linux-stable.git/mm/pgtable-generic.c, branch v6.3.8

mm: avoid unnecessary flush on change_huge_pmd()

2022-05-13T14:20:05+00:00

Calls to change_protection_range() on THP can trigger, at least on x86,
two TLB flushes for one page: one immediately, when pmdp_invalidate() is
called by change_huge_pmd(), and then another one later (that can be
batched) when change_protection_range() finishes.

The first TLB flush is only necessary to prevent the dirty bit (and with a
lesser importance the access bit) from changing while the PTE is modified.
However, this is not necessary as the x86 CPUs set the dirty-bit
atomically with an additional check that the PTE is (still) present.  One
caveat is Intel's Knights Landing that has a bug and does not do so.

Leverage this behavior to eliminate the unnecessary TLB flush in
change_huge_pmd().  Introduce a new arch specific pmdp_invalidate_ad()
that only invalidates the access and dirty bit from further changes.

Link: https://lkml.kernel.org/r/20220401180821.1986781-4-namit@vmware.com
Signed-off-by: Nadav Amit 
Cc: Andrea Arcangeli 
Cc: Andrew Cooper 
Cc: Andy Lutomirski 
Cc: Dave Hansen 
Cc: Peter Xu 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: Yu Zhao 
Cc: Nick Piggin 
Signed-off-by: Andrew Morton

mm: move tlb_flush_pending inline helpers to mm_inline.h

2022-01-15T14:30:27+00:00

linux/mm_types.h should only define structure definitions, to make it
cheap to include elsewhere.  The atomic_t helper function definitions
are particularly large, so it's better to move the helpers using those
into the existing linux/mm_inline.h and only include that where needed.

As a follow-up, we may want to go through all the indirect includes in
mm_types.h and reduce them as much as possible.

Link: https://lkml.kernel.org/r/20211207125710.2503446-2-arnd@kernel.org
Signed-off-by: Arnd Bergmann 
Cc: Al Viro 
Cc: Stephen Rothwell 
Cc: Suren Baghdasaryan 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Peter Xu 
Cc: Peter Zijlstra (Intel) 
Cc: Yu Zhao 
Cc: Vlastimil Babka 
Cc: Matthew Wilcox (Oracle) 
Cc: Eric Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/thp: fix __split_huge_pmd_locked() on shmem migration entry

2021-06-16T16:24:42+00:00

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 
Cc: Kirill A. Shutemov 
Cc: Yang Shi 
Cc: Wang Yugui 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Naoya Horiguchi 
Cc: Alistair Popple 
Cc: Ralph Campbell 
Cc: Zi Yan 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Jue Wang 
Cc: Peter Xu 
Cc: Jan Kara 
Cc: Shakeel Butt 
Cc: Oscar Salvador 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/pgtable-generic.c: optimize the VM_BUG_ON condition in pmdp_huge_clear_flush()

2021-02-24T21:38:30+00:00

The developer will have trouble figuring out why the BUG actually
triggered when there is a complex expression in the VM_BUG_ON.  Because we
can only identify the condition triggered BUG via line number provided by
VM_BUG_ON.  Optimize this by spliting such a complex expression into two
simple conditions.

Link: https://lkml.kernel.org/r/20210203084137.25522-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Suggested-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/pgtable-generic.c: simplify the VM_BUG_ON condition in pmdp_huge_clear_flush()

2021-02-24T21:38:30+00:00

The condition (A && !C && !D) || !A is equivalent to !A || (A && !C && !D)
and can be further simplified to !A || (!C && !D).

Link: https://lkml.kernel.org/r/20210201114319.34720-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce include/linux/pgtable.h

2020-06-09T16:39:13+00:00

The include/linux/pgtable.h is going to be the home of generic page table
manipulation functions.

Start with moving asm-generic/pgtable.h to include/linux/pgtable.h and
make the latter include asm/pgtable.h.

Signed-off-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Brian Cain 
Cc: Catalin Marinas 
Cc: Chris Zankel 
Cc: "David S. Miller" 
Cc: Geert Uytterhoeven 
Cc: Greentime Hu 
Cc: Greg Ungerer 
Cc: Guan Xuetao 
Cc: Guo Ren 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Ley Foon Tan 
Cc: Mark Salter 
Cc: Matthew Wilcox 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Nick Hu 
Cc: Paul Walmsley 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: Vincent Chen 
Cc: Vineet Gupta 
Cc: Will Deacon 
Cc: Yoshinori Sato 
Link: http://lkml.kernel.org/r/20200514170327.31389-3-rppt@kernel.org
Signed-off-by: Linus Torvalds

mm/thp: rename pmd_mknotpresent() as pmd_mkinvalid()

2020-06-04T03:09:49+00:00

pmd_present() is expected to test positive after pmdp_mknotpresent() as
the PMD entry still points to a valid huge page in memory.
pmdp_mknotpresent() implies that given PMD entry is just invalidated from
MMU perspective while still holding on to pmd_page() referred valid huge
page thus also clearing pmd_present() test.  This creates the following
situation which is counter intuitive.

[pmd_present(pmd_mknotpresent(pmd)) = true]

This renames pmd_mknotpresent() as pmd_mkinvalid() reflecting the helper's
functionality more accurately while changing the above mentioned situation
as follows.  This does not create any functional change.

[pmd_present(pmd_mkinvalid(pmd)) = true]

This is not applicable for platforms that define own pmdp_invalidate() via
__HAVE_ARCH_PMDP_INVALIDATE.  Suggestion for renaming came during a
previous discussion here.

https://patchwork.kernel.org/patch/11019637/

[anshuman.khandual@arm.com: change pmd_mknotvalid() to pmd_mkinvalid() per Will]
  Link: http://lkml.kernel.org/r/1587520326-10099-3-git-send-email-anshuman.khandual@arm.com
Suggested-by: Catalin Marinas 
Signed-off-by: Anshuman Khandual 
Signed-off-by: Andrew Morton 
Acked-by: Will Deacon 
Cc: Vineet Gupta 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: Steven Rostedt 
Cc: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: Benjamin Herrenschmidt 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Link: http://lkml.kernel.org/r/1584680057-13753-3-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Linus Torvalds

asm-generic/mm: stub out p{4,u}d_clear_bad() if __PAGETABLE_P{4,U}D_FOLDED

2019-12-01T14:29:19+00:00

This came up when removing __ARCH_HAS_5LEVEL_HACK for ARC as code bloat.
With this patch we see the following code reduction.

| bloat-o-meter2 vmlinux-D-elide-p4d_free_tlb vmlinux-E-elide-p?d_clear_bad
| add/remove: 0/2 grow/shrink: 0/0 up/down: 0/-40 (-40)
| function                                     old     new   delta
| pud_clear_bad                                 20       -     -20
| p4d_clear_bad                                 20       -     -20
| Total: Before=4136930, After=4136890, chg -1.000000%

Link: http://lkml.kernel.org/r/20191016162400.14796-6-vgupta@synopsys.com
Signed-off-by: Vineet Gupta 
Acked-by: Kirill A. Shutemov 
Cc: Arnd Bergmann 
Cc: Will Deacon 
Cc: "Aneesh Kumar K . V" 
Cc: Nick Piggin 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

x86/mm: Page size aware flush_tlb_mm_range()

2018-10-09T14:51:11+00:00

Use the new tlb_get_unmap_shift() to determine the stride of the
INVLPG loop.

Cc: Nick Piggin 
Cc: Will Deacon 
Cc: "Aneesh Kumar K.V" 
Cc: Andrew Morton 
Cc: Dave Hansen 
Signed-off-by: Peter Zijlstra (Intel)

mm: do not lose dirty and accessed bits in pmdp_invalidate()

2018-02-01T01:18:38+00:00

Vlastimil noted that pmdp_invalidate() is not atomic and we can lose
dirty and access bits if CPU sets them after pmdp dereference, but
before set_pmd_at().

The patch change pmdp_invalidate() to make the entry non-present
atomically and return previous value of the entry.  This value can be
used to check if CPU set dirty/accessed bits under us.

The race window is very small and I haven't seen any reports that can be
attributed to the bug.  For this reason, I don't think backporting to
stable trees needed.

Link: http://lkml.kernel.org/r/20171213105756.69879-11-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov 
Reported-by: Vlastimil Babka 
Cc: Hugh Dickins 
Cc: Andrea Arcangeli 
Cc: Aneesh Kumar K.V 
Cc: Catalin Marinas 
Cc: David Daney 
Cc: David Miller 
Cc: H. Peter Anvin 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michal Hocko 
Cc: Nitin Gupta 
Cc: Ralf Baechle 
Cc: Thomas Gleixner 
Cc: Vineet Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds