linux-stable.git/include/linux/mm.h, branch linux-2.6.35.y

mm/futex: fix futex writes on archs with SW tracking of

2011-08-01T20:55:00+00:00

[ upstream commit 2efaca927f5cd7ecd0f1554b8f9b6a9a2c329c03 ]
 dirty & young

I haven't reproduced it myself but the fail scenario is that on such
machines (notably ARM and some embedded powerpc), if you manage to hit
that futex path on a writable page whose dirty bit has gone from the PTE,
you'll livelock inside the kernel from what I can tell.

It will go in a loop of trying the atomic access, failing, trying gup to
"fix it up", getting succcess from gup, go back to the atomic access,
failing again because dirty wasn't fixed etc...

So I think you essentially hang in the kernel.

The scenario is probably rare'ish because affected architecture are
embedded and tend to not swap much (if at all) so we probably rarely hit
the case where dirty is missing or young is missing, but I think Shan has
a piece of SW that can reliably reproduce it using a shared writable
mapping & fork or something like that.

On archs who use SW tracking of dirty & young, a page without dirty is
effectively mapped read-only and a page without young unaccessible in the
PTE.

Additionally, some architectures might lazily flush the TLB when relaxing
write protection (by doing only a local flush), and expect a fault to
invalidate the stale entry if it's still present on another processor.

The futex code assumes that if the "in_atomic()" access -EFAULT's, it can
"fix it up" by causing get_user_pages() which would then be equivalent to
taking the fault.

However that isn't the case.  get_user_pages() will not call
handle_mm_fault() in the case where the PTE seems to have the right
permissions, regardless of the dirty and young state.  It will eventually
update those bits ...  in the struct page, but not in the PTE.

Additionally, it will not handle the lazy TLB flushing that can be
required by some architectures in the fault case.

Basically, gup is the wrong interface for the job.  The patch provides a
more appropriate one which boils down to just calling handle_mm_fault()
since what we are trying to do is simulate a real page fault.

The futex code currently attempts to write to user memory within a
pagefault disabled section, and if that fails, tries to fix it up using
get_user_pages().

This doesn't work on archs where the dirty and young bits are maintained
by software, since they will gate access permission in the TLB, and will
not be updated by gup().

In addition, there's an expectation on some archs that a spurious write
fault triggers a local TLB flush, and that is missing from the picture as
well.

I decided that adding those "features" to gup() would be too much for this
already too complex function, and instead added a new simpler
fixup_user_fault() which is essentially a wrapper around handle_mm_fault()
which the futex code can call.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix some nits Darren saw, fiddle comment layout]
Signed-off-by: Benjamin Herrenschmidt 
Reported-by: Shan Hai 
Tested-by: Shan Hai 
Cc: David Laight 
Acked-by: Peter Zijlstra 
Cc: Darren Hart 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Andi Kleen

mm: Move vma_stack_continue into mm.h

2010-10-29T04:51:47+00:00

commit 39aa3cb3e8250db9188a6f1e3fb62ffa1a717678 upstream.

So it can be used by all that need to check for that.

Signed-off-by: Stefan Bader 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

guard page for stacks that grow upwards

2010-09-27T00:18:41+00:00

commit 8ca3eb08097f6839b2206e2242db4179aee3cfb3 upstream.

pa-risc and ia64 have stacks that grow upwards. Check that
they do not run into other mappings. By making VM_GROWSUP
0x0 on architectures that do not ever use it, we can avoid
some unpleasant #ifdefs in check_stack_guard_page().

Signed-off-by: Tony Luck 
Signed-off-by: Linus Torvalds 
Cc: dann frazier 
Signed-off-by: Greg Kroah-Hartman

mm: add context argument to shrinker callback

2010-07-19T04:56:17+00:00

The current shrinker implementation requires the registered callback
to have global state to work from. This makes it difficult to shrink
caches that are not global (e.g. per-filesystem caches). Pass the shrinker
structure to the callback so that users can embed the shrinker structure
in the context the shrinker needs to operate on and get back to it in the
callback via container_of().

Signed-off-by: Dave Chinner 
Reviewed-by: Christoph Hellwig

mm: make lowmem_page_address() use PFN_PHYS() for improved portability

2010-05-25T15:07:02+00:00

This ensures that platforms with lowmem PAs above 32 bits work correctly
by avoiding truncating the PA during a left shift.

Signed-off-by: Chris Metcalf 
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: compaction: memory compaction core

2010-05-25T15:06:59+00:00

This patch is the core of a mechanism which compacts memory in a zone by
relocating movable pages towards the end of the zone.

A single compaction run involves a migration scanner and a free scanner.
Both scanners operate on pageblock-sized areas in the zone.  The migration
scanner starts at the bottom of the zone and searches for all movable
pages within each area, isolating them onto a private list called
migratelist.  The free scanner starts at the top of the zone and searches
for suitable areas and consumes the free pages within making them
available for the migration scanner.  The pages isolated for migration are
then migrated to the newly isolated free pages.

[aarcange@redhat.com: Fix unsafe optimisation]
[mel@csn.ul.ie: do not schedule work on other CPUs for compaction]
Signed-off-by: Mel Gorman 
Acked-by: Rik van Riel 
Reviewed-by: Minchan Kim 
Cc: KOSAKI Motohiro 
Cc: Christoph Lameter 
Cc: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: migration: avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks

2010-05-25T15:06:59+00:00

Page migration requires rmap to be able to find all ptes mapping a page
at all times, otherwise the migration entry can be instantiated, but it
is possible to leave one behind if the second rmap_walk fails to find
the page.  If this page is later faulted, migration_entry_to_page() will
call BUG because the page is locked indicating the page was migrated by
the migration PTE not cleaned up. For example

  kernel BUG at include/linux/swapops.h:105!
  invalid opcode: 0000 [#1] PREEMPT SMP
  ...
  Call Trace:
   [] handle_mm_fault+0x3f8/0x76a
   [] do_page_fault+0x44a/0x46e
   [] page_fault+0x25/0x30
   [] load_elf_binary+0x152a/0x192b
   [] search_binary_handler+0x173/0x313
   [] do_execve+0x219/0x30a
   [] sys_execve+0x43/0x5e
   [] stub_execve+0x6a/0xc0
  RIP  [] migration_entry_wait+0xc1/0x129

There is a race between shift_arg_pages and migration that triggers this
bug.  A temporary stack is setup during exec and later moved.  If
migration moves a page in the temporary stack and the VMA is then removed
before migration completes, the migration PTE may not be found leading to
a BUG when the stack is faulted.

This patch causes pages within the temporary stack during exec to be
skipped by migration.  It does this by marking the VMA covering the
temporary stack with an otherwise impossible combination of VMA flags.
These flags are cleared when the temporary stack is moved to its final
location.

[kamezawa.hiroyu@jp.fujitsu.com: idea for having migration skip temporary stacks]
Signed-off-by: Mel Gorman 
Reviewed-by: KAMEZAWA Hiroyuki 
Reviewed-by: Rik van Riel 
Acked-by: Linus Torvalds 
Cc: Minchan Kim 
Cc: Christoph Lameter 
Cc: Andrea Arcangeli 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'linus' into perf/core

2010-04-08T11:37:18+00:00

Semantic conflict: arch/x86/kernel/cpu/perf_event_intel_ds.c

Merge reason: pick up latest fixes, fix the conflict

Signed-off-by: Ingo Molnar

pagemap: fix pfn calculation for hugepage

2010-04-07T15:38:04+00:00

When we look into pagemap using page-types with option -p, the value of
pfn for hugepages looks wrong (see below.) This is because pte was
evaluated only once for one vma although it should be updated for each
hugepage.  This patch fixes it.

  $ page-types -p 3277 -Nl -b huge
  voffset   offset  len     flags
  7f21e8a00 11e400  1       ___U___________H_G________________
  7f21e8a01 11e401  1ff     ________________TG________________
               ^^^
  7f21e8c00 11e400  1       ___U___________H_G________________
  7f21e8c01 11e401  1ff     ________________TG________________
               ^^^

One hugepage contains 1 head page and 511 tail pages in x86_64 and each
two lines represent each hugepage.  Voffset and offset mean virtual
address and physical address in the page unit, respectively.  The
different hugepages should not have the same offset value.

With this patch applied:

  $ page-types -p 3386 -Nl -b huge
  voffset   offset   len    flags
  7fec7a600 112c00   1      ___UD__________H_G________________
  7fec7a601 112c01   1ff    ________________TG________________
               ^^^
  7fec7a800 113200   1      ___UD__________H_G________________
  7fec7a801 113201   1ff    ________________TG________________
               ^^^
               OK

More info:

- This patch modifies walk_page_range()'s hugepage walker.  But the
  change only affects pagemap_read(), which is the only caller of hugepage
  callback.

- Without this patch, hugetlb_entry() callback is called per vma, that
  doesn't match the natural expectation from its name.

- With this patch, hugetlb_entry() is called per hugepte entry and the
  callback can become much simpler.

Signed-off-by: Naoya Horiguchi 
Signed-off-by: KAMEZAWA Hiroyuki 
Acked-by: Matt Mackall 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

x86, perf, bts, mm: Delete the never used BTS-ptrace code

2010-03-26T10:33:55+00:00

Support for the PMU's BTS features has been upstreamed in
v2.6.32, but we still have the old and disabled ptrace-BTS,
as Linus noticed it not so long ago.

It's buggy: TIF_DEBUGCTLMSR is trampling all over that MSR without
regard for other uses (perf) and doesn't provide the flexibility
needed for perf either.

Its users are ptrace-block-step and ptrace-bts, since ptrace-bts
was never used and ptrace-block-step can be implemented using a
much simpler approach.

So axe all 3000 lines of it. That includes the *locked_memory*()
APIs in mm/mlock.c as well.

Reported-by: Linus Torvalds 
Signed-off-by: Peter Zijlstra 
Cc: Roland McGrath 
Cc: Oleg Nesterov 
Cc: Markus Metzger 
Cc: Steven Rostedt 
Cc: Andrew Morton 
LKML-Reference: <20100325135413.938004390@chello.nl>
Signed-off-by: Ingo Molnar