From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/md/raid5-log.h | 151 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 drivers/md/raid5-log.h (limited to 'drivers/md/raid5-log.h') diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h new file mode 100644 index 000000000..c83325026 --- /dev/null +++ b/drivers/md/raid5-log.h @@ -0,0 +1,151 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _RAID5_LOG_H +#define _RAID5_LOG_H + +int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev); +void r5l_exit_log(struct r5conf *conf); +int r5l_write_stripe(struct r5l_log *log, struct stripe_head *head_sh); +void r5l_write_stripe_run(struct r5l_log *log); +void r5l_flush_stripe_to_raid(struct r5l_log *log); +void r5l_stripe_write_finished(struct stripe_head *sh); +int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio); +void r5l_quiesce(struct r5l_log *log, int quiesce); +bool r5l_log_disk_error(struct r5conf *conf); +bool r5c_is_writeback(struct r5l_log *log); +int r5c_try_caching_write(struct r5conf *conf, struct stripe_head *sh, + struct stripe_head_state *s, int disks); +void r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh, + struct stripe_head_state *s); +void r5c_release_extra_page(struct stripe_head *sh); +void r5c_use_extra_page(struct stripe_head *sh); +void r5l_wake_reclaim(struct r5l_log *log, sector_t space); +void r5c_handle_cached_data_endio(struct r5conf *conf, + struct stripe_head *sh, int disks); +int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh); +void r5c_make_stripe_write_out(struct stripe_head *sh); +void r5c_flush_cache(struct r5conf *conf, int num); +void r5c_check_stripe_cache_usage(struct r5conf *conf); +void r5c_check_cached_full_stripe(struct r5conf *conf); +extern struct md_sysfs_entry r5c_journal_mode; +void r5c_update_on_rdev_error(struct mddev *mddev, struct md_rdev *rdev); +bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect); +int r5l_start(struct r5l_log *log); + +struct dma_async_tx_descriptor * +ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu, + struct dma_async_tx_descriptor *tx); +int ppl_init_log(struct r5conf *conf); +void ppl_exit_log(struct r5conf *conf); +int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh); +void ppl_write_stripe_run(struct r5conf *conf); +void ppl_stripe_write_finished(struct stripe_head *sh); +int ppl_modify_log(struct r5conf *conf, struct md_rdev *rdev, bool add); +void ppl_quiesce(struct r5conf *conf, int quiesce); +int ppl_handle_flush_request(struct bio *bio); +extern struct md_sysfs_entry ppl_write_hint; + +static inline bool raid5_has_log(struct r5conf *conf) +{ + return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags); +} + +static inline bool raid5_has_ppl(struct r5conf *conf) +{ + return test_bit(MD_HAS_PPL, &conf->mddev->flags); +} + +static inline int log_stripe(struct stripe_head *sh, struct stripe_head_state *s) +{ + struct r5conf *conf = sh->raid_conf; + + if (conf->log) { + if (!test_bit(STRIPE_R5C_CACHING, &sh->state)) { + /* writing out phase */ + if (s->waiting_extra_page) + return 0; + return r5l_write_stripe(conf->log, sh); + } else if (test_bit(STRIPE_LOG_TRAPPED, &sh->state)) { + /* caching phase */ + return r5c_cache_data(conf->log, sh); + } + } else if (raid5_has_ppl(conf)) { + return ppl_write_stripe(conf, sh); + } + + return -EAGAIN; +} + +static inline void log_stripe_write_finished(struct stripe_head *sh) +{ + struct r5conf *conf = sh->raid_conf; + + if (conf->log) + r5l_stripe_write_finished(sh); + else if (raid5_has_ppl(conf)) + ppl_stripe_write_finished(sh); +} + +static inline void log_write_stripe_run(struct r5conf *conf) +{ + if (conf->log) + r5l_write_stripe_run(conf->log); + else if (raid5_has_ppl(conf)) + ppl_write_stripe_run(conf); +} + +static inline void log_flush_stripe_to_raid(struct r5conf *conf) +{ + if (conf->log) + r5l_flush_stripe_to_raid(conf->log); + else if (raid5_has_ppl(conf)) + ppl_write_stripe_run(conf); +} + +static inline int log_handle_flush_request(struct r5conf *conf, struct bio *bio) +{ + int ret = -ENODEV; + + if (conf->log) + ret = r5l_handle_flush_request(conf->log, bio); + else if (raid5_has_ppl(conf)) + ret = ppl_handle_flush_request(bio); + + return ret; +} + +static inline void log_quiesce(struct r5conf *conf, int quiesce) +{ + if (conf->log) + r5l_quiesce(conf->log, quiesce); + else if (raid5_has_ppl(conf)) + ppl_quiesce(conf, quiesce); +} + +static inline void log_exit(struct r5conf *conf) +{ + if (conf->log) + r5l_exit_log(conf); + else if (raid5_has_ppl(conf)) + ppl_exit_log(conf); +} + +static inline int log_init(struct r5conf *conf, struct md_rdev *journal_dev, + bool ppl) +{ + if (journal_dev) + return r5l_init_log(conf, journal_dev); + else if (ppl) + return ppl_init_log(conf); + + return 0; +} + +static inline int log_modify(struct r5conf *conf, struct md_rdev *rdev, bool add) +{ + if (raid5_has_ppl(conf)) + return ppl_modify_log(conf, rdev, add); + + return 0; +} + +#endif -- cgit v1.3.1