> On Oct 27, 2023, at 12:34 PM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > On 10/27, Chuck Lever wrote: >> >> On Thu, Oct 26, 2023 at 04:50:18PM +0200, Oleg Nesterov wrote: >>> The usage of read_seqbegin_or_lock() in nfsd_copy_write_verifier() >>> is wrong. "seq" is always even and thus "or_lock" has no effect, >>> this code can never take ->writeverf_lock for writing. >>> >>> I guess this is fine, nfsd_copy_write_verifier() just copies 8 bytes >>> and nfsd_reset_write_verifier() is supposed to be very rare operation >>> so we do not need the adaptive locking in this case. >>> >>> Yet the code looks wrong and sub-optimal, it can use read_seqbegin() >>> without changing the behaviour. >> >> I was debating whether to add Fixes/Cc-stable, but if the behavior >> doesn't change, this doesn't need a backport. > > Yes, yes, sorry for confusion. This code is not buggy. Just a) it looks > confusing because read_seqbegin_or_lock() doesn't do what it is supposed > to do, and b) I am going to change the semantics of done_seqretry() to > enforce the locking on the 2nd pass. > > Chuck, I can reword the changelog to make it more clear and send V2 if > you think this makes sense. No confusion, the changelog is clear to me. I'm simply stating my intention for other reviewers and the lore archive that I will leave off Fixes/Cc-stable when I commit your patch. So far there has been no review comment that suggests we need a v2. -- Chuck Lever
