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Message-Id: <20210709131647.517281884@linuxfoundation.org>
Date: Fri, 9 Jul 2021 15:20:20 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Yang Shi <shy828301@...il.com>,
Wang Yugui <wangyugui@...-tech.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Naoya Horiguchi <naoya.horiguchi@....com>,
Alistair Popple <apopple@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Minchan Kim <minchan@...nel.org>, Jue Wang <juew@...gle.com>,
Peter Xu <peterx@...hat.com>, Jan Kara <jack@...e.cz>,
Shakeel Butt <shakeelb@...gle.com>,
Oscar Salvador <osalvador@...e.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 04/34] mm/thp: fix __split_huge_pmd_locked() on shmem migration entry
From: Hugh Dickins <hughd@...gle.com>
[ Upstream commit 99fa8a48203d62b3743d866fc48ef6abaee682be ]
Patch series "mm/thp: fix THP splitting unmap BUGs and related", v10.
Here is v2 batch of long-standing THP bug fixes that I had not got
around to sending before, but prompted now by Wang Yugui's report
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/
Wang Yugui has tested a rollup of these fixes applied to 5.10.39, and
they have done no harm, but have *not* fixed that issue: something more
is needed and I have no idea of what.
This patch (of 7):
Stressing huge tmpfs page migration racing hole punch often crashed on
the VM_BUG_ON(!pmd_present) in pmdp_huge_clear_flush(), with DEBUG_VM=y
kernel; or shortly afterwards, on a bad dereference in
__split_huge_pmd_locked() when DEBUG_VM=n. They forgot to allow for pmd
migration entries in the non-anonymous case.
Full disclosure: those particular experiments were on a kernel with more
relaxed mmap_lock and i_mmap_rwsem locking, and were not repeated on the
vanilla kernel: it is conceivable that stricter locking happens to avoid
those cases, or makes them less likely; but __split_huge_pmd_locked()
already allowed for pmd migration entries when handling anonymous THPs,
so this commit brings the shmem and file THP handling into line.
And while there: use old_pmd rather than _pmd, as in the following
blocks; and make it clearer to the eye that the !vma_is_anonymous()
block is self-contained, making an early return after accounting for
unmapping.
Link: https://lkml.kernel.org/r/af88612-1473-2eaa-903-8d1a448b26@google.com
Link: https://lkml.kernel.org/r/dd221a99-efb3-cd1d-6256-7e646af29314@google.com
Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp")
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Yang Shi <shy828301@...il.com>
Cc: Wang Yugui <wangyugui@...-tech.com>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@....com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Jue Wang <juew@...gle.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Jan Kara <jack@...e.cz>
Cc: Shakeel Butt <shakeelb@...gle.com>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Note on stable backport: this commit made intervening cleanups in
pmdp_huge_clear_flush() redundant: here it's rediffed to skip them.
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
mm/huge_memory.c | 27 ++++++++++++++++++---------
mm/pgtable-generic.c | 4 ++--
2 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 7c374c0fcf0c..ce6ca09840bd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2125,7 +2125,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
count_vm_event(THP_SPLIT_PMD);
if (!vma_is_anonymous(vma)) {
- _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+ old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
/*
* We are going to unmap this huge page. So
* just go ahead and zap it
@@ -2134,16 +2134,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
zap_deposited_table(mm, pmd);
if (vma_is_dax(vma))
return;
- page = pmd_page(_pmd);
- if (!PageDirty(page) && pmd_dirty(_pmd))
- set_page_dirty(page);
- if (!PageReferenced(page) && pmd_young(_pmd))
- SetPageReferenced(page);
- page_remove_rmap(page, true);
- put_page(page);
+ if (unlikely(is_pmd_migration_entry(old_pmd))) {
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(old_pmd);
+ page = migration_entry_to_page(entry);
+ } else {
+ page = pmd_page(old_pmd);
+ if (!PageDirty(page) && pmd_dirty(old_pmd))
+ set_page_dirty(page);
+ if (!PageReferenced(page) && pmd_young(old_pmd))
+ SetPageReferenced(page);
+ page_remove_rmap(page, true);
+ put_page(page);
+ }
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
- } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
+ }
+
+ if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_invalidate_range() see comments below inside
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index cf2af04b34b9..36770fcdc358 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -125,8 +125,8 @@ pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,
{
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- VM_BUG_ON((pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) &&
- !pmd_devmap(*pmdp)) || !pmd_present(*pmdp));
+ VM_BUG_ON(pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) &&
+ !pmd_devmap(*pmdp));
pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return pmd;
--
2.30.2
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