afs: Make afs_init_request() get a key if not given a file

In a future patch, AFS directory caching will go through netfslib and this
will involve, at times, running on behalf of ->lookup(), which doesn't
provide us with a file from which we can get an authentication key.

If a file isn't provided, make afs_init_request() get a key from the
process's keyrings instead when setting up a read.

Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
cc: Marc Dionne <[email protected]>
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

Author: dhowells

fs/afs/file.c

@@ -372,10 +372,26 @@ static int afs_symlink_read_folio(struct file *file, struct folio *folio)
 
 static int afs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
+	struct afs_vnode *vnode = AFS_FS_I(rreq->inode);
+
 	if (file)
 		rreq->netfs_priv = key_get(afs_file_key(file));
 	rreq->rsize = 256 * 1024;
 	rreq->wsize = 256 * 1024 * 1024;
+
+	switch (rreq->origin) {
+	case NETFS_READ_SINGLE:
+		if (!file) {
+			struct key *key = afs_request_key(vnode->volume->cell);
+
+			if (IS_ERR(key))
+				return PTR_ERR(key);
+			rreq->netfs_priv = key;
+		}
+		break;
+	default:
+		break;
+	}
 	return 0;
 }