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bcache: remove bcache device self-defined readahead

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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>
This commit is contained in:
Coly Li 2021-06-07 20:50:51 +08:00 committed by Jens Axboe
parent e369edbb0d
commit 1616a4c2ab
5 changed files with 1 additions and 32 deletions
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1
drivers/md/bcache/bcache.h
View file

@ -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;

13
drivers/md/bcache/request.c
View file

@ -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);

14
drivers/md/bcache/stats.c
View file

@ -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);

1
drivers/md/bcache/stats.h
View file

@ -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;
};

4
drivers/md/bcache/sysfs.c
View file

@ -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,