[PATCH v5 09/10] bcache: add io_disable to struct cached_dev

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

If a bcache device is configured to writeback mode, current code does not
handle write I/O errors on backing devices properly.

In writeback mode, write request is written to cache device, and
latter being flushed to backing device. If I/O failed when writing from
cache device to the backing device, bcache code just ignores the error and
upper layer code is NOT noticed that the backing device is broken.

This patch tries to handle backing device failure like how the cache device
failure is handled,
- Add a error counter 'io_errors' and error limit 'error_limit' in struct
cached_dev. Add another io_disable to struct cached_dev to disable I/Os
on the problematic backing device.
- When I/O error happens on backing device, increase io_errors counter. And
if io_errors reaches error_limit, set cache_dev->io_disable to true, and
stop the bcache device.

The result is, if backing device is broken of disconnected, and I/O errors
reach its error limit, backing device will be disabled and the associated
bcache device will be removed from system.

Changelog:
v2: remove "bcache: " prefix in pr_error(), and use correct name string to
print out bcache device gendisk name.
v1: indeed this is new added in v2 patch set.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Michael Lyle <mlyle@lyle.org>
Cc: Junhui Tang <tang.junhui@zte.com.cn>
---
drivers/md/bcache/bcache.h | 6 ++++++
drivers/md/bcache/io.c | 14 ++++++++++++++
drivers/md/bcache/request.c | 14 ++++++++++++--
drivers/md/bcache/super.c | 23 ++++++++++++++++++++++-
drivers/md/bcache/sysfs.c | 15 ++++++++++++++-
5 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 263164490833..c59ce168bd82 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -366,6 +366,7 @@ struct cached_dev {
unsigned sequential_cutoff;
unsigned readahead;

+ unsigned io_disable:1;
unsigned verify:1;
unsigned bypass_torture_test:1;

@@ -387,6 +388,9 @@ struct cached_dev {
unsigned writeback_rate_minimum;

enum stop_on_faliure stop_when_cache_set_failed;
+#define DEFAULT_CACHED_DEV_ERROR_LIMIT 64
+ atomic_t io_errors;
+ unsigned error_limit;
};

enum alloc_reserve {
@@ -896,6 +900,7 @@ static inline void closure_bio_submit(struct cache_set *c,

/* Forward declarations */

+void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio);
void bch_count_io_errors(struct cache *, blk_status_t, int, const char *);
void bch_bbio_count_io_errors(struct cache_set *, struct bio *,
blk_status_t, const char *);
@@ -923,6 +928,7 @@ int bch_bucket_alloc_set(struct cache_set *, unsigned,
struct bkey *, int, bool);
bool bch_alloc_sectors(struct cache_set *, struct bkey *, unsigned,
unsigned, unsigned, bool);
+bool bch_cached_dev_error(struct cached_dev *dc);

__printf(2, 3)
bool bch_cache_set_error(struct cache_set *, const char *, ...);
diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index 8013ecbcdbda..7fac97ae036e 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c
@@ -50,6 +50,20 @@ void bch_submit_bbio(struct bio *bio, struct cache_set *c,
}

/* IO errors */
+void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio)
+{
+ char buf[BDEVNAME_SIZE];
+ unsigned errors;
+
+ WARN_ONCE(!dc, "NULL pointer of struct cached_dev");
+
+ errors = atomic_add_return(1, &dc->io_errors);
+ if (errors < dc->error_limit)
+ pr_err("%s: IO error on backing device, unrecoverable",
+ bio_devname(bio, buf));
+ else
+ bch_cached_dev_error(dc);
+}

void bch_count_io_errors(struct cache *ca,
blk_status_t error,
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 9c6dda3b0068..03245e6980a6 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -637,6 +637,8 @@ static void backing_request_endio(struct bio *bio)

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
@@ -657,6 +659,7 @@ static void backing_request_endio(struct bio *bio)
}
s->recoverable = false;
/* should count I/O error for backing device here */
+ bch_count_backing_io_errors(dc, bio);
}

bio_put(bio);
@@ -1065,8 +1068,14 @@ static void detatched_dev_end_io(struct bio *bio)
bio_data_dir(bio),
&ddip->d->disk->part0, ddip->start_time);

- kfree(ddip);
+ 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);
}

@@ -1105,7 +1114,8 @@ static blk_qc_t cached_dev_make_request(struct request_queue *q,
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))) {
+ 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;
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 4f1a14b99415..40b07d980a20 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1196,7 +1196,10 @@ static int cached_dev_init(struct cached_dev *dc, unsigned block_size)
max(dc->disk.disk->queue->backing_dev_info->ra_pages,
q->backing_dev_info->ra_pages);

- /* default to auto */
+ atomic_set(&dc->io_errors, 0);
+ dc->io_disable = false;
+ dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT;
+ /* default to "auto" */
dc->stop_when_cache_set_failed = BCH_CACHED_DEV_STOP_ATUO;

bch_cached_dev_request_init(dc);
@@ -1350,6 +1353,24 @@ int bch_flash_dev_create(struct cache_set *c, uint64_t size)
return flash_dev_run(c, u);
}

+bool bch_cached_dev_error(struct cached_dev *dc)
+{
+ char name[BDEVNAME_SIZE];
+
+ if (!dc || test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags))
+ return false;
+
+ dc->io_disable = true;
+ /* make others know io_disable is true earlier */
+ smp_mb();
+
+ pr_err("stop %s: too many IO errors on backing device %s\n",
+ dc->disk.disk->disk_name, bdevname(dc->bdev, name));
+
+ bcache_device_stop(&dc->disk);
+ return true;
+}
+
/* Cache set */

__printf(2, 3)
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 91d859a54575..e88fdcc549cd 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -141,7 +141,9 @@ SHOW(__bch_cached_dev)
var_print(writeback_delay);
var_print(writeback_percent);
sysfs_hprint(writeback_rate, dc->writeback_rate.rate << 9);
-
+ sysfs_hprint(io_errors, atomic_read(&dc->io_errors));
+ sysfs_printf(io_error_limit, "%i", dc->error_limit);
+ sysfs_printf(io_disable, "%i", dc->io_disable);
var_print(writeback_rate_update_seconds);
var_print(writeback_rate_i_term_inverse);
var_print(writeback_rate_p_term_inverse);
@@ -232,6 +234,14 @@ STORE(__cached_dev)
d_strtoul(writeback_rate_i_term_inverse);
d_strtoul_nonzero(writeback_rate_p_term_inverse);

+ sysfs_strtoul_clamp(io_error_limit, dc->error_limit, 0, INT_MAX);
+
+ if (attr == &sysfs_io_disable) {
+ int v = strtoul_or_return(buf);
+
+ dc->io_disable = v ? 1 : 0;
+ }
+
d_strtoi_h(sequential_cutoff);
d_strtoi_h(readahead);

@@ -349,6 +359,9 @@ static struct attribute *bch_cached_dev_files[] = {
&sysfs_writeback_rate_i_term_inverse,
&sysfs_writeback_rate_p_term_inverse,
&sysfs_writeback_rate_debug,
+ &sysfs_errors,
+ &sysfs_io_error_limit,
+ &sysfs_io_disable,
&sysfs_dirty_data,
&sysfs_stripe_size,
&sysfs_partial_stripes_expensive,
--
2.16.1