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.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
fs/nfsd/nfssvc.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index c7af1095f6b5..094b765c5397 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -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 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)
--
2.25.1.362.g51ebf55
