linux.git/mm/memory.c, branch v2.6.39

Don't lock guardpage if the stack is growing up

2011-05-09T23:22:07+00:00

Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack
and locking the guard page should be excluded in this case too.

This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc//maps for the
  grows-up case, and to move things around a bit to clean it all up and
  share the infrstructure with the /proc bits.

  Tested on ia64 that has both grow-up and grow-down segments  - Linus ]

Signed-off-by: Mikulas Patocka 
Tested-by: Tony Luck 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

VM: skip the stack guard page lookup in get_user_pages only for mlock

2011-05-05T04:30:28+00:00

The logic in __get_user_pages() used to skip the stack guard page lookup
whenever the caller wasn't interested in seeing what the actual page
was.  But Michel Lespinasse points out that there are cases where we
don't care about the physical page itself (so 'pages' may be NULL), but
do want to make sure a page is mapped into the virtual address space.

So using the existence of the "pages" array as an indication of whether
to look up the guard page or not isn't actually so great, and we really
should just use the FOLL_MLOCK bit.  But because that bit was only set
for the VM_LOCKED case (and not all vma's necessarily have it, even for
mlock()), we couldn't do that originally.

Fix that by moving the VM_LOCKED check deeper into the call-chain, which
actually simplifies many things.  Now mlock() gets simpler, and we can
also check for FOLL_MLOCK in __get_user_pages() and the code ends up
much more straightforward.

Reported-and-reviewed-by: Michel Lespinasse 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

mm: check if PTE is already allocated during page fault

2011-04-28T18:28:21+00:00

With transparent hugepage support, handle_mm_fault() has to be careful
that a normal PMD has been established before handling a PTE fault.  To
achieve this, it used __pte_alloc() directly instead of pte_alloc_map as
pte_alloc_map is unsafe to run against a huge PMD.  pte_offset_map() is
called once it is known the PMD is safe.

pte_alloc_map() is smart enough to check if a PTE is already present
before calling __pte_alloc but this check was lost.  As a consequence,
PTEs may be allocated unnecessarily and the page table lock taken.  Thi
useless PTE does get cleaned up but it's a performance hit which is
visible in page_test from aim9.

This patch simply re-adds the check normally done by pte_alloc_map to
check if the PTE needs to be allocated before taking the page table lock.
The effect is noticable in page_test from aim9.

  AIM9
                  2.6.38-vanilla 2.6.38-checkptenone
  creat-clo      446.10 ( 0.00%)   424.47 (-5.10%)
  page_test       38.10 ( 0.00%)    42.04 ( 9.37%)
  brk_test        52.45 ( 0.00%)    51.57 (-1.71%)
  exec_test      382.00 ( 0.00%)   456.90 (16.39%)
  fork_test       60.11 ( 0.00%)    67.79 (11.34%)
  MMTests Statistics: duration
  Total Elapsed Time (seconds)                611.90    612.22

(While this affects 2.6.38, it is a performance rather than a functional
bug and normally outside the rules -stable.  While the big performance
differences are to a microbench, the difference in fork and exec
performance may be significant enough that -stable wants to consider the
patch)

Reported-by: Raz Ben Yehuda 
Signed-off-by: Mel Gorman 
Reviewed-by: Rik van Riel 
Reviewed-by: Andrea Arcangeli 
Reviewed-by: Minchan Kim 
Acked-by: Johannes Weiner 
Cc: 		[2.6.38.x]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: check that we have the right vma in __access_remote_vm()

2011-04-14T23:06:55+00:00

In __access_remote_vm() we need to check that we have found the right
vma, not the following vma before we try to access it.  Otherwise we
might call the vma's access routine with an address which does not fall
inside the vma.

It was discovered on a current kernel but with an unreleased driver,
from memory it was strace leading to a kernel bad access, but it
obviously depends on what the access implementation does.

Looking at other access implementations I only see:

  $ git grep -A 5 vm_operations|grep access
  arch/powerpc/platforms/cell/spufs/file.c-	.access = spufs_mem_mmap_access,
  arch/x86/pci/i386.c-	.access = generic_access_phys,
  drivers/char/mem.c-	.access = generic_access_phys
  fs/sysfs/bin.c-	.access		= bin_access,

The spufs one looks like it might behave badly given the wrong vma, it
assumes vma->vm_file->private_data is a spu_context, and looks like it
would probably blow up pretty quickly if it wasn't.

generic_access_phys() only uses the vma to check vm_flags and get the
mm, and then walks page tables using the address.  So it should bail on
the vm_flags check, or at worst let you access some other VM_IO mapping.

And bin_access() just proxies to another access implementation.

Signed-off-by: Michael Ellerman 
Reviewed-by: KOSAKI Motohiro 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vm: fix mlock() on stack guard page

2011-04-12T21:15:51+00:00

Commit 53a7706d5ed8 ("mlock: do not hold mmap_sem for extended periods
of time") changed mlock() to care about the exact number of pages that
__get_user_pages() had brought it.  Before, it would only care about
errors.

And that doesn't work, because we also handled one page specially in
__mlock_vma_pages_range(), namely the stack guard page.  So when that
case was handled, the number of pages that the function returned was off
by one.  In particular, it could be zero, and then the caller would end
up not making any progress at all.

Rather than try to fix up that off-by-one error for the mlock case
specially, this just moves the logic to handle the stack guard page
into__get_user_pages() itself, thus making all the counts come out
right automatically.

Reported-by: Robert Święcki 
Cc: Hugh Dickins 
Cc: Oleg Nesterov 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

mm: fix memory.c incorrect kernel-doc

2011-03-28T02:30:18+00:00

Fix mm/memory.c incorrect kernel-doc function notation:

  Warning(mm/memory.c:3718): Cannot understand  * @access_remote_vm - access another process' address space
   on line 3718 - I thought it was a doc line

Signed-off-by: Randy Dunlap 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

2011-03-24T03:51:42+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  deal with races in /proc/*/{syscall,stack,personality}
  proc: enable writing to /proc/pid/mem
  proc: make check_mem_permission() return an mm_struct on success
  proc: hold cred_guard_mutex in check_mem_permission()
  proc: disable mem_write after exec
  mm: implement access_remote_vm
  mm: factor out main logic of access_process_vm
  mm: use mm_struct to resolve gate vma's in __get_user_pages
  mm: arch: rename in_gate_area_no_task to in_gate_area_no_mm
  mm: arch: make in_gate_area take an mm_struct instead of a task_struct
  mm: arch: make get_gate_vma take an mm_struct instead of a task_struct
  x86: mark associated mm when running a task in 32 bit compatibility mode
  x86: add context tag to mark mm when running a task in 32-bit compatibility mode
  auxv: require the target to be tracable (or yourself)
  close race in /proc/*/environ
  report errors in /proc/*/*map* sanely
  pagemap: close races with suid execve
  make sessionid permissions in /proc/*/task/* match those in /proc/*
  fix leaks in path_lookupat()

Fix up trivial conflicts in fs/proc/base.c

memcg: fix ugly initialization of return value is in caller

2011-03-24T02:46:22+00:00

Remove initialization of vaiable in caller of memory cgroup function.
Actually, it's return value of memcg function but it's initialized in
caller.

Some memory cgroup uses following style to bring the result of start
function to the end function for avoiding races.

   mem_cgroup_start_A(&(*ptr))
   /* Something very complicated can happen here. */
   mem_cgroup_end_A(*ptr)

In some calls, *ptr should be initialized to NULL be caller.  But it's
ugly.  This patch fixes that *ptr is initialized by _start function.

Signed-off-by: KAMEZAWA Hiroyuki 
Acked-by: Johannes Weiner 
Acked-by: Daisuke Nishimura 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: implement access_remote_vm

2011-03-23T20:36:57+00:00

Provide an alternative to access_process_vm that allows the caller to obtain a
reference to the supplied mm_struct.

Signed-off-by: Stephen Wilson 
Signed-off-by: Al Viro

mm: factor out main logic of access_process_vm

2011-03-23T20:36:56+00:00

Introduce an internal helper __access_remote_vm and base access_process_vm on
top of it.  This new method may be called with a NULL task_struct if page fault
accounting is not desired.  This code will be shared with a new address space
accessor that is independent of task_struct.

Signed-off-by: Stephen Wilson 
Signed-off-by: Al Viro