From: Trond Myklebust <redacted>

For filesystems that are case insensitive and case preserving, we need
to be able to rename from one case folded variant of the filename to
another.
Currently, if we have looked up the target filename before the call to
rename, then we may have a hashed dentry with that target name in the
dcache, causing the vfs to optimise away the rename.
To avoid that, let's drop the target dentry, and leave it to the server
to optimise away the rename if that is the correct thing to do.

Signed-off-by: Trond Myklebust <redacted>
---
 fs/nfs/dir.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 0c4e8dd6aa96..d9d277d7fa84 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c

@@ -1739,6 +1739,10 @@ nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
 		goto out_bad;
 	}
 
+	if ((flags & LOOKUP_RENAME_TARGET) && d_count(dentry) < 2 &&
+	    nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
+		goto out_bad;
+
 	if (nfs_verifier_is_delegated(dentry))
 		return nfs_lookup_revalidate_delegated(dir, dentry, inode);
 

-- 
2.36.1