For read cache missing, bcache defines a readahead size for the read I/O request to the backing device for the missing data. This readahead size is initialized to 0, and almost no one uses it to avoid unnecessary read amplifying onto backing device and write amplifying onto cache device. Considering upper layer file system code has readahead logic allready and works fine with readahead_cache_policy sysfile interface, we don't have to keep bcache self-defined readahead anymore.

This patch removes the bcache self-defined readahead for cache missing request for backing device, and the readahead sysfs file interfaces are removed as well.

This is the preparation for next patch to fix potential kernel panic due to oversized request in a simpler method.

Reported-by: Alexander Ullrich ealex1979@gmail.com Reported-by: Diego Ercolani diego.ercolani@gmail.com Reported-by: Jan Szubiak jan.szubiak@linuxpolska.pl Reported-by: Marco Rebhan me@dblsaiko.net Reported-by: Matthias Ferdinand bcache@mfedv.net Reported-by: Victor Westerhuis victor@westerhu.is Reported-by: Vojtech Pavlik vojtech@suse.cz Signed-off-by: Coly Li colyli@suse.de Reported-and-tested-by: Rolf Fokkens rolf@rolffokkens.nl Reported-and-tested-by: Thorsten Knabe linux@thorsten-knabe.de Cc: stable@vger.kernel.org Cc: Christoph Hellwig hch@lst.de Cc: Kent Overstreet kent.overstreet@gmail.com Cc: Nix nix@esperi.org.uk Cc: Takashi Iwai tiwai@suse.com --- Changlog, v1, the initial version by hint from Christoph Hellwig.

drivers/md/bcache/bcache.h | 1 - drivers/md/bcache/request.c | 13 +------------ drivers/md/bcache/stats.c | 14 -------------- drivers/md/bcache/stats.h | 1 - drivers/md/bcache/sysfs.c | 4 ---- 5 files changed, 1 insertion(+), 32 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 0a4551e165ab..5fc989a6d452 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -364,7 +364,6 @@ struct cached_dev {

/* The rest of this all shows up in sysfs */ unsigned int sequential_cutoff; - unsigned int readahead;

unsigned int io_disable:1; unsigned int verify:1; diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index 29c231758293..ab8ff18df32a 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -880,7 +880,6 @@ 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;

@@ -892,14 +891,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s, 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_bdev->bd_disk) - - bio_end_sector(bio)); - - s->insert_bio_sectors = min(sectors, bio_sectors(bio) + reada); + s->insert_bio_sectors = min(sectors, bio_sectors(bio));

s->iop.replace_key = KEY(s->iop.inode, bio->bi_iter.bi_sector + s->insert_bio_sectors, @@ -933,9 +925,6 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s, 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); diff --git a/drivers/md/bcache/stats.c b/drivers/md/bcache/stats.c index 503aafe188dc..4c7ee5fedb9d 100644 --- a/drivers/md/bcache/stats.c +++ b/drivers/md/bcache/stats.c @@ -46,7 +46,6 @@ read_attribute(cache_misses); read_attribute(cache_bypass_hits); read_attribute(cache_bypass_misses); read_attribute(cache_hit_ratio); -read_attribute(cache_readaheads); read_attribute(cache_miss_collisions); read_attribute(bypassed);

@@ -64,7 +63,6 @@ SHOW(bch_stats) DIV_SAFE(var(cache_hits) * 100, var(cache_hits) + var(cache_misses)));

- var_print(cache_readaheads); var_print(cache_miss_collisions); sysfs_hprint(bypassed, var(sectors_bypassed) << 9); #undef var @@ -86,7 +84,6 @@ static struct attribute *bch_stats_files[] = { &sysfs_cache_bypass_hits, &sysfs_cache_bypass_misses, &sysfs_cache_hit_ratio, - &sysfs_cache_readaheads, &sysfs_cache_miss_collisions, &sysfs_bypassed, NULL @@ -113,7 +110,6 @@ void bch_cache_accounting_clear(struct cache_accounting *acc) acc->total.cache_misses = 0; acc->total.cache_bypass_hits = 0; acc->total.cache_bypass_misses = 0; - acc->total.cache_readaheads = 0; acc->total.cache_miss_collisions = 0; acc->total.sectors_bypassed = 0; } @@ -145,7 +141,6 @@ static void scale_stats(struct cache_stats *stats, unsigned long rescale_at) scale_stat(&stats->cache_misses); scale_stat(&stats->cache_bypass_hits); scale_stat(&stats->cache_bypass_misses); - scale_stat(&stats->cache_readaheads); scale_stat(&stats->cache_miss_collisions); scale_stat(&stats->sectors_bypassed); } @@ -168,7 +163,6 @@ static void scale_accounting(struct timer_list *t) move_stat(cache_misses); move_stat(cache_bypass_hits); move_stat(cache_bypass_misses); - move_stat(cache_readaheads); move_stat(cache_miss_collisions); move_stat(sectors_bypassed);

@@ -209,14 +203,6 @@ void bch_mark_cache_accounting(struct cache_set *c, struct bcache_device *d, mark_cache_stats(&c->accounting.collector, hit, bypass); }

-void bch_mark_cache_readahead(struct cache_set *c, struct bcache_device *d) -{ - struct cached_dev *dc = container_of(d, struct cached_dev, disk); - - atomic_inc(&dc->accounting.collector.cache_readaheads); - atomic_inc(&c->accounting.collector.cache_readaheads); -} - void bch_mark_cache_miss_collision(struct cache_set *c, struct bcache_device *d) { struct cached_dev *dc = container_of(d, struct cached_dev, disk); diff --git a/drivers/md/bcache/stats.h b/drivers/md/bcache/stats.h index abfaabf7e7fc..ca4f435f7216 100644 --- a/drivers/md/bcache/stats.h +++ b/drivers/md/bcache/stats.h @@ -7,7 +7,6 @@ struct cache_stat_collector { atomic_t cache_misses; atomic_t cache_bypass_hits; atomic_t cache_bypass_misses; - atomic_t cache_readaheads; atomic_t cache_miss_collisions; atomic_t sectors_bypassed; }; diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index cc89f3156d1a..05ac1d6fbbf3 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -137,7 +137,6 @@ rw_attribute(io_disable); rw_attribute(discard); rw_attribute(running); rw_attribute(label); -rw_attribute(readahead); rw_attribute(errors); rw_attribute(io_error_limit); rw_attribute(io_error_halflife); @@ -260,7 +259,6 @@ SHOW(__bch_cached_dev) var_printf(partial_stripes_expensive, "%u");

var_hprint(sequential_cutoff); - var_hprint(readahead);

sysfs_print(running, atomic_read(&dc->running)); sysfs_print(state, states[BDEV_STATE(&dc->sb)]); @@ -365,7 +363,6 @@ STORE(__cached_dev) sysfs_strtoul_clamp(sequential_cutoff, dc->sequential_cutoff, 0, UINT_MAX); - d_strtoi_h(readahead);

if (attr == &sysfs_clear_stats) bch_cache_accounting_clear(&dc->accounting); @@ -538,7 +535,6 @@ static struct attribute *bch_cached_dev_files[] = { &sysfs_running, &sysfs_state, &sysfs_label, - &sysfs_readahead, #ifdef CONFIG_BCACHE_DEBUG &sysfs_verify, &sysfs_bypass_torture_test,