linux-stable.git/mm/memory.c, branch v3.16.4

mm: softdirty: keep bit when zapping file pte

2014-10-05T20:41:07+00:00

commit dbab31aa2ceec2d201966fa0b552f151310ba5f4 upstream.

This fixes the same bug as b43790eedd31 ("mm: softdirty: don't forget to
save file map softdiry bit on unmap") and 9aed8614af5a ("mm/memory.c:
don't forget to set softdirty on file mapped fault") where the return
value of pte_*mksoft_dirty was being ignored.

To be sure that no other pte/pmd "mk" function return values were being
ignored, I annotated the functions in arch/x86/include/asm/pgtable.h
with __must_check and rebuilt.

The userspace effect of this bug is that the softdirty mark might be
lost if a file mapped pte get zapped.

Signed-off-by: Peter Feiner 
Acked-by: Cyrill Gorcunov 
Cc: Pavel Emelyanov 
Cc: Jamie Liu 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

x86,mm: fix pte_special versus pte_numa

2014-09-05T23:36:36+00:00

commit b38af4721f59d0b564468f623b3e52a638195015 upstream.

Sasha Levin has shown oopses on ffffea0003480048 and ffffea0003480008 at
mm/memory.c:1132, running Trinity on different 3.16-rc-next kernels:
where zap_pte_range() checks page->mapping to see if PageAnon(page).

Those addresses fit struct pages for pfns d2001 and d2000, and in each
dump a register or a stack slot showed d2001730 or d2000730: pte flags
0x730 are PCD ACCESSED PROTNONE SPECIAL IOMAP; and Sasha's e820 map has
a hole between cfffffff and 100000000, which would need special access.

Commit c46a7c817e66 ("x86: define _PAGE_NUMA by reusing software bits on
the PMD and PTE levels") has broken vm_normal_page(): a PROTNONE SPECIAL
pte no longer passes the pte_special() test, so zap_pte_range() goes on
to try to access a non-existent struct page.

Fix this by refining pte_special() (SPECIAL with PRESENT or PROTNONE) to
complement pte_numa() (SPECIAL with neither PRESENT nor PROTNONE).  A
hint that this was a problem was that c46a7c817e66 added pte_numa() test
to vm_normal_page(), and moved its is_zero_pfn() test from slow to fast
path: This was papering over a pte_special() snag when the zero page was
encountered during zap.  This patch reverts vm_normal_page() to how it
was before, relying on pte_special().

It still appears that this patch may be incomplete: aren't there other
places which need to be handling PROTNONE along with PRESENT?  For
example, pte_mknuma() clears _PAGE_PRESENT and sets _PAGE_NUMA, but on a
PROT_NONE area, that would make it pte_special().  This is side-stepped
by the fact that NUMA hinting faults skipped PROT_NONE VMAs and there
are no grounds where a NUMA hinting fault on a PROT_NONE VMA would be
interesting.

Fixes: c46a7c817e66 ("x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels")
Reported-by: Sasha Levin 
Tested-by: Sasha Levin 
Signed-off-by: Hugh Dickins 
Signed-off-by: Mel Gorman 
Cc: "Kirill A. Shutemov" 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Johannes Weiner 
Cc: Cyrill Gorcunov 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: debugfs: move rounddown_pow_of_two() out from do_fault path

2014-07-31T00:16:13+00:00

do_fault_around() expects fault_around_bytes rounded down to nearest page
order.  Instead of calling rounddown_pow_of_two every time in
fault_around_pages()/fault_around_mask() we could do round down when user
changes fault_around_bytes via debugfs interface.

This also fixes bug when user set fault_around_bytes to 0.  Result of
rounddown_pow_of_two(0) is not defined, therefore fault_around_bytes == 0
doesn't work without this patch.

Let's set fault_around_bytes to PAGE_SIZE if user sets to something less
than PAGE_SIZE

[akpm@linux-foundation.org: tweak code layout]
Fixes: a9b0f861("mm: nominate faultaround area in bytes rather than page order")
Signed-off-by: Andrey Ryabinin 
Reported-by: Sasha Levin 
Acked-by: Kirill A. Shutemov 
Cc: 	[3.15.x]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: do not call do_fault_around for non-linear fault

2014-07-23T22:10:54+00:00

Ingo Korb reported that "repeated mapping of the same file on tmpfs
using remap_file_pages sometimes triggers a BUG at mm/filemap.c:202 when
the process exits".

He bisected the bug to d7c1755179b8 ("mm: implement ->map_pages for
shmem/tmpfs"), although the bug was actually added by commit
8c6e50b0290c ("mm: introduce vm_ops->map_pages()").

The problem is caused by calling do_fault_around for a _non-linear_
fault.  In this case pgoff is shifted and might become negative during
calculation.

Faulting around non-linear page-fault makes no sense and breaks the
logic in do_fault_around because pgoff is shifted.

Signed-off-by: Konstantin Khlebnikov 
Reported-by: Ingo Korb 
Tested-by: Ingo Korb 
Cc: Hugh Dickins 
Cc: Sasha Levin 
Cc: Dave Jones 
Cc: Ning Qu 
Cc: "Kirill A. Shutemov" 
Cc: 	[3.15.x]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: document do_fault_around() feature

2014-06-04T23:54:12+00:00

Some clarification on how faultaround works.

[akpm@linux-foundation.org: tweak comment text]
Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: nominate faultaround area in bytes rather than page order

2014-06-04T23:54:12+00:00

There is evidencs that the faultaround feature is less relevant on
architectures with page size bigger then 4k.  Which makes sense since page
fault overhead per byte of mapped area should be less there.

Let's rework the feature to specify faultaround area in bytes instead of
page order.  It's 64 kilobytes for now.

The patch effectively disables faultaround on architectures with page size
>= 64k (like ppc64).

It's possible that some other size of faultaround area is relevant for a
platform.  We can expose `fault_around_bytes' variable to arch-specific
code once such platforms will be found.

Signed-off-by: Kirill A. Shutemov 
Cc: Rusty Russell 
Cc: Hugh Dickins 
Cc: Madhavan Srinivasan 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Rik van Riel 
Cc: Mel Gorman 
Cc: Andi Kleen 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Dave Hansen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix typo in comment in do_fault_around()

2014-06-04T23:54:11+00:00

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move get_user_pages()-related code to separate file

2014-06-04T23:54:04+00:00

mm/memory.c is overloaded: over 4k lines. get_user_pages() code is
pretty much self-contained let's move it to separate file.

No other changes made.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels

2014-06-04T23:53:55+00:00

_PAGE_NUMA is currently an alias of _PROT_PROTNONE to trap NUMA hinting
faults on x86.  Care is taken such that _PAGE_NUMA is used only in
situations where the VMA flags distinguish between NUMA hinting faults
and prot_none faults.  This decision was x86-specific and conceptually
it is difficult requiring special casing to distinguish between PROTNONE
and NUMA ptes based on context.

Fundamentally, we only need the _PAGE_NUMA bit to tell the difference
between an entry that is really unmapped and a page that is protected
for NUMA hinting faults as if the PTE is not present then a fault will
be trapped.

Swap PTEs on x86-64 use the bits after _PAGE_GLOBAL for the offset.
This patch shrinks the maximum possible swap size and uses the bit to
uniquely distinguish between NUMA hinting ptes and swap ptes.

Signed-off-by: Mel Gorman 
Cc: David Vrabel 
Cc: Ingo Molnar 
Cc: Peter Anvin 
Cc: Fengguang Wu 
Cc: Linus Torvalds 
Cc: Steven Noonan 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Andrea Arcangeli 
Cc: Dave Hansen 
Cc: Srikar Dronamraju 
Cc: Cyrill Gorcunov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'v3.15-rc6' into sched/core, to pick up the latest fixes

2014-05-22T08:28:56+00:00

Signed-off-by: Ingo Molnar