bcache: Refactor journalling flow control

Making things less asynchronous that don't need to be - bch_journal()
only has to block when the journal or journal entry is full, which is
emphatically not a fast path. So make it a normal function that just
returns when it finishes, to make the code and control flow easier to
follow.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

7 files changed, 207 insertions, 179 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index f960607f1f25..777c01d67ef0 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -2164,9 +2164,6 @@ int bch_btree_insert(struct btree_op *op, struct cache_set *c,
                 }
         }
 
-        if (op->journal)
-                atomic_dec_bug(op->journal);
-        op->journal = NULL;
         return ret;
 }
 
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
index 00039924ea9d..ab011f03801f 100644
--- a/drivers/md/bcache/closure.h
+++ b/drivers/md/bcache/closure.h
@@ -642,7 +642,7 @@ do {									\
 #define continue_at_nobarrier(_cl, _fn, _wq)                            \
 do {                                                                    \
         set_closure_fn(_cl, _fn, _wq);                                  \
-        closure_queue(cl);                                              \
+        closure_queue(_cl);                                             \
         return;                                                         \
 } while (0)
 
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 1bdefdb1fa71..940e89e0d706 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -318,7 +318,6 @@ int bch_journal_replay(struct cache_set *s, struct list_head *list,
                         bch_keylist_push(&op->keys);
 
                         op->journal = i->pin;
-                        atomic_inc(op->journal);
 
                         ret = bch_btree_insert(op, s, &op->keys);
                         if (ret)
@@ -357,48 +356,35 @@ static void btree_flush_write(struct cache_set *c)
          * Try to find the btree node with that references the oldest journal
          * entry, best is our current candidate and is locked if non NULL:
          */
-        struct btree *b, *best = NULL;
-        unsigned iter;
+        struct btree *b, *best;
+        unsigned i;
+retry:
+        best = NULL;
+
+        for_each_cached_btree(b, c, i)
+                if (btree_current_write(b)->journal) {
+                        if (!best)
+                                best = b;
+                        else if (journal_pin_cmp(c,
+                                                 btree_current_write(best),
+                                                 btree_current_write(b))) {
+                                best = b;
+                        }
+                }
 
-        for_each_cached_btree(b, c, iter) {
-                if (!down_write_trylock(&b->lock))
-                        continue;
+        b = best;
+        if (b) {
+                rw_lock(true, b, b->level);
 
-                if (!btree_node_dirty(b) ||
-                    !btree_current_write(b)->journal) {
+                if (!btree_current_write(b)->journal) {
                         rw_unlock(true, b);
-                        continue;
+                        /* We raced */
+                        goto retry;
                 }
 
-                if (!best)
-                        best = b;
-                else if (journal_pin_cmp(c,
-                                         btree_current_write(best),
-                                         btree_current_write(b))) {
-                        rw_unlock(true, best);
-                        best = b;
-                } else
-                        rw_unlock(true, b);
+                bch_btree_node_write(b, NULL);
+                rw_unlock(true, b);
         }
-
-        if (best)
-                goto out;
-
-        /* We can't find the best btree node, just pick the first */
-        list_for_each_entry(b, &c->btree_cache, list)
-                if (!b->level && btree_node_dirty(b)) {
-                        best = b;
-                        rw_lock(true, best, best->level);
-                        goto found;
-                }
-
-out:
-        if (!best)
-                return;
-found:
-        if (btree_node_dirty(best))
-                bch_btree_node_write(best, NULL);
-        rw_unlock(true, best);
 }
 
 #define last_seq(j)     ((j)->seq - fifo_used(&(j)->pin) + 1)
@@ -494,7 +480,7 @@ static void journal_reclaim(struct cache_set *c)
                 do_journal_discard(ca);
 
         if (c->journal.blocks_free)
-                return;
+                goto out;
 
         /*
          * Allocate:
@@ -520,7 +506,7 @@ static void journal_reclaim(struct cache_set *c)
 
         if (n)
                 c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
-
+out:
         if (!journal_full(&c->journal))
                 __closure_wake_up(&c->journal.wait);
 }
@@ -659,7 +645,7 @@ static void journal_write(struct closure *cl)
         journal_write_unlocked(cl);
 }
 
-static void __journal_try_write(struct cache_set *c, bool noflush)
+static void journal_try_write(struct cache_set *c)
         __releases(c->journal.lock)
 {
         struct closure *cl = &c->journal.io;
@@ -667,29 +653,59 @@ static void __journal_try_write(struct cache_set *c, bool noflush)
 
         w->need_write = true;
 
-        if (!closure_trylock(cl, &c->cl))
-                spin_unlock(&c->journal.lock);
-        else if (noflush && journal_full(&c->journal)) {
-                spin_unlock(&c->journal.lock);
-                continue_at(cl, journal_write, system_wq);
-        } else
+        if (closure_trylock(cl, &c->cl))
                 journal_write_unlocked(cl);
+        else
+                spin_unlock(&c->journal.lock);
 }
 
-#define journal_try_write(c)    __journal_try_write(c, false)
-
-void bch_journal_meta(struct cache_set *c, struct closure *cl)
+static struct journal_write *journal_wait_for_write(struct cache_set *c,
+                                                    unsigned nkeys)
 {
-        struct journal_write *w;
+        size_t sectors;
+        struct closure cl;
 
-        if (CACHE_SYNC(&c->sb)) {
-                spin_lock(&c->journal.lock);
-                w = c->journal.cur;
+        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,
+                                       c) * c->sb.block_size;
+
+                if (sectors <= min_t(size_t,
+                                     c->journal.blocks_free * c->sb.block_size,
+                                     PAGE_SECTORS << JSET_BITS))
+                        return w;
+
+                /* XXX: tracepoint */
+                if (!journal_full(&c->journal)) {
+                        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);
+
+                        closure_wait(&w->wait, &cl);
+                        journal_try_write(c); /* unlocks */
+                } else {
+                        trace_bcache_journal_full(c);
+
+                        closure_wait(&c->journal.wait, &cl);
+                        journal_reclaim(c);
+                        spin_unlock(&c->journal.lock);
 
-                if (cl)
-                        BUG_ON(!closure_wait(&w->wait, cl));
+                        btree_flush_write(c);
+                }
 
-                __journal_try_write(c, true);
+                closure_sync(&cl);
+                spin_lock(&c->journal.lock);
         }
 }
 
@@ -708,68 +724,26 @@ static void journal_write_work(struct work_struct *work)
  * bch_journal() hands those same keys off to btree_insert_async()
  */
 
-void bch_journal(struct closure *cl)
+atomic_t *bch_journal(struct cache_set *c,
+                      struct keylist *keys,
+                      struct closure *parent)
 {
-        struct btree_op *op = container_of(cl, struct btree_op, cl);
-        struct cache_set *c = op->c;
         struct journal_write *w;
-        size_t sectors, nkeys;
-
-        if (op->type != BTREE_INSERT ||
-            !CACHE_SYNC(&c->sb))
-                goto out;
-
-        /*
-         * If we're looping because we errored, might already be waiting on
-         * another journal write:
-         */
-        while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
-                closure_sync(cl->parent);
-
-        spin_lock(&c->journal.lock);
-
-        if (journal_full(&c->journal)) {
-                trace_bcache_journal_full(c);
-
-                closure_wait(&c->journal.wait, cl);
-
-                journal_reclaim(c);
-                spin_unlock(&c->journal.lock);
-
-                btree_flush_write(c);
-                continue_at(cl, bch_journal, bcache_wq);
-        }
+        atomic_t *ret;
 
-        w = c->journal.cur;
-        nkeys = w->data->keys + bch_keylist_nkeys(&op->keys);
-        sectors = __set_blocks(w->data, nkeys, c) * c->sb.block_size;
+        if (!CACHE_SYNC(&c->sb))
+                return NULL;
 
-        if (sectors > min_t(size_t,
-                            c->journal.blocks_free * c->sb.block_size,
-                            PAGE_SECTORS << JSET_BITS)) {
-                trace_bcache_journal_entry_full(c);
+        w = journal_wait_for_write(c, bch_keylist_nkeys(keys));
 
-                /*
-                 * 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);
+        memcpy(end(w->data), keys->keys, bch_keylist_bytes(keys));
+        w->data->keys += bch_keylist_nkeys(keys);
 
-                BUG_ON(!closure_wait(&w->wait, cl));
+        ret = &fifo_back(&c->journal.pin);
+        atomic_inc(ret);
 
-                journal_try_write(c);
-                continue_at(cl, bch_journal, bcache_wq);
-        }
-
-        memcpy(end(w->data), op->keys.keys, bch_keylist_bytes(&op->keys));
-        w->data->keys += bch_keylist_nkeys(&op->keys);
-
-        op->journal = &fifo_back(&c->journal.pin);
-        atomic_inc(op->journal);
-
-        if (op->flush_journal) {
-                closure_wait(&w->wait, cl->parent);
+        if (parent) {
+                closure_wait(&w->wait, parent);
                 journal_try_write(c);
         } else if (!w->need_write) {
                 schedule_delayed_work(&c->journal.work,
@@ -778,8 +752,21 @@ void bch_journal(struct closure *cl)
         } else {
                 spin_unlock(&c->journal.lock);
         }
-out:
-        bch_btree_insert_async(cl);
+
+
+        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)
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
index 3ca93d3d566c..7045e6fd2d5a 100644
--- a/drivers/md/bcache/journal.h
+++ b/drivers/md/bcache/journal.h
@@ -200,8 +200,9 @@ struct journal_device {
 struct closure;
 struct cache_set;
 struct btree_op;
+struct keylist;
 
-void bch_journal(struct closure *);
+atomic_t *bch_journal(struct cache_set *, struct keylist *, struct closure *);
 void bch_journal_next(struct journal *);
 void bch_journal_mark(struct cache_set *, struct list_head *);
 void bch_journal_meta(struct cache_set *, struct closure *);
diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
index dd8a035c5ae1..2c42377a65aa 100644
--- a/drivers/md/bcache/movinggc.c
+++ b/drivers/md/bcache/movinggc.c
@@ -110,7 +110,7 @@ static void write_moving(struct closure *cl)
                 bkey_copy(&s->op.replace, &io->w->key);
 
                 closure_init(&s->op.cl, cl);
-                bch_insert_data(&s->op.cl);
+                bch_data_insert(&s->op.cl);
         }
 
         continue_at(cl, write_moving_finish, bch_gc_wq);
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 3b85f33ae4c7..1c3af44b097b 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -25,6 +25,8 @@
 
 struct kmem_cache *bch_search_cache;
 
+static void bch_data_insert_start(struct closure *);
+
 /* Cgroup interface */
 
 #ifdef CONFIG_CGROUP_BCACHE
@@ -211,31 +213,42 @@ static void bio_csum(struct bio *bio, struct bkey *k)
 
 /* Insert data into cache */
 
-static void bio_invalidate(struct closure *cl)
+static void bch_data_insert_keys(struct closure *cl)
 {
         struct btree_op *op = container_of(cl, struct btree_op, cl);
-        struct bio *bio = op->cache_bio;
+        struct search *s = container_of(op, struct search, op);
 
-        pr_debug("invalidating %i sectors from %llu",
-                 bio_sectors(bio), (uint64_t) bio->bi_sector);
+        /*
+         * If we're looping, might already be waiting on
+         * another journal write - can't wait on more than one journal write at
+         * a time
+         *
+         * XXX: this looks wrong
+         */
+#if 0
+        while (atomic_read(&s->cl.remaining) & CLOSURE_WAITING)
+                closure_sync(&s->cl);
+#endif
 
-        while (bio_sectors(bio)) {
-                unsigned len = min(bio_sectors(bio), 1U << 14);
+        if (s->write)
+                op->journal = bch_journal(op->c, &op->keys,
+                                          op->flush_journal
+                                          ? &s->cl : NULL);
 
-                if (bch_keylist_realloc(&op->keys, 0, op->c))
-                        goto out;
+        if (bch_btree_insert(op, op->c, &op->keys)) {
+                s->error                = -ENOMEM;
+                op->insert_data_done    = true;
+        }
 
-                bio->bi_sector  += len;
-                bio->bi_size    -= len << 9;
+        if (op->journal)
+                atomic_dec_bug(op->journal);
+        op->journal = NULL;
 
-                bch_keylist_add(&op->keys,
-                                &KEY(op->inode, bio->bi_sector, len));
-        }
+        if (!op->insert_data_done)
+                continue_at(cl, bch_data_insert_start, bcache_wq);
 
-        op->insert_data_done = true;
-        bio_put(bio);
-out:
-        continue_at(cl, bch_journal, bcache_wq);
+        bch_keylist_free(&op->keys);
+        closure_return(cl);
 }
 
 struct open_bucket {
@@ -423,7 +436,34 @@ static bool bch_alloc_sectors(struct bkey *k, unsigned sectors,
         return true;
 }
 
-static void bch_insert_data_error(struct closure *cl)
+static void bch_data_invalidate(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct bio *bio = op->cache_bio;
+
+        pr_debug("invalidating %i sectors from %llu",
+                 bio_sectors(bio), (uint64_t) bio->bi_sector);
+
+        while (bio_sectors(bio)) {
+                unsigned len = min(bio_sectors(bio), 1U << 14);
+
+                if (bch_keylist_realloc(&op->keys, 0, op->c))
+                        goto out;
+
+                bio->bi_sector  += len;
+                bio->bi_size    -= len << 9;
+
+                bch_keylist_add(&op->keys, &KEY(op->inode,
+                                                bio->bi_sector, len));
+        }
+
+        op->insert_data_done = true;
+        bio_put(bio);
+out:
+        continue_at(cl, bch_data_insert_keys, bcache_wq);
+}
+
+static void bch_data_insert_error(struct closure *cl)
 {
         struct btree_op *op = container_of(cl, struct btree_op, cl);
 
@@ -450,10 +490,10 @@ static void bch_insert_data_error(struct closure *cl)
 
         op->keys.top = dst;
 
-        bch_journal(cl);
+        bch_data_insert_keys(cl);
 }
 
-static void bch_insert_data_endio(struct bio *bio, int error)
+static void bch_data_insert_endio(struct bio *bio, int error)
 {
         struct closure *cl = bio->bi_private;
         struct btree_op *op = container_of(cl, struct btree_op, cl);
@@ -464,7 +504,7 @@ static void bch_insert_data_endio(struct bio *bio, int error)
                 if (s->writeback)
                         s->error = error;
                 else if (s->write)
-                        set_closure_fn(cl, bch_insert_data_error, bcache_wq);
+                        set_closure_fn(cl, bch_data_insert_error, bcache_wq);
                 else
                         set_closure_fn(cl, NULL, NULL);
         }
@@ -472,14 +512,14 @@ static void bch_insert_data_endio(struct bio *bio, int error)
         bch_bbio_endio(op->c, bio, error, "writing data to cache");
 }
 
-static void bch_insert_data_loop(struct closure *cl)
+static void bch_data_insert_start(struct closure *cl)
 {
         struct btree_op *op = container_of(cl, struct btree_op, cl);
         struct search *s = container_of(op, struct search, op);
         struct bio *bio = op->cache_bio, *n;
 
         if (op->bypass)
-                return bio_invalidate(cl);
+                return bch_data_invalidate(cl);
 
         if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0) {
                 set_gc_sectors(op->c);
@@ -502,7 +542,7 @@ static void bch_insert_data_loop(struct closure *cl)
                 if (bch_keylist_realloc(&op->keys,
                                         1 + (op->csum ? 1 : 0),
                                         op->c))
-                        continue_at(cl, bch_journal, bcache_wq);
+                        continue_at(cl, bch_data_insert_keys, bcache_wq);
 
                 k = op->keys.top;
                 bkey_init(k);
@@ -514,7 +554,7 @@ static void bch_insert_data_loop(struct closure *cl)
 
                 n = bch_bio_split(bio, KEY_SIZE(k), GFP_NOIO, split);
 
-                n->bi_end_io    = bch_insert_data_endio;
+                n->bi_end_io    = bch_data_insert_endio;
                 n->bi_private   = cl;
 
                 if (s->writeback) {
@@ -537,7 +577,7 @@ static void bch_insert_data_loop(struct closure *cl)
         } while (n != bio);
 
         op->insert_data_done = true;
-        continue_at(cl, bch_journal, bcache_wq);
+        continue_at(cl, bch_data_insert_keys, bcache_wq);
 err:
         /* bch_alloc_sectors() blocks if s->writeback = true */
         BUG_ON(s->writeback);
@@ -556,7 +596,7 @@ err:
                  * rest of the write.
                  */
                 op->bypass = true;
-                return bio_invalidate(cl);
+                return bch_data_invalidate(cl);
         } else {
                 /*
                  * From a cache miss, we can just insert the keys for the data
@@ -566,14 +606,14 @@ err:
                 bio_put(bio);
 
                 if (!bch_keylist_empty(&op->keys))
-                        continue_at(cl, bch_journal, bcache_wq);
+                        continue_at(cl, bch_data_insert_keys, bcache_wq);
                 else
                         closure_return(cl);
         }
 }
 
 /**
- * bch_insert_data - stick some data in the cache
+ * bch_data_insert - stick some data in the cache
  *
  * This is the starting point for any data to end up in a cache device; it could
  * be from a normal write, or a writeback write, or a write to a flash only
@@ -591,30 +631,13 @@ err:
  * If op->bypass is true, instead of inserting the data it invalidates the
  * region of the cache represented by op->cache_bio and op->inode.
  */
-void bch_insert_data(struct closure *cl)
+void bch_data_insert(struct closure *cl)
 {
         struct btree_op *op = container_of(cl, struct btree_op, cl);
 
         bch_keylist_init(&op->keys);
         bio_get(op->cache_bio);
-        bch_insert_data_loop(cl);
-}
-
-void bch_btree_insert_async(struct closure *cl)
-{
-        struct btree_op *op = container_of(cl, struct btree_op, cl);
-        struct search *s = container_of(op, struct search, op);
-
-        if (bch_btree_insert(op, op->c, &op->keys)) {
-                s->error                = -ENOMEM;
-                op->insert_data_done    = true;
-        }
-
-        if (op->insert_data_done) {
-                bch_keylist_free(&op->keys);
-                closure_return(cl);
-        } else
-                continue_at(cl, bch_insert_data_loop, bcache_wq);
+        bch_data_insert_start(cl);
 }
 
 /* Common code for the make_request functions */
@@ -969,7 +992,7 @@ static void cached_dev_read_done(struct closure *cl)
         if (s->op.cache_bio &&
             !test_bit(CACHE_SET_STOPPING, &s->op.c->flags)) {
                 s->op.type = BTREE_REPLACE;
-                closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+                closure_call(&s->op.cl, bch_data_insert, NULL, cl);
         }
 
         continue_at(cl, cached_dev_cache_miss_done, NULL);
@@ -1147,13 +1170,13 @@ static void cached_dev_write(struct cached_dev *dc, struct search *s)
                 closure_bio_submit(bio, cl, s->d);
         }
 
-        closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+        closure_call(&s->op.cl, bch_data_insert, NULL, cl);
         continue_at(cl, cached_dev_write_complete, NULL);
 }
 
-static void cached_dev_nodata(struct cached_dev *dc, struct search *s)
+static void cached_dev_nodata(struct closure *cl)
 {
-        struct closure *cl = &s->cl;
+        struct search *s = container_of(cl, struct search, cl);
         struct bio *bio = &s->bio.bio;
 
         if (s->op.flush_journal)
@@ -1186,9 +1209,15 @@ static void cached_dev_make_request(struct request_queue *q, struct bio *bio)
                 s = search_alloc(bio, d);
                 trace_bcache_request_start(s, bio);
 
-                if (!bio->bi_size)
-                        cached_dev_nodata(dc, s);
-                else {
+                if (!bio->bi_size) {
+                        /*
+                         * can't call bch_journal_meta from under
+                         * generic_make_request
+                         */
+                        continue_at_nobarrier(&s->cl,
+                                              cached_dev_nodata,
+                                              bcache_wq);
+                } else {
                         s->op.bypass = check_should_bypass(dc, s);
 
                         if (rw)
@@ -1275,6 +1304,16 @@ static int flash_dev_cache_miss(struct btree *b, struct search *s,
         return 0;
 }
 
+static void flash_dev_nodata(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+
+        if (s->op.flush_journal)
+                bch_journal_meta(s->op.c, cl);
+
+        continue_at(cl, search_free, NULL);
+}
+
 static void flash_dev_make_request(struct request_queue *q, struct bio *bio)
 {
         struct search *s;
@@ -1294,8 +1333,13 @@ static void flash_dev_make_request(struct request_queue *q, struct bio *bio)
         trace_bcache_request_start(s, bio);
 
         if (!bio->bi_size) {
-                if (s->op.flush_journal)
-                        bch_journal_meta(s->op.c, cl);
+                /*
+                 * can't call bch_journal_meta from under
+                 * generic_make_request
+                 */
+                continue_at_nobarrier(&s->cl,
+                                      flash_dev_nodata,
+                                      bcache_wq);
         } else if (rw) {
                 bch_keybuf_check_overlapping(&s->op.c->moving_gc_keys,
                                         &KEY(d->id, bio->bi_sector, 0),
@@ -1305,7 +1349,7 @@ static void flash_dev_make_request(struct request_queue *q, struct bio *bio)
                 s->writeback    = true;
                 s->op.cache_bio = bio;
 
-                closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+                closure_call(&s->op.cl, bch_data_insert, NULL, cl);
         } else {
                 closure_call(&s->op.cl, btree_read_async, NULL, cl);
         }
diff --git a/drivers/md/bcache/request.h b/drivers/md/bcache/request.h
index 57dc4784f4f4..1f1b59d38db5 100644
--- a/drivers/md/bcache/request.h
+++ b/drivers/md/bcache/request.h
@@ -31,8 +31,7 @@ struct search {
 
 void bch_cache_read_endio(struct bio *, int);
 unsigned bch_get_congested(struct cache_set *);
-void bch_insert_data(struct closure *cl);
-void bch_btree_insert_async(struct closure *);
+void bch_data_insert(struct closure *cl);
 void bch_cache_read_endio(struct bio *, int);
 
 void bch_open_buckets_free(struct cache_set *);