From: Coly Li Date: Sat, 1 Feb 2020 14:42:33 +0000 (+0800) Subject: bcache: add readahead cache policy options via sysfs interface X-Git-Tag: Ubuntu-4.15.0-92.93~55 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=b03a2a0650d569bb16bd858f147e51dc842996bf;p=mirror_ubuntu-bionic-kernel.git bcache: add readahead cache policy options via sysfs interface BugLink: https://bugs.launchpad.net/bugs/1866678 commit 038ba8cc1bffc51250add4a9b9249d4331576d8f upstream. In year 2007 high performance SSD was still expensive, in order to save more space for real workload or meta data, the readahead I/Os for non-meta data was bypassed and not cached on SSD. In now days, SSD price drops a lot and people can find larger size SSD with more comfortable price. It is unncessary to alway bypass normal readahead I/Os to save SSD space for now. This patch adds options for readahead data cache policies via sysfs file /sys/block/bcache/readahead_cache_policy, the options are, - "all": cache all readahead data I/Os. - "meta-only": only cache meta data, and bypass other regular I/Os. If users want to make bcache continue to only cache readahead request for metadata and bypass regular data readahead, please set "meta-only" to this sysfs file. By default, bcache will back to cache all read- ahead requests now. Cc: stable@vger.kernel.org Signed-off-by: Coly Li Acked-by: Eric Wheeler Cc: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa Signed-off-by: Khalid Elmously --- diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index da5d7a6698f7..f650cd5f8c24 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -328,6 +328,9 @@ struct cached_dev { */ atomic_t has_dirty; +#define BCH_CACHE_READA_ALL 0 +#define BCH_CACHE_READA_META_ONLY 1 + unsigned int cache_readahead_policy; struct bch_ratelimit writeback_rate; struct delayed_work writeback_rate_update; diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index fa31fb3bd3be..4d429ad35980 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -388,13 +388,20 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio) goto skip; /* - * Flag for bypass if the IO is for read-ahead or background, - * unless the read-ahead request is for metadata + * If the bio is for read-ahead or background IO, bypass it or + * not depends on the following situations, + * - If the IO is for meta data, always cache it and no bypass + * - If the IO is not meta data, check dc->cache_reada_policy, + * BCH_CACHE_READA_ALL: cache it and not bypass + * BCH_CACHE_READA_META_ONLY: not cache it and bypass + * That is, read-ahead request for metadata always get cached * (eg, for gfs2 or xfs). */ - if (bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND) && - !(bio->bi_opf & (REQ_META|REQ_PRIO))) - goto skip; + if ((bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND))) { + if (!(bio->bi_opf & (REQ_META|REQ_PRIO)) && + (dc->cache_readahead_policy != BCH_CACHE_READA_ALL)) + goto skip; + } if (bio->bi_iter.bi_sector & (c->sb.block_size - 1) || bio_sectors(bio) & (c->sb.block_size - 1)) { diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index 6ce8f73d1318..29060b4d9bb4 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -25,6 +25,12 @@ static const char * const bch_cache_modes[] = { NULL }; +static const char * const bch_reada_cache_policies[] = { + "all", + "meta-only", + NULL +}; + /* Default is -1; we skip past it for stop_when_cache_set_failed */ static const char * const bch_stop_on_failure_modes[] = { "auto", @@ -94,6 +100,7 @@ rw_attribute(congested_write_threshold_us); rw_attribute(sequential_cutoff); rw_attribute(data_csum); rw_attribute(cache_mode); +rw_attribute(readahead_cache_policy); rw_attribute(stop_when_cache_set_failed); rw_attribute(writeback_metadata); rw_attribute(writeback_running); @@ -157,6 +164,11 @@ SHOW(__bch_cached_dev) bch_cache_modes, BDEV_CACHE_MODE(&dc->sb)); + if (attr == &sysfs_readahead_cache_policy) + return bch_snprint_string_list(buf, PAGE_SIZE, + bch_reada_cache_policies, + dc->cache_readahead_policy); + if (attr == &sysfs_stop_when_cache_set_failed) return bch_snprint_string_list(buf, PAGE_SIZE, bch_stop_on_failure_modes, @@ -302,6 +314,15 @@ STORE(__cached_dev) } } + if (attr == &sysfs_readahead_cache_policy) { + v = __sysfs_match_string(bch_reada_cache_policies, -1, buf); + if (v < 0) + return v; + + if ((unsigned int) v != dc->cache_readahead_policy) + dc->cache_readahead_policy = v; + } + if (attr == &sysfs_stop_when_cache_set_failed) { v = __sysfs_match_string(bch_stop_on_failure_modes, -1, buf); if (v < 0) @@ -394,6 +415,7 @@ static struct attribute *bch_cached_dev_files[] = { &sysfs_data_csum, #endif &sysfs_cache_mode, + &sysfs_readahead_cache_policy, &sysfs_stop_when_cache_set_failed, &sysfs_writeback_metadata, &sysfs_writeback_running,