From: Eric Sandeen Subject: [PATCH] debugfs: properly set up extent header in do_write Date: Wed, 24 Jul 2013 10:11:25 -0500 Message-ID: <51EFEE9D.9070501@redhat.com> References: <51EF975E.2090700@windriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Darrick J. Wong" , linux-ext4@vger.kernel.org, "Theodore Ts'o" , Darren Hart To: Robert Yang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:16590 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751645Ab3GXPLb (ORCPT ); Wed, 24 Jul 2013 11:11:31 -0400 In-Reply-To: <51EF975E.2090700@windriver.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: do_write doesn't fully set up the first extent header on a new inode, so if we write a 0-length file, and don't write any data to the new file, we end up creating something that looks corrupt to kernelspace: EXT4-fs error (device loop0): ext4_ext_check_inode:464: inode #12: comm ls: bad header/extent: invalid magic - magic 0, entries 0, max 0(0), depth 0(0) Do something similar to ext4_ext_tree_init() here, and fill out the first extent header upon creation to avoid this. Reported-by: Robert Yang Signed-off-by: Eric Sandeen --- diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c index dcf16e2..2660218 100644 --- a/debugfs/debugfs.c +++ b/debugfs/debugfs.c @@ -1677,8 +1677,19 @@ void do_write(int argc, char *argv[]) inode.i_links_count = 1; inode.i_size = statbuf.st_size; if (current_fs->super->s_feature_incompat & - EXT3_FEATURE_INCOMPAT_EXTENTS) + EXT3_FEATURE_INCOMPAT_EXTENTS) { + int i; + struct ext3_extent_header *eh; + + eh = (struct ext3_extent_header *) &inode.i_block[0]; + eh->eh_depth = 0; + eh->eh_entries = 0; + eh->eh_magic = EXT3_EXT_MAGIC; + i = (sizeof(inode.i_block) - sizeof(*eh)) / + sizeof(struct ext3_extent); + eh->eh_max = ext2fs_cpu_to_le16(i); inode.i_flags |= EXT4_EXTENTS_FL; + } if (debugfs_write_new_inode(newfile, &inode, argv[0])) { close(fd); return;