> On Dec 13, 2021, at 2:54 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Mon, 2021-12-13 at 19:42 +0000, Chuck Lever III wrote: >> Hi Rick- >> >>> On Dec 9, 2021, at 6:15 PM, Rick Macklem <rmacklem@xxxxxxxxxxx> >>> wrote: >>> >>> Hi, >>> >>> When testing against the knfsd in a Linux 5.15.1 kernel, I received >>> a >>> write reply with FILE_SYNC and a writeverf of all 0 bytes. >>> (Previous write verifiers were not all 0 bytes.) >>> >>> The server seemed to be functioning normally and had not rebooted. >>> >>> Is this intended behaviour? >>> >>> Normally I would not expect the writeverf in a Write operation >>> reply >>> to change unless the server had rebooted, but I can see there might >>> be circumstances where the knfsd server wants all non-FILE_SYNC >>> writes to be redone by the client and would choose to change the >>> writeverf. >>> However, changing it to all 0 bytes seems particularly odd? >> >> I don't immediately see a code path for WRITE or COMMIT that would >> set the verifier to zeroes. When Linux NFSD resets its write >> verifier, >> it sets it to the current time. >> >> Do you have a reproducer you can share? >> > > Rick is using FILE_SYNC, whereas nfsd_vfs_write() only actually sets > the boot verifier if the write is unstable or DATA_SYNC. It wasn't clear from Rick's note that the verifier change he observed was not permanent. So then the answer to "Is this intended behavior?" is "Yes, Linux NFSD returns an all-zero verifier for FILE_SYNC writes, since the client does not use the verifier in this case. The boot verifier for subsequent non-FILE_SYNC writes is not altered." -- Chuck Lever
