bcache: remove bcache device self-defined readahead

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>
Reported-and-tested-by: Rolf Fokkens <rolf@rolffokkens.nl>
Reported-and-tested-by: Thorsten Knabe <linux@thorsten-knabe.de>
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Nix <nix@esperi.org.uk>
Cc: Takashi Iwai <tiwai@suse.com>
Link: https://lore.kernel.org/r/20210607125052.21277-2-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 0 insertions, 14 deletions

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);