OSCL-LXR linux-6.0.1/​drivers/​md/​bcache/​journal.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * bcache journalling code, for btree insertions
  *
  * Copyright 2012 Google, Inc.
  */
 
 #include "bcache.h"
 #include "btree.h"
 #include "debug.h"
 #include "extents.h"
 
 #include <trace/events/bcache.h>
 
 /*
  * Journal replay/recovery:
  *
  * This code is all driven from run_cache_set(); we first read the journal
  * entries, do some other stuff, then we mark all the keys in the journal
  * entries (same as garbage collection would), then we replay them - reinserting
  * them into the cache in precisely the same order as they appear in the
  * journal.
  *
  * We only journal keys that go in leaf nodes, which simplifies things quite a
  * bit.
  */
 
 static void journal_read_endio(struct bio *bio)
 {
     struct closure *cl = bio->bi_private;
 
     closure_put(cl);
 }
 
 static int journal_read_bucket(struct cache *ca, struct list_head *list,
                    unsigned int bucket_index)
 {
     struct journal_device *ja = &ca->journal;
     struct bio *bio = &ja->bio;
 
     struct journal_replay *i;
     struct jset *j, *data = ca->set->journal.w[0].data;
     struct closure cl;
     unsigned int len, left, offset = 0;
     int ret = 0;
     sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
 
     closure_init_stack(&cl);
 
     pr_debug("reading %u\n", bucket_index);
 
     while (offset < ca->sb.bucket_size) {
 reread:     left = ca->sb.bucket_size - offset;
         len = min_t(unsigned int, left, PAGE_SECTORS << JSET_BITS);
 
         bio_reset(bio, ca->bdev, REQ_OP_READ);
         bio->bi_iter.bi_sector  = bucket + offset;
         bio->bi_iter.bi_size    = len << 9;
 
         bio->bi_end_io  = journal_read_endio;
         bio->bi_private = &cl;
         bch_bio_map(bio, data);
 
         closure_bio_submit(ca->set, bio, &cl);
         closure_sync(&cl);
 
         /* This function could be simpler now since we no longer write
          * journal entries that overlap bucket boundaries; this means
          * the start of a bucket will always have a valid journal entry
          * if it has any journal entries at all.
          */
 
         j = data;
         while (len) {
             struct list_head *where;
             size_t blocks, bytes = set_bytes(j);
 
             if (j->magic != jset_magic(&ca->sb)) {
                 pr_debug("%u: bad magic\n", bucket_index);
                 return ret;
             }
 
             if (bytes > left << 9 ||
                 bytes > PAGE_SIZE << JSET_BITS) {
                 pr_info("%u: too big, %zu bytes, offset %u\n",
                     bucket_index, bytes, offset);
                 return ret;
             }
 
             if (bytes > len << 9)
                 goto reread;
 
             if (j->csum != csum_set(j)) {
                 pr_info("%u: bad csum, %zu bytes, offset %u\n",
                     bucket_index, bytes, offset);
                 return ret;
             }
 
             blocks = set_blocks(j, block_bytes(ca));
 
             /*
              * Nodes in 'list' are in linear increasing order of
              * i->j.seq, the node on head has the smallest (oldest)
              * journal seq, the node on tail has the biggest
              * (latest) journal seq.
              */
 
             /*
              * Check from the oldest jset for last_seq. If
              * i->j.seq < j->last_seq, it means the oldest jset
              * in list is expired and useless, remove it from
              * this list. Otherwise, j is a candidate jset for
              * further following checks.
              */
             while (!list_empty(list)) {
                 i = list_first_entry(list,
                     struct journal_replay, list);
                 if (i->j.seq >= j->last_seq)
                     break;
                 list_del(&i->list);
                 kfree(i);
             }
 
             /* iterate list in reverse order (from latest jset) */
             list_for_each_entry_reverse(i, list, list) {
                 if (j->seq == i->j.seq)
                     goto next_set;
 
                 /*
                  * if j->seq is less than any i->j.last_seq
                  * in list, j is an expired and useless jset.
                  */
                 if (j->seq < i->j.last_seq)
                     goto next_set;
 
                 /*
                  * 'where' points to first jset in list which
                  * is elder then j.
                  */
                 if (j->seq > i->j.seq) {
                     where = &i->list;
                     goto add;
                 }
             }
 
             where = list;
 add:
             i = kmalloc(offsetof(struct journal_replay, j) +
                     bytes, GFP_KERNEL);
             if (!i)
                 return -ENOMEM;
             memcpy(&i->j, j, bytes);
             /* Add to the location after 'where' points to */
             list_add(&i->list, where);
             ret = 1;
 
             if (j->seq > ja->seq[bucket_index])
                 ja->seq[bucket_index] = j->seq;
 next_set:
             offset  += blocks * ca->sb.block_size;
             len -= blocks * ca->sb.block_size;
             j = ((void *) j) + blocks * block_bytes(ca);
         }
     }
 
     return ret;
 }
 
 int bch_journal_read(struct cache_set *c, struct list_head *list)
 {
 #define read_bucket(b)                          \
     ({                              \
         ret = journal_read_bucket(ca, list, b);         \
         __set_bit(b, bitmap);                   \
         if (ret < 0)                        \
             return ret;                 \
         ret;                            \
     })
 
     struct cache *ca = c->cache;
     int ret = 0;
     struct journal_device *ja = &ca->journal;
     DECLARE_BITMAP(bitmap, SB_JOURNAL_BUCKETS);
     unsigned int i, l, r, m;
     uint64_t seq;
 
     bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
     pr_debug("%u journal buckets\n", ca->sb.njournal_buckets);
 
     /*
      * Read journal buckets ordered by golden ratio hash to quickly
      * find a sequence of buckets with valid journal entries
      */
     for (i = 0; i < ca->sb.njournal_buckets; i++) {
         /*
          * We must try the index l with ZERO first for
          * correctness due to the scenario that the journal
          * bucket is circular buffer which might have wrapped
          */
         l = (i * 2654435769U) % ca->sb.njournal_buckets;
 
         if (test_bit(l, bitmap))
             break;
 
         if (read_bucket(l))
             goto bsearch;
     }
 
     /*
      * If that fails, check all the buckets we haven't checked
      * already
      */
     pr_debug("falling back to linear search\n");
 
     for_each_clear_bit(l, bitmap, ca->sb.njournal_buckets)
         if (read_bucket(l))
             goto bsearch;
 
     /* no journal entries on this device? */
     if (l == ca->sb.njournal_buckets)
         goto out;
 bsearch:
     BUG_ON(list_empty(list));
 
     /* Binary search */
     m = l;
     r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
     pr_debug("starting binary search, l %u r %u\n", l, r);
 
     while (l + 1 < r) {
         seq = list_entry(list->prev, struct journal_replay,
                  list)->j.seq;
 
         m = (l + r) >> 1;
         read_bucket(m);
 
         if (seq != list_entry(list->prev, struct journal_replay,
                       list)->j.seq)
             l = m;
         else
             r = m;
     }
 
     /*
      * Read buckets in reverse order until we stop finding more
      * journal entries
      */
     pr_debug("finishing up: m %u njournal_buckets %u\n",
          m, ca->sb.njournal_buckets);
     l = m;
 
     while (1) {
         if (!l--)
             l = ca->sb.njournal_buckets - 1;
 
         if (l == m)
             break;
 
         if (test_bit(l, bitmap))
             continue;
 
         if (!read_bucket(l))
             break;
     }
 
     seq = 0;
 
     for (i = 0; i < ca->sb.njournal_buckets; i++)
         if (ja->seq[i] > seq) {
             seq = ja->seq[i];
             /*
              * When journal_reclaim() goes to allocate for
              * the first time, it'll use the bucket after
              * ja->cur_idx
              */
             ja->cur_idx = i;
             ja->last_idx = ja->discard_idx = (i + 1) %
                 ca->sb.njournal_buckets;
 
         }
 
 out:
     if (!list_empty(list))
         c->journal.seq = list_entry(list->prev,
                         struct journal_replay,
                         list)->j.seq;
 
     return 0;
 #undef read_bucket
 }
 
 void bch_journal_mark(struct cache_set *c, struct list_head *list)
 {
     atomic_t p = { 0 };
     struct bkey *k;
     struct journal_replay *i;
     struct journal *j = &c->journal;
     uint64_t last = j->seq;
 
     /*
      * journal.pin should never fill up - we never write a journal
      * entry when it would fill up. But if for some reason it does, we
      * iterate over the list in reverse order so that we can just skip that
      * refcount instead of bugging.
      */
 
     list_for_each_entry_reverse(i, list, list) {
         BUG_ON(last < i->j.seq);
         i->pin = NULL;
 
         while (last-- != i->j.seq)
             if (fifo_free(&j->pin) > 1) {
                 fifo_push_front(&j->pin, p);
                 atomic_set(&fifo_front(&j->pin), 0);
             }
 
         if (fifo_free(&j->pin) > 1) {
             fifo_push_front(&j->pin, p);
             i->pin = &fifo_front(&j->pin);
             atomic_set(i->pin, 1);
         }
 
         for (k = i->j.start;
              k < bset_bkey_last(&i->j);
              k = bkey_next(k))
             if (!__bch_extent_invalid(c, k)) {
                 unsigned int j;
 
                 for (j = 0; j < KEY_PTRS(k); j++)
                     if (ptr_available(c, k, j))
                         atomic_inc(&PTR_BUCKET(c, k, j)->pin);
 
                 bch_initial_mark_key(c, 0, k);
             }
     }
 }
 
 static bool is_discard_enabled(struct cache_set *s)
 {
     struct cache *ca = s->cache;
 
     if (ca->discard)
         return true;
 
     return false;
 }
 
 int bch_journal_replay(struct cache_set *s, struct list_head *list)
 {
     int ret = 0, keys = 0, entries = 0;
     struct bkey *k;
     struct journal_replay *i =
         list_entry(list->prev, struct journal_replay, list);
 
     uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
     struct keylist keylist;
 
     list_for_each_entry(i, list, list) {
         BUG_ON(i->pin && atomic_read(i->pin) != 1);
 
         if (n != i->j.seq) {
             if (n == start && is_discard_enabled(s))
                 pr_info("journal entries %llu-%llu may be discarded! (replaying %llu-%llu)\n",
                     n, i->j.seq - 1, start, end);
             else {
                 pr_err("journal entries %llu-%llu missing! (replaying %llu-%llu)\n",
                     n, i->j.seq - 1, start, end);
                 ret = -EIO;
                 goto err;
             }
         }
 
         for (k = i->j.start;
              k < bset_bkey_last(&i->j);
              k = bkey_next(k)) {
             trace_bcache_journal_replay_key(k);
 
             bch_keylist_init_single(&keylist, k);
 
             ret = bch_btree_insert(s, &keylist, i->pin, NULL);
             if (ret)
                 goto err;
 
             BUG_ON(!bch_keylist_empty(&keylist));
             keys++;
 
             cond_resched();
         }
 
         if (i->pin)
             atomic_dec(i->pin);
         n = i->j.seq + 1;
         entries++;
     }
 
     pr_info("journal replay done, %i keys in %i entries, seq %llu\n",
         keys, entries, end);
 err:
     while (!list_empty(list)) {
         i = list_first_entry(list, struct journal_replay, list);
         list_del(&i->list);
         kfree(i);
     }
 
     return ret;
 }
 
 void bch_journal_space_reserve(struct journal *j)
 {
     j->do_reserve = true;
 }
 
 /* Journalling */
 
 static void btree_flush_write(struct cache_set *c)
 {
     struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
     unsigned int i, nr;
     int ref_nr;
     atomic_t *fifo_front_p, *now_fifo_front_p;
     size_t mask;
 
     if (c->journal.btree_flushing)
         return;
 
     spin_lock(&c->journal.flush_write_lock);
     if (c->journal.btree_flushing) {
         spin_unlock(&c->journal.flush_write_lock);
         return;
     }
     c->journal.btree_flushing = true;
     spin_unlock(&c->journal.flush_write_lock);
 
     /* get the oldest journal entry and check its refcount */
     spin_lock(&c->journal.lock);
     fifo_front_p = &fifo_front(&c->journal.pin);
     ref_nr = atomic_read(fifo_front_p);
     if (ref_nr <= 0) {
         /*
          * do nothing if no btree node references
          * the oldest journal entry
          */
         spin_unlock(&c->journal.lock);
         goto out;
     }
     spin_unlock(&c->journal.lock);
 
     mask = c->journal.pin.mask;
     nr = 0;
     atomic_long_inc(&c->flush_write);
     memset(btree_nodes, 0, sizeof(btree_nodes));
 
     mutex_lock(&c->bucket_lock);
     list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
         /*
          * It is safe to get now_fifo_front_p without holding
          * c->journal.lock here, because we don't need to know
          * the exactly accurate value, just check whether the
          * front pointer of c->journal.pin is changed.
          */
         now_fifo_front_p = &fifo_front(&c->journal.pin);
         /*
          * If the oldest journal entry is reclaimed and front
          * pointer of c->journal.pin changes, it is unnecessary
          * to scan c->btree_cache anymore, just quit the loop and
          * flush out what we have already.
          */
         if (now_fifo_front_p != fifo_front_p)
             break;
         /*
          * quit this loop if all matching btree nodes are
          * scanned and record in btree_nodes[] already.
          */
         ref_nr = atomic_read(fifo_front_p);
         if (nr >= ref_nr)
             break;
 
         if (btree_node_journal_flush(b))
             pr_err("BUG: flush_write bit should not be set here!\n");
 
         mutex_lock(&b->write_lock);
 
         if (!btree_node_dirty(b)) {
             mutex_unlock(&b->write_lock);
             continue;
         }
 
         if (!btree_current_write(b)->journal) {
             mutex_unlock(&b->write_lock);
             continue;
         }
 
         /*
          * Only select the btree node which exactly references
          * the oldest journal entry.
          *
          * If the journal entry pointed by fifo_front_p is
          * reclaimed in parallel, don't worry:
          * - the list_for_each_xxx loop will quit when checking
          *   next now_fifo_front_p.
          * - If there are matched nodes recorded in btree_nodes[],
          *   they are clean now (this is why and how the oldest
          *   journal entry can be reclaimed). These selected nodes
          *   will be ignored and skipped in the following for-loop.
          */
         if (((btree_current_write(b)->journal - fifo_front_p) &
              mask) != 0) {
             mutex_unlock(&b->write_lock);
             continue;
         }
 
         set_btree_node_journal_flush(b);
 
         mutex_unlock(&b->write_lock);
 
         btree_nodes[nr++] = b;
         /*
          * To avoid holding c->bucket_lock too long time,
          * only scan for BTREE_FLUSH_NR matched btree nodes
          * at most. If there are more btree nodes reference
          * the oldest journal entry, try to flush them next
          * time when btree_flush_write() is called.
          */
         if (nr == BTREE_FLUSH_NR)
             break;
     }
     mutex_unlock(&c->bucket_lock);
 
     for (i = 0; i < nr; i++) {
         b = btree_nodes[i];
         if (!b) {
             pr_err("BUG: btree_nodes[%d] is NULL\n", i);
             continue;
         }
 
         /* safe to check without holding b->write_lock */
         if (!btree_node_journal_flush(b)) {
             pr_err("BUG: bnode %p: journal_flush bit cleaned\n", b);
             continue;
         }
 
         mutex_lock(&b->write_lock);
         if (!btree_current_write(b)->journal) {
             clear_bit(BTREE_NODE_journal_flush, &b->flags);
             mutex_unlock(&b->write_lock);
             pr_debug("bnode %p: written by others\n", b);
             continue;
         }
 
         if (!btree_node_dirty(b)) {
             clear_bit(BTREE_NODE_journal_flush, &b->flags);
             mutex_unlock(&b->write_lock);
             pr_debug("bnode %p: dirty bit cleaned by others\n", b);
             continue;
         }
 
         __bch_btree_node_write(b, NULL);
         clear_bit(BTREE_NODE_journal_flush, &b->flags);
         mutex_unlock(&b->write_lock);
     }
 
 out:
     spin_lock(&c->journal.flush_write_lock);
     c->journal.btree_flushing = false;
     spin_unlock(&c->journal.flush_write_lock);
 }
 
 #define last_seq(j) ((j)->seq - fifo_used(&(j)->pin) + 1)
 
 static void journal_discard_endio(struct bio *bio)
 {
     struct journal_device *ja =
         container_of(bio, struct journal_device, discard_bio);
     struct cache *ca = container_of(ja, struct cache, journal);
 
     atomic_set(&ja->discard_in_flight, DISCARD_DONE);
 
     closure_wake_up(&ca->set->journal.wait);
     closure_put(&ca->set->cl);
 }
 
 static void journal_discard_work(struct work_struct *work)
 {
     struct journal_device *ja =
         container_of(work, struct journal_device, discard_work);
 
     submit_bio(&ja->discard_bio);
 }
 
 static void do_journal_discard(struct cache *ca)
 {
     struct journal_device *ja = &ca->journal;
     struct bio *bio = &ja->discard_bio;
 
     if (!ca->discard) {
         ja->discard_idx = ja->last_idx;
         return;
     }
 
     switch (atomic_read(&ja->discard_in_flight)) {
     case DISCARD_IN_FLIGHT:
         return;
 
     case DISCARD_DONE:
         ja->discard_idx = (ja->discard_idx + 1) %
             ca->sb.njournal_buckets;
 
         atomic_set(&ja->discard_in_flight, DISCARD_READY);
         fallthrough;
 
     case DISCARD_READY:
         if (ja->discard_idx == ja->last_idx)
             return;
 
         atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);
 
         bio_init(bio, ca->bdev, bio->bi_inline_vecs, 1, REQ_OP_DISCARD);
         bio->bi_iter.bi_sector  = bucket_to_sector(ca->set,
                         ca->sb.d[ja->discard_idx]);
         bio->bi_iter.bi_size    = bucket_bytes(ca);
         bio->bi_end_io      = journal_discard_endio;
 
         closure_get(&ca->set->cl);
         INIT_WORK(&ja->discard_work, journal_discard_work);
         queue_work(bch_journal_wq, &ja->discard_work);
     }
 }
 
 static unsigned int free_journal_buckets(struct cache_set *c)
 {
     struct journal *j = &c->journal;
     struct cache *ca = c->cache;
     struct journal_device *ja = &c->cache->journal;
     unsigned int n;
 
     /* In case njournal_buckets is not power of 2 */
     if (ja->cur_idx >= ja->discard_idx)
         n = ca->sb.njournal_buckets +  ja->discard_idx - ja->cur_idx;
     else
         n = ja->discard_idx - ja->cur_idx;
 
     if (n > (1 + j->do_reserve))
         return n - (1 + j->do_reserve);
 
     return 0;
 }
 
 static void journal_reclaim(struct cache_set *c)
 {
     struct bkey *k = &c->journal.key;
     struct cache *ca = c->cache;
     uint64_t last_seq;
     struct journal_device *ja = &ca->journal;
     atomic_t p __maybe_unused;
 
     atomic_long_inc(&c->reclaim);
 
     while (!atomic_read(&fifo_front(&c->journal.pin)))
         fifo_pop(&c->journal.pin, p);
 
     last_seq = last_seq(&c->journal);
 
     /* Update last_idx */
 
     while (ja->last_idx != ja->cur_idx &&
            ja->seq[ja->last_idx] < last_seq)
         ja->last_idx = (ja->last_idx + 1) %
             ca->sb.njournal_buckets;
 
     do_journal_discard(ca);
 
     if (c->journal.blocks_free)
         goto out;
 
     if (!free_journal_buckets(c))
         goto out;
 
     ja->cur_idx = (ja->cur_idx + 1) % ca->sb.njournal_buckets;
     k->ptr[0] = MAKE_PTR(0,
                  bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
                  ca->sb.nr_this_dev);
     atomic_long_inc(&c->reclaimed_journal_buckets);
 
     bkey_init(k);
     SET_KEY_PTRS(k, 1);
     c->journal.blocks_free = ca->sb.bucket_size >> c->block_bits;
 
 out:
     if (!journal_full(&c->journal))
         __closure_wake_up(&c->journal.wait);
 }
 
 void bch_journal_next(struct journal *j)
 {
     atomic_t p = { 1 };
 
     j->cur = (j->cur == j->w)
         ? &j->w[1]
         : &j->w[0];
 
     /*
      * The fifo_push() needs to happen at the same time as j->seq is
      * incremented for last_seq() to be calculated correctly
      */
     BUG_ON(!fifo_push(&j->pin, p));
     atomic_set(&fifo_back(&j->pin), 1);
 
     j->cur->data->seq   = ++j->seq;
     j->cur->dirty       = false;
     j->cur->need_write  = false;
     j->cur->data->keys  = 0;
 
     if (fifo_full(&j->pin))
         pr_debug("journal_pin full (%zu)\n", fifo_used(&j->pin));
 }
 
 static void journal_write_endio(struct bio *bio)
 {
     struct journal_write *w = bio->bi_private;
 
     cache_set_err_on(bio->bi_status, w->c, "journal io error");
     closure_put(&w->c->journal.io);
 }
 
 static void journal_write(struct closure *cl);
 
 static void journal_write_done(struct closure *cl)
 {
     struct journal *j = container_of(cl, struct journal, io);
     struct journal_write *w = (j->cur == j->w)
         ? &j->w[1]
         : &j->w[0];
 
     __closure_wake_up(&w->wait);
     continue_at_nobarrier(cl, journal_write, bch_journal_wq);
 }
 
 static void journal_write_unlock(struct closure *cl)
     __releases(&c->journal.lock)
 {
     struct cache_set *c = container_of(cl, struct cache_set, journal.io);
 
     c->journal.io_in_flight = 0;
     spin_unlock(&c->journal.lock);
 }
 
 static void journal_write_unlocked(struct closure *cl)
     __releases(c->journal.lock)
 {
     struct cache_set *c = container_of(cl, struct cache_set, journal.io);
     struct cache *ca = c->cache;
     struct journal_write *w = c->journal.cur;
     struct bkey *k = &c->journal.key;
     unsigned int i, sectors = set_blocks(w->data, block_bytes(ca)) *
         ca->sb.block_size;
 
     struct bio *bio;
     struct bio_list list;
 
     bio_list_init(&list);
 
     if (!w->need_write) {
         closure_return_with_destructor(cl, journal_write_unlock);
         return;
     } else if (journal_full(&c->journal)) {
         journal_reclaim(c);
         spin_unlock(&c->journal.lock);
 
         btree_flush_write(c);
         continue_at(cl, journal_write, bch_journal_wq);
         return;
     }
 
     c->journal.blocks_free -= set_blocks(w->data, block_bytes(ca));
 
     w->data->btree_level = c->root->level;
 
     bkey_copy(&w->data->btree_root, &c->root->key);
     bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
 
     w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
     w->data->magic      = jset_magic(&ca->sb);
     w->data->version    = BCACHE_JSET_VERSION;
     w->data->last_seq   = last_seq(&c->journal);
     w->data->csum       = csum_set(w->data);
 
     for (i = 0; i < KEY_PTRS(k); i++) {
         ca = c->cache;
         bio = &ca->journal.bio;
 
         atomic_long_add(sectors, &ca->meta_sectors_written);
 
         bio_reset(bio, ca->bdev, REQ_OP_WRITE | 
               REQ_SYNC | REQ_META | REQ_PREFLUSH | REQ_FUA);
         bio->bi_iter.bi_sector  = PTR_OFFSET(k, i);
         bio->bi_iter.bi_size = sectors << 9;
 
         bio->bi_end_io  = journal_write_endio;
         bio->bi_private = w;
         bch_bio_map(bio, w->data);
 
         trace_bcache_journal_write(bio, w->data->keys);
         bio_list_add(&list, bio);
 
         SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
 
         ca->journal.seq[ca->journal.cur_idx] = w->data->seq;
     }
 
     /* If KEY_PTRS(k) == 0, this jset gets lost in air */
     BUG_ON(i == 0);
 
     atomic_dec_bug(&fifo_back(&c->journal.pin));
     bch_journal_next(&c->journal);
     journal_reclaim(c);
 
     spin_unlock(&c->journal.lock);
 
     while ((bio = bio_list_pop(&list)))
         closure_bio_submit(c, bio, cl);
 
     continue_at(cl, journal_write_done, NULL);
 }
 
 static void journal_write(struct closure *cl)
 {
     struct cache_set *c = container_of(cl, struct cache_set, journal.io);
 
     spin_lock(&c->journal.lock);
     journal_write_unlocked(cl);
 }
 
 static void journal_try_write(struct cache_set *c)
     __releases(c->journal.lock)
 {
     struct closure *cl = &c->journal.io;
     struct journal_write *w = c->journal.cur;
 
     w->need_write = true;
 
     if (!c->journal.io_in_flight) {
         c->journal.io_in_flight = 1;
         closure_call(cl, journal_write_unlocked, NULL, &c->cl);
     } else {
         spin_unlock(&c->journal.lock);
     }
 }
 
 static struct journal_write *journal_wait_for_write(struct cache_set *c,
                             unsigned int nkeys)
     __acquires(&c->journal.lock)
 {
     size_t sectors;
     struct closure cl;
     bool wait = false;
     struct cache *ca = c->cache;
 
     closure_init_stack(&cl);
 
     spin_lock(&c->journal.lock);
 
     while (1) {
         struct journal_write *w = c->journal.cur;
 
         sectors = __set_blocks(w->data, w->data->keys + nkeys,
                        block_bytes(ca)) * ca->sb.block_size;
 
         if (sectors <= min_t(size_t,
                      c->journal.blocks_free * ca->sb.block_size,
                      PAGE_SECTORS << JSET_BITS))
             return w;
 
         if (wait)
             closure_wait(&c->journal.wait, &cl);
 
         if (!journal_full(&c->journal)) {
             if (wait)
                 trace_bcache_journal_entry_full(c);
 
             /*
              * XXX: If we were inserting so many keys that they
              * won't fit in an _empty_ journal write, we'll
              * deadlock. For now, handle this in
              * bch_keylist_realloc() - but something to think about.
              */
             BUG_ON(!w->data->keys);
 
             journal_try_write(c); /* unlocks */
         } else {
             if (wait)
                 trace_bcache_journal_full(c);
 
             journal_reclaim(c);
             spin_unlock(&c->journal.lock);
 
             btree_flush_write(c);
         }
 
         closure_sync(&cl);
         spin_lock(&c->journal.lock);
         wait = true;
     }
 }
 
 static void journal_write_work(struct work_struct *work)
 {
     struct cache_set *c = container_of(to_delayed_work(work),
                        struct cache_set,
                        journal.work);
     spin_lock(&c->journal.lock);
     if (c->journal.cur->dirty)
         journal_try_write(c);
     else
         spin_unlock(&c->journal.lock);
 }
 
 /*
  * Entry point to the journalling code - bio_insert() and btree_invalidate()
  * pass bch_journal() a list of keys to be journalled, and then
  * bch_journal() hands those same keys off to btree_insert_async()
  */
 
 atomic_t *bch_journal(struct cache_set *c,
               struct keylist *keys,
               struct closure *parent)
 {
     struct journal_write *w;
     atomic_t *ret;
 
     /* No journaling if CACHE_SET_IO_DISABLE set already */
     if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags)))
         return NULL;
 
     if (!CACHE_SYNC(&c->cache->sb))
         return NULL;
 
     w = journal_wait_for_write(c, bch_keylist_nkeys(keys));
 
     memcpy(bset_bkey_last(w->data), keys->keys, bch_keylist_bytes(keys));
     w->data->keys += bch_keylist_nkeys(keys);
 
     ret = &fifo_back(&c->journal.pin);
     atomic_inc(ret);
 
     if (parent) {
         closure_wait(&w->wait, parent);
         journal_try_write(c);
     } else if (!w->dirty) {
         w->dirty = true;
         queue_delayed_work(bch_flush_wq, &c->journal.work,
                    msecs_to_jiffies(c->journal_delay_ms));
         spin_unlock(&c->journal.lock);
     } else {
         spin_unlock(&c->journal.lock);
     }
 
 
     return ret;
 }
 
 void bch_journal_meta(struct cache_set *c, struct closure *cl)
 {
     struct keylist keys;
     atomic_t *ref;
 
     bch_keylist_init(&keys);
 
     ref = bch_journal(c, &keys, cl);
     if (ref)
         atomic_dec_bug(ref);
 }
 
 void bch_journal_free(struct cache_set *c)
 {
     free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
     free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
     free_fifo(&c->journal.pin);
 }
 
 int bch_journal_alloc(struct cache_set *c)
 {
     struct journal *j = &c->journal;
 
     spin_lock_init(&j->lock);
     spin_lock_init(&j->flush_write_lock);
     INIT_DELAYED_WORK(&j->work, journal_write_work);
 
     c->journal_delay_ms = 100;
 
     j->w[0].c = c;
     j->w[1].c = c;
 
     if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
         !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP, JSET_BITS)) ||
         !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP, JSET_BITS)))
         return -ENOMEM;
 
     return 0;
 }

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