On 2017/2/24 上午7:14, NeilBrown wrote: > On Thu, Feb 23 2017, Coly Li wrote: > >> >> I tried to set up a 4 layer stacked md raid1, and reduce I/O >> barrier bucket size to 8MB, running for 10 hours, there is no >> deadlock observed, > > Try setting BARRIER_BUCKETS_NR to '1' and BARRIER_UNIT_SECTOR_BITS > to 3 and make sure the write requests are larger than 1 page (and > have resync happen at the same time as writes). Hi Neil, Yes, the above method triggers deadlock easily. After come to understand how bios are handled in stacked raid1 and the relationship between current->bio_list, plug->pending and conf->pending_bio_list, I think I come to understand what you worried and the meaning of your fix. I totally agree and understand there will be hash conflict sooner or later now. Yes we need this fix. Thanks to you and Shaohua, explaining the details to me, and help me to catch up your mind :-) Coly -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
