linux-stable.git/include/linux/mm_types.h, branch v4.2.1

mm: make page pfmemalloc check more robust

2015-08-21T21:30:10+00:00

Commit c48a11c7ad26 ("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: c48a11c7ad26 ("netvm: propagate page->pfmemalloc to skb")
Signed-off-by: Michal Hocko 
Debugged-by: Vlastimil Babka 
Debugged-by: Jiri Bohac 
Cc: Eric Dumazet 
Cc: David Miller 
Acked-by: Mel Gorman 
Cc: 	[3.6+]
Signed-off-by: Andrew Morton 

Signed-off-by: Linus Torvalds

mm/net: Rename and move page fragment handling from net/ to mm/

2015-05-12T14:39:26+00:00

This change moves the __alloc_page_frag functionality out of the networking
stack and into the page allocation portion of mm.  The idea it so help make
this maintainable by placing it with other page allocation functions.

Since we are moving it from skbuff.c to page_alloc.c I have also renamed
the basic defines and structure from netdev_alloc_cache to page_frag_cache
to reflect that this is now part of a different kernel subsystem.

I have also added a simple __free_page_frag function which can handle
freeing the frags based on the skb->head pointer.  The model for this is
based off of __free_pages since we don't actually need to deal with all of
the cases that put_page handles.  I incorporated the virt_to_head_page call
and compound_order into the function as it actually allows for a signficant
size reduction by reducing code duplication.

Signed-off-by: Alexander Duyck 
Signed-off-by: David S. Miller

mm: rcu-protected get_mm_exe_file()

2015-04-17T13:04:07+00:00

This patch removes mm->mmap_sem from mm->exe_file read side.
Also it kills dup_mm_exe_file() and moves exe_file duplication into
dup_mmap() where both mmap_sems are locked.

[akpm@linux-foundation.org: fix comment typo]
Signed-off-by: Konstantin Khlebnikov 
Cc: Davidlohr Bueso 
Cc: Al Viro 
Cc: Oleg Nesterov 
Cc: "Paul E. McKenney" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: do not add nr_pmds into mm_struct if PMD is folded

2015-04-14T23:49:02+00:00

CONFIG_PGTABLE_LEVELS is now available on every architecture and we can
use it to check if we need to add nr_pmds into mm_struct.

Signed-off-by: Kirill A. Shutemov 
Tested-by: Guenter Roeck 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: "David S. Miller" 
Cc: "H. Peter Anvin" 
Cc: "James E.J. Bottomley" 
Cc: Benjamin Herrenschmidt 
Cc: Catalin Marinas 
Cc: Chris Metcalf 
Cc: David Howells 
Cc: Fenghua Yu 
Cc: Geert Uytterhoeven 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jeff Dike 
Cc: Kirill A. Shutemov 
Cc: Koichi Yasutake 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Cc: Ralf Baechle 
Cc: Richard Weinberger 
Cc: Russell King 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: account pmd page tables to the process

2015-02-12T01:06:04+00:00

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 
	#include 
	#include 
	#include 
	#include 
	#include 

	#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: Kirill A. Shutemov 
Reported-by: Dave Hansen 
Cc: Hugh Dickins 
Reviewed-by: Cyrill Gorcunov 
Cc: Pavel Emelyanov 
Cc: David Rientjes 
Tested-by: Sedat Dilek 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add fields for compound destructor and order into struct page

2015-02-12T01:06:00+00:00

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: Kirill A. Shutemov 
Acked-by: Jerome Marchand 
Acked-by: Christoph Lameter 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace vma->sharead.linear with vma->shared

2015-02-10T22:30:31+00:00

After removing vma->shared.nonlinear we have only one member of
vma->shared union, which doesn't make much sense.

This patch drops the union and move struct vma->shared.linear to
vma->shared.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

rmap: drop support of non-linear mappings

2015-02-10T22:30:31+00:00

We don't create non-linear mappings anymore.  Let's drop code which
handles them in rmap.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/debug-pagealloc: prepare boottime configurable on/off

2014-12-13T20:42:48+00:00

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: Joonsoo Kim 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Cc: Minchan Kim 
Cc: Dave Hansen 
Cc: Michal Nazarewicz 
Cc: Jungsoo Son 
Cc: Ingo Molnar 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move swp_entry_t definition to include/linux/mm_types.h

2014-12-13T20:42:47+00:00

swp_entry_t being defined in include/linux/swap.h instead of
include/linux/mm_types.h causes cyclic include dependency later when
include/linux/page_cgroup.h is included from writeback path.  Move the
definition to include/linux/mm_types.h.

While at it, reformat the comment above it.

Signed-off-by: Tejun Heo 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds