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  1. 17 2月, 2015 1 次提交
    • M
      mm: allow page fault handlers to perform the COW · 2e4cdab0
      由 Matthew Wilcox 提交于 
      Currently COW of an XIP file is done by first bringing in a read-only
mapping, then retrying the fault and copying the page.  It is much more
efficient to tell the fault handler that a COW is being attempted (by
passing in the pre-allocated page in the vm_fault structure), and allow
the handler to perform the COW operation itself.

The handler cannot insert the page itself if there is already a read-only
mapping at that address, so allow the handler to return VM_FAULT_LOCKED
and set the fault_page to be NULL.  This indicates to the MM code that the
i_mmap_lock is held instead of the page lock.
Signed-off-by: NMatthew Wilcox <matthew.r.wilcox@intel.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2e4cdab0
  3. 13 2月, 2015 3 次提交
  5. 12 2月, 2015 8 次提交
    • N
      pagewalk: add walk_page_vma() · 900fc5f1
      由 Naoya Horiguchi 提交于 
      Introduce walk_page_vma(), which is useful for the callers which want to
walk over a given vma.  It's used by later patches.
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      900fc5f1
    • N
      pagewalk: improve vma handling · fafaa426
      由 Naoya Horiguchi 提交于 
      Current implementation of page table walker has a fundamental problem in
vma handling, which started when we tried to handle vma(VM_HUGETLB).
Because it's done in pgd loop, considering vma boundary makes code
complicated and bug-prone.

From the users viewpoint, some user checks some vma-related condition to
determine whether the user really does page walk over the vma.

In order to solve these, this patch moves vma check outside pgd loop and
introduce a new callback ->test_walk().
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      fafaa426
    • N
      mm/pagewalk: remove pgd_entry() and pud_entry() · 0b1fbfe5
      由 Naoya Horiguchi 提交于 
      Currently no user of page table walker sets ->pgd_entry() or
->pud_entry(), so checking their existence in each loop is just wasting
CPU cycle.  So let's remove it to reduce overhead.
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0b1fbfe5
    • A
      mm: gup: add __get_user_pages_unlocked to customize gup_flags · 0fd71a56
      由 Andrea Arcangeli 提交于 
      Some callers (like KVM) may want to set the gup_flags like FOLL_HWPOSION
to get a proper -EHWPOSION retval instead of -EFAULT to take a more
appropriate action if get_user_pages runs into a memory failure.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Reviewed-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0fd71a56
    • A
      mm: gup: add get_user_pages_locked and get_user_pages_unlocked · f0818f47
      由 Andrea Arcangeli 提交于 
      FAULT_FOLL_ALLOW_RETRY allows the page fault to drop the mmap_sem for
reading to reduce the mmap_sem contention (for writing), like while
waiting for I/O completion.  The problem is that right now practically no
get_user_pages call uses FAULT_FOLL_ALLOW_RETRY, so we're not leveraging
that nifty feature.

Andres fixed it for the KVM page fault.  However get_user_pages_fast
remains uncovered, and 99% of other get_user_pages aren't using it either
(the only exception being FOLL_NOWAIT in KVM which is really nonblocking
and in fact it doesn't even release the mmap_sem).

So this patchsets extends the optimization Andres did in the KVM page
fault to the whole kernel.  It makes most important places (including
gup_fast) to use FAULT_FOLL_ALLOW_RETRY to reduce the mmap_sem hold times
during I/O.

The only few places that remains uncovered are drivers like v4l and other
exceptions that tends to work on their own memory and they're not working
on random user memory (for example like O_DIRECT that uses gup_fast and is
fully covered by this patch).

A follow up patch should probably also add a printk_once warning to
get_user_pages that should go obsolete and be phased out eventually.  The
"vmas" parameter of get_user_pages makes it fundamentally incompatible
with FAULT_FOLL_ALLOW_RETRY (vmas array becomes meaningless the moment the
mmap_sem is released).

While this is just an optimization, this becomes an absolute requirement
for the userfaultfd feature http://lwn.net/Articles/615086/ .

The userfaultfd allows to block the page fault, and in order to do so I
need to drop the mmap_sem first.  So this patch also ensures that all
memory where userfaultfd could be registered by KVM, the very first fault
(no matter if it is a regular page fault, or a get_user_pages) always has
FAULT_FOLL_ALLOW_RETRY set.  Then the userfaultfd blocks and it is waken
only when the pagetable is already mapped.  The second fault attempt after
the wakeup doesn't need FAULT_FOLL_ALLOW_RETRY, so it's ok to retry
without it.

This patch (of 5):

We can leverage the VM_FAULT_RETRY functionality in the page fault paths
better by using either get_user_pages_locked or get_user_pages_unlocked.

The former allows conversion of get_user_pages invocations that will have
to pass a "&locked" parameter to know if the mmap_sem was dropped during
the call.  Example from:

    down_read(&mm->mmap_sem);
    do_something()
    get_user_pages(tsk, mm, ..., pages, NULL);
    up_read(&mm->mmap_sem);

to:

    int locked = 1;
    down_read(&mm->mmap_sem);
    do_something()
    get_user_pages_locked(tsk, mm, ..., pages, &locked);
    if (locked)
        up_read(&mm->mmap_sem);

The latter is suitable only as a drop in replacement of the form:

    down_read(&mm->mmap_sem);
    get_user_pages(tsk, mm, ..., pages, NULL);
    up_read(&mm->mmap_sem);

into:

    get_user_pages_unlocked(tsk, mm, ..., pages);

Where tsk, mm, the intermediate "..." paramters and "pages" can be any
value as before.  Just the last parameter of get_user_pages (vmas) must be
NULL for get_user_pages_locked|unlocked to be usable (the latter original
form wouldn't have been safe anyway if vmas wasn't null, for the former we
just make it explicit by dropping the parameter).

If vmas is not NULL these two methods cannot be used.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Reviewed-by: NAndres Lagar-Cavilla <andreslc@google.com>
Reviewed-by: NPeter Feiner <pfeiner@google.com>
Reviewed-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f0818f47
    • K
      mm: account pmd page tables to the process · dc6c9a35
      由 Kirill A. Shutemov 提交于 
      Dave noticed that unprivileged process can allocate significant amount of
memory -- >500 MiB on x86_64 -- and stay unnoticed by oom-killer and
memory cgroup.  The trick is to allocate a lot of PMD page tables.  Linux
kernel doesn't account PMD tables to the process, only PTE.

The use-cases below use few tricks to allocate a lot of PMD page tables
while keeping VmRSS and VmPTE low.  oom_score for the process will be 0.

	#include <errno.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <sys/mman.h>
	#include <sys/prctl.h>

	#define PUD_SIZE (1UL << 30)
	#define PMD_SIZE (1UL << 21)

	#define NR_PUD 130000

	int main(void)
	{
		char *addr = NULL;
		unsigned long i;

		prctl(PR_SET_THP_DISABLE);
		for (i = 0; i < NR_PUD ; i++) {
			addr = mmap(addr + PUD_SIZE, PUD_SIZE, PROT_WRITE|PROT_READ,
					MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
			if (addr == MAP_FAILED) {
				perror("mmap");
				break;
			}
			*addr = 'x';
			munmap(addr, PMD_SIZE);
			mmap(addr, PMD_SIZE, PROT_WRITE|PROT_READ,
					MAP_ANONYMOUS|MAP_PRIVATE|MAP_FIXED, -1, 0);
			if (addr == MAP_FAILED)
				perror("re-mmap"), exit(1);
		}
		printf("PID %d consumed %lu KiB in PMD page tables\n",
				getpid(), i * 4096 >> 10);
		return pause();
	}

The patch addresses the issue by account PMD tables to the process the
same way we account PTE.

The main place where PMD tables is accounted is __pmd_alloc() and
free_pmd_range(). But there're few corner cases:

 - HugeTLB can share PMD page tables. The patch handles by accounting
   the table to all processes who share it.

 - x86 PAE pre-allocates few PMD tables on fork.

 - Architectures with FIRST_USER_ADDRESS > 0. We need to adjust sanity
   check on exit(2).

Accounting only happens on configuration where PMD page table's level is
present (PMD is not folded).  As with nr_ptes we use per-mm counter.  The
counter value is used to calculate baseline for badness score by
oom-killer.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: NDave Hansen <dave.hansen@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Reviewed-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: David Rientjes <rientjes@google.com>
Tested-by: NSedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      dc6c9a35
    • W
      mm: add VM_BUG_ON_PAGE() to page_mapcount() · 1d148e21
      由 Wang, Yalin 提交于 
      Add VM_BUG_ON_PAGE() for slab pages.  _mapcount is an union with slab
struct in struct page, so we must avoid accessing _mapcount if this page
is a slab page.  Also remove the unneeded bracket.
Signed-off-by: NYalin Wang <yalin.wang@sonymobile.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1d148e21
    • K
      mm: add fields for compound destructor and order into struct page · e4b294c2
      由 Kirill A. Shutemov 提交于 
      Currently, we use lru.next/lru.prev plus cast to access or set
destructor and order of compound page.

Let's replace it with explicit fields in struct page.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NJerome Marchand <jmarchan@redhat.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e4b294c2
  7. 11 2月, 2015 6 次提交
  9. 30 1月, 2015 1 次提交
    • L
      vm: add VM_FAULT_SIGSEGV handling support · 33692f27
      由 Linus Torvalds 提交于 
      The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.
Reported-and-tested-by: NTakashi Iwai <tiwai@suse.de>
Tested-by: NJan Engelhardt <jengelh@inai.de>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      33692f27
  11. 28 1月, 2015 1 次提交
    • D
      mm: provide a find_special_page vma operation · 667a0a06
      由 David Vrabel 提交于 
      The optional find_special_page VMA operation is used to lookup the
pages backing a VMA.  This is useful in cases where the normal
mechanisms for finding the page don't work.  This is only called if
the PTE is special.

One use case is a Xen PV guest mapping foreign pages into userspace.

In a Xen PV guest, the PTEs contain MFNs so get_user_pages() (for
example) must do an MFN to PFN (M2P) lookup before it can get the
page.  For foreign pages (those owned by another guest) the M2P lookup
returns the PFN as seen by the foreign guest (which would be
completely the wrong page for the local guest).

This cannot be fixed up improving the M2P lookup since one MFN may be
mapped onto two or more pages so getting the right page is impossible
given just the MFN.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>
      667a0a06
  13. 07 1月, 2015 1 次提交
    • L
      mm: propagate error from stack expansion even for guard page · fee7e49d
      由 Linus Torvalds 提交于 
      Jay Foad reports that the address sanitizer test (asan) sometimes gets
confused by a stack pointer that ends up being outside the stack vma
that is reported by /proc/maps.

This happens due to an interaction between RLIMIT_STACK and the guard
page: when we do the guard page check, we ignore the potential error
from the stack expansion, which effectively results in a missing guard
page, since the expected stack expansion won't have been done.

And since /proc/maps explicitly ignores the guard page (commit
d7824370: "mm: fix up some user-visible effects of the stack guard
page"), the stack pointer ends up being outside the reported stack area.

This is the minimal patch: it just propagates the error.  It also
effectively makes the guard page part of the stack limit, which in turn
measn that the actual real stack is one page less than the stack limit.

Let's see if anybody notices.  We could teach acct_stack_growth() to
allow an extra page for a grow-up/grow-down stack in the rlimit test,
but I don't want to add more complexity if it isn't needed.
Reported-and-tested-by: NJay Foad <jay.foad@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      fee7e49d
  15. 17 12月, 2014 1 次提交
  17. 14 12月, 2014 3 次提交
    • J
      mm: vmscan: invoke slab shrinkers from shrink_zone() · 6b4f7799
      由 Johannes Weiner 提交于 
      The slab shrinkers are currently invoked from the zonelist walkers in
kswapd, direct reclaim, and zone reclaim, all of which roughly gauge the
eligible LRU pages and assemble a nodemask to pass to NUMA-aware
shrinkers, which then again have to walk over the nodemask.  This is
redundant code, extra runtime work, and fairly inaccurate when it comes to
the estimation of actually scannable LRU pages.  The code duplication will
only get worse when making the shrinkers cgroup-aware and requiring them
to have out-of-band cgroup hierarchy walks as well.

Instead, invoke the shrinkers from shrink_zone(), which is where all
reclaimers end up, to avoid this duplication.

Take the count for eligible LRU pages out of get_scan_count(), which
considers many more factors than just the availability of swap space, like
zone_reclaimable_pages() currently does.  Accumulate the number over all
visited lruvecs to get the per-zone value.

Some nodes have multiple zones due to memory addressing restrictions.  To
avoid putting too much pressure on the shrinkers, only invoke them once
for each such node, using the class zone of the allocation as the pivot
zone.

For now, this integrates the slab shrinking better into the reclaim logic
and gets rid of duplicative invocations from kswapd, direct reclaim, and
zone reclaim.  It also prepares for cgroup-awareness, allowing
memcg-capable shrinkers to be added at the lruvec level without much
duplication of both code and runtime work.

This changes kswapd behavior, which used to invoke the shrinkers for each
zone, but with scan ratios gathered from the entire node, resulting in
meaningless pressure quantities on multi-zone nodes.

Zone reclaim behavior also changes.  It used to shrink slabs until the
same amount of pages were shrunk as were reclaimed from the LRUs.  Now it
merely invokes the shrinkers once with the zone's scan ratio, which makes
the shrinkers go easier on caches that implement aging and would prefer
feeding back pressure from recently used slab objects to unused LRU pages.

[vdavydov@parallels.com: assure class zone is populated]
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: NVladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      6b4f7799
    • J
      mm/debug-pagealloc: make debug-pagealloc boottime configurable · 031bc574
      由 Joonsoo Kim 提交于 
      Now, we have prepared to avoid using debug-pagealloc in boottime.  So
introduce new kernel-parameter to disable debug-pagealloc in boottime, and
makes related functions to be disabled in this case.

Only non-intuitive part is change of guard page functions.  Because guard
page is effective only if debug-pagealloc is enabled, turning off
according to debug-pagealloc is reasonable thing to do.
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      031bc574
    • J
      mm/debug-pagealloc: prepare boottime configurable on/off · e30825f1
      由 Joonsoo Kim 提交于 
      Until now, debug-pagealloc needs extra flags in struct page, so we need to
recompile whole source code when we decide to use it.  This is really
painful, because it takes some time to recompile and sometimes rebuild is
not possible due to third party module depending on struct page.  So, we
can't use this good feature in many cases.

Now, we have the page extension feature that allows us to insert extra
flags to outside of struct page.  This gets rid of third party module
issue mentioned above.  And, this allows us to determine if we need extra
memory for this page extension in boottime.  With these property, we can
avoid using debug-pagealloc in boottime with low computational overhead in
the kernel built with CONFIG_DEBUG_PAGEALLOC.  This will help our
development process greatly.

This patch is the preparation step to achive above goal.  debug-pagealloc
originally uses extra field of struct page, but, after this patch, it will
use field of struct page_ext.  Because memory for page_ext is allocated
later than initialization of page allocator in CONFIG_SPARSEMEM, we should
disable debug-pagealloc feature temporarily until initialization of
page_ext.  This patch implements this.
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Jungsoo Son <jungsoo.son@lge.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e30825f1
  19. 18 11月, 2014 1 次提交
    • Q
      x86, mpx: Introduce VM_MPX to indicate that a VMA is MPX specific · 4aae7e43
      由 Qiaowei Ren 提交于 
      MPX-enabled applications using large swaths of memory can
potentially have large numbers of bounds tables in process
address space to save bounds information. These tables can take
up huge swaths of memory (as much as 80% of the memory on the
system) even if we clean them up aggressively. In the worst-case
scenario, the tables can be 4x the size of the data structure
being tracked. IOW, a 1-page structure can require 4 bounds-table
pages.

Being this huge, our expectation is that folks using MPX are
going to be keen on figuring out how much memory is being
dedicated to it. So we need a way to track memory use for MPX.

If we want to specifically track MPX VMAs we need to be able to
distinguish them from normal VMAs, and keep them from getting
merged with normal VMAs. A new VM_ flag set only on MPX VMAs does
both of those things. With this flag, MPX bounds-table VMAs can
be distinguished from other VMAs, and userspace can also walk
/proc/$pid/smaps to get memory usage for MPX.

In addition to this flag, we also introduce a special ->vm_ops
specific to MPX VMAs (see the patch "add MPX specific mmap
interface"), but currently different ->vm_ops do not by
themselves prevent VMA merging, so we still need this flag.

We understand that VM_ flags are scarce and are open to other
options.
Signed-off-by: NQiaowei Ren <qiaowei.ren@intel.com>
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Cc: linux-mm@kvack.org
Cc: linux-mips@linux-mips.org
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141114151825.565625B3@viggo.jf.intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
      4aae7e43
  21. 30 10月, 2014 1 次提交
  23. 27 10月, 2014 1 次提交
  25. 14 10月, 2014 2 次提交
    • P
      mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared · 64e45507
      由 Peter Feiner 提交于 
      For VMAs that don't want write notifications, PTEs created for read faults
have their write bit set.  If the read fault happens after VM_SOFTDIRTY is
cleared, then the PTE's softdirty bit will remain clear after subsequent
writes.

Here's a simple code snippet to demonstrate the bug:

  char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
                 MAP_ANONYMOUS | MAP_SHARED, -1, 0);
  system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */
  assert(*m == '\0');     /* new PTE allows write access */
  assert(!soft_dirty(x));
  *m = 'x';               /* should dirty the page */
  assert(soft_dirty(x));  /* fails */

With this patch, write notifications are enabled when VM_SOFTDIRTY is
cleared.  Furthermore, to avoid unnecessary faults, write notifications
are disabled when VM_SOFTDIRTY is set.

As a side effect of enabling and disabling write notifications with
care, this patch fixes a bug in mprotect where vm_page_prot bits set by
drivers were zapped on mprotect.  An analogous bug was fixed in mmap by
commit c9d0bf24 ("mm: uncached vma support with writenotify").
Signed-off-by: NPeter Feiner <pfeiner@google.com>
Reported-by: NPeter Feiner <pfeiner@google.com>
Suggested-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      64e45507
    • M
      x86: optimize resource lookups for ioremap · 67cf13ce
      由 Mike Travis 提交于 
      We have a large university system in the UK that is experiencing very long
delays modprobing the driver for a specific I/O device.  The delay is from
8-10 minutes per device and there are 31 devices in the system.  This 4 to
5 hour delay in starting up those I/O devices is very much a burden on the
customer.

There are two causes for requiring a restart/reload of the drivers.  First
is periodic preventive maintenance (PM) and the second is if any of the
devices experience a fatal error.  Both of these trigger this excessively
long delay in bringing the system back up to full capability.

The problem was tracked down to a very slow IOREMAP operation and the
excessively long ioresource lookup to insure that the user is not
attempting to ioremap RAM.  These patches provide a speed up to that
function.

The modprobe time appears to be affected quite a bit by previous activity
on the ioresource list, which I suspect is due to cache preloading.  While
the overall improvement is impacted by other overhead of starting the
devices, this drastically improves the modprobe time.

Also our system is considerably smaller so the percentages gained will not
be the same.  Best case improvement with the modprobe on our 20 device
smallish system was from 'real 5m51.913s' to 'real 0m18.275s'.

This patch (of 2):

Since the ioremap operation is verifying that the specified address range
is NOT RAM, it will search the entire ioresource list if the condition is
true.  To make matters worse, it does this one 4k page at a time.  For a
128M BAR region this is 32 passes to determine the entire region does not
contain any RAM addresses.

This patch provides another resource lookup function, region_is_ram, that
searches for the entire region specified, verifying that it is completely
contained within the resource region.  If it is found, then it is checked
to be RAM or not, within a single pass.

The return result reflects if it was found or not (-1), and whether it is
RAM (1) or not (0).  This allows the caller to fallback to the previous
page by page search if it was not found.

[akpm@linux-foundation.org: fix spellos and typos in comment]
Signed-off-by: NMike Travis <travis@sgi.com>
Acked-by: NAlex Thorlton <athorlton@sgi.com>
Reviewed-by: NCliff Wickman <cpw@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      67cf13ce
  27. 10 10月, 2014 3 次提交
    • K
      mm/balloon_compaction: redesign ballooned pages management · d6d86c0a
      由 Konstantin Khlebnikov 提交于 
      Sasha Levin reported KASAN splash inside isolate_migratepages_range().
Problem is in the function __is_movable_balloon_page() which tests
AS_BALLOON_MAP in page->mapping->flags.  This function has no protection
against anonymous pages.  As result it tried to check address space flags
inside struct anon_vma.

Further investigation shows more problems in current implementation:

* Special branch in __unmap_and_move() never works:
  balloon_page_movable() checks page flags and page_count.  In
  __unmap_and_move() page is locked, reference counter is elevated, thus
  balloon_page_movable() always fails.  As a result execution goes to the
  normal migration path.  virtballoon_migratepage() returns
  MIGRATEPAGE_BALLOON_SUCCESS instead of MIGRATEPAGE_SUCCESS,
  move_to_new_page() thinks this is an error code and assigns
  newpage->mapping to NULL.  Newly migrated page lose connectivity with
  balloon an all ability for further migration.

* lru_lock erroneously required in isolate_migratepages_range() for
  isolation ballooned page.  This function releases lru_lock periodically,
  this makes migration mostly impossible for some pages.

* balloon_page_dequeue have a tight race with balloon_page_isolate:
  balloon_page_isolate could be executed in parallel with dequeue between
  picking page from list and locking page_lock.  Race is rare because they
  use trylock_page() for locking.

This patch fixes all of them.

Instead of fake mapping with special flag this patch uses special state of
page->_mapcount: PAGE_BALLOON_MAPCOUNT_VALUE = -256.  Buddy allocator uses
PAGE_BUDDY_MAPCOUNT_VALUE = -128 for similar purpose.  Storing mark
directly in struct page makes everything safer and easier.

PagePrivate is used to mark pages present in page list (i.e.  not
isolated, like PageLRU for normal pages).  It replaces special rules for
reference counter and makes balloon migration similar to migration of
normal pages.  This flag is protected by page_lock together with link to
the balloon device.
Signed-off-by: NKonstantin Khlebnikov <k.khlebnikov@samsung.com>
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Link: http://lkml.kernel.org/p/53E6CEAA.9020105@oracle.com
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: <stable@vger.kernel.org>	[3.8+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d6d86c0a
    • C
      mm: introduce check_data_rlimit helper · 9c599024
      由 Cyrill Gorcunov 提交于 
      To eliminate code duplication lets introduce check_data_rlimit helper
which we will use in brk() and prctl() syscalls.
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9c599024
    • O
      proc/maps: make vm_is_stack() logic namespace-friendly · 58cb6548
      由 Oleg Nesterov 提交于 
      - Rename vm_is_stack() to task_of_stack() and change it to return
  "struct task_struct *" rather than the global (and thus wrong in
  general) pid_t.

- Add the new pid_of_stack() helper which calls task_of_stack() and
  uses the right namespace to report the correct pid_t.

  Unfortunately we need to define this helper twice, in task_mmu.c
  and in task_nommu.c. perhaps it makes sense to add fs/proc/util.c
  and move at least pid_of_stack/task_of_stack there to avoid the
  code duplication.

- Change show_map_vma() and show_numa_map() to use the new helper.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      58cb6548
  29. 02 10月, 2014 1 次提交
    • J
      vfs: fix data corruption when blocksize < pagesize for mmaped data · 90a80202
      由 Jan Kara 提交于 
      ->page_mkwrite() is used by filesystems to allocate blocks under a page
which is becoming writeably mmapped in some process' address space. This
allows a filesystem to return a page fault if there is not enough space
available, user exceeds quota or similar problem happens, rather than
silently discarding data later when writepage is called.

However VFS fails to call ->page_mkwrite() in all the cases where
filesystems need it when blocksize < pagesize. For example when
blocksize = 1024, pagesize = 4096 the following is problematic:
  ftruncate(fd, 0);
  pwrite(fd, buf, 1024, 0);
  map = mmap(NULL, 1024, PROT_WRITE, MAP_SHARED, fd, 0);
  map[0] = 'a';       ----> page_mkwrite() for index 0 is called
  ftruncate(fd, 10000); /* or even pwrite(fd, buf, 1, 10000) */
  mremap(map, 1024, 10000, 0);
  map[4095] = 'a';    ----> no page_mkwrite() called

At the moment ->page_mkwrite() is called, filesystem can allocate only
one block for the page because i_size == 1024. Otherwise it would create
blocks beyond i_size which is generally undesirable. But later at
->writepage() time, we also need to store data at offset 4095 but we
don't have block allocated for it.

This patch introduces a helper function filesystems can use to have
->page_mkwrite() called at all the necessary moments.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
      90a80202
  31. 24 9月, 2014 1 次提交
    • A
      kvm: Faults which trigger IO release the mmap_sem · 234b239b
      由 Andres Lagar-Cavilla 提交于 
      When KVM handles a tdp fault it uses FOLL_NOWAIT. If the guest memory
has been swapped out or is behind a filemap, this will trigger async
readahead and return immediately. The rationale is that KVM will kick
back the guest with an "async page fault" and allow for some other
guest process to take over.

If async PFs are enabled the fault is retried asap from an async
workqueue. If not, it's retried immediately in the same code path. In
either case the retry will not relinquish the mmap semaphore and will
block on the IO. This is a bad thing, as other mmap semaphore users
now stall as a function of swap or filemap latency.

This patch ensures both the regular and async PF path re-enter the
fault allowing for the mmap semaphore to be relinquished in the case
of IO wait.
Reviewed-by: NRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NAndres Lagar-Cavilla <andreslc@google.com>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      234b239b
  33. 09 8月, 2014 1 次提交
    • A
      arm64,ia64,ppc,s390,sh,tile,um,x86,mm: remove default gate area · a6c19dfe
      由 Andy Lutomirski 提交于 
      The core mm code will provide a default gate area based on
FIXADDR_USER_START and FIXADDR_USER_END if
!defined(__HAVE_ARCH_GATE_AREA) && defined(AT_SYSINFO_EHDR).

This default is only useful for ia64.  arm64, ppc, s390, sh, tile, 64-bit
UML, and x86_32 have their own code just to disable it.  arm, 32-bit UML,
and x86_64 have gate areas, but they have their own implementations.

This gets rid of the default and moves the code into ia64.

This should save some code on architectures without a gate area: it's now
possible to inline the gate_area functions in the default case.
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Acked-by: NNathan Lynch <nathan_lynch@mentor.com>
Acked-by: NH. Peter Anvin <hpa@linux.intel.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [in principle]
Acked-by: Richard Weinberger <richard@nod.at> [for um]
Acked-by: Will Deacon <will.deacon@arm.com> [for arm64]
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Nathan Lynch <Nathan_Lynch@mentor.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a6c19dfe
  35. 05 6月, 2014 1 次提交
    • J
      mm: introdule compound_head_by_tail() · d2ee40ea
      由 Jianyu Zhan 提交于 
      Currently, in put_compound_page(), we have

======
if (likely(!PageTail(page))) {                  <------  (1)
        if (put_page_testzero(page)) {
                 /*
                 ¦* By the time all refcounts have been released
                 ¦* split_huge_page cannot run anymore from under us.
                 ¦*/
                 if (PageHead(page))
                         __put_compound_page(page);
                 else
                         __put_single_page(page);
         }
         return;
}

/* __split_huge_page_refcount can run under us */
page_head = compound_head(page);        <------------ (2)
======

if at (1) ,  we fail the check, this means page is *likely* a tail page.

Then at (2), as compoud_head(page) is inlined, it is :

======
static inline struct page *compound_head(struct page *page)
{
          if (unlikely(PageTail(page))) {           <----------- (3)
              struct page *head = page->first_page;

                smp_rmb();
                if (likely(PageTail(page)))
                        return head;
        }
        return page;
}
======

here, the (3) unlikely in the case is a negative hint, because it is
*likely* a tail page.  So the check (3) in this case is not good, so I
introduce a helper for this case.

So this patch introduces compound_head_by_tail() which deals with a
possible tail page(though it could be spilt by a racy thread), and make
compound_head() a wrapper on it.

This patch has no functional change, and it reduces the object
size slightly:
   text    data     bss     dec     hex  filename
  11003    1328      16   12347    303b  mm/swap.o.orig
  10971    1328      16   12315    301b  mm/swap.o.patched

I've ran "perf top -e branch-miss" to observe branch-miss in this case.
As Michael points out, it's a slow path, so only very few times this case
happens.  But I grep'ed the code base, and found there still are some
other call sites could be benifited from this helper.  And given that it
only bloating up the source by only 5 lines, but with a reduced object
size.  I still believe this helper deserves to exsit.
Signed-off-by: NJianyu Zhan <nasa4836@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d2ee40ea
  37. 21 5月, 2014 2 次提交
  39. 07 5月, 2014 1 次提交