> On Nov 21, 2021, at 8:59 PM, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > On Sun, Nov 21, 2021 at 02:57:14PM -0500, Chuck Lever wrote: >> To address this error: >> >> CC [M] fs/nfsd/filecache.o >> CHECK /home/cel/src/linux/linux/fs/nfsd/filecache.c >> /home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9: error: incompatible types in comparison expression (different address spaces): >> /home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9: struct net [noderef] __rcu * >> /home/cel/src/linux/linux/fs/nfsd/filecache.c:772:9: struct net * >> >> The "net" field in struct nfsd_fcache_disposal is not annotated as >> requiring an RCU assignment. > > I am not immediately seeing this field indirected through by RCU readers, > though maybe that is happening in some other file. > > However, it does look like this field is being accessed locklessly by > read-side code. What prevents the compiler from applying unfortunate > optimizations? > > See tools/memory-model/Documentation/access-marking.txt in a recent > kernel or these LWN articles: https://lwn.net/Articles/816854 and > https://lwn.net/Articles/793253. > > Thanx, Paul Thank you, Paul. I’ll look into it. >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> >> --- >> fs/nfsd/filecache.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c >> index fdf89fcf1a0c..3fa172f86441 100644 >> --- a/fs/nfsd/filecache.c >> +++ b/fs/nfsd/filecache.c >> @@ -772,7 +772,7 @@ nfsd_alloc_fcache_disposal(struct net *net) >> static void >> nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l) >> { >> - rcu_assign_pointer(l->net, NULL); >> + l->net = NULL; >> cancel_work_sync(&l->work); >> nfsd_file_dispose_list(&l->freeme); >> kfree_rcu(l, rcu); >>
