From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:30574 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752122AbdJFWIl (ORCPT ); Fri, 6 Oct 2017 18:08:41 -0400 From: Allison Henderson Subject: [PATCH 09/17] xfs: define parent pointer xattr format Date: Fri, 6 Oct 2017 15:05:40 -0700 Message-Id: <1507327548-3221-10-git-send-email-allison.henderson@oracle.com> In-Reply-To: <1507327548-3221-1-git-send-email-allison.henderson@oracle.com> References: <1507327548-3221-1-git-send-email-allison.henderson@oracle.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs@vger.kernel.org Cc: Dave Chinner , Allison Henderson From: Dave Chinner We need to define the parent pointer attribute format before we start adding support for it into all the code that needs to use it. The EA format we will use encodes the following information: name={parent inode #, parent inode generation, dirent offset} value={dirent filename} The inode/gen gives all the information we need to reliably identify the parent without requiring child->parent lock ordering, and allows userspace to do pathname component level reconstruction without the kernel ever needing to verify the parent itself as part of ioctl calls. By using the dirent offset in the EA name, we have a method of knowing the exact parent pointer EA we need to modify/remove in rename/unlink without an unbound EA name search. By keeping the dirent name in the value, we have enough information to be able to validate and reconstruct damaged directory trees. While the diroffset of a filename alone is not unique enough to identify the child, the {diroffset,filename,child_inode} tuple is sufficient. That is, if the diroffset gets reused and points to a different filename, we can detect that from the contents of EA. If a link of the same name is created, then we can check whether it points at the same inode as the parent EA we current have. [achender: rebased, changed __unint32_t to xfs_dir2_dataptr_t] Signed-off-by: Dave Chinner Signed-off-by: Allison Henderson --- v2: changed p_ino to xfs_ino_t and p_namelen to uint8_t Signed-off-by: Allison Henderson --- :100644 100644 d4d9bef... a887f21... M fs/xfs/libxfs/xfs_format.h fs/xfs/libxfs/xfs_format.h | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h index d4d9bef..a887f21 100644 --- a/fs/xfs/libxfs/xfs_format.h +++ b/fs/xfs/libxfs/xfs_format.h @@ -18,6 +18,8 @@ #ifndef __XFS_FORMAT_H__ #define __XFS_FORMAT_H__ +#include "xfs_da_format.h" + /* * XFS On Disk Format Definitions * @@ -1721,4 +1723,29 @@ struct xfs_acl { #define SGI_ACL_FILE_SIZE (sizeof(SGI_ACL_FILE)-1) #define SGI_ACL_DEFAULT_SIZE (sizeof(SGI_ACL_DEFAULT)-1) +/* + * Parent pointer attribute format definition + * + * EA name encodes the parent inode number, generation and the offset of + * the dirent that points to the child inode. The EA value contains the + * same name as the dirent in the parent directory. + */ +struct xfs_parent_name_rec { + __be64 p_ino; + __be32 p_gen; + __be32 p_diroffset; +}; + +/* + * incore version of the above, also contains name pointers so callers + * can pass/obtain all the parent pointer information in a single structure + */ +struct xfs_parent_name_irec { + xfs_ino_t p_ino; + uint32_t p_gen; + xfs_dir2_dataptr_t p_diroffset; + const char *p_name; + uint8_t p_namelen; +}; + #endif /* __XFS_FORMAT_H__ */ -- 2.7.4