On Thu, Apr 20, 2023 at 4:31 AM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > Currently, there is no limit for raid1/raid10 plugged bio. While flushing > writes, raid1 has cond_resched() while raid10 doesn't, and too many > writes can cause soft lockup. > > Follow up soft lockup can be triggered easily with writeback test for > raid10 with ramdisks: > > watchdog: BUG: soft lockup - CPU#10 stuck for 27s! [md0_raid10:1293] > Call Trace: > <TASK> > call_rcu+0x16/0x20 > put_object+0x41/0x80 > __delete_object+0x50/0x90 > delete_object_full+0x2b/0x40 > kmemleak_free+0x46/0xa0 > slab_free_freelist_hook.constprop.0+0xed/0x1a0 > kmem_cache_free+0xfd/0x300 > mempool_free_slab+0x1f/0x30 > mempool_free+0x3a/0x100 > bio_free+0x59/0x80 > bio_put+0xcf/0x2c0 > free_r10bio+0xbf/0xf0 > raid_end_bio_io+0x78/0xb0 > one_write_done+0x8a/0xa0 > raid10_end_write_request+0x1b4/0x430 > bio_endio+0x175/0x320 > brd_submit_bio+0x3b9/0x9b7 [brd] > __submit_bio+0x69/0xe0 > submit_bio_noacct_nocheck+0x1e6/0x5a0 > submit_bio_noacct+0x38c/0x7e0 > flush_pending_writes+0xf0/0x240 > raid10d+0xac/0x1ed0 > > This patch fix the problem by adding cond_resched() to raid10 like what > raid1 did. nit: per submitting-patches.rst: Describe your changes in imperative mood, e.g. "make xyzzy do frotz" instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy to do frotz", as if you are giving orders to the codebase to change its behaviour. > > Note that unlimited plugged bio still need to be optimized because in > the case of writeback lots of dirty pages, this will take lots of memory > and io latecy is quite bad. typo: latency. > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> > --- > drivers/md/raid10.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c > index 6590aa49598c..a116b7c9d9f3 100644 > --- a/drivers/md/raid10.c > +++ b/drivers/md/raid10.c > @@ -921,6 +921,7 @@ static void flush_pending_writes(struct r10conf *conf) > else > submit_bio_noacct(bio); > bio = next; > + cond_resched(); > } > blk_finish_plug(&plug); > } else > @@ -1140,6 +1141,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule) > else > submit_bio_noacct(bio); > bio = next; > + cond_resched(); > } > kfree(plug); > } > -- > 2.39.2 >
