This is a note to let you know that I've just added the patch titled
thp: reduce indentation level in change_huge_pmd()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
thp-reduce-indentation-level-in-change_huge_pmd.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0a85e51d37645e9ce57e5e1a30859e07810ed07c Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Thu, 13 Apr 2017 14:56:17 -0700
Subject: thp: reduce indentation level in change_huge_pmd()
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream.
Patch series "thp: fix few MADV_DONTNEED races"
For MADV_DONTNEED to work properly with huge pages, it's critical to not
clear pmd intermittently unless you hold down_write(mmap_sem).
Otherwise MADV_DONTNEED can miss the THP which can lead to userspace
breakage.
See example of such race in commit message of patch 2/4.
All these races are found by code inspection. I haven't seen them
triggered. I don't think it's worth to apply them to stable@.
This patch (of 4):
Restructure code in preparation for a fix.
Link: http://lkml.kernel.org/r/20170302151034.27829-2-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[jwang: adjust context for 4.4 kernel]
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 54 ++++++++++++++++++++++++++++--------------------------
1 file changed, 28 insertions(+), 26 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1566,35 +1566,37 @@ int change_huge_pmd(struct vm_area_struc
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
+ pmd_t entry;
+ bool preserve_write;
+
int ret = 0;
- if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
- pmd_t entry;
- bool preserve_write = prot_numa && pmd_write(*pmd);
- ret = 1;
-
- /*
- * Avoid trapping faults against the zero page. The read-only
- * data is likely to be read-cached on the local CPU and
- * local/remote hits to the zero page are not interesting.
- */
- if (prot_numa && is_huge_zero_pmd(*pmd)) {
- spin_unlock(ptl);
- return ret;
- }
-
- if (!prot_numa || !pmd_protnone(*pmd)) {
- entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
- entry = pmd_modify(entry, newprot);
- if (preserve_write)
- entry = pmd_mkwrite(entry);
- ret = HPAGE_PMD_NR;
- set_pmd_at(mm, addr, pmd, entry);
- BUG_ON(!preserve_write && pmd_write(entry));
- }
- spin_unlock(ptl);
- }
+ if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
+ return 0;
+
+ preserve_write = prot_numa && pmd_write(*pmd);
+ ret = 1;
+
+ /*
+ * Avoid trapping faults against the zero page. The read-only
+ * data is likely to be read-cached on the local CPU and
+ * local/remote hits to the zero page are not interesting.
+ */
+ if (prot_numa && is_huge_zero_pmd(*pmd))
+ goto unlock;
+
+ if (prot_numa && pmd_protnone(*pmd))
+ goto unlock;
+ entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
+ entry = pmd_modify(entry, newprot);
+ if (preserve_write)
+ entry = pmd_mkwrite(entry);
+ ret = HPAGE_PMD_NR;
+ set_pmd_at(mm, addr, pmd, entry);
+ BUG_ON(!preserve_write && pmd_write(entry));
+unlock:
+ spin_unlock(ptl);
return ret;
}
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.4/mm-drop-unused-pmdp_huge_get_and_clear_notify.patch
queue-4.4/thp-fix-madv_dontneed-vs.-numa-balancing-race.patch
queue-4.4/thp-reduce-indentation-level-in-change_huge_pmd.patch