On Mon, Nov 07, 2022 at 10:36:48PM +0800, Long Li wrote: > The following error occurred during the fsstress test: > > XFS: Assertion failed: VFS_I(ip)->i_nlink >= 2, file: fs/xfs/xfs_inode.c, line: 2925 > > The problem was that inode race condition causes incorrect i_nlink to be > written to disk, and then it is read into memory. Consider the following > call graph, inodes that are marked as both XFS_IFLUSHING and > XFS_IRECLAIMABLE, i_nlink will be reset to 1 and then restored to original > value in xfs_reinit_inode(). Therefore, the i_nlink of directory on disk > may be set to 1. > > xfsaild > xfs_inode_item_push > xfs_iflush_cluster > xfs_iflush > xfs_inode_to_disk > > xfs_iget > xfs_iget_cache_hit > xfs_iget_recycle > xfs_reinit_inode > inode_init_always > > So skip inodes that being flushed and markded as XFS_IRECLAIMABLE, prevent > concurrent read and write to inodes. urk. xfs_reinit_inode() needs to hold the ILOCK_EXCL as it is changing internal inode state and can race with other RCU protected inode lookups. Have a look at what xfs_iflush_cluster() does - it grabs the ILOCK_SHARED while under rcu + ip->i_flags_lock, and so xfs_iflush/xfs_inode_to_disk() are protected from racing inode updates (during transactions) by that lock. Hence it looks to me that I_FLUSHING isn't the problem here - it's that we have a transient modified inode state in xfs_reinit_inode() that is externally visisble... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
