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. Thanks, Oleg.
