much we may use for a particular
 *     operation.
 *
 *   -> Use
 *     Entrance: btrfs_use_block_rsv
 *
 *     When we do a btrfs_alloc_tree_block() we call into btrfs_use_block_rsv()
 *     to determine the appropriate block_rsv to use, and then verify that
 *     ->reserved has enough space for our tree block allocation.  Once
 *     successful we subtract fs_info->nodesize from ->reserved.
 *
 *   -> Finish
 *     Entrance: btrfs_block_rsv_release
 *
 *     We are finished with our operation, subtract our individual reservation
 *     from ->size, and then subtract ->size from ->reserved and free up the
 *     excess if there is any.
 *
 *     There is some logic here to refill the delayed refs rsv or the global rsv
 *     as needed, otherwise the excess is subtracted from
 *     space_info->bytes_may_use.
 *
 * TYPES OF BLOCK RESERVES
 *
 * BLOCK_RSV_TRANS, BLOCK_RSV_DELOPS, BLOCK_RSV_CHUNK
 *   These behave normally, as described above, just within the confines of the
 *   lifetime of their particular operation (transaction for the whole trans
 *   handle lifetime, for example).
 *
 * BLOCK_RSV_GLOBAL
 *   It is impossible to properly account for all the space that may be required
 *   to make our extent tree updates.  This block reserve acts as an overflow
 *   buffer in case our delayed refs reserve does not reserve enough space to
 *   update the extent tree.
 *
 *   We can steal from this in some cases as well, notably on evict() or
 *   truncate() in order to help users recover from ENOSPC conditions.
 *
 * BLOCK_RSV_DELALLOC
 *   The individual item sizes are determined by the per-inode size
 *   calculations, which are described with the delalloc code.  This is pretty
 *   straightforward, it's just the calculation of ->size encodes a lot of
 *   different items, and thus it gets used when updating inodes, inserting file
 *   extents, and inserting checksums.
 *
 * BLOCK_RSV_DELREFS
 *   We keep a running tally of how many delayed refs we have on the system.
 *   We assume each one of these delayed refs are going to use a full
 *   reservation.  We use the transaction items and pre-reserve space for every
 *   operation, and use this reservation to refill any gap between ->size and
 *   ->reserved that may exist.
 *
 *   From there it's straightforward, removing a delayed ref means we remove its
 *   count from ->size and free up reservations as necessary.  Since this is
 *   the most dynamic block reserve in the system, we will try to refill this
 *   block reserve first with any excess returned by any other block reserve.
 *
 * BLOCK_RSV_EMPTY
 *   This is the fallback block reserve to make us try to reserve space if we
 *   don't have a specific bucket for this allocation.  It is mostly used for
 *   updating the device tree and such, since that is a separate pool we're
 *   content to just reserve space from the space_info on demand.
 *
 * BLOCK_RSV_TEMP
 *   This is used by things like truncate and iput.  We will temporarily
 *   allocate a block reserve, set it to some size, and then truncate bytes
 *   until we have no space left.  With ->failfast set we'll simply return
 *   ENOSPC from btrfs_use_block_rsv() to signal that we need to unwind and try
 *   to make a new reservation.  This is because these operations are
 *   unbounded, so we want to do as much work as we can, and then back off and
 *   re-reserve.
 */

static u64 block_rsv_release_bytes(struct btrfs_fs_info *fs_info,
                                    struct btrfs_block_rsv *block_rsv,
                                    struct btrfs_block_rsv *dest, u64 num_bytes,
                                    u64 *qgroup_to_release_ret)
{
        struct btrfs_space_info *space_info = block_rsv->space_info;
        u64 qgroup_to_release = 0;
        u64 ret;

        spin_lock(&block_rsv->lock);
        if (num_bytes == (u64)-1) {
                num_bytes = block_rsv->size;
                qgroup_to_release = block_rsv->qgroup_rsv_size;
        }
        block_rsv->size -= num_bytes;
        if (block_rsv->reserved >= block_rsv->size) {
                num_bytes = block_rsv->reserved - block_rsv->size;
                block_rsv->reserved = block_rsv->size;
                block_rsv->full = 1;
        } else {
                num_bytes = 0;
        }
        if (block_rsv->qgroup_rsv_reserved >= block_rsv->qgroup_rsv_size) {
                qgroup_to_release = block_rsv->qgroup_rsv_reserved -
                                    block_rsv->qgroup_rsv_size;
                block_rsv->qgroup_rsv_reserved = block_rsv->qgroup_rsv_size;
        } else {
                qgroup_to_release = 0;
        }
        spin_unlock(&block_rsv->lock);

        ret = num_bytes;
        if (num_bytes > 0) {
                if (dest) {
                        spin_lock(&dest->lock);
                        if (!dest->full) {
                                u64 bytes_to_add;

                                bytes_to_add = dest->size - dest->reserved;
                                bytes_to_add = min(num_bytes, bytes_to_add);
                                dest->reserved += bytes_to_add;
                                if (dest->reserved >= dest->size)
                                        dest->full = 1;
                                num_bytes -= bytes_to_add;
                        }
                        spin_unlock(&dest->lock);
                }
                if (num_bytes)
                        btrfs_space_info_free_bytes_may_use(fs_info,
                                                            space_info,
                                                            num_bytes);
        }
        if (qgroup_to_release_ret)
                *qgroup_to_release_ret = qgroup_to_release;
        return ret;
}

int btrfs_block_rsv_migrate(struct btrfs_block_rsv *src,
                            struct btrfs_block_rsv *dst, u64 num_bytes,
                            bool update_size)
{
        int ret;

        ret = btrfs_block_rsv_use_bytes(src, num_bytes);
        if (ret)
                return ret;

        btrfs_block_rsv_add_bytes(dst, num_bytes, update_size);
        return 0;
}

void btrfs_init_block_rsv(struct btrfs_block_rsv *rsv, unsigned short type)
{
        memset(rsv, 0, sizeof(*rsv));
        spin_lock_init(&rsv->lock);
        rsv->type = type;
}

void btrfs_init_metadata_block_rsv(struct btrfs_fs_info *fs_info,
                                   struct btrfs_block_rsv *rsv,
                                   unsigned short type)
{
        btrfs_init_block_rsv(rsv, type);
        rsv->space_info = btrfs_find_space_info(fs_info,
                                            BTRFS_BLOCK_GROUP_METADATA);
}

struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_fs_info *fs_info,
                                              unsigned short type)
{
        struct btrfs_block_rsv *block_rsv;

        block_rsv = kmalloc(sizeof(*block_rsv), GFP_NOFS);
        if (!block_rsv)
                return NULL;

        btrfs_init_metadata_block_rsv(fs_info, block_rsv, type);
        return block_rsv;
}

void btrfs_free_block_rsv(struct btrfs_fs_info *fs_info,
                          struct btrfs_block_rsv *rsv)
{
        if (!rsv)
                return;
        btrfs_block_rsv_release(fs_info, rsv, (u64)-1, NULL);
        kfree(rsv);
}

int btrfs_block_rsv_add(struct btrfs_root *root,
                        struct btrfs_block_rsv *block_rsv, u64 num_bytes,
                        enum btrfs_reserve_flush_enum flush)
{
        int ret;

        if (num_bytes == 0)
                return 0;

        ret = btrfs_reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
        if (!ret)
                btrfs_block_rsv_add_bytes(block_rsv, num_bytes, true);

        return ret;
}

int btrfs_block_rsv_check(struct btrfs_block_rsv *block_rsv, int min_factor)
{
        u64 num_bytes = 0;
        int ret = -ENOSPC;

        if (!block_rsv)
                return 0;

        spin_lock(&block_rsv->lock);
        num_bytes = div_factor(block_rsv->size, min_factor);
        if (block_rsv->reserved >= num_bytes)
                ret = 0;
        spin_unlock(&block_rsv->lock);

        return ret;
}

int btrfs_block_rsv_refill(struct btrfs_root *root,
                           struct btrfs_block_rsv *block_rsv, u64 min_reserved,
                           enum btrfs_reserve_flush_enum flush)
{
        u64 num_bytes = 0;
        int ret = -ENOSPC;

        if (!block_rsv)
                return 0;

        spin_lock(&block_rsv->lock);
        num_bytes = min_reserved;
        if (block_rsv->reserved >= num_bytes)
                ret = 0;
        else
                num_bytes -= block_rsv->reserved;
        spin_unlock(&block_rsv->lock);

        if (!ret)
                return 0;

        ret = btrfs_reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
        if (!ret) {
                btrfs_block_rsv_add_bytes(block_rsv, num_bytes, false);
                return 0;
        }

        return ret;
}

u64 btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
                            struct btrfs_block_rsv *block_rsv, u64 num_bytes,
                            u64 *qgroup_to_release)
{
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
        struct btrfs_block_rsv *target = NULL;

        /*
         * If we are the delayed_rsv then push to the global rsv, otherwise dump
         * into the delayed rsv if it is not full.
         */
        if (block_rsv == delayed_rsv)
                target = global_rsv;
        else if (block_rsv != global_rsv && !delayed_rsv->full)
                target = delayed_rsv;

        if (target && block_rsv->space_info != target->space_info)
                target = NULL;

        return block_rsv_release_bytes(fs_info, block_rsv, target, num_bytes,
                                       qgroup_to_release);
}

int btrfs_block_rsv_use_bytes(struct btrfs_block_rsv *block_rsv, u64 num_bytes)
{
        int ret = -ENOSPC;

        spin_lock(&block_rsv->lock);
        if (block_rsv->reserved >= num_bytes) {
                block_rsv->reserved -= num_bytes;
                if (block_rsv->reserved < block_rsv->size)
                        block_rsv->full = 0;
                ret = 0;
        }
        spin_unlock(&block_rsv->lock);
        return ret;
}

void btrfs_block_rsv_add_bytes(struct btrfs_block_rsv *block_rsv,
                               u64 num_bytes, bool update_size)
{
        spin_lock(&block_rsv->lock);
        block_rsv->reserved += num_bytes;
        if (update_size)
                block_rsv->size += num_bytes;
        else if (block_rsv->reserved >= block_rsv->size)
                block_rsv->full = 1;
        spin_unlock(&block_rsv->lock);
}

int btrfs_cond_migrate_bytes(struct btrfs_fs_info *fs_info,
                             struct btrfs_block_rsv *dest, u64 num_bytes,
                             int min_factor)
{
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        u64 min_bytes;

        if (global_rsv->space_info != dest->space_info)
                return -ENOSPC;

        spin_lock(&global_rsv->lock);
        min_bytes = div_factor(global_rsv->size, min_factor);
        if (global_rsv->reserved < min_bytes + num_bytes) {
                spin_unlock(&global_rsv->lock);
                return -ENOSPC;
        }
        global_rsv->reserved -= num_bytes;
        if (global_rsv->reserved < global_rsv->size)
                global_rsv->full = 0;
        spin_unlock(&global_rsv->lock);

        btrfs_block_rsv_add_bytes(dest, num_bytes, true);
        return 0;
}

void btrfs_update_global_block_rsv(struct btrfs_fs_info *fs_info)
{
        struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
        struct btrfs_space_info *sinfo = block_rsv->space_info;
        u64 num_bytes;
        unsigned min_items;

        /*
         * The global block rsv is based on the size of the extent tree, the
         * checksum tree and the root tree.  If the fs is empty we want to set
         * it to a minimal amount for safety.
         */
        num_bytes = btrfs_root_used(&fs_info->extent_root->root_item) +
                btrfs_root_used(&fs_info->csum_root->root_item) +
                btrfs_root_used(&fs_info->tree_root->root_item);

        /*
         * We at a minimum are going to modify the csum root, the tree root, and
         * the extent root.
         */
        min_items = 3;

        /*
         * But we also want to reserve enough space so we can do the fallback
         * global reserve for an unlink, which is an additional 5 items (see the
         * comment in __unlink_start_trans for what we're modifying.)
         *
         * But we also need space for the delayed ref updates from the unlink,
         * so its 10, 5 for the actual operation, and 5 for the delayed ref
         * updates.
         */
        min_items += 10;

        num_bytes = max_t(u64, num_bytes,
                          btrfs_calc_insert_metadata_size(fs_info, min_items));

        spin_lock(&sinfo->lock);
        spin_lock(&block_rsv->lock);

        block_rsv->size = min_t(u64, num_bytes, SZ_512M);

        if (block_rsv->reserved < block_rsv->size) {
                num_bytes = block_rsv->size - block_rsv->reserved;
                btrfs_space_info_update_bytes_may_use(fs_info, sinfo,
                                                      num_bytes);
                block_rsv->reserved = block_rsv->size;
        } else if (block_rsv->reserved > block_rsv->size) {
                num_bytes = block_rsv->reserved - block_rsv->size;
                btrfs_space_info_update_bytes_may_use(fs_info, sinfo,
                                                      -num_bytes);
                block_rsv->reserved = block_rsv->size;
                btrfs_try_granting_tickets(fs_info, sinfo);
        }

        if (block_rsv->reserved == block_rsv->size)
                block_rsv->full = 1;
        else
                block_rsv->full = 0;

        if (block_rsv->size >= sinfo->total_bytes)
                sinfo->force_alloc = CHUNK_ALLOC_FORCE;
        spin_unlock(&block_rsv->lock);
        spin_unlock(&sinfo->lock);
}

void btrfs_init_global_block_rsv(struct btrfs_fs_info *fs_info)
{
        struct btrfs_space_info *space_info;

        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
        fs_info->chunk_block_rsv.space_info = space_info;

        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
        fs_info->global_block_rsv.space_info = space_info;
        fs_info->trans_block_rsv.space_info = space_info;
        fs_info->empty_block_rsv.space_info = space_info;
        fs_info->delayed_block_rsv.space_info = space_info;
        fs_info->delayed_refs_rsv.space_info = space_info;

        /*
         * Our various recovery options can leave us with NULL roots, so check
         * here and just bail before we go dereferencing NULLs everywhere.
         */
        if (!fs_info->extent_root || !fs_info->csum_root ||
            !fs_info->dev_root || !fs_info->chunk_root || !fs_info->tree_root)
                return;

        fs_info->extent_root->block_rsv = &fs_info->delayed_refs_rsv;
        fs_info->csum_root->block_rsv = &fs_info->delayed_refs_rsv;
        fs_info->dev_root->block_rsv = &fs_info->global_block_rsv;
        fs_info->tree_root->block_rsv = &fs_info->global_block_rsv;
        if (fs_info->quota_root)
                fs_info->quota_root->block_rsv = &fs_info->global_block_rsv;
        fs_info->chunk_root->block_rsv = &fs_info->chunk_block_rsv;

        btrfs_update_global_block_rsv(fs_info);
}

void btrfs_release_global_block_rsv(struct btrfs_fs_info *fs_info)
{
        btrfs_block_rsv_release(fs_info, &fs_info->global_block_rsv, (u64)-1,
                                NULL);
        WARN_ON(fs_info->trans_block_rsv.size > 0);
        WARN_ON(fs_info->trans_block_rsv.reserved > 0);
        WARN_ON(fs_info->chunk_block_rsv.size > 0);
        WARN_ON(fs_info->chunk_block_rsv.reserved > 0);
        WARN_ON(fs_info->delayed_block_rsv.size > 0);
        WARN_ON(fs_info->delayed_block_rsv.reserved > 0);
        WARN_ON(fs_info->delayed_refs_rsv.reserved > 0);
        WARN_ON(fs_info->delayed_refs_rsv.size > 0);
}

static struct btrfs_block_rsv *get_block_rsv(
                                        const struct btrfs_trans_handle *trans,
                                        const struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_rsv *block_rsv = NULL;

        if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
            (root == fs_info->csum_root && trans->adding_csums) ||
            (root == fs_info->uuid_root))
                block_rsv = trans->block_rsv;

        if (!block_rsv)
                block_rsv = root->block_rsv;

        if (!block_rsv)
                block_rsv = &fs_info->empty_block_rsv;

        return block_rsv;
}

struct btrfs_block_rsv *btrfs_use_block_rsv(struct btrfs_trans_handle *trans,
                                            struct btrfs_root *root,
                                            u32 blocksize)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_rsv *block_rsv;
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        int ret;
        bool global_updated = false;

        block_rsv = get_block_rsv(trans, root);

        if (unlikely(block_rsv->size == 0))
                goto try_reserve;
again:
        ret = btrfs_block_rsv_use_bytes(block_rsv, blocksize);
        if (!ret)
                return block_rsv;

        if (block_rsv->failfast)
                return ERR_PTR(ret);

        if (block_rsv->type == BTRFS_BLOCK_RSV_GLOBAL && !global_updated) {
                global_updated = true;
                btrfs_update_global_block_rsv(fs_info);
                goto again;
        }

        /*
         * The global reserve still exists to save us from ourselves, so don't
         * warn_on if we are short on our delayed refs reserve.
         */
        if (block_rsv->type != BTRFS_BLOCK_RSV_DELREFS &&
            btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
                static DEFINE_RATELIMIT_STATE(_rs,
                                DEFAULT_RATELIMIT_INTERVAL * 10,
                                /*DEFAULT_RATELIMIT_BURST*/ 1);
                if (__ratelimit(&_rs))
                        WARN(1, KERN_DEBUG
                                "BTRFS: block rsv %d returned %d\n",
                                block_rsv->type, ret);
        }
try_reserve:
        ret = btrfs_reserve_metadata_bytes(root, block_rsv, blocksize,
                                           BTRFS_RESERVE_NO_FLUSH);
        if (!ret)
                return block_rsv;
        /*
         * If we couldn't reserve metadata bytes try and use some from
         * the global reserve if its space type is the same as the global
         * reservation.
         */
        if (block_rsv->type != BTRFS_BLOCK_RSV_GLOBAL &&
            block_rsv->space_info == global_rsv->space_info) {
                ret = btrfs_block_rsv_use_bytes(global_rsv, blocksize);
                if (!ret)
                        return global_rsv;
        }
        return ERR_PTR(ret);
}