Hi, Xiao Any ideas on this issue? Cheers, Miao Wang > 2021年06月09日 17:03，Wang Shanker <shankerwangmiao@xxxxxxxxx> 写道： > >> >> 2021年06月09日 16:44，Xiao Ni <xni@xxxxxxxxxx> 写道： >> >> Hi all >> >> Thanks for reporting about this. I did a test in my environment. >> time blkdiscard /dev/nvme5n1 (477GB) >> real 0m0.398s >> time blkdiscard /dev/md0 >> real 9m16.569s >> >> I'm not familiar with the block layer codes. I'll try to understand >> the codes related with discard request and >> try to fix this problem. >> >> I have a question for raid5 discard, it needs to consider more than >> raid0 and raid10. For example, there is a raid5 with 3 disks. >> D11 D21 P1 (stripe size is 4KB) >> D12 D22 P2 >> D13 D23 P3 >> D14 D24 P4 >> ... (chunk size is 512KB) >> If there is a discard request on D13 and D14, and there is no discard >> request on D23 D24. It can't send >> discard request to D13 and D14, right? P3 = D23 xor D13. If we discard >> D13 and disk2 is broken, it can't >> get the right data from D13 and P3. The discard request on D13 can >> write 0 to the discard region, right? > > Yes. It can be seen at the beginning of make_discard_request(), where > the requested range being discarded is aligned to ``stripe_sectors", > which should be chunk_sectors * nr_data_disks. > > Cheers, > > Miao Wang
