On 01/14/2018 03:42 PM, Coly Li wrote:
> 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.
>
> Signed-off-by: Coly Li <col...@suse.de>
> Cc: Michael Lyle <ml...@lyle.org>
> Cc: Hannes Reinecke <h...@suse.com>
> Cc: Junhui Tang <tang.jun...@zte.com.cn>
> ---
> drivers/md/bcache/bcache.h | 7 +++++++
> drivers/md/bcache/io.c | 14 ++++++++++++++
> drivers/md/bcache/request.c | 14 ++++++++++++--
> drivers/md/bcache/super.c | 22 ++++++++++++++++++++++
> drivers/md/bcache/sysfs.c | 15 ++++++++++++++-
> 5 files changed, 69 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index c41736960045..5a811959392d 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -360,6 +360,7 @@ struct cached_dev {
> unsigned sequential_cutoff;
> unsigned readahead;
>
> + unsigned io_disable:1;
> unsigned verify:1;
> unsigned bypass_torture_test:1;
>
> @@ -379,6 +380,10 @@ struct cached_dev {
> unsigned writeback_rate_i_term_inverse;
> unsigned writeback_rate_p_term_inverse;
> unsigned writeback_rate_minimum;
> +
> +#define DEFAULT_CACHED_DEV_ERROR_LIMIT 64
> + atomic_t io_errors;
> + unsigned error_limit;
> };
>
> enum alloc_reserve {
> @@ -882,6 +887,7 @@ 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 *);
> @@ -909,6 +915,7 @@ 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 ad4cf71f7eab..386b388ce296 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);
> @@ -1067,8 +1070,14 @@ 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);
> }
>
> @@ -1107,7 +1116,8 @@ 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 08a0b541a4da..14fce3623770 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1188,6 +1188,10 @@ 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);
>
> + atomic_set(&dc->io_errors, 0);
> + dc->io_disable = false;
> + dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT;
> +
> bch_cached_dev_request_init(dc);
> bch_cached_dev_writeback_init(dc);
> return 0;
> @@ -1339,6 +1343,24 @@ 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("bcache: stop %s: too many IO errors on backing device %s\n",
> + dc->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 afb051bcfca1..7288927f2a47 100644
> --- a/drivers/md/bcache/sysfs.c
> +++ b/drivers/md/bcache/sysfs.c
> @@ -131,7 +131,9 @@ 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);
> @@ -223,6 +225,14 @@ 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);
>
> @@ -330,6 +340,9 @@ 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,
>
Personally, I'm not a big fan of using smp_mb() and not proper locking.
But in this case it should be okay.
Reviewed-by: Hannes Reinecke <h...@suse.com>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
h...@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
