linux-kernel - Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of walk_page

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Message-Id: <20250609105513.10901-1-21cnbao@gmail.com>
Date: Mon,  9 Jun 2025 22:55:13 +1200
From: Barry Song <21cnbao@...il.com>
To: lorenzo.stoakes@...cle.com,
	akpm@...ux-foundation.org
Cc: 21cnbao@...il.com,
	Liam.Howlett@...cle.com,
	anshuman.khandual@....com,
	david@...hat.com,
	dev.jain@....com,
	jannh@...gle.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	lokeshgidra@...gle.com,
	osalvador@...e.de,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	vbabka@...e.cz,
	zhengtangquan@...o.com
Subject: Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of walk_page_range()

> Yeah dear god I missed this oops!
>
> Yeah Barry - could you revert this change for the guard region bits please? So
> this is intentional as we do not want anything non-mm to have access to
> install_pte.

All my fault! I wrote a multi-process/thread test to issue lots of madvise  
calls, but it looks like I missed INSTALL_GUARD.

Thanks, Ryan & Lorenzo! Does Andrew prefer to pick up the fix below, or  
would it be better to send a new version? He’s handled fixes like this in  
the past—happy to resend if needed.

From: Barry Song <v-songbaohua@...o.com>
Date: Mon, 9 Jun 2025 22:42:13 +1200
Subject: [PATCH] mm: madvise: revert the walk_page_range_vma change for
 MADV_GUARD_INSTALL

Fix the broken MADV_GUARD_INSTALL reported by Ryan.
 # guard-regions.c:719:split_merge:Expected madvise(ptr, 10 * page_size,
 MADV_GUARD_INSTALL) (-1) == 0 (0)

Reported-by: Ryan Roberts <ryan.roberts@....com>
Closes: https://lore.kernel.org/linux-mm/671f8164-a90b-48d7-9446-359eb9493500@arm.com/
Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
 mm/madvise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 8382614b71d1..381eedde8f6d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1141,7 +1141,7 @@ static long madvise_guard_install(struct vm_area_struct *vma,
 		unsigned long nr_pages = 0;
 
 		/* Returns < 0 on error, == 0 if success, > 0 if zap needed. */
-		err = walk_page_range_vma(vma, start, end,
+		err = walk_page_range_mm(vma->vm_mm, start, end,
 					 &guard_install_walk_ops, &nr_pages);
 		if (err < 0)
 			return err;
-- 
2.39.3 (Apple Git-146)