+ mm-hugetlb_vmemmap-disable-hugetlb_optimize_vmemmap-when-struct-page-crosses-page-boundaries.patch added to mm-unstable branch

* + mm-hugetlb_vmemmap-disable-hugetlb_optimize_vmemmap-when-struct-page-crosses-page-boundaries.patch added to mm-unstable branch
@ 2022-04-29 16:46 Andrew Morton
  0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2022-04-29 16:46 UTC (permalink / raw)
  To: mm-commits, yzaikin, osalvador, mike.kravetz, mcgrof, masahiroy,
	keescook, duanxiongchun, david, corbet, songmuchun, akpm


The patch titled
     Subject: mm: hugetlb_vmemmap: disable hugetlb_optimize_vmemmap when struct page crosses page boundaries
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hugetlb_vmemmap-disable-hugetlb_optimize_vmemmap-when-struct-page-crosses-page-boundaries.patch

This patch should soon appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: hugetlb_vmemmap: disable hugetlb_optimize_vmemmap when struct page crosses page boundaries

Patch series "add hugetlb_optimize_vmemmap sysctl", v9.

This series aims to add hugetlb_optimize_vmemmap sysctl to enable or
disable the feature of optimizing vmemmap pages associated with HugeTLB
pages.


This patch (of 4):

If the size of "struct page" is not the power of two but with the feature
of minimizing overhead of struct page associated with each HugeTLB is
enabled, then the vmemmap pages of HugeTLB will be corrupted after
remapping (panic is about to happen in theory).  But this only exists when
!CONFIG_MEMCG && !CONFIG_SLUB on x86_64.  However, it is not a
conventional configuration nowadays.  So it is not a real word issue, just
the result of a code review.

But we cannot prevent anyone from configuring that combined configure. 
This hugetlb_optimize_vmemmap should be disable in this case to fix this
issue.

Link: https://lkml.kernel.org/r/20220429121816.37541-1-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220429121816.37541-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb_vmemmap.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/mm/hugetlb_vmemmap.c~mm-hugetlb_vmemmap-disable-hugetlb_optimize_vmemmap-when-struct-page-crosses-page-boundaries
+++ a/mm/hugetlb_vmemmap.c
@@ -28,12 +28,6 @@ EXPORT_SYMBOL(hugetlb_optimize_vmemmap_k
 
 static int __init hugetlb_vmemmap_early_param(char *buf)
 {
-	/* We cannot optimize if a "struct page" crosses page boundaries. */
-	if (!is_power_of_2(sizeof(struct page))) {
-		pr_warn("cannot free vmemmap pages because \"struct page\" crosses page boundaries\n");
-		return 0;
-	}
-
 	if (!buf)
 		return -EINVAL;
 
@@ -119,6 +113,12 @@ void __init hugetlb_vmemmap_init(struct
 	if (!hugetlb_optimize_vmemmap_enabled())
 		return;
 
+	if (!is_power_of_2(sizeof(struct page))) {
+		pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n");
+		static_branch_disable(&hugetlb_optimize_vmemmap_key);
+		return;
+	}
+
 	vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;
 	/*
 	 * The head page is not to be freed to buddy allocator, the other tail
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-hugetlb_vmemmap-disable-hugetlb_optimize_vmemmap-when-struct-page-crosses-page-boundaries.patch
mm-memory_hotplug-override-memmap_on_memory-when-hugetlb_free_vmemmap=on.patch
mm-hugetlb_vmemmap-use-kstrtobool-for-hugetlb_vmemmap-param-parsing.patch
mm-hugetlb_vmemmap-add-hugetlb_optimize_vmemmap-sysctl.patch


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