linux-stable.git/fs/proc/task_mmu.c, branch linux-4.3.y

mm: introduce idle page tracking

2015-09-10T20:29:01+00:00

Knowing the portion of memory that is not used by a certain application or
memory cgroup (idle memory) can be useful for partitioning the system
efficiently, e.g.  by setting memory cgroup limits appropriately.
Currently, the only means to estimate the amount of idle memory provided
by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the
access bit for all pages mapped to a particular process by writing 1 to
clear_refs, wait for some time, and then count smaps:Referenced.  However,
this method has two serious shortcomings:

 - it does not count unmapped file pages
 - it affects the reclaimer logic

To overcome these drawbacks, this patch introduces two new page flags,
Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap.
A page's Idle flag can only be set from userspace by setting bit in
/sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page,
and it is cleared whenever the page is accessed either through page tables
(it is cleared in page_referenced() in this case) or using the read(2)
system call (mark_page_accessed()). Thus by setting the Idle flag for
pages of a particular workload, which can be found e.g.  by reading
/proc/PID/pagemap, waiting for some time to let the workload access its
working set, and then reading the bitmap file, one can estimate the amount
of pages that are not used by the workload.

The Young page flag is used to avoid interference with the memory
reclaimer.  A page's Young flag is set whenever the Access bit of a page
table entry pointing to the page is cleared by writing to the bitmap file.
If page_referenced() is called on a Young page, it will add 1 to its
return value, therefore concealing the fact that the Access bit was
cleared.

Note, since there is no room for extra page flags on 32 bit, this feature
uses extended page flags when compiled on 32 bit.

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: kpageidle requires an MMU]
[akpm@linux-foundation.org: decouple from page-flags rework]
Signed-off-by: Vladimir Davydov 
Reviewed-by: Andres Lagar-Cavilla 
Cc: Minchan Kim 
Cc: Raghavendra K T 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Greg Thelen 
Cc: Michel Lespinasse 
Cc: David Rientjes 
Cc: Pavel Emelyanov 
Cc: Cyrill Gorcunov 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: /proc/pid/smaps:: show proportional swap share of the mapping

2015-09-08T22:35:28+00:00

We want to know per-process workingset size for smart memory management
on userland and we use swap(ex, zram) heavily to maximize memory
efficiency so workingset includes swap as well as RSS.

On such system, if there are lots of shared anonymous pages, it's really
hard to figure out exactly how many each process consumes memory(ie, rss
+ wap) if the system has lots of shared anonymous memory(e.g, android).

This patch introduces SwapPss field on /proc//smaps so we can get
more exact workingset size per process.

Bongkyu tested it. Result is below.

1. 50M used swap
SwapTotal: 461976 kB
SwapFree: 411192 kB

$ adb shell cat /proc/*/smaps | grep "SwapPss:" | awk '{sum += $2} END {print sum}';
48236
$ adb shell cat /proc/*/smaps | grep "Swap:" | awk '{sum += $2} END {print sum}';
141184

2. 240M used swap
SwapTotal: 461976 kB
SwapFree: 216808 kB

$ adb shell cat /proc/*/smaps | grep "SwapPss:" | awk '{sum += $2} END {print sum}';
230315
$ adb shell cat /proc/*/smaps | grep "Swap:" | awk '{sum += $2} END {print sum}';
1387744

[akpm@linux-foundation.org: simplify kunmap_atomic() call]
Signed-off-by: Minchan Kim 
Reported-by: Bongkyu Kim 
Tested-by: Bongkyu Kim 
Cc: Hugh Dickins 
Cc: Sergey Senozhatsky 
Cc: Jonathan Corbet 
Cc: Jerome Marchand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pagemap: add mmap-exclusive bit for marking pages mapped only here

2015-09-08T22:35:28+00:00

This patch sets bit 56 in pagemap if this page is mapped only once.  It
allows to detect exclusively used pages without exposing PFN:

present file exclusive state
0       0    0         non-present
1       1    0         file page mapped somewhere else
1       1    1         file page mapped only here
1       0    0         anon non-CoWed page (shared with parent/child)
1       0    1         anon CoWed page (or never forked)

CoWed pages in (MAP_FILE | MAP_PRIVATE) areas are anon in this context.

MMap-exclusive bit doesn't reflect potential page-sharing via swapcache:
page could be mapped once but has several swap-ptes which point to it.
Application could detect that by swap bit in pagemap entry and touch that
pte via /proc/pid/mem to get real information.

See http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@mail.gmail.com

Requested by Mark Williamson.

[akpm@linux-foundation.org: fix spello]
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Mark Williamson 
Tested-by:  Mark Williamson 
Reviewed-by: Naoya Horiguchi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pagemap: hide physical addresses from non-privileged users

2015-09-08T22:35:28+00:00

This patch makes pagemap readable for normal users and hides physical
addresses from them.  For some use-cases PFN isn't required at all.

See http://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name

Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace")
Signed-off-by: Konstantin Khlebnikov 
Cc: Naoya Horiguchi 
Reviewed-by: Mark Williamson 
Tested-by:  Mark Williamson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pagemap: rework hugetlb and thp report

2015-09-08T22:35:28+00:00

This patch moves pmd dissection out of reporting loop: huge pages are
reported as bunch of normal pages with contiguous PFNs.

Add missing "FILE" bit in hugetlb vmas.

Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Naoya Horiguchi 
Reviewed-by: Mark Williamson 
Tested-by:  Mark Williamson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pagemap: switch to the new format and do some cleanup

2015-09-08T22:35:28+00:00

This patch removes page-shift bits (scheduled to remove since 3.11) and
completes migration to the new bit layout.  Also it cleans messy macro.

Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Naoya Horiguchi 
Cc: Mark Williamson 
Tested-by:  Mark Williamson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pagemap: check permissions and capabilities at open time

2015-09-08T22:35:28+00:00

This patchset makes pagemap useable again in the safe way (after row
hammer bug it was made CAP_SYS_ADMIN-only).  This patchset restores access
for non-privileged users but hides PFNs from them.

Also it adds bit 'map-exclusive' which is set if page is mapped only here:
it helps in estimation of working set without exposing pfns and allows to
distinguish CoWed and non-CoWed private anonymous pages.

Second patch removes page-shift bits and completes migration to the new
pagemap format: flags soft-dirty and mmap-exclusive are available only in
the new format.

This patch (of 5):

This patch moves permission checks from pagemap_read() into pagemap_open().

Pointer to mm is saved in file->private_data. This reference pins only
mm_struct itself. /proc/*/mem, maps, smaps already work in the same way.

See http://lkml.kernel.org/r/CA+55aFyKpWrt_Ajzh1rzp_GcwZ4=6Y=kOv8hBz172CFJp6L8Tg@mail.gmail.com

Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Naoya Horiguchi 
Reviewed-by: Mark Williamson 
Tested-by:  Mark Williamson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP

2015-09-04T23:54:41+00:00

These two flags gets set in vma->vm_flags to tell the VM common code
if the userfaultfd is armed and in which mode (only tracking missing
faults, only tracking wrprotect faults or both). If neither flags is
set it means the userfaultfd is not armed on the vma.

Signed-off-by: Andrea Arcangeli 
Acked-by: Pavel Emelyanov 
Cc: Sanidhya Kashyap 
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" 
Cc: Andres Lagar-Cavilla 
Cc: Dave Hansen 
Cc: Paolo Bonzini 
Cc: Rik van Riel 
Cc: Mel Gorman 
Cc: Andy Lutomirski 
Cc: Hugh Dickins 
Cc: Peter Feiner 
Cc: "Dr. David Alan Gilbert" 
Cc: Johannes Weiner 
Cc: "Huangpeng (Peter)" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vfs: add seq_file_path() helper

2015-06-23T22:01:07+00:00

Turn
	seq_path(..., &file->f_path, ...);
into
	seq_file_path(..., file, ...);

Signed-off-by: Miklos Szeredi 
Signed-off-by: Al Viro

pagemap: do not leak physical addresses to non-privileged userspace

2015-03-17T16:31:30+00:00

As pointed by recent post[1] on exploiting DRAM physical imperfection,
/proc/PID/pagemap exposes sensitive information which can be used to do
attacks.

This disallows anybody without CAP_SYS_ADMIN to read the pagemap.

[1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html

[ Eventually we might want to do anything more finegrained, but for now
  this is the simple model.   - Linus ]

Signed-off-by: Kirill A. Shutemov 
Acked-by: Konstantin Khlebnikov 
Acked-by: Andy Lutomirski 
Cc: Pavel Emelyanov 
Cc: Andrew Morton 
Cc: Mark Seaborn 
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds