From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Andrea Arcangeli <aarcange@redhat.com>,
David Hildenbrand <david@redhat.com>,
linuxppc-dev@lists.ozlabs.org,
Anshuman Khandual <anshuman.khandual@arm.com>,
Dave Chinner <david@fromorbit.com>,
Mel Gorman <mgorman@techsingularity.net>,
Peter Xu <peterx@redhat.com>,
linux-mm@kvack.org, Hugh Dickins <hughd@google.com>,
Nadav Amit <namit@vmware.com>,
Nicholas Piggin <npiggin@gmail.com>,
Mike Rapoport <rppt@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH RFC 2/5] mm/mprotect: minor can_change_pte_writable() cleanups
Date: Mon, 26 Sep 2022 17:26:15 +0200 [thread overview]
Message-ID: <20220926152618.194810-3-david@redhat.com> (raw)
In-Reply-To: <20220926152618.194810-1-david@redhat.com>
We want to replicate this code for handling PMDs soon. No need to crash
the kernel, warning and rejecting is good enough. As this will no longer
get optimized out, drop the pte_write() check: no harm would be done.
While at it, add a comment why PROT_NONE mapped pages are excluded.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/mprotect.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/mprotect.c b/mm/mprotect.c
index c6c13a0a4bcc..95323bc9a951 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -43,8 +43,10 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma,
{
struct page *page;
- VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte));
+ if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
+ return false;
+ /* Don't touch entries that are not even readable (NUMA hinting). */
if (pte_protnone(pte))
return false;
--
2.37.3
next prev parent reply other threads:[~2022-09-26 15:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 15:26 [PATCH RFC 0/5] mm/autonuma: replace savedwrite infrastructure David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 1/5] mm/mprotect: allow clean exclusive anon pages to be writable David Hildenbrand
2022-09-26 15:26 ` David Hildenbrand [this message]
2022-09-26 15:26 ` [PATCH RFC 3/5] mm/huge_memory: try avoiding write faults when changing PMD protection David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 4/5] mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 5/5] mm: remove unused savedwrite infrastructure David Hildenbrand
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