1 files changed, 125 insertions, 29 deletions

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index a16872541038..854743e85e76 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -638,24 +638,9 @@ void bch_data_insert(struct closure *cl)
 	bch_data_insert_start(cl);
 }
 
-/* Common code for the make_request functions */
+/* Cache lookup */
 
-static void request_endio(struct bio *bio, int error)
-{
-	struct closure *cl = bio->bi_private;
-
-	if (error) {
-		struct search *s = container_of(cl, struct search, cl);
-		s->error = error;
-		/* Only cache read errors are recoverable */
-		s->recoverable = false;
-	}
-
-	bio_put(bio);
-	closure_put(cl);
-}
-
-void bch_cache_read_endio(struct bio *bio, int error)
+static void bch_cache_read_endio(struct bio *bio, int error)
 {
 	struct bbio *b = container_of(bio, struct bbio, bio);
 	struct closure *cl = bio->bi_private;
@@ -678,6 +663,120 @@ void bch_cache_read_endio(struct bio *bio, int error)
 	bch_bbio_endio(s->op.c, bio, error, "reading from cache");
 }
 
+static int submit_partial_cache_miss(struct btree *b, struct search *s,
+				     struct bkey *k)
+{
+	struct bio *bio = &s->bio.bio;
+	int ret = MAP_CONTINUE;
+
+	do {
+		unsigned sectors = INT_MAX;
+
+		if (KEY_INODE(k) == s->op.inode) {
+			if (KEY_START(k) <= bio->bi_sector)
+				break;
+
+			sectors = min_t(uint64_t, sectors,
+					KEY_START(k) - bio->bi_sector);
+		}
+
+		ret = s->d->cache_miss(b, s, bio, sectors);
+	} while (ret == MAP_CONTINUE);
+
+	return ret;
+}
+
+/*
+ * Read from a single key, handling the initial cache miss if the key starts in
+ * the middle of the bio
+ */
+static int submit_partial_cache_hit(struct btree_op *op, struct btree *b,
+				    struct bkey *k)
+{
+	struct search *s = container_of(op, struct search, op);
+	struct bio *bio = &s->bio.bio;
+	unsigned ptr;
+	struct bio *n;
+
+	int ret = submit_partial_cache_miss(b, s, k);
+	if (ret != MAP_CONTINUE || !KEY_SIZE(k))
+		return ret;
+
+	/* XXX: figure out best pointer - for multiple cache devices */
+	ptr = 0;
+
+	PTR_BUCKET(b->c, k, ptr)->prio = INITIAL_PRIO;
+
+	while (ret == MAP_CONTINUE &&
+	       KEY_INODE(k) == op->inode &&
+	       bio->bi_sector < KEY_OFFSET(k)) {
+		struct bkey *bio_key;
+		sector_t sector = PTR_OFFSET(k, ptr) +
+			(bio->bi_sector - KEY_START(k));
+		unsigned sectors = min_t(uint64_t, INT_MAX,
+					 KEY_OFFSET(k) - bio->bi_sector);
+
+		n = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
+		if (n == bio)
+			ret = MAP_DONE;
+
+		bio_key = &container_of(n, struct bbio, bio)->key;
+
+		/*
+		 * The bucket we're reading from might be reused while our bio
+		 * is in flight, and we could then end up reading the wrong
+		 * data.
+		 *
+		 * We guard against this by checking (in cache_read_endio()) if
+		 * the pointer is stale again; if so, we treat it as an error
+		 * and reread from the backing device (but we don't pass that
+		 * error up anywhere).
+		 */
+
+		bch_bkey_copy_single_ptr(bio_key, k, ptr);
+		SET_PTR_OFFSET(bio_key, 0, sector);
+
+		n->bi_end_io	= bch_cache_read_endio;
+		n->bi_private	= &s->cl;
+
+		__bch_submit_bbio(n, b->c);
+	}
+
+	return ret;
+}
+
+static void cache_lookup(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 = &s->bio.bio;
+
+	int ret = bch_btree_map_keys(op, op->c,
+				     &KEY(op->inode, bio->bi_sector, 0),
+				     submit_partial_cache_hit, 1);
+	if (ret == -EAGAIN)
+		continue_at(cl, cache_lookup, bcache_wq);
+
+	closure_return(cl);
+}
+
+/* Common code for the make_request functions */
+
+static void request_endio(struct bio *bio, int error)
+{
+	struct closure *cl = bio->bi_private;
+
+	if (error) {
+		struct search *s = container_of(cl, struct search, cl);
+		s->error = error;
+		/* Only cache read errors are recoverable */
+		s->recoverable = false;
+	}
+
+	bio_put(bio);
+	closure_put(cl);
+}
+
 static void bio_complete(struct search *s)
 {
 	if (s->orig_bio) {
@@ -1005,15 +1104,14 @@ static void cached_dev_read_done_bh(struct closure *cl)
 static int cached_dev_cache_miss(struct btree *b, struct search *s,
 				 struct bio *bio, unsigned sectors)
 {
-	int ret = 0;
+	int ret = MAP_CONTINUE;
 	unsigned reada = 0;
 	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
 	struct bio *miss, *cache_bio;
 
 	if (s->cache_miss || s->op.bypass) {
 		miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
-		if (miss == bio)
-			s->op.lookup_done = true;
+		ret = miss == bio ? MAP_DONE : MAP_CONTINUE;
 		goto out_submit;
 	}
 
@@ -1033,11 +1131,9 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s,
 		return ret;
 
 	miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
-	if (miss == bio)
-		s->op.lookup_done = true;
-	else
-		/* btree_search_recurse()'s btree iterator is no good anymore */
-		ret = -EINTR;
+
+	/* btree_search_recurse()'s btree iterator is no good anymore */
+	ret = miss == bio ? MAP_DONE : -EINTR;
 
 	cache_bio = bio_alloc_bioset(GFP_NOWAIT,
 			DIV_ROUND_UP(s->cache_bio_sectors, PAGE_SECTORS),
@@ -1075,7 +1171,7 @@ static void cached_dev_read(struct cached_dev *dc, struct search *s)
 {
 	struct closure *cl = &s->cl;
 
-	closure_call(&s->op.cl, bch_btree_search_async, NULL, cl);
+	closure_call(&s->op.cl, cache_lookup, NULL, cl);
 	continue_at(cl, cached_dev_read_done_bh, NULL);
 }
 
@@ -1287,9 +1383,9 @@ static int flash_dev_cache_miss(struct btree *b, struct search *s,
 	bio_advance(bio, min(sectors << 9, bio->bi_size));
 
 	if (!bio->bi_size)
-		s->op.lookup_done = true;
+		return MAP_DONE;
 
-	return 0;
+	return MAP_CONTINUE;
 }
 
 static void flash_dev_nodata(struct closure *cl)
@@ -1339,7 +1435,7 @@ static void flash_dev_make_request(struct request_queue *q, struct bio *bio)
 
 		closure_call(&s->op.cl, bch_data_insert, NULL, cl);
 	} else {
-		closure_call(&s->op.cl, bch_btree_search_async, NULL, cl);
+		closure_call(&s->op.cl, cache_lookup, NULL, cl);
 	}
 
 	continue_at(cl, search_free, NULL);