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xfs: fix incorrect i_nlink caused by inode racing 

commit 28b4b05963 upstream.

The following error occurred during the fsstress test:

XFS: Assertion failed: VFS_I(ip)->i_nlink >= 2, file: fs/xfs/xfs_inode.c, line: 2452

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

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. On the
read side, xfs_iflush_cluster() 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.

Fixes: ff7bebeb91 ("xfs: refactor the inode recycling code") # goes further back than this
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
Reviewed-by: Hui Li <caelli@tencent.com>
Signed-off-by: Jianping Liu <frankjpliu@tencent.com>
This commit is contained in:
Long Li 2022-11-17 13:02:56 -08:00 committed by Jianping Liu
parent 793b06ed32
commit 739bb98579
1 changed files with 6 additions and 0 deletions
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6
fs/xfs/xfs_icache.c
View File

@ -412,6 +412,11 @@ xfs_iget_cache_hit(
goto out_error;
}
if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
error = -EAGAIN;
goto out_error;
}
/*
* We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
* from stomping over us while we recycle the inode. We can't
@ -424,6 +429,7 @@ xfs_iget_cache_hit(
rcu_read_unlock();
error = xfs_reinit_inode(mp, inode);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
if (error) {
bool wake;
/*