lockd: use locks_inode_context helper

lockd currently doesn't access i_flctx safely. This requires a
smp_load_acquire, as the pointer is set via cmpxchg (a release
operation).

Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

Author: jtlayton

fs/lockd/svcsubs.c

@@ -207,7 +207,7 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
 {
 	struct inode	 *inode = nlmsvc_file_inode(file);
 	struct file_lock *fl;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 	struct nlm_host	 *lockhost;
 
 	if (!flctx || list_empty_careful(&flctx->flc_posix))
@@ -262,7 +262,7 @@ nlm_file_inuse(struct nlm_file *file)
 {
 	struct inode	 *inode = nlmsvc_file_inode(file);
 	struct file_lock *fl;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 
 	if (file->f_count || !list_empty(&file->f_blocks) || file->f_shares)
 		return 1;