printf: Remove unused 'bprintf'

[drm/drm-misc.git] / fs / bcachefs / btree_write_buffer.c

// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "bkey_buf.h"
#include "btree_locking.h"
#include "btree_update.h"
#include "btree_update_interior.h"
#include "btree_write_buffer.h"
#include "disk_accounting.h"
#include "error.h"
#include "extents.h"
#include "journal.h"
#include "journal_io.h"
#include "journal_reclaim.h"

#include <linux/prefetch.h>
#include <linux/sort.h>

static int bch2_btree_write_buffer_journal_flush(struct journal *,
                                struct journal_entry_pin *, u64);

static int bch2_journal_keys_to_write_buffer(struct bch_fs *, struct journal_buf *);

static inline bool __wb_key_ref_cmp(const struct wb_key_ref *l, const struct wb_key_ref *r)
{
        return (cmp_int(l->hi, r->hi) ?:
                cmp_int(l->mi, r->mi) ?:
                cmp_int(l->lo, r->lo)) >= 0;
}

static inline bool wb_key_ref_cmp(const struct wb_key_ref *l, const struct wb_key_ref *r)
{
#ifdef CONFIG_X86_64
        int cmp;

        asm("mov   (%[l]), %%rax;"
            "sub   (%[r]), %%rax;"
            "mov  8(%[l]), %%rax;"
            "sbb  8(%[r]), %%rax;"
            "mov 16(%[l]), %%rax;"
            "sbb 16(%[r]), %%rax;"
            : "=@ccae" (cmp)
            : [l] "r" (l), [r] "r" (r)
            : "rax", "cc");

        EBUG_ON(cmp != __wb_key_ref_cmp(l, r));
        return cmp;
#else
        return __wb_key_ref_cmp(l, r);
#endif
}

static int wb_key_seq_cmp(const void *_l, const void *_r)
{
        const struct btree_write_buffered_key *l = _l;
        const struct btree_write_buffered_key *r = _r;

        return cmp_int(l->journal_seq, r->journal_seq);
}

/* Compare excluding idx, the low 24 bits: */
static inline bool wb_key_eq(const void *_l, const void *_r)
{
        const struct wb_key_ref *l = _l;
        const struct wb_key_ref *r = _r;

        return !((l->hi ^ r->hi)|
                 (l->mi ^ r->mi)|
                 ((l->lo >> 24) ^ (r->lo >> 24)));
}

static noinline void wb_sort(struct wb_key_ref *base, size_t num)
{
        size_t n = num, a = num / 2;

        if (!a)         /* num < 2 || size == 0 */
                return;

        for (;;) {
                size_t b, c, d;

                if (a)                  /* Building heap: sift down --a */
                        --a;
                else if (--n)           /* Sorting: Extract root to --n */
                        swap(base[0], base[n]);
                else                    /* Sort complete */
                        break;

                /*
                 * Sift element at "a" down into heap.  This is the
                 * "bottom-up" variant, which significantly reduces
                 * calls to cmp_func(): we find the sift-down path all
                 * the way to the leaves (one compare per level), then
                 * backtrack to find where to insert the target element.
                 *
                 * Because elements tend to sift down close to the leaves,
                 * this uses fewer compares than doing two per level
                 * on the way down.  (A bit more than half as many on
                 * average, 3/4 worst-case.)
                 */
                for (b = a; c = 2*b + 1, (d = c + 1) < n;)
                        b = wb_key_ref_cmp(base + c, base + d) ? c : d;
                if (d == n)             /* Special case last leaf with no sibling */
                        b = c;

                /* Now backtrack from "b" to the correct location for "a" */
                while (b != a && wb_key_ref_cmp(base + a, base + b))
                        b = (b - 1) / 2;
                c = b;                  /* Where "a" belongs */
                while (b != a) {        /* Shift it into place */
                        b = (b - 1) / 2;
                        swap(base[b], base[c]);
                }
        }
}

static noinline int wb_flush_one_slowpath(struct btree_trans *trans,
                                          struct btree_iter *iter,
                                          struct btree_write_buffered_key *wb)
{
        struct btree_path *path = btree_iter_path(trans, iter);

        bch2_btree_node_unlock_write(trans, path, path->l[0].b);

        trans->journal_res.seq = wb->journal_seq;

        return bch2_trans_update(trans, iter, &wb->k,
                                 BTREE_UPDATE_internal_snapshot_node) ?:
                bch2_trans_commit(trans, NULL, NULL,
                                  BCH_TRANS_COMMIT_no_enospc|
                                  BCH_TRANS_COMMIT_no_check_rw|
                                  BCH_TRANS_COMMIT_no_journal_res|
                                  BCH_TRANS_COMMIT_journal_reclaim);
}

static inline int wb_flush_one(struct btree_trans *trans, struct btree_iter *iter,
                               struct btree_write_buffered_key *wb,
                               bool *write_locked,
                               bool *accounting_accumulated,
                               size_t *fast)
{
        struct btree_path *path;
        int ret;

        EBUG_ON(!wb->journal_seq);
        EBUG_ON(!trans->c->btree_write_buffer.flushing.pin.seq);
        EBUG_ON(trans->c->btree_write_buffer.flushing.pin.seq > wb->journal_seq);

        ret = bch2_btree_iter_traverse(iter);
        if (ret)
                return ret;

        if (!*accounting_accumulated && wb->k.k.type == KEY_TYPE_accounting) {
                struct bkey u;
                struct bkey_s_c k = bch2_btree_path_peek_slot_exact(btree_iter_path(trans, iter), &u);

                if (k.k->type == KEY_TYPE_accounting)
                        bch2_accounting_accumulate(bkey_i_to_accounting(&wb->k),
                                                   bkey_s_c_to_accounting(k));
        }
        *accounting_accumulated = true;

        /*
         * We can't clone a path that has write locks: unshare it now, before
         * set_pos and traverse():
         */
        if (btree_iter_path(trans, iter)->ref > 1)
                iter->path = __bch2_btree_path_make_mut(trans, iter->path, true, _THIS_IP_);

        path = btree_iter_path(trans, iter);

        if (!*write_locked) {
                ret = bch2_btree_node_lock_write(trans, path, &path->l[0].b->c);
                if (ret)
                        return ret;

                bch2_btree_node_prep_for_write(trans, path, path->l[0].b);
                *write_locked = true;
        }

        if (unlikely(!bch2_btree_node_insert_fits(path->l[0].b, wb->k.k.u64s))) {
                *write_locked = false;
                return wb_flush_one_slowpath(trans, iter, wb);
        }

        bch2_btree_insert_key_leaf(trans, path, &wb->k, wb->journal_seq);
        (*fast)++;
        return 0;
}

/*
 * Update a btree with a write buffered key using the journal seq of the
 * original write buffer insert.
 *
 * It is not safe to rejournal the key once it has been inserted into the write
 * buffer because that may break recovery ordering. For example, the key may
 * have already been modified in the active write buffer in a seq that comes
 * before the current transaction. If we were to journal this key again and
 * crash, recovery would process updates in the wrong order.
 */
static int
btree_write_buffered_insert(struct btree_trans *trans,
                          struct btree_write_buffered_key *wb)
{
        struct btree_iter iter;
        int ret;

        bch2_trans_iter_init(trans, &iter, wb->btree, bkey_start_pos(&wb->k.k),
                             BTREE_ITER_cached|BTREE_ITER_intent);

        trans->journal_res.seq = wb->journal_seq;

        ret   = bch2_btree_iter_traverse(&iter) ?:
                bch2_trans_update(trans, &iter, &wb->k,
                                  BTREE_UPDATE_internal_snapshot_node);
        bch2_trans_iter_exit(trans, &iter);
        return ret;
}

static void move_keys_from_inc_to_flushing(struct btree_write_buffer *wb)
{
        struct bch_fs *c = container_of(wb, struct bch_fs, btree_write_buffer);
        struct journal *j = &c->journal;

        if (!wb->inc.keys.nr)
                return;

        bch2_journal_pin_add(j, wb->inc.keys.data[0].journal_seq, &wb->flushing.pin,
                             bch2_btree_write_buffer_journal_flush);

        darray_resize(&wb->flushing.keys, min_t(size_t, 1U << 20, wb->flushing.keys.nr + wb->inc.keys.nr));
        darray_resize(&wb->sorted, wb->flushing.keys.size);

        if (!wb->flushing.keys.nr && wb->sorted.size >= wb->inc.keys.nr) {
                swap(wb->flushing.keys, wb->inc.keys);
                goto out;
        }

        size_t nr = min(darray_room(wb->flushing.keys),
                        wb->sorted.size - wb->flushing.keys.nr);
        nr = min(nr, wb->inc.keys.nr);

        memcpy(&darray_top(wb->flushing.keys),
               wb->inc.keys.data,
               sizeof(wb->inc.keys.data[0]) * nr);

        memmove(wb->inc.keys.data,
                wb->inc.keys.data + nr,
               sizeof(wb->inc.keys.data[0]) * (wb->inc.keys.nr - nr));

        wb->flushing.keys.nr    += nr;
        wb->inc.keys.nr         -= nr;
out:
        if (!wb->inc.keys.nr)
                bch2_journal_pin_drop(j, &wb->inc.pin);
        else
                bch2_journal_pin_update(j, wb->inc.keys.data[0].journal_seq, &wb->inc.pin,
                                        bch2_btree_write_buffer_journal_flush);

        if (j->watermark) {
                spin_lock(&j->lock);
                bch2_journal_set_watermark(j);
                spin_unlock(&j->lock);
        }

        BUG_ON(wb->sorted.size < wb->flushing.keys.nr);
}

static int bch2_btree_write_buffer_flush_locked(struct btree_trans *trans)
{
        struct bch_fs *c = trans->c;
        struct journal *j = &c->journal;
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        struct btree_iter iter = { NULL };
        size_t overwritten = 0, fast = 0, slowpath = 0, could_not_insert = 0;
        bool write_locked = false;
        bool accounting_replay_done = test_bit(BCH_FS_accounting_replay_done, &c->flags);
        int ret = 0;

        ret = bch2_journal_error(&c->journal);
        if (ret)
                return ret;

        bch2_trans_unlock(trans);
        bch2_trans_begin(trans);

        mutex_lock(&wb->inc.lock);
        move_keys_from_inc_to_flushing(wb);
        mutex_unlock(&wb->inc.lock);

        for (size_t i = 0; i < wb->flushing.keys.nr; i++) {
                wb->sorted.data[i].idx = i;
                wb->sorted.data[i].btree = wb->flushing.keys.data[i].btree;
                memcpy(&wb->sorted.data[i].pos, &wb->flushing.keys.data[i].k.k.p, sizeof(struct bpos));
        }
        wb->sorted.nr = wb->flushing.keys.nr;

        /*
         * We first sort so that we can detect and skip redundant updates, and
         * then we attempt to flush in sorted btree order, as this is most
         * efficient.
         *
         * However, since we're not flushing in the order they appear in the
         * journal we won't be able to drop our journal pin until everything is
         * flushed - which means this could deadlock the journal if we weren't
         * passing BCH_TRANS_COMMIT_journal_reclaim. This causes the update to fail
         * if it would block taking a journal reservation.
         *
         * If that happens, simply skip the key so we can optimistically insert
         * as many keys as possible in the fast path.
         */
        wb_sort(wb->sorted.data, wb->sorted.nr);

        darray_for_each(wb->sorted, i) {
                struct btree_write_buffered_key *k = &wb->flushing.keys.data[i->idx];

                for (struct wb_key_ref *n = i + 1; n < min(i + 4, &darray_top(wb->sorted)); n++)
                        prefetch(&wb->flushing.keys.data[n->idx]);

                BUG_ON(!k->journal_seq);

                if (!accounting_replay_done &&
                    k->k.k.type == KEY_TYPE_accounting) {
                        slowpath++;
                        continue;
                }

                if (i + 1 < &darray_top(wb->sorted) &&
                    wb_key_eq(i, i + 1)) {
                        struct btree_write_buffered_key *n = &wb->flushing.keys.data[i[1].idx];

                        if (k->k.k.type == KEY_TYPE_accounting &&
                            n->k.k.type == KEY_TYPE_accounting)
                                bch2_accounting_accumulate(bkey_i_to_accounting(&n->k),
                                                           bkey_i_to_s_c_accounting(&k->k));

                        overwritten++;
                        n->journal_seq = min_t(u64, n->journal_seq, k->journal_seq);
                        k->journal_seq = 0;
                        continue;
                }

                if (write_locked) {
                        struct btree_path *path = btree_iter_path(trans, &iter);

                        if (path->btree_id != i->btree ||
                            bpos_gt(k->k.k.p, path->l[0].b->key.k.p)) {
                                bch2_btree_node_unlock_write(trans, path, path->l[0].b);
                                write_locked = false;

                                ret = lockrestart_do(trans,
                                        bch2_btree_iter_traverse(&iter) ?:
                                        bch2_foreground_maybe_merge(trans, iter.path, 0,
                                                        BCH_WATERMARK_reclaim|
                                                        BCH_TRANS_COMMIT_journal_reclaim|
                                                        BCH_TRANS_COMMIT_no_check_rw|
                                                        BCH_TRANS_COMMIT_no_enospc));
                                if (ret)
                                        goto err;
                        }
                }

                if (!iter.path || iter.btree_id != k->btree) {
                        bch2_trans_iter_exit(trans, &iter);
                        bch2_trans_iter_init(trans, &iter, k->btree, k->k.k.p,
                                             BTREE_ITER_intent|BTREE_ITER_all_snapshots);
                }

                bch2_btree_iter_set_pos(&iter, k->k.k.p);
                btree_iter_path(trans, &iter)->preserve = false;

                bool accounting_accumulated = false;
                do {
                        if (race_fault()) {
                                ret = -BCH_ERR_journal_reclaim_would_deadlock;
                                break;
                        }

                        ret = wb_flush_one(trans, &iter, k, &write_locked,
                                           &accounting_accumulated, &fast);
                        if (!write_locked)
                                bch2_trans_begin(trans);
                } while (bch2_err_matches(ret, BCH_ERR_transaction_restart));

                if (!ret) {
                        k->journal_seq = 0;
                } else if (ret == -BCH_ERR_journal_reclaim_would_deadlock) {
                        slowpath++;
                        ret = 0;
                } else
                        break;
        }

        if (write_locked) {
                struct btree_path *path = btree_iter_path(trans, &iter);
                bch2_btree_node_unlock_write(trans, path, path->l[0].b);
        }
        bch2_trans_iter_exit(trans, &iter);

        if (ret)
                goto err;

        if (slowpath) {
                /*
                 * Flush in the order they were present in the journal, so that
                 * we can release journal pins:
                 * The fastpath zapped the seq of keys that were successfully flushed so
                 * we can skip those here.
                 */
                trace_and_count(c, write_buffer_flush_slowpath, trans, slowpath, wb->flushing.keys.nr);

                sort(wb->flushing.keys.data,
                     wb->flushing.keys.nr,
                     sizeof(wb->flushing.keys.data[0]),
                     wb_key_seq_cmp, NULL);

                darray_for_each(wb->flushing.keys, i) {
                        if (!i->journal_seq)
                                continue;

                        if (!accounting_replay_done &&
                            i->k.k.type == KEY_TYPE_accounting) {
                                could_not_insert++;
                                continue;
                        }

                        if (!could_not_insert)
                                bch2_journal_pin_update(j, i->journal_seq, &wb->flushing.pin,
                                                        bch2_btree_write_buffer_journal_flush);

                        bch2_trans_begin(trans);

                        ret = commit_do(trans, NULL, NULL,
                                        BCH_WATERMARK_reclaim|
                                        BCH_TRANS_COMMIT_journal_reclaim|
                                        BCH_TRANS_COMMIT_no_check_rw|
                                        BCH_TRANS_COMMIT_no_enospc|
                                        BCH_TRANS_COMMIT_no_journal_res ,
                                        btree_write_buffered_insert(trans, i));
                        if (ret)
                                goto err;

                        i->journal_seq = 0;
                }

                /*
                 * If journal replay hasn't finished with accounting keys we
                 * can't flush accounting keys at all - condense them and leave
                 * them for next time.
                 *
                 * Q: Can the write buffer overflow?
                 * A Shouldn't be any actual risk. It's just new accounting
                 * updates that the write buffer can't flush, and those are only
                 * going to be generated by interior btree node updates as
                 * journal replay has to split/rewrite nodes to make room for
                 * its updates.
                 *
                 * And for those new acounting updates, updates to the same
                 * counters get accumulated as they're flushed from the journal
                 * to the write buffer - see the patch for eytzingcer tree
                 * accumulated. So we could only overflow if the number of
                 * distinct counters touched somehow was very large.
                 */
                if (could_not_insert) {
                        struct btree_write_buffered_key *dst = wb->flushing.keys.data;

                        darray_for_each(wb->flushing.keys, i)
                                if (i->journal_seq)
                                        *dst++ = *i;
                        wb->flushing.keys.nr = dst - wb->flushing.keys.data;
                }
        }
err:
        if (ret || !could_not_insert) {
                bch2_journal_pin_drop(j, &wb->flushing.pin);
                wb->flushing.keys.nr = 0;
        }

        bch2_fs_fatal_err_on(ret, c, "%s", bch2_err_str(ret));
        trace_write_buffer_flush(trans, wb->flushing.keys.nr, overwritten, fast, 0);
        return ret;
}

static int fetch_wb_keys_from_journal(struct bch_fs *c, u64 seq)
{
        struct journal *j = &c->journal;
        struct journal_buf *buf;
        int ret = 0;

        while (!ret && (buf = bch2_next_write_buffer_flush_journal_buf(j, seq))) {
                ret = bch2_journal_keys_to_write_buffer(c, buf);
                mutex_unlock(&j->buf_lock);
        }

        return ret;
}

static int btree_write_buffer_flush_seq(struct btree_trans *trans, u64 seq,
                                        bool *did_work)
{
        struct bch_fs *c = trans->c;
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        int ret = 0, fetch_from_journal_err;

        do {
                bch2_trans_unlock(trans);

                fetch_from_journal_err = fetch_wb_keys_from_journal(c, seq);

                *did_work |= wb->inc.keys.nr || wb->flushing.keys.nr;

                /*
                 * On memory allocation failure, bch2_btree_write_buffer_flush_locked()
                 * is not guaranteed to empty wb->inc:
                 */
                mutex_lock(&wb->flushing.lock);
                ret = bch2_btree_write_buffer_flush_locked(trans);
                mutex_unlock(&wb->flushing.lock);
        } while (!ret &&
                 (fetch_from_journal_err ||
                  (wb->inc.pin.seq && wb->inc.pin.seq <= seq) ||
                  (wb->flushing.pin.seq && wb->flushing.pin.seq <= seq)));

        return ret;
}

static int bch2_btree_write_buffer_journal_flush(struct journal *j,
                                struct journal_entry_pin *_pin, u64 seq)
{
        struct bch_fs *c = container_of(j, struct bch_fs, journal);
        bool did_work = false;

        return bch2_trans_run(c, btree_write_buffer_flush_seq(trans, seq, &did_work));
}

int bch2_btree_write_buffer_flush_sync(struct btree_trans *trans)
{
        struct bch_fs *c = trans->c;
        bool did_work = false;

        trace_and_count(c, write_buffer_flush_sync, trans, _RET_IP_);

        return btree_write_buffer_flush_seq(trans, journal_cur_seq(&c->journal), &did_work);
}

/*
 * The write buffer requires flushing when going RO: keys in the journal for the
 * write buffer don't have a journal pin yet
 */
bool bch2_btree_write_buffer_flush_going_ro(struct bch_fs *c)
{
        if (bch2_journal_error(&c->journal))
                return false;

        bool did_work = false;
        bch2_trans_run(c, btree_write_buffer_flush_seq(trans,
                                journal_cur_seq(&c->journal), &did_work));
        return did_work;
}

int bch2_btree_write_buffer_flush_nocheck_rw(struct btree_trans *trans)
{
        struct bch_fs *c = trans->c;
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        int ret = 0;

        if (mutex_trylock(&wb->flushing.lock)) {
                ret = bch2_btree_write_buffer_flush_locked(trans);
                mutex_unlock(&wb->flushing.lock);
        }

        return ret;
}

int bch2_btree_write_buffer_tryflush(struct btree_trans *trans)
{
        struct bch_fs *c = trans->c;

        if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_btree_write_buffer))
                return -BCH_ERR_erofs_no_writes;

        int ret = bch2_btree_write_buffer_flush_nocheck_rw(trans);
        bch2_write_ref_put(c, BCH_WRITE_REF_btree_write_buffer);
        return ret;
}

/*
 * In check and repair code, when checking references to write buffer btrees we
 * need to issue a flush before we have a definitive error: this issues a flush
 * if this is a key we haven't yet checked.
 */
int bch2_btree_write_buffer_maybe_flush(struct btree_trans *trans,
                                        struct bkey_s_c referring_k,
                                        struct bkey_buf *last_flushed)
{
        struct bch_fs *c = trans->c;
        struct bkey_buf tmp;
        int ret = 0;

        bch2_bkey_buf_init(&tmp);

        if (!bkey_and_val_eq(referring_k, bkey_i_to_s_c(last_flushed->k))) {
                bch2_bkey_buf_reassemble(&tmp, c, referring_k);

                if (bkey_is_btree_ptr(referring_k.k)) {
                        bch2_trans_unlock(trans);
                        bch2_btree_interior_updates_flush(c);
                }

                ret = bch2_btree_write_buffer_flush_sync(trans);
                if (ret)
                        goto err;

                bch2_bkey_buf_copy(last_flushed, c, tmp.k);
                ret = -BCH_ERR_transaction_restart_write_buffer_flush;
        }
err:
        bch2_bkey_buf_exit(&tmp, c);
        return ret;
}

static void bch2_btree_write_buffer_flush_work(struct work_struct *work)
{
        struct bch_fs *c = container_of(work, struct bch_fs, btree_write_buffer.flush_work);
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        int ret;

        mutex_lock(&wb->flushing.lock);
        do {
                ret = bch2_trans_run(c, bch2_btree_write_buffer_flush_locked(trans));
        } while (!ret && bch2_btree_write_buffer_should_flush(c));
        mutex_unlock(&wb->flushing.lock);

        bch2_write_ref_put(c, BCH_WRITE_REF_btree_write_buffer);
}

static void wb_accounting_sort(struct btree_write_buffer *wb)
{
        eytzinger0_sort(wb->accounting.data, wb->accounting.nr,
                        sizeof(wb->accounting.data[0]),
                        wb_key_cmp, NULL);
}

int bch2_accounting_key_to_wb_slowpath(struct bch_fs *c, enum btree_id btree,
                                       struct bkey_i_accounting *k)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        struct btree_write_buffered_key new = { .btree = btree };

        bkey_copy(&new.k, &k->k_i);

        int ret = darray_push(&wb->accounting, new);
        if (ret)
                return ret;

        wb_accounting_sort(wb);
        return 0;
}

int bch2_journal_key_to_wb_slowpath(struct bch_fs *c,
                             struct journal_keys_to_wb *dst,
                             enum btree_id btree, struct bkey_i *k)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        int ret;
retry:
        ret = darray_make_room_gfp(&dst->wb->keys, 1, GFP_KERNEL);
        if (!ret && dst->wb == &wb->flushing)
                ret = darray_resize(&wb->sorted, wb->flushing.keys.size);

        if (unlikely(ret)) {
                if (dst->wb == &c->btree_write_buffer.flushing) {
                        mutex_unlock(&dst->wb->lock);
                        dst->wb = &c->btree_write_buffer.inc;
                        bch2_journal_pin_add(&c->journal, dst->seq, &dst->wb->pin,
                                             bch2_btree_write_buffer_journal_flush);
                        goto retry;
                }

                return ret;
        }

        dst->room = darray_room(dst->wb->keys);
        if (dst->wb == &wb->flushing)
                dst->room = min(dst->room, wb->sorted.size - wb->flushing.keys.nr);
        BUG_ON(!dst->room);
        BUG_ON(!dst->seq);

        struct btree_write_buffered_key *wb_k = &darray_top(dst->wb->keys);
        wb_k->journal_seq       = dst->seq;
        wb_k->btree             = btree;
        bkey_copy(&wb_k->k, k);
        dst->wb->keys.nr++;
        dst->room--;
        return 0;
}

void bch2_journal_keys_to_write_buffer_start(struct bch_fs *c, struct journal_keys_to_wb *dst, u64 seq)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;

        if (mutex_trylock(&wb->flushing.lock)) {
                mutex_lock(&wb->inc.lock);
                move_keys_from_inc_to_flushing(wb);

                /*
                 * Attempt to skip wb->inc, and add keys directly to
                 * wb->flushing, saving us a copy later:
                 */

                if (!wb->inc.keys.nr) {
                        dst->wb = &wb->flushing;
                } else {
                        mutex_unlock(&wb->flushing.lock);
                        dst->wb = &wb->inc;
                }
        } else {
                mutex_lock(&wb->inc.lock);
                dst->wb = &wb->inc;
        }

        dst->room = darray_room(dst->wb->keys);
        if (dst->wb == &wb->flushing)
                dst->room = min(dst->room, wb->sorted.size - wb->flushing.keys.nr);
        dst->seq = seq;

        bch2_journal_pin_add(&c->journal, seq, &dst->wb->pin,
                             bch2_btree_write_buffer_journal_flush);

        darray_for_each(wb->accounting, i)
                memset(&i->k.v, 0, bkey_val_bytes(&i->k.k));
}

int bch2_journal_keys_to_write_buffer_end(struct bch_fs *c, struct journal_keys_to_wb *dst)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;
        unsigned live_accounting_keys = 0;
        int ret = 0;

        darray_for_each(wb->accounting, i)
                if (!bch2_accounting_key_is_zero(bkey_i_to_s_c_accounting(&i->k))) {
                        i->journal_seq = dst->seq;
                        live_accounting_keys++;
                        ret = __bch2_journal_key_to_wb(c, dst, i->btree, &i->k);
                        if (ret)
                                break;
                }

        if (live_accounting_keys * 2 < wb->accounting.nr) {
                struct btree_write_buffered_key *dst = wb->accounting.data;

                darray_for_each(wb->accounting, src)
                        if (!bch2_accounting_key_is_zero(bkey_i_to_s_c_accounting(&src->k)))
                                *dst++ = *src;
                wb->accounting.nr = dst - wb->accounting.data;
                wb_accounting_sort(wb);
        }

        if (!dst->wb->keys.nr)
                bch2_journal_pin_drop(&c->journal, &dst->wb->pin);

        if (bch2_btree_write_buffer_should_flush(c) &&
            __bch2_write_ref_tryget(c, BCH_WRITE_REF_btree_write_buffer) &&
            !queue_work(system_unbound_wq, &c->btree_write_buffer.flush_work))
                bch2_write_ref_put(c, BCH_WRITE_REF_btree_write_buffer);

        if (dst->wb == &wb->flushing)
                mutex_unlock(&wb->flushing.lock);
        mutex_unlock(&wb->inc.lock);

        return ret;
}

static int bch2_journal_keys_to_write_buffer(struct bch_fs *c, struct journal_buf *buf)
{
        struct journal_keys_to_wb dst;
        int ret = 0;

        bch2_journal_keys_to_write_buffer_start(c, &dst, le64_to_cpu(buf->data->seq));

        for_each_jset_entry_type(entry, buf->data, BCH_JSET_ENTRY_write_buffer_keys) {
                jset_entry_for_each_key(entry, k) {
                        ret = bch2_journal_key_to_wb(c, &dst, entry->btree_id, k);
                        if (ret)
                                goto out;
                }

                entry->type = BCH_JSET_ENTRY_btree_keys;
        }

        spin_lock(&c->journal.lock);
        buf->need_flush_to_write_buffer = false;
        spin_unlock(&c->journal.lock);
out:
        ret = bch2_journal_keys_to_write_buffer_end(c, &dst) ?: ret;
        return ret;
}

static int wb_keys_resize(struct btree_write_buffer_keys *wb, size_t new_size)
{
        if (wb->keys.size >= new_size)
                return 0;

        if (!mutex_trylock(&wb->lock))
                return -EINTR;

        int ret = darray_resize(&wb->keys, new_size);
        mutex_unlock(&wb->lock);
        return ret;
}

int bch2_btree_write_buffer_resize(struct bch_fs *c, size_t new_size)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;

        return wb_keys_resize(&wb->flushing, new_size) ?:
                wb_keys_resize(&wb->inc, new_size);
}

void bch2_fs_btree_write_buffer_exit(struct bch_fs *c)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;

        BUG_ON((wb->inc.keys.nr || wb->flushing.keys.nr) &&
               !bch2_journal_error(&c->journal));

        darray_exit(&wb->accounting);
        darray_exit(&wb->sorted);
        darray_exit(&wb->flushing.keys);
        darray_exit(&wb->inc.keys);
}

int bch2_fs_btree_write_buffer_init(struct bch_fs *c)
{
        struct btree_write_buffer *wb = &c->btree_write_buffer;

        mutex_init(&wb->inc.lock);
        mutex_init(&wb->flushing.lock);
        INIT_WORK(&wb->flush_work, bch2_btree_write_buffer_flush_work);

        /* Will be resized by journal as needed: */
        unsigned initial_size = 1 << 16;

        return  darray_make_room(&wb->inc.keys, initial_size) ?:
                darray_make_room(&wb->flushing.keys, initial_size) ?:
                darray_make_room(&wb->sorted, initial_size);
}