linux-kernel - Re: [PATCH v4 09/14] mm: add ability to take further action in vm_area

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Message-ID: <20f1c97d-b958-474c-b3a1-8ea9a177e096@lucifer.local>
Date: Thu, 18 Sep 2025 10:14:23 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
        Guo Ren <guoren@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
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Subject: Re: [PATCH v4 09/14] mm: add ability to take further action in
 vm_area_desc

Hi Andrew,

Finally could you apply the below, which has us return an error in case of
somebody implementing a buggy nommu action.

I also include a fix for the VMA unit tests where an enum declare was not
correctly propagated.

Cheers, Lorenzo

----8<----
>From 17c8037bc3bfd5cdd52369dc6140d0fbbd03480d Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Date: Thu, 18 Sep 2025 08:08:31 +0100
Subject: [PATCH] fixup: return error on broken path, update vma_internal.h

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 mm/util.c                        | 6 ++++--
 tools/testing/vma/vma_internal.h | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index 0c1c68285675..30ed284bb819 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1385,17 +1385,19 @@ EXPORT_SYMBOL(mmap_action_prepare);
 int mmap_action_complete(struct mmap_action *action,
 			struct vm_area_struct *vma)
 {
+	int err = 0;
+
 	switch (action->type) {
 	case MMAP_NOTHING:
 		break;
 	case MMAP_REMAP_PFN:
 	case MMAP_IO_REMAP_PFN:
 		WARN_ON_ONCE(1); /* nommu cannot handle this. */
-
+		err = -EINVAL;
 		break;
 	}

-	return mmap_action_finish(action, vma, /* err = */0);
+	return mmap_action_finish(action, vma, err);
 }
 EXPORT_SYMBOL(mmap_action_complete);
 #endif
diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index 22ed38e8714e..d5028e5e905b 100644
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -279,6 +279,7 @@ struct vm_area_struct;
 enum mmap_action_type {
 	MMAP_NOTHING,		/* Mapping is complete, no further action. */
 	MMAP_REMAP_PFN,		/* Remap PFN range. */
+	MMAP_IO_REMAP_PFN,	/* I/O remap PFN range. */
 };

 /*
--
2.51.0