Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1346 insertions, 0 deletions

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
new file mode 100644
index 000000000..97895262f
--- /dev/null
+++ b/drivers/md/bcache/request.c
@@ -0,0 +1,1346 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Main bcache entry point - handle a read or a write request and decide what to
+ * do with it; the make_request functions are called by the block layer.
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+#include "writeback.h"
+
+#include <linux/module.h>
+#include <linux/hash.h>
+#include <linux/random.h>
+#include <linux/backing-dev.h>
+
+#include <trace/events/bcache.h>
+
+#define CUTOFF_CACHE_ADD	95
+#define CUTOFF_CACHE_READA	90
+
+struct kmem_cache *bch_search_cache;
+
+static void bch_data_insert_start(struct closure *cl);
+
+static unsigned int cache_mode(struct cached_dev *dc)
+{
+	return BDEV_CACHE_MODE(&dc->sb);
+}
+
+static bool verify(struct cached_dev *dc)
+{
+	return dc->verify;
+}
+
+static void bio_csum(struct bio *bio, struct bkey *k)
+{
+	struct bio_vec bv;
+	struct bvec_iter iter;
+	uint64_t csum = 0;
+
+	bio_for_each_segment(bv, bio, iter) {
+		void *d = kmap(bv.bv_page) + bv.bv_offset;
+
+		csum = bch_crc64_update(csum, d, bv.bv_len);
+		kunmap(bv.bv_page);
+	}
+
+	k->ptr[KEY_PTRS(k)] = csum & (~0ULL >> 1);
+}
+
+/* Insert data into cache */
+
+static void bch_data_insert_keys(struct closure *cl)
+{
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+	atomic_t *journal_ref = NULL;
+	struct bkey *replace_key = op->replace ? &op->replace_key : NULL;
+	int ret;
+
+	if (!op->replace)
+		journal_ref = bch_journal(op->c, &op->insert_keys,
+					  op->flush_journal ? cl : NULL);
+
+	ret = bch_btree_insert(op->c, &op->insert_keys,
+			       journal_ref, replace_key);
+	if (ret == -ESRCH) {
+		op->replace_collision = true;
+	} else if (ret) {
+		op->status		= BLK_STS_RESOURCE;
+		op->insert_data_done	= true;
+	}
+
+	if (journal_ref)
+		atomic_dec_bug(journal_ref);
+
+	if (!op->insert_data_done) {
+		continue_at(cl, bch_data_insert_start, op->wq);
+		return;
+	}
+
+	bch_keylist_free(&op->insert_keys);
+	closure_return(cl);
+}
+
+static int bch_keylist_realloc(struct keylist *l, unsigned int u64s,
+			       struct cache_set *c)
+{
+	size_t oldsize = bch_keylist_nkeys(l);
+	size_t newsize = oldsize + u64s;
+
+	/*
+	 * The journalling code doesn't handle the case where the keys to insert
+	 * is bigger than an empty write: If we just return -ENOMEM here,
+	 * bch_data_insert_keys() will insert the keys created so far
+	 * and finish the rest when the keylist is empty.
+	 */
+	if (newsize * sizeof(uint64_t) > block_bytes(c->cache) - sizeof(struct jset))
+		return -ENOMEM;
+
+	return __bch_keylist_realloc(l, u64s);
+}
+
+static void bch_data_invalidate(struct closure *cl)
+{
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+	struct bio *bio = op->bio;
+
+	pr_debug("invalidating %i sectors from %llu\n",
+		 bio_sectors(bio), (uint64_t) bio->bi_iter.bi_sector);
+
+	while (bio_sectors(bio)) {
+		unsigned int sectors = min(bio_sectors(bio),
+				       1U << (KEY_SIZE_BITS - 1));
+
+		if (bch_keylist_realloc(&op->insert_keys, 2, op->c))
+			goto out;
+
+		bio->bi_iter.bi_sector	+= sectors;
+		bio->bi_iter.bi_size	-= sectors << 9;
+
+		bch_keylist_add(&op->insert_keys,
+				&KEY(op->inode,
+				     bio->bi_iter.bi_sector,
+				     sectors));
+	}
+
+	op->insert_data_done = true;
+	/* get in bch_data_insert() */
+	bio_put(bio);
+out:
+	continue_at(cl, bch_data_insert_keys, op->wq);
+}
+
+static void bch_data_insert_error(struct closure *cl)
+{
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+
+	/*
+	 * Our data write just errored, which means we've got a bunch of keys to
+	 * insert that point to data that wasn't successfully written.
+	 *
+	 * We don't have to insert those keys but we still have to invalidate
+	 * that region of the cache - so, if we just strip off all the pointers
+	 * from the keys we'll accomplish just that.
+	 */
+
+	struct bkey *src = op->insert_keys.keys, *dst = op->insert_keys.keys;
+
+	while (src != op->insert_keys.top) {
+		struct bkey *n = bkey_next(src);
+
+		SET_KEY_PTRS(src, 0);
+		memmove(dst, src, bkey_bytes(src));
+
+		dst = bkey_next(dst);
+		src = n;
+	}
+
+	op->insert_keys.top = dst;
+
+	bch_data_insert_keys(cl);
+}
+
+static void bch_data_insert_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+
+	if (bio->bi_status) {
+		/* TODO: We could try to recover from this. */
+		if (op->writeback)
+			op->status = bio->bi_status;
+		else if (!op->replace)
+			set_closure_fn(cl, bch_data_insert_error, op->wq);
+		else
+			set_closure_fn(cl, NULL, NULL);
+	}
+
+	bch_bbio_endio(op->c, bio, bio->bi_status, "writing data to cache");
+}
+
+static void bch_data_insert_start(struct closure *cl)
+{
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+	struct bio *bio = op->bio, *n;
+
+	if (op->bypass)
+		return bch_data_invalidate(cl);
+
+	if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0)
+		wake_up_gc(op->c);
+
+	/*
+	 * Journal writes are marked REQ_PREFLUSH; if the original write was a
+	 * flush, it'll wait on the journal write.
+	 */
+	bio->bi_opf &= ~(REQ_PREFLUSH|REQ_FUA);
+
+	do {
+		unsigned int i;
+		struct bkey *k;
+		struct bio_set *split = &op->c->bio_split;
+
+		/* 1 for the device pointer and 1 for the chksum */
+		if (bch_keylist_realloc(&op->insert_keys,
+					3 + (op->csum ? 1 : 0),
+					op->c)) {
+			continue_at(cl, bch_data_insert_keys, op->wq);
+			return;
+		}
+
+		k = op->insert_keys.top;
+		bkey_init(k);
+		SET_KEY_INODE(k, op->inode);
+		SET_KEY_OFFSET(k, bio->bi_iter.bi_sector);
+
+		if (!bch_alloc_sectors(op->c, k, bio_sectors(bio),
+				       op->write_point, op->write_prio,
+				       op->writeback))
+			goto err;
+
+		n = bio_next_split(bio, KEY_SIZE(k), GFP_NOIO, split);
+
+		n->bi_end_io	= bch_data_insert_endio;
+		n->bi_private	= cl;
+
+		if (op->writeback) {
+			SET_KEY_DIRTY(k, true);
+
+			for (i = 0; i < KEY_PTRS(k); i++)
+				SET_GC_MARK(PTR_BUCKET(op->c, k, i),
+					    GC_MARK_DIRTY);
+		}
+
+		SET_KEY_CSUM(k, op->csum);
+		if (KEY_CSUM(k))
+			bio_csum(n, k);
+
+		trace_bcache_cache_insert(k);
+		bch_keylist_push(&op->insert_keys);
+
+		bio_set_op_attrs(n, REQ_OP_WRITE, 0);
+		bch_submit_bbio(n, op->c, k, 0);
+	} while (n != bio);
+
+	op->insert_data_done = true;
+	continue_at(cl, bch_data_insert_keys, op->wq);
+	return;
+err:
+	/* bch_alloc_sectors() blocks if s->writeback = true */
+	BUG_ON(op->writeback);
+
+	/*
+	 * But if it's not a writeback write we'd rather just bail out if
+	 * there aren't any buckets ready to write to - it might take awhile and
+	 * we might be starving btree writes for gc or something.
+	 */
+
+	if (!op->replace) {
+		/*
+		 * Writethrough write: We can't complete the write until we've
+		 * updated the index. But we don't want to delay the write while
+		 * we wait for buckets to be freed up, so just invalidate the
+		 * rest of the write.
+		 */
+		op->bypass = true;
+		return bch_data_invalidate(cl);
+	} else {
+		/*
+		 * From a cache miss, we can just insert the keys for the data
+		 * we have written or bail out if we didn't do anything.
+		 */
+		op->insert_data_done = true;
+		bio_put(bio);
+
+		if (!bch_keylist_empty(&op->insert_keys))
+			continue_at(cl, bch_data_insert_keys, op->wq);
+		else
+			closure_return(cl);
+	}
+}
+
+/**
+ * bch_data_insert - stick some data in the cache
+ * @cl: closure pointer.
+ *
+ * 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
+ * volume - it's also used by the moving garbage collector to compact data in
+ * mostly empty buckets.
+ *
+ * It first writes the data to the cache, creating a list of keys to be inserted
+ * (if the data had to be fragmented there will be multiple keys); after the
+ * data is written it calls bch_journal, and after the keys have been added to
+ * the next journal write they're inserted into the btree.
+ *
+ * It inserts the data in op->bio; bi_sector is used for the key offset,
+ * and op->inode is used for the key inode.
+ *
+ * If op->bypass is true, instead of inserting the data it invalidates the
+ * region of the cache represented by op->bio and op->inode.
+ */
+void bch_data_insert(struct closure *cl)
+{
+	struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
+
+	trace_bcache_write(op->c, op->inode, op->bio,
+			   op->writeback, op->bypass);
+
+	bch_keylist_init(&op->insert_keys);
+	bio_get(op->bio);
+	bch_data_insert_start(cl);
+}
+
+/*
+ * Congested?  Return 0 (not congested) or the limit (in sectors)
+ * beyond which we should bypass the cache due to congestion.
+ */
+unsigned int bch_get_congested(const struct cache_set *c)
+{
+	int i;
+
+	if (!c->congested_read_threshold_us &&
+	    !c->congested_write_threshold_us)
+		return 0;
+
+	i = (local_clock_us() - c->congested_last_us) / 1024;
+	if (i < 0)
+		return 0;
+
+	i += atomic_read(&c->congested);
+	if (i >= 0)
+		return 0;
+
+	i += CONGESTED_MAX;
+
+	if (i > 0)
+		i = fract_exp_two(i, 6);
+
+	i -= hweight32(get_random_u32());
+
+	return i > 0 ? i : 1;
+}
+
+static void add_sequential(struct task_struct *t)
+{
+	ewma_add(t->sequential_io_avg,
+		 t->sequential_io, 8, 0);
+
+	t->sequential_io = 0;
+}
+
+static struct hlist_head *iohash(struct cached_dev *dc, uint64_t k)
+{
+	return &dc->io_hash[hash_64(k, RECENT_IO_BITS)];
+}
+
+static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
+{
+	struct cache_set *c = dc->disk.c;
+	unsigned int mode = cache_mode(dc);
+	unsigned int sectors, congested;
+	struct task_struct *task = current;
+	struct io *i;
+
+	if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
+	    c->gc_stats.in_use > CUTOFF_CACHE_ADD ||
+	    (bio_op(bio) == REQ_OP_DISCARD))
+		goto skip;
+
+	if (mode == CACHE_MODE_NONE ||
+	    (mode == CACHE_MODE_WRITEAROUND &&
+	     op_is_write(bio_op(bio))))
+		goto skip;
+
+	/*
+	 * If the bio is for read-ahead or background IO, bypass it or
+	 * not depends on the following situations,
+	 * - If the IO is for meta data, always cache it and no bypass
+	 * - If the IO is not meta data, check dc->cache_reada_policy,
+	 *      BCH_CACHE_READA_ALL: cache it and not bypass
+	 *      BCH_CACHE_READA_META_ONLY: not cache it and bypass
+	 * That is, read-ahead request for metadata always get cached
+	 * (eg, for gfs2 or xfs).
+	 */
+	if ((bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND))) {
+		if (!(bio->bi_opf & (REQ_META|REQ_PRIO)) &&
+		    (dc->cache_readahead_policy != BCH_CACHE_READA_ALL))
+			goto skip;
+	}
+
+	if (bio->bi_iter.bi_sector & (c->cache->sb.block_size - 1) ||
+	    bio_sectors(bio) & (c->cache->sb.block_size - 1)) {
+		pr_debug("skipping unaligned io\n");
+		goto skip;
+	}
+
+	if (bypass_torture_test(dc)) {
+		if ((get_random_int() & 3) == 3)
+			goto skip;
+		else
+			goto rescale;
+	}
+
+	congested = bch_get_congested(c);
+	if (!congested && !dc->sequential_cutoff)
+		goto rescale;
+
+	spin_lock(&dc->io_lock);
+
+	hlist_for_each_entry(i, iohash(dc, bio->bi_iter.bi_sector), hash)
+		if (i->last == bio->bi_iter.bi_sector &&
+		    time_before(jiffies, i->jiffies))
+			goto found;
+
+	i = list_first_entry(&dc->io_lru, struct io, lru);
+
+	add_sequential(task);
+	i->sequential = 0;
+found:
+	if (i->sequential + bio->bi_iter.bi_size > i->sequential)
+		i->sequential	+= bio->bi_iter.bi_size;
+
+	i->last			 = bio_end_sector(bio);
+	i->jiffies		 = jiffies + msecs_to_jiffies(5000);
+	task->sequential_io	 = i->sequential;
+
+	hlist_del(&i->hash);
+	hlist_add_head(&i->hash, iohash(dc, i->last));
+	list_move_tail(&i->lru, &dc->io_lru);
+
+	spin_unlock(&dc->io_lock);
+
+	sectors = max(task->sequential_io,
+		      task->sequential_io_avg) >> 9;
+
+	if (dc->sequential_cutoff &&
+	    sectors >= dc->sequential_cutoff >> 9) {
+		trace_bcache_bypass_sequential(bio);
+		goto skip;
+	}
+
+	if (congested && sectors >= congested) {
+		trace_bcache_bypass_congested(bio);
+		goto skip;
+	}
+
+rescale:
+	bch_rescale_priorities(c, bio_sectors(bio));
+	return false;
+skip:
+	bch_mark_sectors_bypassed(c, dc, bio_sectors(bio));
+	return true;
+}
+
+/* Cache lookup */
+
+struct search {
+	/* Stack frame for bio_complete */
+	struct closure		cl;
+
+	struct bbio		bio;
+	struct bio		*orig_bio;
+	struct bio		*cache_miss;
+	struct bcache_device	*d;
+
+	unsigned int		insert_bio_sectors;
+	unsigned int		recoverable:1;
+	unsigned int		write:1;
+	unsigned int		read_dirty_data:1;
+	unsigned int		cache_missed:1;
+
+	struct hd_struct	*part;
+	unsigned long		start_time;
+
+	struct btree_op		op;
+	struct data_insert_op	iop;
+};
+
+static void bch_cache_read_endio(struct bio *bio)
+{
+	struct bbio *b = container_of(bio, struct bbio, bio);
+	struct closure *cl = bio->bi_private;
+	struct search *s = container_of(cl, struct search, cl);
+
+	/*
+	 * If the bucket was reused while our bio was in flight, we might have
+	 * read the wrong data. Set s->error but not error so it doesn't get
+	 * counted against the cache device, but we'll still reread the data
+	 * from the backing device.
+	 */
+
+	if (bio->bi_status)
+		s->iop.status = bio->bi_status;
+	else if (!KEY_DIRTY(&b->key) &&
+		 ptr_stale(s->iop.c, &b->key, 0)) {
+		atomic_long_inc(&s->iop.c->cache_read_races);
+		s->iop.status = BLK_STS_IOERR;
+	}
+
+	bch_bbio_endio(s->iop.c, bio, bio->bi_status, "reading from cache");
+}
+
+/*
+ * Read from a single key, handling the initial cache miss if the key starts in
+ * the middle of the bio
+ */
+static int cache_lookup_fn(struct btree_op *op, struct btree *b, struct bkey *k)
+{
+	struct search *s = container_of(op, struct search, op);
+	struct bio *n, *bio = &s->bio.bio;
+	struct bkey *bio_key;
+	unsigned int ptr;
+
+	if (bkey_cmp(k, &KEY(s->iop.inode, bio->bi_iter.bi_sector, 0)) <= 0)
+		return MAP_CONTINUE;
+
+	if (KEY_INODE(k) != s->iop.inode ||
+	    KEY_START(k) > bio->bi_iter.bi_sector) {
+		unsigned int bio_sectors = bio_sectors(bio);
+		unsigned int sectors = KEY_INODE(k) == s->iop.inode
+			? min_t(uint64_t, INT_MAX,
+				KEY_START(k) - bio->bi_iter.bi_sector)
+			: INT_MAX;
+		int ret = s->d->cache_miss(b, s, bio, sectors);
+
+		if (ret != MAP_CONTINUE)
+			return ret;
+
+		/* if this was a complete miss we shouldn't get here */
+		BUG_ON(bio_sectors <= sectors);
+	}
+
+	if (!KEY_SIZE(k))
+		return MAP_CONTINUE;
+
+	/* XXX: figure out best pointer - for multiple cache devices */
+	ptr = 0;
+
+	PTR_BUCKET(b->c, k, ptr)->prio = INITIAL_PRIO;
+
+	if (KEY_DIRTY(k))
+		s->read_dirty_data = true;
+
+	n = bio_next_split(bio, min_t(uint64_t, INT_MAX,
+				      KEY_OFFSET(k) - bio->bi_iter.bi_sector),
+			   GFP_NOIO, &s->d->bio_split);
+
+	bio_key = &container_of(n, struct bbio, bio)->key;
+	bch_bkey_copy_single_ptr(bio_key, k, ptr);
+
+	bch_cut_front(&KEY(s->iop.inode, n->bi_iter.bi_sector, 0), bio_key);
+	bch_cut_back(&KEY(s->iop.inode, bio_end_sector(n), 0), bio_key);
+
+	n->bi_end_io	= bch_cache_read_endio;
+	n->bi_private	= &s->cl;
+
+	/*
+	 * 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_submit_bbio(n, b->c);
+	return n == bio ? MAP_DONE : MAP_CONTINUE;
+}
+
+static void cache_lookup(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, iop.cl);
+	struct bio *bio = &s->bio.bio;
+	struct cached_dev *dc;
+	int ret;
+
+	bch_btree_op_init(&s->op, -1);
+
+	ret = bch_btree_map_keys(&s->op, s->iop.c,
+				 &KEY(s->iop.inode, bio->bi_iter.bi_sector, 0),
+				 cache_lookup_fn, MAP_END_KEY);
+	if (ret == -EAGAIN) {
+		continue_at(cl, cache_lookup, bcache_wq);
+		return;
+	}
+
+	/*
+	 * We might meet err when searching the btree, If that happens, we will
+	 * get negative ret, in this scenario we should not recover data from
+	 * backing device (when cache device is dirty) because we don't know
+	 * whether bkeys the read request covered are all clean.
+	 *
+	 * And after that happened, s->iop.status is still its initial value
+	 * before we submit s->bio.bio
+	 */
+	if (ret < 0) {
+		BUG_ON(ret == -EINTR);
+		if (s->d && s->d->c &&
+				!UUID_FLASH_ONLY(&s->d->c->uuids[s->d->id])) {
+			dc = container_of(s->d, struct cached_dev, disk);
+			if (dc && atomic_read(&dc->has_dirty))
+				s->recoverable = false;
+		}
+		if (!s->iop.status)
+			s->iop.status = BLK_STS_IOERR;
+	}
+
+	closure_return(cl);
+}
+
+/* Common code for the make_request functions */
+
+static void request_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+
+	if (bio->bi_status) {
+		struct search *s = container_of(cl, struct search, cl);
+
+		s->iop.status = bio->bi_status;
+		/* Only cache read errors are recoverable */
+		s->recoverable = false;
+	}
+
+	bio_put(bio);
+	closure_put(cl);
+}
+
+static void backing_request_endio(struct bio *bio)
+{
+	struct closure *cl = bio->bi_private;
+
+	if (bio->bi_status) {
+		struct search *s = container_of(cl, struct search, cl);
+		struct cached_dev *dc = container_of(s->d,
+						     struct cached_dev, disk);
+		/*
+		 * If a bio has REQ_PREFLUSH for writeback mode, it is
+		 * speically assembled in cached_dev_write() for a non-zero
+		 * write request which has REQ_PREFLUSH. we don't set
+		 * s->iop.status by this failure, the status will be decided
+		 * by result of bch_data_insert() operation.
+		 */
+		if (unlikely(s->iop.writeback &&
+			     bio->bi_opf & REQ_PREFLUSH)) {
+			pr_err("Can't flush %s: returned bi_status %i\n",
+				dc->backing_dev_name, bio->bi_status);
+		} else {
+			/* set to orig_bio->bi_status in bio_complete() */
+			s->iop.status = bio->bi_status;
+		}
+		s->recoverable = false;
+		/* should count I/O error for backing device here */
+		bch_count_backing_io_errors(dc, bio);
+	}
+
+	bio_put(bio);
+	closure_put(cl);
+}
+
+static void bio_complete(struct search *s)
+{
+	if (s->orig_bio) {
+		/* Count on bcache device */
+		part_end_io_acct(s->part, s->orig_bio, s->start_time);
+
+		trace_bcache_request_end(s->d, s->orig_bio);
+		s->orig_bio->bi_status = s->iop.status;
+		bio_endio(s->orig_bio);
+		s->orig_bio = NULL;
+	}
+}
+
+static void do_bio_hook(struct search *s,
+			struct bio *orig_bio,
+			bio_end_io_t *end_io_fn)
+{
+	struct bio *bio = &s->bio.bio;
+
+	bio_init(bio, NULL, 0);
+	__bio_clone_fast(bio, orig_bio);
+	/*
+	 * bi_end_io can be set separately somewhere else, e.g. the
+	 * variants in,
+	 * - cache_bio->bi_end_io from cached_dev_cache_miss()
+	 * - n->bi_end_io from cache_lookup_fn()
+	 */
+	bio->bi_end_io		= end_io_fn;
+	bio->bi_private		= &s->cl;
+
+	bio_cnt_set(bio, 3);
+}
+
+static void search_free(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+
+	atomic_dec(&s->iop.c->search_inflight);
+
+	if (s->iop.bio)
+		bio_put(s->iop.bio);
+
+	bio_complete(s);
+	closure_debug_destroy(cl);
+	mempool_free(s, &s->iop.c->search);
+}
+
+static inline struct search *search_alloc(struct bio *bio,
+					  struct bcache_device *d)
+{
+	struct search *s;
+
+	s = mempool_alloc(&d->c->search, GFP_NOIO);
+
+	closure_init(&s->cl, NULL);
+	do_bio_hook(s, bio, request_endio);
+	atomic_inc(&d->c->search_inflight);
+
+	s->orig_bio		= bio;
+	s->cache_miss		= NULL;
+	s->cache_missed		= 0;
+	s->d			= d;
+	s->recoverable		= 1;
+	s->write		= op_is_write(bio_op(bio));
+	s->read_dirty_data	= 0;
+	/* Count on the bcache device */
+	s->start_time		= part_start_io_acct(d->disk, &s->part, bio);
+	s->iop.c		= d->c;
+	s->iop.bio		= NULL;
+	s->iop.inode		= d->id;
+	s->iop.write_point	= hash_long((unsigned long) current, 16);
+	s->iop.write_prio	= 0;
+	s->iop.status		= 0;
+	s->iop.flags		= 0;
+	s->iop.flush_journal	= op_is_flush(bio->bi_opf);
+	s->iop.wq		= bcache_wq;
+
+	return s;
+}
+
+/* Cached devices */
+
+static void cached_dev_bio_complete(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+	cached_dev_put(dc);
+	search_free(cl);
+}
+
+/* Process reads */
+
+static void cached_dev_read_error_done(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+
+	if (s->iop.replace_collision)
+		bch_mark_cache_miss_collision(s->iop.c, s->d);
+
+	if (s->iop.bio)
+		bio_free_pages(s->iop.bio);
+
+	cached_dev_bio_complete(cl);
+}
+
+static void cached_dev_read_error(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct bio *bio = &s->bio.bio;
+
+	/*
+	 * If read request hit dirty data (s->read_dirty_data is true),
+	 * then recovery a failed read request from cached device may
+	 * get a stale data back. So read failure recovery is only
+	 * permitted when read request hit clean data in cache device,
+	 * or when cache read race happened.
+	 */
+	if (s->recoverable && !s->read_dirty_data) {
+		/* Retry from the backing device: */
+		trace_bcache_read_retry(s->orig_bio);
+
+		s->iop.status = 0;
+		do_bio_hook(s, s->orig_bio, backing_request_endio);
+
+		/* XXX: invalidate cache */
+
+		/* I/O request sent to backing device */
+		closure_bio_submit(s->iop.c, bio, cl);
+	}
+
+	continue_at(cl, cached_dev_read_error_done, NULL);
+}
+
+static void cached_dev_cache_miss_done(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct bcache_device *d = s->d;
+
+	if (s->iop.replace_collision)
+		bch_mark_cache_miss_collision(s->iop.c, s->d);
+
+	if (s->iop.bio)
+		bio_free_pages(s->iop.bio);
+
+	cached_dev_bio_complete(cl);
+	closure_put(&d->cl);
+}
+
+static void cached_dev_read_done(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+	/*
+	 * We had a cache miss; cache_bio now contains data ready to be inserted
+	 * into the cache.
+	 *
+	 * First, we copy the data we just read from cache_bio's bounce buffers
+	 * to the buffers the original bio pointed to:
+	 */
+
+	if (s->iop.bio) {
+		bio_reset(s->iop.bio);
+		s->iop.bio->bi_iter.bi_sector =
+			s->cache_miss->bi_iter.bi_sector;
+		bio_copy_dev(s->iop.bio, s->cache_miss);
+		s->iop.bio->bi_iter.bi_size = s->insert_bio_sectors << 9;
+		bch_bio_map(s->iop.bio, NULL);
+
+		bio_copy_data(s->cache_miss, s->iop.bio);
+
+		bio_put(s->cache_miss);
+		s->cache_miss = NULL;
+	}
+
+	if (verify(dc) && s->recoverable && !s->read_dirty_data)
+		bch_data_verify(dc, s->orig_bio);
+
+	closure_get(&dc->disk.cl);
+	bio_complete(s);
+
+	if (s->iop.bio &&
+	    !test_bit(CACHE_SET_STOPPING, &s->iop.c->flags)) {
+		BUG_ON(!s->iop.replace);
+		closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
+	}
+
+	continue_at(cl, cached_dev_cache_miss_done, NULL);
+}
+
+static void cached_dev_read_done_bh(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+	bch_mark_cache_accounting(s->iop.c, s->d,
+				  !s->cache_missed, s->iop.bypass);
+	trace_bcache_read(s->orig_bio, !s->cache_missed, s->iop.bypass);
+
+	if (s->iop.status)
+		continue_at_nobarrier(cl, cached_dev_read_error, bcache_wq);
+	else if (s->iop.bio || verify(dc))
+		continue_at_nobarrier(cl, cached_dev_read_done, bcache_wq);
+	else
+		continue_at_nobarrier(cl, cached_dev_bio_complete, NULL);
+}
+
+static int cached_dev_cache_miss(struct btree *b, struct search *s,
+				 struct bio *bio, unsigned int sectors)
+{
+	int ret = MAP_CONTINUE;
+	unsigned int reada = 0;
+	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+	struct bio *miss, *cache_bio;
+
+	s->cache_missed = 1;
+
+	if (s->cache_miss || s->iop.bypass) {
+		miss = bio_next_split(bio, sectors, GFP_NOIO, &s->d->bio_split);
+		ret = miss == bio ? MAP_DONE : MAP_CONTINUE;
+		goto out_submit;
+	}
+
+	if (!(bio->bi_opf & REQ_RAHEAD) &&
+	    !(bio->bi_opf & (REQ_META|REQ_PRIO)) &&
+	    s->iop.c->gc_stats.in_use < CUTOFF_CACHE_READA)
+		reada = min_t(sector_t, dc->readahead >> 9,
+			      get_capacity(bio->bi_disk) - bio_end_sector(bio));
+
+	s->insert_bio_sectors = min(sectors, bio_sectors(bio) + reada);
+
+	s->iop.replace_key = KEY(s->iop.inode,
+				 bio->bi_iter.bi_sector + s->insert_bio_sectors,
+				 s->insert_bio_sectors);
+
+	ret = bch_btree_insert_check_key(b, &s->op, &s->iop.replace_key);
+	if (ret)
+		return ret;
+
+	s->iop.replace = true;
+
+	miss = bio_next_split(bio, sectors, GFP_NOIO, &s->d->bio_split);
+
+	/* 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->insert_bio_sectors, PAGE_SECTORS),
+			&dc->disk.bio_split);
+	if (!cache_bio)
+		goto out_submit;
+
+	cache_bio->bi_iter.bi_sector	= miss->bi_iter.bi_sector;
+	bio_copy_dev(cache_bio, miss);
+	cache_bio->bi_iter.bi_size	= s->insert_bio_sectors << 9;
+
+	cache_bio->bi_end_io	= backing_request_endio;
+	cache_bio->bi_private	= &s->cl;
+
+	bch_bio_map(cache_bio, NULL);
+	if (bch_bio_alloc_pages(cache_bio, __GFP_NOWARN|GFP_NOIO))
+		goto out_put;
+
+	if (reada)
+		bch_mark_cache_readahead(s->iop.c, s->d);
+
+	s->cache_miss	= miss;
+	s->iop.bio	= cache_bio;
+	bio_get(cache_bio);
+	/* I/O request sent to backing device */
+	closure_bio_submit(s->iop.c, cache_bio, &s->cl);
+
+	return ret;
+out_put:
+	bio_put(cache_bio);
+out_submit:
+	miss->bi_end_io		= backing_request_endio;
+	miss->bi_private	= &s->cl;
+	/* I/O request sent to backing device */
+	closure_bio_submit(s->iop.c, miss, &s->cl);
+	return ret;
+}
+
+static void cached_dev_read(struct cached_dev *dc, struct search *s)
+{
+	struct closure *cl = &s->cl;
+
+	closure_call(&s->iop.cl, cache_lookup, NULL, cl);
+	continue_at(cl, cached_dev_read_done_bh, NULL);
+}
+
+/* Process writes */
+
+static void cached_dev_write_complete(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+	up_read_non_owner(&dc->writeback_lock);
+	cached_dev_bio_complete(cl);
+}
+
+static void cached_dev_write(struct cached_dev *dc, struct search *s)
+{
+	struct closure *cl = &s->cl;
+	struct bio *bio = &s->bio.bio;
+	struct bkey start = KEY(dc->disk.id, bio->bi_iter.bi_sector, 0);
+	struct bkey end = KEY(dc->disk.id, bio_end_sector(bio), 0);
+
+	bch_keybuf_check_overlapping(&s->iop.c->moving_gc_keys, &start, &end);
+
+	down_read_non_owner(&dc->writeback_lock);
+	if (bch_keybuf_check_overlapping(&dc->writeback_keys, &start, &end)) {
+		/*
+		 * We overlap with some dirty data undergoing background
+		 * writeback, force this write to writeback
+		 */
+		s->iop.bypass = false;
+		s->iop.writeback = true;
+	}
+
+	/*
+	 * Discards aren't _required_ to do anything, so skipping if
+	 * check_overlapping returned true is ok
+	 *
+	 * But check_overlapping drops dirty keys for which io hasn't started,
+	 * so we still want to call it.
+	 */
+	if (bio_op(bio) == REQ_OP_DISCARD)
+		s->iop.bypass = true;
+
+	if (should_writeback(dc, s->orig_bio,
+			     cache_mode(dc),
+			     s->iop.bypass)) {
+		s->iop.bypass = false;
+		s->iop.writeback = true;
+	}
+
+	if (s->iop.bypass) {
+		s->iop.bio = s->orig_bio;
+		bio_get(s->iop.bio);
+
+		if (bio_op(bio) == REQ_OP_DISCARD &&
+		    !blk_queue_discard(bdev_get_queue(dc->bdev)))
+			goto insert_data;
+
+		/* I/O request sent to backing device */
+		bio->bi_end_io = backing_request_endio;
+		closure_bio_submit(s->iop.c, bio, cl);
+
+	} else if (s->iop.writeback) {
+		bch_writeback_add(dc);
+		s->iop.bio = bio;
+
+		if (bio->bi_opf & REQ_PREFLUSH) {
+			/*
+			 * Also need to send a flush to the backing
+			 * device.
+			 */
+			struct bio *flush;
+
+			flush = bio_alloc_bioset(GFP_NOIO, 0,
+						 &dc->disk.bio_split);
+			if (!flush) {
+				s->iop.status = BLK_STS_RESOURCE;
+				goto insert_data;
+			}
+			bio_copy_dev(flush, bio);
+			flush->bi_end_io = backing_request_endio;
+			flush->bi_private = cl;
+			flush->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
+			/* I/O request sent to backing device */
+			closure_bio_submit(s->iop.c, flush, cl);
+		}
+	} else {
+		s->iop.bio = bio_clone_fast(bio, GFP_NOIO, &dc->disk.bio_split);
+		/* I/O request sent to backing device */
+		bio->bi_end_io = backing_request_endio;
+		closure_bio_submit(s->iop.c, bio, cl);
+	}
+
+insert_data:
+	closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
+	continue_at(cl, cached_dev_write_complete, NULL);
+}
+
+static void cached_dev_nodata(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct bio *bio = &s->bio.bio;
+
+	if (s->iop.flush_journal)
+		bch_journal_meta(s->iop.c, cl);
+
+	/* If it's a flush, we send the flush to the backing device too */
+	bio->bi_end_io = backing_request_endio;
+	closure_bio_submit(s->iop.c, bio, cl);
+
+	continue_at(cl, cached_dev_bio_complete, NULL);
+}
+
+struct detached_dev_io_private {
+	struct bcache_device	*d;
+	unsigned long		start_time;
+	bio_end_io_t		*bi_end_io;
+	void			*bi_private;
+	struct hd_struct	*part;
+};
+
+static void detached_dev_end_io(struct bio *bio)
+{
+	struct detached_dev_io_private *ddip;
+
+	ddip = bio->bi_private;
+	bio->bi_end_io = ddip->bi_end_io;
+	bio->bi_private = ddip->bi_private;
+
+	/* Count on the bcache device */
+	part_end_io_acct(ddip->part, bio, ddip->start_time);
+
+	if (bio->bi_status) {
+		struct cached_dev *dc = container_of(ddip->d,
+						     struct cached_dev, disk);
+		/* should count I/O error for backing device here */
+		bch_count_backing_io_errors(dc, bio);
+	}
+
+	kfree(ddip);
+	bio->bi_end_io(bio);
+}
+
+static void detached_dev_do_request(struct bcache_device *d, struct bio *bio)
+{
+	struct detached_dev_io_private *ddip;
+	struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+
+	/*
+	 * no need to call closure_get(&dc->disk.cl),
+	 * because upper layer had already opened bcache device,
+	 * which would call closure_get(&dc->disk.cl)
+	 */
+	ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
+	if (!ddip) {
+		bio->bi_status = BLK_STS_RESOURCE;
+		bio->bi_end_io(bio);
+		return;
+	}
+
+	ddip->d = d;
+	/* Count on the bcache device */
+	ddip->start_time = part_start_io_acct(d->disk, &ddip->part, bio);
+	ddip->bi_end_io = bio->bi_end_io;
+	ddip->bi_private = bio->bi_private;
+	bio->bi_end_io = detached_dev_end_io;
+	bio->bi_private = ddip;
+
+	if ((bio_op(bio) == REQ_OP_DISCARD) &&
+	    !blk_queue_discard(bdev_get_queue(dc->bdev)))
+		bio->bi_end_io(bio);
+	else
+		submit_bio_noacct(bio);
+}
+
+static void quit_max_writeback_rate(struct cache_set *c,
+				    struct cached_dev *this_dc)
+{
+	int i;
+	struct bcache_device *d;
+	struct cached_dev *dc;
+
+	/*
+	 * mutex bch_register_lock may compete with other parallel requesters,
+	 * or attach/detach operations on other backing device. Waiting to
+	 * the mutex lock may increase I/O request latency for seconds or more.
+	 * To avoid such situation, if mutext_trylock() failed, only writeback
+	 * rate of current cached device is set to 1, and __update_write_back()
+	 * will decide writeback rate of other cached devices (remember now
+	 * c->idle_counter is 0 already).
+	 */
+	if (mutex_trylock(&bch_register_lock)) {
+		for (i = 0; i < c->devices_max_used; i++) {
+			if (!c->devices[i])
+				continue;
+
+			if (UUID_FLASH_ONLY(&c->uuids[i]))
+				continue;
+
+			d = c->devices[i];
+			dc = container_of(d, struct cached_dev, disk);
+			/*
+			 * set writeback rate to default minimum value,
+			 * then let update_writeback_rate() to decide the
+			 * upcoming rate.
+			 */
+			atomic_long_set(&dc->writeback_rate.rate, 1);
+		}
+		mutex_unlock(&bch_register_lock);
+	} else
+		atomic_long_set(&this_dc->writeback_rate.rate, 1);
+}
+
+/* Cached devices - read & write stuff */
+
+blk_qc_t cached_dev_submit_bio(struct bio *bio)
+{
+	struct search *s;
+	struct bcache_device *d = bio->bi_disk->private_data;
+	struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+	int rw = bio_data_dir(bio);
+
+	if (unlikely((d->c && test_bit(CACHE_SET_IO_DISABLE, &d->c->flags)) ||
+		     dc->io_disable)) {
+		bio->bi_status = BLK_STS_IOERR;
+		bio_endio(bio);
+		return BLK_QC_T_NONE;
+	}
+
+	if (likely(d->c)) {
+		if (atomic_read(&d->c->idle_counter))
+			atomic_set(&d->c->idle_counter, 0);
+		/*
+		 * If at_max_writeback_rate of cache set is true and new I/O
+		 * comes, quit max writeback rate of all cached devices
+		 * attached to this cache set, and set at_max_writeback_rate
+		 * to false.
+		 */
+		if (unlikely(atomic_read(&d->c->at_max_writeback_rate) == 1)) {
+			atomic_set(&d->c->at_max_writeback_rate, 0);
+			quit_max_writeback_rate(d->c, dc);
+		}
+	}
+
+	bio_set_dev(bio, dc->bdev);
+	bio->bi_iter.bi_sector += dc->sb.data_offset;
+
+	if (cached_dev_get(dc)) {
+		s = search_alloc(bio, d);
+		trace_bcache_request_start(s->d, bio);
+
+		if (!bio->bi_iter.bi_size) {
+			/*
+			 * can't call bch_journal_meta from under
+			 * submit_bio_noacct
+			 */
+			continue_at_nobarrier(&s->cl,
+					      cached_dev_nodata,
+					      bcache_wq);
+		} else {
+			s->iop.bypass = check_should_bypass(dc, bio);
+
+			if (rw)
+				cached_dev_write(dc, s);
+			else
+				cached_dev_read(dc, s);
+		}
+	} else
+		/* I/O request sent to backing device */
+		detached_dev_do_request(d, bio);
+
+	return BLK_QC_T_NONE;
+}
+
+static int cached_dev_ioctl(struct bcache_device *d, fmode_t mode,
+			    unsigned int cmd, unsigned long arg)
+{
+	struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+
+	if (dc->io_disable)
+		return -EIO;
+
+	return __blkdev_driver_ioctl(dc->bdev, mode, cmd, arg);
+}
+
+void bch_cached_dev_request_init(struct cached_dev *dc)
+{
+	dc->disk.cache_miss			= cached_dev_cache_miss;
+	dc->disk.ioctl				= cached_dev_ioctl;
+}
+
+/* Flash backed devices */
+
+static int flash_dev_cache_miss(struct btree *b, struct search *s,
+				struct bio *bio, unsigned int sectors)
+{
+	unsigned int bytes = min(sectors, bio_sectors(bio)) << 9;
+
+	swap(bio->bi_iter.bi_size, bytes);
+	zero_fill_bio(bio);
+	swap(bio->bi_iter.bi_size, bytes);
+
+	bio_advance(bio, bytes);
+
+	if (!bio->bi_iter.bi_size)
+		return MAP_DONE;
+
+	return MAP_CONTINUE;
+}
+
+static void flash_dev_nodata(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+
+	if (s->iop.flush_journal)
+		bch_journal_meta(s->iop.c, cl);
+
+	continue_at(cl, search_free, NULL);
+}
+
+blk_qc_t flash_dev_submit_bio(struct bio *bio)
+{
+	struct search *s;
+	struct closure *cl;
+	struct bcache_device *d = bio->bi_disk->private_data;
+
+	if (unlikely(d->c && test_bit(CACHE_SET_IO_DISABLE, &d->c->flags))) {
+		bio->bi_status = BLK_STS_IOERR;
+		bio_endio(bio);
+		return BLK_QC_T_NONE;
+	}
+
+	s = search_alloc(bio, d);
+	cl = &s->cl;
+	bio = &s->bio.bio;
+
+	trace_bcache_request_start(s->d, bio);
+
+	if (!bio->bi_iter.bi_size) {
+		/*
+		 * can't call bch_journal_meta from under submit_bio_noacct
+		 */
+		continue_at_nobarrier(&s->cl,
+				      flash_dev_nodata,
+				      bcache_wq);
+		return BLK_QC_T_NONE;
+	} else if (bio_data_dir(bio)) {
+		bch_keybuf_check_overlapping(&s->iop.c->moving_gc_keys,
+					&KEY(d->id, bio->bi_iter.bi_sector, 0),
+					&KEY(d->id, bio_end_sector(bio), 0));
+
+		s->iop.bypass		= (bio_op(bio) == REQ_OP_DISCARD) != 0;
+		s->iop.writeback	= true;
+		s->iop.bio		= bio;
+
+		closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
+	} else {
+		closure_call(&s->iop.cl, cache_lookup, NULL, cl);
+	}
+
+	continue_at(cl, search_free, NULL);
+	return BLK_QC_T_NONE;
+}
+
+static int flash_dev_ioctl(struct bcache_device *d, fmode_t mode,
+			   unsigned int cmd, unsigned long arg)
+{
+	return -ENOTTY;
+}
+
+void bch_flash_dev_request_init(struct bcache_device *d)
+{
+	d->cache_miss				= flash_dev_cache_miss;
+	d->ioctl				= flash_dev_ioctl;
+}
+
+void bch_request_exit(void)
+{
+	kmem_cache_destroy(bch_search_cache);
+}
+
+int __init bch_request_init(void)
+{
+	bch_search_cache = KMEM_CACHE(search, 0);
+	if (!bch_search_cache)
+		return -ENOMEM;
+
+	return 0;
+}