Hi,
this is a backport of commit 7aa54be297655 ("locking/qspinlock, x86:
Provide liveness guarantee") for the v4.9 stable tree.
For the v4.4 tree the ARCH_USE_QUEUED_SPINLOCKS option got disabled on
x86.
For v4.9 it has been decided to do a minimal backport of the final fix
(including all its dependencies).
With this backport I can't reproduce the issue in the latest v4.9-RT
tree. I was able to boot (and use) an arm64 box with these patches so it
is not broken in an abvious way.
Sebastian
The patch titled
Subject: mm: thp: fix flags for pmd migration when split
has been added to the -mm tree. Its filename is
mm-thp-fix-flags-for-pmd-migration-when-split.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-fix-flags-for-pmd-migration…
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-fix-flags-for-pmd-migration…
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peter Xu <peterx(a)redhat.com>
Subject: mm: thp: fix flags for pmd migration when split
When splitting a huge migrating PMD, we'll transfer all the existing PMD
bits and apply them again onto the small PTEs. However we are fetching
the bits unconditionally via pmd_soft_dirty(), pmd_write() or pmd_yound()
while actually they don't make sense at all when it's a migration entry.
Fix them up. Since at it, drop the ifdef together as not needed.
Note that if my understanding is correct about the problem then if without
the patch there is chance to lose some of the dirty bits in the migrating
pmd pages (on x86_64 we're fetching bit 11 which is part of swap offset
instead of bit 2) and it could potentially corrupt the memory of an
userspace program which depends on the dirty bit.
Link: http://lkml.kernel.org/r/20181213051510.20306-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx(a)redhat.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov(a)yandex-team.ru>
Reviewed-by: William Kucharski <william.kucharski(a)oracle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov(a)linux.intel.com>
Cc: Andrea Arcangeli <aarcange(a)redhat.com>
Cc: Matthew Wilcox <willy(a)infradead.org>
Cc: Michal Hocko <mhocko(a)suse.com>
Cc: Dave Jiang <dave.jiang(a)intel.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar(a)linux.vnet.ibm.com>
Cc: Souptick Joarder <jrdr.linux(a)gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov(a)yandex-team.ru>
Cc: Zi Yan <zi.yan(a)cs.rutgers.edu>
Cc: <stable(a)vger.kernel.org> [4.14+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
--- a/mm/huge_memory.c~mm-thp-fix-flags-for-pmd-migration-when-split
+++ a/mm/huge_memory.c
@@ -2144,23 +2144,25 @@ static void __split_huge_pmd_locked(stru
*/
old_pmd = pmdp_invalidate(vma, haddr, pmd);
-#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
pmd_migration = is_pmd_migration_entry(old_pmd);
- if (pmd_migration) {
+ if (unlikely(pmd_migration)) {
swp_entry_t entry;
entry = pmd_to_swp_entry(old_pmd);
page = pfn_to_page(swp_offset(entry));
- } else
-#endif
+ write = is_write_migration_entry(entry);
+ young = false;
+ soft_dirty = pmd_swp_soft_dirty(old_pmd);
+ } else {
page = pmd_page(old_pmd);
+ if (pmd_dirty(old_pmd))
+ SetPageDirty(page);
+ write = pmd_write(old_pmd);
+ young = pmd_young(old_pmd);
+ soft_dirty = pmd_soft_dirty(old_pmd);
+ }
VM_BUG_ON_PAGE(!page_count(page), page);
page_ref_add(page, HPAGE_PMD_NR - 1);
- if (pmd_dirty(old_pmd))
- SetPageDirty(page);
- write = pmd_write(old_pmd);
- young = pmd_young(old_pmd);
- soft_dirty = pmd_soft_dirty(old_pmd);
/*
* Withdraw the table only after we mark the pmd entry invalid.
_
Patches currently in -mm which might be from peterx(a)redhat.com are
mm-thp-fix-flags-for-pmd-migration-when-split.patch
userfaultfd-clear-flag-if-remap-event-not-enabled.patch