> 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
