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  1. 16 2月, 2016 1 次提交
    • D
      mm/gup: Introduce get_user_pages_remote() · 1e987790
      由 Dave Hansen 提交于 
      For protection keys, we need to understand whether protections
should be enforced in software or not.  In general, we enforce
protections when working on our own task, but not when on others.
We call these "current" and "remote" operations.

This patch introduces a new get_user_pages() variant:

        get_user_pages_remote()

Which is a replacement for when get_user_pages() is called on
non-current tsk/mm.

We also introduce a new gup flag: FOLL_REMOTE which can be used
for the "__" gup variants to get this new behavior.

The uprobes is_trap_at_addr() location holds mmap_sem and
calls get_user_pages(current->mm) on an instruction address.  This
makes it a pretty unique gup caller.  Being an instruction access
and also really originating from the kernel (vs. the app), I opted
to consider this a 'remote' access where protection keys will not
be enforced.

Without protection keys, this patch should not change any behavior.
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: jack@suse.cz
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210154.3F0E51EA@viggo.jf.intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      1e987790
  3. 04 2月, 2016 2 次提交
    • K
      mm: polish virtual memory accounting · 30bdbb78
      由 Konstantin Khlebnikov 提交于 
      * add VM_STACK as alias for VM_GROWSUP/DOWN depending on architecture
* always account VMAs with flag VM_STACK as stack (as it was before)
* cleanup classifying helpers
* update comments and documentation
Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com>
Tested-by: NSudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      30bdbb78
    • J
      proc: revert /proc/<pid>/maps [stack:TID] annotation · 65376df5
      由 Johannes Weiner 提交于 
      Commit b7643757 ("procfs: mark thread stack correctly in
proc/<pid>/maps") added [stack:TID] annotation to /proc/<pid>/maps.

Finding the task of a stack VMA requires walking the entire thread list,
turning this into quadratic behavior: a thousand threads means a
thousand stacks, so the rendering of /proc/<pid>/maps needs to look at a
million combinations.

The cost is not in proportion to the usefulness as described in the
patch.

Drop the [stack:TID] annotation to make /proc/<pid>/maps (and
/proc/<pid>/numa_maps) usable again for higher thread counts.

The [stack] annotation inside /proc/<pid>/task/<tid>/maps is retained, as
identifying the stack VMA there is an O(1) operation.

Siddesh said:
 "The end users needed a way to identify thread stacks programmatically and
  there wasn't a way to do that.  I'm afraid I no longer remember (or have
  access to the resources that would aid my memory since I changed
  employers) the details of their requirement.  However, I did do this on my
  own time because I thought it was an interesting project for me and nobody
  really gave any feedback then as to its utility, so as far as I am
  concerned you could roll back the main thread maps information since the
  information is available in the thread-specific files"
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
Cc: Shaohua Li <shli@fb.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      65376df5
  5. 16 1月, 2016 14 次提交
  7. 15 1月, 2016 4 次提交
    • K
      mm: rework virtual memory accounting · 84638335
      由 Konstantin Khlebnikov 提交于 
      When inspecting a vague code inside prctl(PR_SET_MM_MEM) call (which
testing the RLIMIT_DATA value to figure out if we're allowed to assign
new @start_brk, @brk, @start_data, @end_data from mm_struct) it's been
commited that RLIMIT_DATA in a form it's implemented now doesn't do
anything useful because most of user-space libraries use mmap() syscall
for dynamic memory allocations.

Linus suggested to convert RLIMIT_DATA rlimit into something suitable
for anonymous memory accounting.  But in this patch we go further, and
the changes are bundled together as:

 * keep vma counting if CONFIG_PROC_FS=n, will be used for limits
 * replace mm->shared_vm with better defined mm->data_vm
 * account anonymous executable areas as executable
 * account file-backed growsdown/up areas as stack
 * drop struct file* argument from vm_stat_account
 * enforce RLIMIT_DATA for size of data areas

This way code looks cleaner: now code/stack/data classification depends
only on vm_flags state:

 VM_EXEC & ~VM_WRITE            -> code  (VmExe + VmLib in proc)
 VM_GROWSUP | VM_GROWSDOWN      -> stack (VmStk)
 VM_WRITE & ~VM_SHARED & !stack -> data  (VmData)

The rest (VmSize - VmData - VmStk - VmExe - VmLib) could be called
"shared", but that might be strange beast like readonly-private or VM_IO
area.

 - RLIMIT_AS            limits whole address space "VmSize"
 - RLIMIT_STACK         limits stack "VmStk" (but each vma individually)
 - RLIMIT_DATA          now limits "VmData"
Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@google.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      84638335
    • M
      mm: allow GFP_{FS,IO} for page_cache_read page cache allocation · c20cd45e
      由 Michal Hocko 提交于 
      page_cache_read has been historically using page_cache_alloc_cold to
allocate a new page.  This means that mapping_gfp_mask is used as the
base for the gfp_mask.  Many filesystems are setting this mask to
GFP_NOFS to prevent from fs recursion issues.  page_cache_read is called
from the vm_operations_struct::fault() context during the page fault.
This context doesn't need the reclaim protection normally.

ceph and ocfs2 which call filemap_fault from their fault handlers seem
to be OK because they are not taking any fs lock before invoking generic
implementation.  xfs which takes XFS_MMAPLOCK_SHARED is safe from the
reclaim recursion POV because this lock serializes truncate and punch
hole with the page faults and it doesn't get involved in the reclaim.

There is simply no reason to deliberately use a weaker allocation
context when a __GFP_FS | __GFP_IO can be used.  The GFP_NOFS protection
might be even harmful.  There is a push to fail GFP_NOFS allocations
rather than loop within allocator indefinitely with a very limited
reclaim ability.  Once we start failing those requests the OOM killer
might be triggered prematurely because the page cache allocation failure
is propagated up the page fault path and end up in
pagefault_out_of_memory.

We cannot play with mapping_gfp_mask directly because that would be racy
wrt.  parallel page faults and it might interfere with other users who
really rely on NOFS semantic from the stored gfp_mask.  The mask is also
inode proper so it would even be a layering violation.  What we can do
instead is to push the gfp_mask into struct vm_fault and allow fs layer
to overwrite it should the callback need to be called with a different
allocation context.

Initialize the default to (mapping_gfp_mask | __GFP_FS | __GFP_IO)
because this should be safe from the page fault path normally.  Why do
we care about mapping_gfp_mask at all then? Because this doesn't hold
only reclaim protection flags but it also might contain zone and
movability restrictions (GFP_DMA32, __GFP_MOVABLE and others) so we have
to respect those.
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: NJan Kara <jack@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c20cd45e
    • D
      mm: mmap: add new /proc tunable for mmap_base ASLR · d07e2259
      由 Daniel Cashman 提交于 
      Address Space Layout Randomization (ASLR) provides a barrier to
exploitation of user-space processes in the presence of security
vulnerabilities by making it more difficult to find desired code/data
which could help an attack.  This is done by adding a random offset to
the location of regions in the process address space, with a greater
range of potential offset values corresponding to better protection/a
larger search-space for brute force, but also to greater potential for
fragmentation.

The offset added to the mmap_base address, which provides the basis for
the majority of the mappings for a process, is set once on process exec
in arch_pick_mmap_layout() and is done via hard-coded per-arch values,
which reflect, hopefully, the best compromise for all systems.  The
trade-off between increased entropy in the offset value generation and
the corresponding increased variability in address space fragmentation
is not absolute, however, and some platforms may tolerate higher amounts
of entropy.  This patch introduces both new Kconfig values and a sysctl
interface which may be used to change the amount of entropy used for
offset generation on a system.

The direct motivation for this change was in response to the
libstagefright vulnerabilities that affected Android, specifically to
information provided by Google's project zero at:

  http://googleprojectzero.blogspot.com/2015/09/stagefrightened.html

The attack presented therein, by Google's project zero, specifically
targeted the limited randomness used to generate the offset added to the
mmap_base address in order to craft a brute-force-based attack.
Concretely, the attack was against the mediaserver process, which was
limited to respawning every 5 seconds, on an arm device.  The hard-coded
8 bits used resulted in an average expected success rate of defeating
the mmap ASLR after just over 10 minutes (128 tries at 5 seconds a
piece).  With this patch, and an accompanying increase in the entropy
value to 16 bits, the same attack would take an average expected time of
over 45 hours (32768 tries), which makes it both less feasible and more
likely to be noticed.

The introduced Kconfig and sysctl options are limited by per-arch
minimum and maximum values, the minimum of which was chosen to match the
current hard-coded value and the maximum of which was chosen so as to
give the greatest flexibility without generating an invalid mmap_base
address, generally a 3-4 bits less than the number of bits in the
user-space accessible virtual address space.

When decided whether or not to change the default value, a system
developer should consider that mmap_base address could be placed
anywhere up to 2^(value) bits away from the non-randomized location,
which would introduce variable-sized areas above and below the mmap_base
address such that the maximum vm_area_struct size may be reduced,
preventing very large allocations.

This patch (of 4):

ASLR only uses as few as 8 bits to generate the random offset for the
mmap base address on 32 bit architectures.  This value was chosen to
prevent a poorly chosen value from dividing the address space in such a
way as to prevent large allocations.  This may not be an issue on all
platforms.  Allow the specification of a minimum number of bits so that
platforms desiring greater ASLR protection may determine where to place
the trade-off.
Signed-off-by: NDaniel Cashman <dcashman@google.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: NKees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Nick Kralevich <nnk@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>
Cc: Borislav Petkov <bp@suse.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.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>
      d07e2259
    • J
      mm, shmem: add internal shmem resident memory accounting · eca56ff9
      由 Jerome Marchand 提交于 
      Currently looking at /proc/<pid>/status or statm, there is no way to
distinguish shmem pages from pages mapped to a regular file (shmem pages
are mapped to /dev/zero), even though their implication in actual memory
use is quite different.

The internal accounting currently counts shmem pages together with
regular files.  As a preparation to extend the userspace interfaces,
this patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for
shmem pages separately from MM_FILEPAGES.  The next patch will expose it
to userspace - this patch doesn't change the exported values yet, by
adding up MM_SHMEMPAGES to MM_FILEPAGES at places where MM_FILEPAGES was
used before.  The only user-visible change after this patch is the OOM
killer message that separates the reported "shmem-rss" from "file-rss".

[vbabka@suse.cz: forward-porting, tweak changelog]
Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NHugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      eca56ff9
  9. 12 1月, 2016 1 次提交
    • A
      mm: Add vm_insert_pfn_prot() · 1745cbc5
      由 Andy Lutomirski 提交于 
      The x86 vvar vma contains pages with differing cacheability
flags.  x86 currently implements this by manually inserting all
the ptes using (io_)remap_pfn_range when the vma is set up.

x86 wants to move to using .fault with VM_FAULT_NOPAGE to set up
the mappings as needed.  The correct API to use to insert a pfn
in .fault is vm_insert_pfn(), but vm_insert_pfn() can't override the
vma's cache mode, and the HPET page in particular needs to be
uncached despite the fact that the rest of the VMA is cached.

Add vm_insert_pfn_prot() to support varying cacheability within
the same non-COW VMA in a more sane manner.

x86 could alternatively use multiple VMAs, but that's messy,
would break CRIU, and would create unnecessary VMAs that would
waste memory.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d2938d1eb37be7a5e4f86182db646551f11e45aa.1451446564.git.luto@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      1745cbc5
  11. 07 11月, 2015 3 次提交
  13. 06 11月, 2015 3 次提交
    • E
      mm: introduce VM_LOCKONFAULT · de60f5f1
      由 Eric B Munson 提交于 
      The cost of faulting in all memory to be locked can be very high when
working with large mappings.  If only portions of the mapping will be used
this can incur a high penalty for locking.

For the example of a large file, this is the usage pattern for a large
statical language model (probably applies to other statical or graphical
models as well).  For the security example, any application transacting in
data that cannot be swapped out (credit card data, medical records, etc).

This patch introduces the ability to request that pages are not
pre-faulted, but are placed on the unevictable LRU when they are finally
faulted in.  The VM_LOCKONFAULT flag will be used together with VM_LOCKED
and has no effect when set without VM_LOCKED.  Setting the VM_LOCKONFAULT
flag for a VMA will cause pages faulted into that VMA to be added to the
unevictable LRU when they are faulted or if they are already present, but
will not cause any missing pages to be faulted in.

Exposing this new lock state means that we cannot overload the meaning of
the FOLL_POPULATE flag any longer.  Prior to this patch it was used to
mean that the VMA for a fault was locked.  This means we need the new
FOLL_MLOCK flag to communicate the locked state of a VMA.  FOLL_POPULATE
will now only control if the VMA should be populated and in the case of
VM_LOCKONFAULT, it will not be set.
Signed-off-by: NEric B Munson <emunson@akamai.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      de60f5f1
    • V
      mm: do not inc NR_PAGETABLE if ptlock_init failed · 706874e9
      由 Vladimir Davydov 提交于 
      If ALLOC_SPLIT_PTLOCKS is defined, ptlock_init may fail, in which case we
shouldn't increment NR_PAGETABLE.

Since small allocations, such as ptlock, normally do not fail (currently
they can fail if kmemcg is used though), this patch does not really fix
anything and should be considered as a code cleanup.
Signed-off-by: NVladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      706874e9
    • R
      mm: use only per-device readahead limit · 600e19af
      由 Roman Gushchin 提交于 
      Maximal readahead size is limited now by two values:
 1) by global 2Mb constant (MAX_READAHEAD in max_sane_readahead())
 2) by configurable per-device value* (bdi->ra_pages)

There are devices, which require custom readahead limit.
For instance, for RAIDs it's calculated as number of devices
multiplied by chunk size times 2.

Readahead size can never be larger than bdi->ra_pages * 2 value
(POSIX_FADV_SEQUNTIAL doubles readahead size).

If so, why do we need two limits?
I suggest to completely remove this max_sane_readahead() stuff and
use per-device readahead limit everywhere.

Also, using right readahead size for RAID disks can significantly
increase i/o performance:

before:
  dd if=/dev/md2 of=/dev/null bs=100M count=100
  100+0 records in
  100+0 records out
  10485760000 bytes (10 GB) copied, 12.9741 s, 808 MB/s

after:
  $ dd if=/dev/md2 of=/dev/null bs=100M count=100
  100+0 records in
  100+0 records out
  10485760000 bytes (10 GB) copied, 8.91317 s, 1.2 GB/s

(It's an 8-disks RAID5 storage).

This patch doesn't change sys_readahead and madvise(MADV_WILLNEED)
behavior introduced by 6d2be915 ("mm/readahead.c: fix readahead
failure for memoryless NUMA nodes and limit readahead pages").
Signed-off-by: NRoman Gushchin <klamm@yandex-team.ru>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: onstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      600e19af
  15. 02 10月, 2015 1 次提交
    • G
      memcg: fix dirty page migration · 0610c25d
      由 Greg Thelen 提交于 
      The problem starts with a file backed dirty page which is charged to a
memcg.  Then page migration is used to move oldpage to newpage.

Migration:
 - copies the oldpage's data to newpage
 - clears oldpage.PG_dirty
 - sets newpage.PG_dirty
 - uncharges oldpage from memcg
 - charges newpage to memcg

Clearing oldpage.PG_dirty decrements the charged memcg's dirty page
count.

However, because newpage is not yet charged, setting newpage.PG_dirty
does not increment the memcg's dirty page count.  After migration
completes newpage.PG_dirty is eventually cleared, often in
account_page_cleaned().  At this time newpage is charged to a memcg so
the memcg's dirty page count is decremented which causes underflow
because the count was not previously incremented by migration.  This
underflow causes balance_dirty_pages() to see a very large unsigned
number of dirty memcg pages which leads to aggressive throttling of
buffered writes by processes in non root memcg.

This issue:
 - can harm performance of non root memcg buffered writes.
 - can report too small (even negative) values in
   memory.stat[(total_)dirty] counters of all memcg, including the root.

To avoid polluting migrate.c with #ifdef CONFIG_MEMCG checks, introduce
page_memcg() and set_page_memcg() helpers.

Test:
    0) setup and enter limited memcg
    mkdir /sys/fs/cgroup/test
    echo 1G > /sys/fs/cgroup/test/memory.limit_in_bytes
    echo $$ > /sys/fs/cgroup/test/cgroup.procs

    1) buffered writes baseline
    dd if=/dev/zero of=/data/tmp/foo bs=1M count=1k
    sync
    grep ^dirty /sys/fs/cgroup/test/memory.stat

    2) buffered writes with compaction antagonist to induce migration
    yes 1 > /proc/sys/vm/compact_memory &
    rm -rf /data/tmp/foo
    dd if=/dev/zero of=/data/tmp/foo bs=1M count=1k
    kill %
    sync
    grep ^dirty /sys/fs/cgroup/test/memory.stat

    3) buffered writes without antagonist, should match baseline
    rm -rf /data/tmp/foo
    dd if=/dev/zero of=/data/tmp/foo bs=1M count=1k
    sync
    grep ^dirty /sys/fs/cgroup/test/memory.stat

                       (speed, dirty residue)
             unpatched                       patched
    1) 841 MB/s 0 dirty pages          886 MB/s 0 dirty pages
    2) 611 MB/s -33427456 dirty pages  793 MB/s 0 dirty pages
    3) 114 MB/s -33427456 dirty pages  891 MB/s 0 dirty pages

    Notice that unpatched baseline performance (1) fell after
    migration (3): 841 -> 114 MB/s.  In the patched kernel, post
    migration performance matches baseline.

Fixes: c4843a75 ("memcg: add per cgroup dirty page accounting")
Signed-off-by: NGreg Thelen <gthelen@google.com>
Reported-by: NDave Hansen <dave.hansen@intel.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>	[4.2+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0610c25d
  17. 11 9月, 2015 1 次提交
  19. 09 9月, 2015 5 次提交
  21. 05 9月, 2015 3 次提交
  23. 22 8月, 2015 1 次提交
    • M
      mm: make page pfmemalloc check more robust · 2f064f34
      由 Michal Hocko 提交于 
      Commit c48a11c7 ("netvm: propagate page->pfmemalloc to skb") added
checks for page->pfmemalloc to __skb_fill_page_desc():

        if (page->pfmemalloc && !page->mapping)
                skb->pfmemalloc = true;

It assumes page->mapping == NULL implies that page->pfmemalloc can be
trusted.  However, __delete_from_page_cache() can set set page->mapping
to NULL and leave page->index value alone.  Due to being in union, a
non-zero page->index will be interpreted as true page->pfmemalloc.

So the assumption is invalid if the networking code can see such a page.
And it seems it can.  We have encountered this with a NFS over loopback
setup when such a page is attached to a new skbuf.  There is no copying
going on in this case so the page confuses __skb_fill_page_desc which
interprets the index as pfmemalloc flag and the network stack drops
packets that have been allocated using the reserves unless they are to
be queued on sockets handling the swapping which is the case here and
that leads to hangs when the nfs client waits for a response from the
server which has been dropped and thus never arrive.

The struct page is already heavily packed so rather than finding another
hole to put it in, let's do a trick instead.  We can reuse the index
again but define it to an impossible value (-1UL).  This is the page
index so it should never see the value that large.  Replace all direct
users of page->pfmemalloc by page_is_pfmemalloc which will hide this
nastiness from unspoiled eyes.

The information will get lost if somebody wants to use page->index
obviously but that was the case before and the original code expected
that the information should be persisted somewhere else if that is
really needed (e.g.  what SLAB and SLUB do).

[akpm@linux-foundation.org: fix blooper in slub]
Fixes: c48a11c7 ("netvm: propagate page->pfmemalloc to skb")
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Debugged-by: NVlastimil Babka <vbabka@suse.com>
Debugged-by: NJiri Bohac <jbohac@suse.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>	[3.6+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2f064f34
  25. 17 8月, 2015 1 次提交