afs: Fix getattr to report server i_size on dirs, not local size

Fix afs_getattr() to report the server's idea of the file size of a
directory rather than the local size.  The local size may differ as we edit
the local copy to avoid having to redownload it and we may end up with a
differently structured blob of a different size.

However, if the directory is discarded from the pagecache we then download
it again and the user may see the directory file size apparently change.

Fixes: 63a4681ff3 ("afs: Locally edit directory data for mkdir/create/unlink/...")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

fs/afs/inode.c

@@ -450,7 +450,7 @@ static void afs_get_inode_cache(struct afs_vnode *vnode)
 				    0 : FSCACHE_ADV_SINGLE_CHUNK,
 				    &key, sizeof(key),
 				    &aux, sizeof(aux),
-				    vnode->status.size));
+				    i_size_read(&vnode->netfs.inode)));
 #endif
 }
 
@@ -777,6 +777,13 @@ int afs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		if (test_bit(AFS_VNODE_SILLY_DELETED, &vnode->flags) &&
 		    stat->nlink > 0)
 			stat->nlink -= 1;
+
+		/* Lie about the size of directories.  We maintain a locally
+		 * edited copy and may make different allocation decisions on
+		 * it, but we need to give userspace the server's size.
+		 */
+		if (S_ISDIR(inode->i_mode))
+			stat->size = vnode->netfs.remote_i_size;
 	} while (need_seqretry(&vnode->cb_lock, seq));
 
 	done_seqretry(&vnode->cb_lock, seq);