NFS: Add a helper to remove case-insensitive aliases

When dealing with case insensitive names, the client has no idea how the
server performs the mapping, so cannot collapse the dentries into a
single representative. So both rename and unlink need to deal with the
fact that there could be several dentries representing the file, and
have to somehow force them to be revalidated. Use d_prune_aliases() as a
big hammer approach.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/dir.c

@@ -1819,6 +1819,14 @@ struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, unsigned in
 }
 EXPORT_SYMBOL_GPL(nfs_lookup);
 
+void nfs_d_prune_case_insensitive_aliases(struct inode *inode)
+{
+	/* Case insensitive server? Revalidate dentries */
+	if (inode && nfs_server_capable(inode, NFS_CAP_CASE_INSENSITIVE))
+		d_prune_aliases(inode);
+}
+EXPORT_SYMBOL_GPL(nfs_d_prune_case_insensitive_aliases);
+
 #if IS_ENABLED(CONFIG_NFS_V4)
 static int nfs4_lookup_revalidate(struct dentry *, unsigned int);
 
@@ -2199,8 +2207,10 @@ static void nfs_dentry_remove_handle_error(struct inode *dir,
 	switch (error) {
 	case -ENOENT:
 		d_delete(dentry);
-		fallthrough;
+		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
+		break;
 	case 0:
+		nfs_d_prune_case_insensitive_aliases(d_inode(dentry));
 		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
 	}
 }

fs/nfs/internal.h

@@ -373,6 +373,7 @@ extern unsigned long nfs_access_cache_count(struct shrinker *shrink,
 extern unsigned long nfs_access_cache_scan(struct shrinker *shrink,
 					   struct shrink_control *sc);
 struct dentry *nfs_lookup(struct inode *, struct dentry *, unsigned int);
+void nfs_d_prune_case_insensitive_aliases(struct inode *inode);
 int nfs_create(struct user_namespace *, struct inode *, struct dentry *,
 	       umode_t, bool);
 int nfs_mkdir(struct user_namespace *, struct inode *, struct dentry *,

fs/nfs/nfs4proc.c

@@ -4670,8 +4670,10 @@ static void nfs4_proc_unlink_setup(struct rpc_message *msg,
 
 	nfs_fattr_init(res->dir_attr);
 
-	if (inode)
+	if (inode) {
 		nfs4_inode_return_delegation(inode);
+		nfs_d_prune_case_insensitive_aliases(inode);
+	}
 }
 
 static void nfs4_proc_unlink_rpc_prepare(struct rpc_task *task, struct nfs_unlinkdata *data)
@@ -4737,6 +4739,7 @@ static int nfs4_proc_rename_done(struct rpc_task *task, struct inode *old_dir,
 		return 0;
 
 	if (task->tk_status == 0) {
+		nfs_d_prune_case_insensitive_aliases(d_inode(data->old_dentry));
 		if (new_dir != old_dir) {
 			/* Note: If we moved a directory, nlink will change */
 			nfs4_update_changeattr(old_dir, &res->old_cinfo,