Messages in this thread | | | Subject | Re: [PATCH -next 1/8] md/raid10: prevent soft lockup while flush writes | From | Yu Kuai <> | Date | Tue, 25 Apr 2023 14:16:34 +0800 |
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Hi,
在 2023/04/25 8:23, Song Liu 写道: > On Thu, Apr 20, 2023 at 4:31 AM Yu Kuai <yukuai1@huaweicloud.com> wrote: >> >> From: Yu Kuai <yukuai3@huawei.com> >> >> 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 > > Is it possible to trigger this with a mdadm test? >
The test I mentioned in patch 8 can trigger this problem reliablity, so I this add a new test can achieve this.
Thanks, Kuai > Thanks, > Song > >> >> This patch fix the problem by adding cond_resched() to raid10 like what >> raid1 did. >> >> 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. >> >> Signed-off-by: Yu Kuai <yukuai3@huawei.com> >> --- >> 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 >> > . >
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