From 22419ac9fe5e79483596cebdbd1d1209c18bac1a Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Fri, 29 May 2015 08:14:55 +1000 Subject: [PATCH] xfs: fix broken i_nlink accounting for whiteout tmpfile inode XFS uses the internal tmpfile() infrastructure for the whiteout inode used for RENAME_WHITEOUT operations. For tmpfile inodes, XFS allocates the inode, drops di_nlink, adds the inode to the agi unlinked list, calls d_tmpfile() which correspondingly drops i_nlink of the vfs inode, and then finishes the common inode setup (e.g., clear I_NEW and unlock). The d_tmpfile() call was originally made inxfs_create_tmpfile(), but was pulled up out of that function as part of the following commit to resolve a deadlock issue: 330033d6 xfs: fix tmpfile/selinux deadlock and initialize security As a result, callers of xfs_create_tmpfile() are responsible for either calling d_tmpfile() or fixing up i_nlink appropriately. The whiteout tmpfile allocation helper does neither. As a result, the vfs ->i_nlink becomes inconsistent with the on-disk ->di_nlink once xfs_rename() links it back into the source dentry and calls xfs_bumplink(). Update the assert in xfs_rename() to help detect this problem in the future and update xfs_rename_alloc_whiteout() to decrement the link count as part of the manual tmpfile inode setup. Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- fs/xfs/xfs_inode.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 1117dd3ba123..539a85fddbc2 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -2879,7 +2879,13 @@ xfs_rename_alloc_whiteout( if (error) return error; - /* Satisfy xfs_bumplink that this is a real tmpfile */ + /* + * Prepare the tmpfile inode as if it were created through the VFS. + * Otherwise, the link increment paths will complain about nlink 0->1. + * Drop the link count as done by d_tmpfile(), complete the inode setup + * and flag it as linkable. + */ + drop_nlink(VFS_I(tmpfile)); xfs_finish_inode_setup(tmpfile); VFS_I(tmpfile)->i_state |= I_LINKABLE; @@ -3147,7 +3153,7 @@ xfs_rename( * intermediate state on disk. */ if (wip) { - ASSERT(wip->i_d.di_nlink == 0); + ASSERT(VFS_I(wip)->i_nlink == 0 && wip->i_d.di_nlink == 0); error = xfs_bumplink(tp, wip); if (error) goto out_trans_abort; -- 2.20.1