x86/resctrl: Fix potential lockdep warning

rdtgroup_cpus_write() and mkdir_rdt_prepare() call
rdtgroup_kn_lock_live() -> kernfs_to_rdtgroup() to get 'rdtgrp', and
then call the rdt_last_cmd_{clear,puts,...}() functions which will check
if rdtgroup_mutex is held/requires its caller to hold rdtgroup_mutex.

But if 'rdtgrp' returned from kernfs_to_rdtgroup() is NULL,
rdtgroup_mutex is not held and calling rdt_last_cmd_{clear,puts,...}()
will result in a self-incurred, potential lockdep warning.

Remove the rdt_last_cmd_{clear,puts,...}() calls in these two paths.
Just returning error should be sufficient to report to the user that the
entry doesn't exist any more.

 [ bp: Massage. ]

Fixes: 94457b3 ("x86/intel_rdt: Add diagnostics when writing the cpus file")
Fixes: cfd0f34 ("x86/intel_rdt: Add diagnostics when making directories")
Signed-off-by: Xiaochen Shen <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Reviewed-by: Fenghua Yu <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: xiaochenshen

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -461,10 +461,8 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
 	}
 
 	rdtgrp = rdtgroup_kn_lock_live(of->kn);
-	rdt_last_cmd_clear();
 	if (!rdtgrp) {
 		ret = -ENOENT;
-		rdt_last_cmd_puts("Directory was removed\n");
 		goto unlock;
 	}
 
@@ -2648,10 +2646,8 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 	int ret;
 
 	prdtgrp = rdtgroup_kn_lock_live(prgrp_kn);
-	rdt_last_cmd_clear();
 	if (!prdtgrp) {
 		ret = -ENODEV;
-		rdt_last_cmd_puts("Directory was removed\n");
 		goto out_unlock;
 	}