cifs: use locks_inode_context helper

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

Cc: Steve French <smfrench@samba.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

fs/cifs/file.c

@@ -1413,7 +1413,7 @@ cifs_push_posix_locks(struct cifsFileInfo *cfile)
 	struct inode *inode = d_inode(cfile->dentry);
 	struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
 	struct file_lock *flock;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 	unsigned int count = 0, i;
 	int rc = 0, xid, type;
 	struct list_head locks_to_send, *el;