[PATCH] nfsd: add lock annotations to e_start and e_stop

e_start acquires svc_export_cache.hash_lock, and e_stop releases it.  Add
lock annotations to these two functions so that sparse can check callers
for lock pairing, and so that sparse will not complain about these
functions since they intentionally use locks in this manner.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/export.c

@@ -1078,6 +1078,7 @@ exp_pseudoroot(struct auth_domain *clp, struct svc_fh *fhp,
 /* Iterator */
 
 static void *e_start(struct seq_file *m, loff_t *pos)
+	__acquires(svc_export_cache.hash_lock)
 {
 	loff_t n = *pos;
 	unsigned hash, export;
@@ -1131,6 +1132,7 @@ static void *e_next(struct seq_file *m, void *p, loff_t *pos)
 }
 
 static void e_stop(struct seq_file *m, void *p)
+	__releases(svc_export_cache.hash_lock)
 {
 	read_unlock(&svc_export_cache.hash_lock);
 	exp_readunlock();