[PATCH 2/2] xfs: unhash a removed name in ascii-ci mode instead of invalidating it

[Christian Brauner <brauner@kernel.org>]

xfs_vn_unlink() uses d_invalidate() on the dentry of a removed name on a
case-insensitive filesystem, so that d_delete() doesn't leave a negative
dentry behind. The next create() would otherwise reuse with the wrong
spelling. But as the comment already states all it wants is the unhash.

But d_invalidate() is the wrong primitive for that. It's for a name that
went stale. It walks the subtree, prunes it and detaches every mount it
finds, under namespace_sem, and here that runs from inside the
filesystem's own directory operation. There is nothing below a file or
an empty directory to prune, and vfs_unlink() and vfs_rmdir() detach the
mounts a few lines later as for every other filesystem.

The previous patch moved ext4, f2fs and tmpfs over to d_delete()
unhashing the dentry for them. ascii-ci doesn't set S_CASEFOLD, so the
VFS can't tell these directories apart, and the feature is deprecated
anyway. So just d_drop() the dentry. d_delete() finds it unhashed and
turns it negative without hashing it, exactly as before.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/xfs/xfs_iops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index d307ec97fac8..bed8372e4bcb 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -416,10 +416,10 @@ xfs_vn_unlink(
 	/*
 	 * With unlink, the VFS makes the dentry "negative": no inode,
 	 * but still hashed. This is incompatible with case-insensitive
-	 * mode, so invalidate (unhash) the dentry in CI-mode.
+	 * mode, so unhash the dentry in CI-mode.
 	 */
 	if (xfs_has_asciici(XFS_M(dir->i_sb)))
-		d_invalidate(dentry);
+		d_drop(dentry);
 	return 0;
 }
 

-- 
2.53.0