Commit f3734cc4 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Chuck Lever
Browse files

NFSD: use read_seqbegin() rather than read_seqbegin_or_lock() 



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.

[ cel: Note also that it eliminates this Sparse warning:

fs/nfsd/nfssvc.c:360:6: warning: context imbalance in 'nfsd_copy_write_verifier' -
	different lock contexts for basic block

]

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 74fd4873

fs/nfsd/nfssvc.c

+3 −4
Original line number Diff line number Diff line
@@ -359,13 +359,12 @@ static bool nfsd_needs_lockd(struct nfsd_net *nn) 
 */

void nfsd_copy_write_verifier(__be32 verf[2], struct nfsd_net *nn)

{

	int seq = 0;

	unsigned int seq;



	do {

		read_seqbegin_or_lock(&nn->writeverf_lock, &seq);

		seq = read_seqbegin(&nn->writeverf_lock);

		memcpy(verf, nn->writeverf, sizeof(nn->writeverf));

	} while (need_seqretry(&nn->writeverf_lock, seq));

	done_seqretry(&nn->writeverf_lock, seq);

	} while (read_seqretry(&nn->writeverf_lock, seq));

}



static void nfsd_reset_write_verifier_locked(struct nfsd_net *nn)