[PATCH v5 08/10] bcache: add backing_request_endio() for bi_end_io of attached backing device I/O

Coly Li
2018-02-06T04:22:15Z

In order to catch I/O error of backing device, a separate bi_end_io
call back is required. Then a per backing device counter can record I/O
errors number and retire the backing device if the counter reaches a
per backing device I/O error limit.

This patch adds backing_request_endio() to bcache backing device I/O code
path, this is a preparation for further complicated backing device failure
handling. So far there is no real code logic change, I make this change a
separate patch to make sure it is stable and reliable for further work.

Changelog:
v2: Fix code comments typo, remove a redundant bch_writeback_add() line
added in v4 patch set.
v1: indeed this is new added in this patch set.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Junhui Tang <tang.junhui@zte.com.cn>
Cc: Michael Lyle <mlyle@lyle.org>
---
drivers/md/bcache/request.c | 93 +++++++++++++++++++++++++++++++++++--------
drivers/md/bcache/super.c | 1 +
drivers/md/bcache/writeback.c | 1 +
3 files changed, 79 insertions(+), 16 deletions(-)

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index e09c5ae745be..9c6dda3b0068 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -139,6 +139,7 @@ static void bch_data_invalidate(struct closure *cl)
}

op->insert_data_done = true;
+ /* get in bch_data_insert() */
bio_put(bio);
out:
continue_at(cl, bch_data_insert_keys, op->wq);
@@ -630,6 +631,38 @@ static void request_endio(struct bio *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);
+ /*
+ * 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)) {
+ char buf[BDEVNAME_SIZE];
+
+ bio_devname(bio, buf);
+ pr_err("Can't flush %s: returned bi_status %i",
+ buf, 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 */
+ }
+
+ bio_put(bio);
+ closure_put(cl);
+}
+
static void bio_complete(struct search *s)
{
if (s->orig_bio) {
@@ -644,13 +677,21 @@ static void bio_complete(struct search *s)
}
}

-static void do_bio_hook(struct search *s, struct bio *orig_bio)
+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);
- bio->bi_end_io = request_endio;
+ /*
+ * 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);
@@ -676,7 +717,7 @@ static inline struct search *search_alloc(struct bio *bio,
s = mempool_alloc(d->c->search, GFP_NOIO);

closure_init(&s->cl, NULL);
- do_bio_hook(s, bio);
+ do_bio_hook(s, bio, request_endio);

s->orig_bio = bio;
s->cache_miss = NULL;
@@ -743,10 +784,11 @@ static void cached_dev_read_error(struct closure *cl)
trace_bcache_read_retry(s->orig_bio);

s->iop.status = 0;
- do_bio_hook(s, s->orig_bio);
+ 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);
}

@@ -859,7 +901,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s,
bio_copy_dev(cache_bio, miss);
cache_bio->bi_iter.bi_size = s->insert_bio_sectors << 9;

- cache_bio->bi_end_io = request_endio;
+ cache_bio->bi_end_io = backing_request_endio;
cache_bio->bi_private = &s->cl;

bch_bio_map(cache_bio, NULL);
@@ -872,14 +914,16 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s,
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 = request_endio;
+ 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;
}
@@ -943,31 +987,46 @@ static void cached_dev_write(struct cached_dev *dc, struct search *s)
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)))
- closure_bio_submit(s->iop.c, bio, cl);
+ 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 = bio_alloc_bioset(GFP_NOIO, 0,
- dc->disk.bio_split);
-
+ /*
+ * 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 = request_endio;
+ 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);
}
@@ -981,6 +1040,7 @@ static void cached_dev_nodata(struct closure *cl)
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);
@@ -1078,6 +1138,7 @@ static blk_qc_t cached_dev_make_request(struct request_queue *q,
cached_dev_read(dc, s);
}
} else
+ /* I/O request sent to backing device */
detached_dev_do_request(d, bio);

return BLK_QC_T_NONE;
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index e335433bdfb7..4f1a14b99415 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -273,6 +273,7 @@ void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent)
bio->bi_private = dc;

closure_get(cl);
+ /* I/O request sent to backing device */
__write_super(&dc->sb, bio);

closure_return_with_destructor(cl, bch_write_bdev_super_unlock);
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 3d7d8452e0de..4ebe0119ea7e 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -289,6 +289,7 @@ static void write_dirty(struct closure *cl)
bio_set_dev(&io->bio, io->dc->bdev);
io->bio.bi_end_io = dirty_endio;

+ /* I/O request sent to backing device */
closure_bio_submit(io->dc->disk.c, &io->bio, cl);
}

--
2.16.1