From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Fri, 27 Mar 2020 08:06:42 +0100
Subject: s390/gmap: return proper error code on ksm unsharing
Git-commit: 7a2653612bb6f18fb236c5b0c4d28f7b459bf7c2
Patch-mainline: v5.7-rc1
References: git-fixes

If a signal is pending we might return -ENOMEM instead of -EINTR.
We should propagate the proper error during KSM unsharing.
unmerge_ksm_pages returns -ERESTARTSYS on signal_pending. This gets
translated by entry.S to -EINTR. It is important to get this error
code so that userspace can retry.

To make this clearer we also add -EINTR to the documentation of the
PV_ENABLE call, which calls unmerge_ksm_pages.

Fixes: 3ac8e38015d4 ("s390/mm: disable KSM for storage key enabled pages")
Reviewed-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Tested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[ ptesarik: Documentaiton part omitted, becase SLE15 lacks upstream
  commit 04ed89dc4aeba57ab99df16edbd9d06e43d0a2c4.
  The patched code is in s390_enable_skey(), because we do not have
  commit fa0c5eabbdd33012b369cf75d6a39389cc9ae707 either. ]
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/mm/gmap.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2198,10 +2198,10 @@ int s390_enable_skey(void)
 
 	mm->context.uses_skeys = 1;
 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
-		if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
-				MADV_UNMERGEABLE, &vma->vm_flags)) {
+		rc = ksm_madvise(vma, vma->vm_start, vma->vm_end,
+				 MADV_UNMERGEABLE, &vma->vm_flags);
+		if (rc) {
 			mm->context.uses_skeys = 0;
-			rc = -ENOMEM;
 			goto out_up;
 		}
 	}