bcache: Abstract out stuff needed for sorting

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

9 files changed, 423 insertions, 289 deletions

diff --git a/drivers/md/bcache/Makefile b/drivers/md/bcache/Makefile
index 0e9c82523be..c488b846f83 100644
--- a/drivers/md/bcache/Makefile
+++ b/drivers/md/bcache/Makefile
@@ -1,7 +1,8 @@
 
 obj-$(CONFIG_BCACHE)	+= bcache.o
 
-bcache-y		:= alloc.o btree.o bset.o io.o journal.o writeback.o\
-	movinggc.o request.o super.o sysfs.o debug.o util.o trace.o stats.o closure.o
+bcache-y		:= alloc.o bset.o btree.o closure.o debug.o extents.o\
+	io.o journal.o movinggc.o request.o stats.o super.o sysfs.o trace.o\
+	util.o writeback.o
 
 CFLAGS_request.o	+= -Iblock
diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index e04e5908e29..c2c42cbbe88 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -63,140 +63,6 @@ void bch_keylist_pop_front(struct keylist *l)
 		bch_keylist_bytes(l));
 }
 
-/* Pointer validation */
-
-static bool __ptr_invalid(struct cache_set *c, const struct bkey *k)
-{
-	unsigned i;
-
-	for (i = 0; i < KEY_PTRS(k); i++)
-		if (ptr_available(c, k, i)) {
-			struct cache *ca = PTR_CACHE(c, k, i);
-			size_t bucket = PTR_BUCKET_NR(c, k, i);
-			size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
-
-			if (KEY_SIZE(k) + r > c->sb.bucket_size ||
-			    bucket <  ca->sb.first_bucket ||
-			    bucket >= ca->sb.nbuckets)
-				return true;
-		}
-
-	return false;
-}
-
-bool bch_btree_ptr_invalid(struct cache_set *c, const struct bkey *k)
-{
-	char buf[80];
-
-	if (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k))
-		goto bad;
-
-	if (__ptr_invalid(c, k))
-		goto bad;
-
-	return false;
-bad:
-	bch_bkey_to_text(buf, sizeof(buf), k);
-	cache_bug(c, "spotted btree ptr %s: %s", buf, bch_ptr_status(c, k));
-	return true;
-}
-
-bool bch_extent_ptr_invalid(struct cache_set *c, const struct bkey *k)
-{
-	char buf[80];
-
-	if (!KEY_SIZE(k))
-		return true;
-
-	if (KEY_SIZE(k) > KEY_OFFSET(k))
-		goto bad;
-
-	if (__ptr_invalid(c, k))
-		goto bad;
-
-	return false;
-bad:
-	bch_bkey_to_text(buf, sizeof(buf), k);
-	cache_bug(c, "spotted extent %s: %s", buf, bch_ptr_status(c, k));
-	return true;
-}
-
-static bool ptr_bad_expensive_checks(struct btree *b, const struct bkey *k,
-				     unsigned ptr)
-{
-	struct bucket *g = PTR_BUCKET(b->c, k, ptr);
-	char buf[80];
-
-	if (mutex_trylock(&b->c->bucket_lock)) {
-		if (b->level) {
-			if (KEY_DIRTY(k) ||
-			    g->prio != BTREE_PRIO ||
-			    (b->c->gc_mark_valid &&
-			     GC_MARK(g) != GC_MARK_METADATA))
-				goto err;
-
-		} else {
-			if (g->prio == BTREE_PRIO)
-				goto err;
-
-			if (KEY_DIRTY(k) &&
-			    b->c->gc_mark_valid &&
-			    GC_MARK(g) != GC_MARK_DIRTY)
-				goto err;
-		}
-		mutex_unlock(&b->c->bucket_lock);
-	}
-
-	return false;
-err:
-	mutex_unlock(&b->c->bucket_lock);
-	bch_bkey_to_text(buf, sizeof(buf), k);
-	btree_bug(b,
-"inconsistent pointer %s: bucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
-		  buf, PTR_BUCKET_NR(b->c, k, ptr), atomic_read(&g->pin),
-		  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
-	return true;
-}
-
-bool bch_ptr_bad(struct btree *b, const struct bkey *k)
-{
-	struct bucket *g;
-	unsigned i, stale;
-
-	if (!bkey_cmp(k, &ZERO_KEY) ||
-	    !KEY_PTRS(k) ||
-	    bch_ptr_invalid(b, k))
-		return true;
-
-	for (i = 0; i < KEY_PTRS(k); i++)
-		if (!ptr_available(b->c, k, i))
-			return true;
-
-	if (!expensive_debug_checks(b->c) && KEY_DIRTY(k))
-		return false;
-
-	for (i = 0; i < KEY_PTRS(k); i++) {
-		g = PTR_BUCKET(b->c, k, i);
-		stale = ptr_stale(b->c, k, i);
-
-		btree_bug_on(stale > 96, b,
-			     "key too stale: %i, need_gc %u",
-			     stale, b->c->need_gc);
-
-		btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
-			     b, "stale dirty pointer");
-
-		if (stale)
-			return true;
-
-		if (expensive_debug_checks(b->c) &&
-		    ptr_bad_expensive_checks(b, k, i))
-			return true;
-	}
-
-	return false;
-}
-
 /* Key/pointer manipulation */
 
 void bch_bkey_copy_single_ptr(struct bkey *dest, const struct bkey *src,
@@ -251,57 +117,6 @@ bool __bch_cut_back(const struct bkey *where, struct bkey *k)
 	return true;
 }
 
-static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
-{
-	return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
-		~((uint64_t)1 << 63);
-}
-
-/* Tries to merge l and r: l should be lower than r
- * Returns true if we were able to merge. If we did merge, l will be the merged
- * key, r will be untouched.
- */
-bool bch_bkey_try_merge(struct btree *b, struct bkey *l, struct bkey *r)
-{
-	unsigned i;
-
-	if (key_merging_disabled(b->c))
-		return false;
-
-	if (KEY_PTRS(l) != KEY_PTRS(r) ||
-	    KEY_DIRTY(l) != KEY_DIRTY(r) ||
-	    bkey_cmp(l, &START_KEY(r)))
-		return false;
-
-	for (i = 0; i < KEY_PTRS(l); i++)
-		if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
-		    PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
-			return false;
-
-	/* Keys with no pointers aren't restricted to one bucket and could
-	 * overflow KEY_SIZE
-	 */
-	if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
-		SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
-		SET_KEY_SIZE(l, USHRT_MAX);
-
-		bch_cut_front(l, r);
-		return false;
-	}
-
-	if (KEY_CSUM(l)) {
-		if (KEY_CSUM(r))
-			l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
-		else
-			SET_KEY_CSUM(l, 0);
-	}
-
-	SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
-	SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));
-
-	return true;
-}
-
 /* Auxiliary search trees */
 
 /* 32 bits total: */
@@ -1099,85 +914,6 @@ int bch_bset_sort_state_init(struct bset_sort_state *state, unsigned page_order)
 	return 0;
 }
 
-static void sort_key_next(struct btree_iter *iter,
-			  struct btree_iter_set *i)
-{
-	i->k = bkey_next(i->k);
-
-	if (i->k == i->end)
-		*i = iter->data[--iter->used];
-}
-
-/*
- * Returns true if l > r - unless l == r, in which case returns true if l is
- * older than r.
- *
- * Necessary for btree_sort_fixup() - if there are multiple keys that compare
- * equal in different sets, we have to process them newest to oldest.
- */
-static inline bool sort_extent_cmp(struct btree_iter_set l,
-				   struct btree_iter_set r)
-{
-	int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
-
-	return c ? c > 0 : l.k < r.k;
-}
-
-static inline bool sort_cmp(struct btree_iter_set l,
-			    struct btree_iter_set r)
-{
-	int64_t c = bkey_cmp(l.k, r.k);
-
-	return c ? c > 0 : l.k < r.k;
-}
-
-static struct bkey *btree_sort_fixup_extents(struct btree_iter *iter,
-					     struct bkey *tmp)
-{
-	while (iter->used > 1) {
-		struct btree_iter_set *top = iter->data, *i = top + 1;
-
-		if (iter->used > 2 &&
-		    sort_extent_cmp(i[0], i[1]))
-			i++;
-
-		if (bkey_cmp(top->k, &START_KEY(i->k)) <= 0)
-			break;
-
-		if (!KEY_SIZE(i->k)) {
-			sort_key_next(iter, i);
-			heap_sift(iter, i - top, sort_extent_cmp);
-			continue;
-		}
-
-		if (top->k > i->k) {
-			if (bkey_cmp(top->k, i->k) >= 0)
-				sort_key_next(iter, i);
-			else
-				bch_cut_front(top->k, i->k);
-
-			heap_sift(iter, i - top, sort_extent_cmp);
-		} else {
-			/* can't happen because of comparison func */
-			BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));
-
-			if (bkey_cmp(i->k, top->k) < 0) {
-				bkey_copy(tmp, top->k);
-
-				bch_cut_back(&START_KEY(i->k), tmp);
-				bch_cut_front(i->k, top->k);
-				heap_sift(iter, 0, btree_iter_cmp);
-
-				return tmp;
-			} else {
-				bch_cut_back(&START_KEY(i->k), top->k);
-			}
-		}
-	}
-
-	return NULL;
-}
-
 static void btree_mergesort(struct btree *b, struct bset *out,
 			    struct btree_iter *iter,
 			    bool fixup, bool remove_stale)
@@ -1185,25 +921,22 @@ static void btree_mergesort(struct btree *b, struct bset *out,
 	int i;
 	struct bkey *k, *last = NULL;
 	BKEY_PADDED(k) tmp;
-	btree_iter_cmp_fn *cmp = b->level
-		? sort_cmp
-		: sort_extent_cmp;
 	bool (*bad)(struct btree *, const struct bkey *) = remove_stale
 		? bch_ptr_bad
 		: bch_ptr_invalid;
 
 	/* Heapify the iterator, using our comparison function */
 	for (i = iter->used / 2 - 1; i >= 0; --i)
-		heap_sift(iter, i, cmp);
+		heap_sift(iter, i, b->ops->sort_cmp);
 
 	while (!btree_iter_end(iter)) {
-		if (fixup && !b->level)
-			k = btree_sort_fixup_extents(iter, &tmp.k);
+		if (b->ops->sort_fixup && fixup)
+			k = b->ops->sort_fixup(iter, &tmp.k);
 		else
 			k = NULL;
 
 		if (!k)
-			k = __bch_btree_iter_next(iter, cmp);
+			k = __bch_btree_iter_next(iter, b->ops->sort_cmp);
 
 		if (bad(b, k))
 			continue;
@@ -1211,8 +944,7 @@ static void btree_mergesort(struct btree *b, struct bset *out,
 		if (!last) {
 			last = out->start;
 			bkey_copy(last, k);
-		} else if (b->level ||
-			   !bch_bkey_try_merge(b, last, k)) {
+		} else if (!bch_bkey_try_merge(b, last, k)) {
 			last = bkey_next(last);
 			bkey_copy(last, k);
 		}
@@ -1300,6 +1032,7 @@ void bch_btree_sort_partial(struct btree *b, unsigned start,
 
 	EBUG_ON(b->written && oldsize >= 0 && bch_count_data(b) != oldsize);
 }
+EXPORT_SYMBOL(bch_btree_sort_partial);
 
 void bch_btree_sort_and_fix_extents(struct btree *b, struct btree_iter *iter,
 				    struct bset_sort_state *state)
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index ab31f3fc8d4..b5797129e91 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -376,14 +376,6 @@ int __bch_keylist_realloc(struct keylist *, unsigned);
 
 struct cache_set;
 const char *bch_ptr_status(struct cache_set *, const struct bkey *);
-bool bch_btree_ptr_invalid(struct cache_set *, const struct bkey *);
-bool bch_extent_ptr_invalid(struct cache_set *, const struct bkey *);
-bool bch_btree_ptr_bad(struct btree *, const struct bkey *);
-bool bch_extent_ptr_bad(struct btree *, const struct bkey *);
-
-bool bch_ptr_bad(struct btree *, const struct bkey *);
-
-bool bch_bkey_try_merge(struct btree *, struct bkey *, struct bkey *);
 
 int bch_bset_print_stats(struct cache_set *, char *);
 
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 89252e7f287..6734e2759b9 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -23,6 +23,7 @@
 #include "bcache.h"
 #include "btree.h"
 #include "debug.h"
+#include "extents.h"
 #include "writeback.h"
 
 #include <linux/slab.h>
@@ -931,6 +932,11 @@ out:
 	b->level	= level;
 	b->parent	= (void *) ~0UL;
 
+	if (!b->level)
+		b->ops	= &bch_extent_keys_ops;
+	else
+		b->ops	= &bch_btree_keys_ops;
+
 	mca_reinit(b);
 
 	return b;
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index b3541173ccf..0b436079db7 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -113,7 +113,28 @@ struct btree_write {
 	int			prio_blocked;
 };
 
+struct btree_keys_ops {
+	bool			(*sort_cmp)(struct btree_iter_set,
+					    struct btree_iter_set);
+	struct bkey		*(*sort_fixup)(struct btree_iter *,
+					       struct bkey *);
+	bool			(*key_invalid)(struct btree *,
+					       const struct bkey *);
+	bool			(*key_bad)(struct btree *,
+					   const struct bkey *);
+	bool			(*key_merge)(struct btree *,
+					     struct bkey *, struct bkey *);
+
+
+	/*
+	 * Only used for deciding whether to use START_KEY(k) or just the key
+	 * itself in a couple places
+	 */
+	bool		is_extents;
+};
+
 struct btree {
+	const struct btree_keys_ops	*ops;
 	/* Hottest entries first */
 	struct hlist_node	hash;
 
@@ -232,10 +253,23 @@ static inline void set_gc_sectors(struct cache_set *c)
 
 static inline bool bch_ptr_invalid(struct btree *b, const struct bkey *k)
 {
-	if (b->level)
-		return bch_btree_ptr_invalid(b->c, k);
-	else
-		return bch_extent_ptr_invalid(b->c, k);
+	return b->ops->key_invalid(b, k);
+}
+
+static inline bool bch_ptr_bad(struct btree *b, const struct bkey *k)
+{
+	return b->ops->key_bad(b, k);
+}
+
+/*
+ * Tries to merge l and r: l should be lower than r
+ * Returns true if we were able to merge. If we did merge, l will be the merged
+ * key, r will be untouched.
+ */
+static inline bool bch_bkey_try_merge(struct btree *b,
+				      struct bkey *l, struct bkey *r)
+{
+	return b->ops->key_merge ?  b->ops->key_merge(b, l, r) : false;
 }
 
 void bkey_put(struct cache_set *c, struct bkey *k);
diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index 5a78137c420..2c6587d016d 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c
@@ -145,6 +145,7 @@ void bch_btree_verify(struct btree *b)
 	bkey_copy(&v->key, &b->key);
 	v->written = 0;
 	v->level = b->level;
+	v->ops = b->ops;
 
 	bio = bch_bbio_alloc(b->c);
 	bio->bi_bdev		= PTR_CACHE(b->c, &b->key, 0)->bdev;
diff --git a/drivers/md/bcache/extents.c b/drivers/md/bcache/extents.c
new file mode 100644
index 00000000000..8fe6aaece41
--- /dev/null
+++ b/drivers/md/bcache/extents.c
@@ -0,0 +1,354 @@
+/*
+ * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
+ *
+ * Uses a block device as cache for other block devices; optimized for SSDs.
+ * All allocation is done in buckets, which should match the erase block size
+ * of the device.
+ *
+ * Buckets containing cached data are kept on a heap sorted by priority;
+ * bucket priority is increased on cache hit, and periodically all the buckets
+ * on the heap have their priority scaled down. This currently is just used as
+ * an LRU but in the future should allow for more intelligent heuristics.
+ *
+ * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
+ * counter. Garbage collection is used to remove stale pointers.
+ *
+ * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
+ * as keys are inserted we only sort the pages that have not yet been written.
+ * When garbage collection is run, we resort the entire node.
+ *
+ * All configuration is done via sysfs; see Documentation/bcache.txt.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "extents.h"
+#include "writeback.h"
+
+static void sort_key_next(struct btree_iter *iter,
+			  struct btree_iter_set *i)
+{
+	i->k = bkey_next(i->k);
+
+	if (i->k == i->end)
+		*i = iter->data[--iter->used];
+}
+
+static bool bch_key_sort_cmp(struct btree_iter_set l,
+			     struct btree_iter_set r)
+{
+	int64_t c = bkey_cmp(l.k, r.k);
+
+	return c ? c > 0 : l.k < r.k;
+}
+
+static bool __ptr_invalid(struct cache_set *c, const struct bkey *k)
+{
+	unsigned i;
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		if (ptr_available(c, k, i)) {
+			struct cache *ca = PTR_CACHE(c, k, i);
+			size_t bucket = PTR_BUCKET_NR(c, k, i);
+			size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
+
+			if (KEY_SIZE(k) + r > c->sb.bucket_size ||
+			    bucket <  ca->sb.first_bucket ||
+			    bucket >= ca->sb.nbuckets)
+				return true;
+		}
+
+	return false;
+}
+
+/* Btree ptrs */
+
+bool __bch_btree_ptr_invalid(struct cache_set *c, const struct bkey *k)
+{
+	char buf[80];
+
+	if (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k))
+		goto bad;
+
+	if (__ptr_invalid(c, k))
+		goto bad;
+
+	return false;
+bad:
+	bch_bkey_to_text(buf, sizeof(buf), k);
+	cache_bug(c, "spotted btree ptr %s: %s", buf, bch_ptr_status(c, k));
+	return true;
+}
+
+static bool bch_btree_ptr_invalid(struct btree *b, const struct bkey *k)
+{
+	return __bch_btree_ptr_invalid(b->c, k);
+}
+
+static bool btree_ptr_bad_expensive(struct btree *b, const struct bkey *k)
+{
+	unsigned i;
+	char buf[80];
+	struct bucket *g;
+
+	if (mutex_trylock(&b->c->bucket_lock)) {
+		for (i = 0; i < KEY_PTRS(k); i++)
+			if (ptr_available(b->c, k, i)) {
+				g = PTR_BUCKET(b->c, k, i);
+
+				if (KEY_DIRTY(k) ||
+				    g->prio != BTREE_PRIO ||
+				    (b->c->gc_mark_valid &&
+				     GC_MARK(g) != GC_MARK_METADATA))
+					goto err;
+			}
+
+		mutex_unlock(&b->c->bucket_lock);
+	}
+
+	return false;
+err:
+	mutex_unlock(&b->c->bucket_lock);
+	bch_bkey_to_text(buf, sizeof(buf), k);
+	btree_bug(b,
+"inconsistent btree pointer %s: bucket %li pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
+		  buf, PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
+		  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
+	return true;
+}
+
+static bool bch_btree_ptr_bad(struct btree *b, const struct bkey *k)
+{
+	unsigned i;
+
+	if (!bkey_cmp(k, &ZERO_KEY) ||
+	    !KEY_PTRS(k) ||
+	    bch_ptr_invalid(b, k))
+		return true;
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		if (!ptr_available(b->c, k, i) ||
+		    ptr_stale(b->c, k, i))
+			return true;
+
+	if (expensive_debug_checks(b->c) &&
+	    btree_ptr_bad_expensive(b, k))
+		return true;
+
+	return false;
+}
+
+const struct btree_keys_ops bch_btree_keys_ops = {
+	.sort_cmp	= bch_key_sort_cmp,
+	.key_invalid	= bch_btree_ptr_invalid,
+	.key_bad	= bch_btree_ptr_bad,
+};
+
+/* Extents */
+
+/*
+ * Returns true if l > r - unless l == r, in which case returns true if l is
+ * older than r.
+ *
+ * Necessary for btree_sort_fixup() - if there are multiple keys that compare
+ * equal in different sets, we have to process them newest to oldest.
+ */
+static bool bch_extent_sort_cmp(struct btree_iter_set l,
+				struct btree_iter_set r)
+{
+	int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
+
+	return c ? c > 0 : l.k < r.k;
+}
+
+static struct bkey *bch_extent_sort_fixup(struct btree_iter *iter,
+					  struct bkey *tmp)
+{
+	while (iter->used > 1) {
+		struct btree_iter_set *top = iter->data, *i = top + 1;
+
+		if (iter->used > 2 &&
+		    bch_extent_sort_cmp(i[0], i[1]))
+			i++;
+
+		if (bkey_cmp(top->k, &START_KEY(i->k)) <= 0)
+			break;
+
+		if (!KEY_SIZE(i->k)) {
+			sort_key_next(iter, i);
+			heap_sift(iter, i - top, bch_extent_sort_cmp);
+			continue;
+		}
+
+		if (top->k > i->k) {
+			if (bkey_cmp(top->k, i->k) >= 0)
+				sort_key_next(iter, i);
+			else
+				bch_cut_front(top->k, i->k);
+
+			heap_sift(iter, i - top, bch_extent_sort_cmp);
+		} else {
+			/* can't happen because of comparison func */
+			BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));
+
+			if (bkey_cmp(i->k, top->k) < 0) {
+				bkey_copy(tmp, top->k);
+
+				bch_cut_back(&START_KEY(i->k), tmp);
+				bch_cut_front(i->k, top->k);
+				heap_sift(iter, 0, bch_extent_sort_cmp);
+
+				return tmp;
+			} else {
+				bch_cut_back(&START_KEY(i->k), top->k);
+			}
+		}
+	}
+
+	return NULL;
+}
+
+static bool bch_extent_invalid(struct btree *b, const struct bkey *k)
+{
+	char buf[80];
+
+	if (!KEY_SIZE(k))
+		return true;
+
+	if (KEY_SIZE(k) > KEY_OFFSET(k))
+		goto bad;
+
+	if (__ptr_invalid(b->c, k))
+		goto bad;
+
+	return false;
+bad:
+	bch_bkey_to_text(buf, sizeof(buf), k);
+	cache_bug(b->c, "spotted extent %s: %s", buf, bch_ptr_status(b->c, k));
+	return true;
+}
+
+static bool bch_extent_bad_expensive(struct btree *b, const struct bkey *k,
+				     unsigned ptr)
+{
+	struct bucket *g = PTR_BUCKET(b->c, k, ptr);
+	char buf[80];
+
+	if (mutex_trylock(&b->c->bucket_lock)) {
+		if (b->c->gc_mark_valid &&
+		    ((GC_MARK(g) != GC_MARK_DIRTY &&
+		      KEY_DIRTY(k)) ||
+		     GC_MARK(g) == GC_MARK_METADATA))
+			goto err;
+
+		if (g->prio == BTREE_PRIO)
+			goto err;
+
+		mutex_unlock(&b->c->bucket_lock);
+	}
+
+	return false;
+err:
+	mutex_unlock(&b->c->bucket_lock);
+	bch_bkey_to_text(buf, sizeof(buf), k);
+	btree_bug(b,
+"inconsistent extent pointer %s:\nbucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
+		  buf, PTR_BUCKET_NR(b->c, k, ptr), atomic_read(&g->pin),
+		  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
+	return true;
+}
+
+static bool bch_extent_bad(struct btree *b, const struct bkey *k)
+{
+	struct bucket *g;
+	unsigned i, stale;
+
+	if (!KEY_PTRS(k) ||
+	    bch_extent_invalid(b, k))
+		return true;
+
+	for (i = 0; i < KEY_PTRS(k); i++)
+		if (!ptr_available(b->c, k, i))
+			return true;
+
+	if (!expensive_debug_checks(b->c) && KEY_DIRTY(k))
+		return false;
+
+	for (i = 0; i < KEY_PTRS(k); i++) {
+		g = PTR_BUCKET(b->c, k, i);
+		stale = ptr_stale(b->c, k, i);
+
+		btree_bug_on(stale > 96, b,
+			     "key too stale: %i, need_gc %u",
+			     stale, b->c->need_gc);
+
+		btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
+			     b, "stale dirty pointer");
+
+		if (stale)
+			return true;
+
+		if (expensive_debug_checks(b->c) &&
+		    bch_extent_bad_expensive(b, k, i))
+			return true;
+	}
+
+	return false;
+}
+
+static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
+{
+	return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
+		~((uint64_t)1 << 63);
+}
+
+static bool bch_extent_merge(struct btree *b, struct bkey *l, struct bkey *r)
+{
+	unsigned i;
+
+	if (key_merging_disabled(b->c))
+		return false;
+
+	if (KEY_PTRS(l) != KEY_PTRS(r) ||
+	    KEY_DIRTY(l) != KEY_DIRTY(r) ||
+	    bkey_cmp(l, &START_KEY(r)))
+		return false;
+
+	for (i = 0; i < KEY_PTRS(l); i++)
+		if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
+		    PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
+			return false;
+
+	/* Keys with no pointers aren't restricted to one bucket and could
+	 * overflow KEY_SIZE
+	 */
+	if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
+		SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
+		SET_KEY_SIZE(l, USHRT_MAX);
+
+		bch_cut_front(l, r);
+		return false;
+	}
+
+	if (KEY_CSUM(l)) {
+		if (KEY_CSUM(r))
+			l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
+		else
+			SET_KEY_CSUM(l, 0);
+	}
+
+	SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
+	SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));
+
+	return true;
+}
+
+const struct btree_keys_ops bch_extent_keys_ops = {
+	.sort_cmp	= bch_extent_sort_cmp,
+	.sort_fixup	= bch_extent_sort_fixup,
+	.key_invalid	= bch_extent_invalid,
+	.key_bad	= bch_extent_bad,
+	.key_merge	= bch_extent_merge,
+	.is_extents	= true,
+};
diff --git a/drivers/md/bcache/extents.h b/drivers/md/bcache/extents.h
new file mode 100644
index 00000000000..e0c0b685d2f
--- /dev/null
+++ b/drivers/md/bcache/extents.h
@@ -0,0 +1,12 @@
+#ifndef _BCACHE_EXTENTS_H
+#define _BCACHE_EXTENTS_H
+
+extern const struct btree_keys_ops bch_btree_keys_ops;
+extern const struct btree_keys_ops bch_extent_keys_ops;
+
+struct bkey;
+struct cache_set;
+
+bool __bch_btree_ptr_invalid(struct cache_set *, const struct bkey *);
+
+#endif /* _BCACHE_EXTENTS_H */
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 12057a43e01..6d6a7a15043 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -9,6 +9,7 @@
 #include "bcache.h"
 #include "btree.h"
 #include "debug.h"
+#include "extents.h"
 #include "request.h"
 #include "writeback.h"
 
@@ -399,7 +400,7 @@ static char *uuid_read(struct cache_set *c, struct jset *j, struct closure *cl)
 {
 	struct bkey *k = &j->uuid_bucket;
 
-	if (bch_btree_ptr_invalid(c, k))
+	if (__bch_btree_ptr_invalid(c, k))
 		return "bad uuid pointer";
 
 	bkey_copy(&c->uuid_bucket, k);
@@ -1575,7 +1576,7 @@ static void run_cache_set(struct cache_set *c)
 		k = &j->btree_root;
 
 		err = "bad btree root";
-		if (bch_btree_ptr_invalid(c, k))
+		if (__bch_btree_ptr_invalid(c, k))
 			goto err;
 
 		err = "error reading btree root";