linux-toradex.git/mm/ksm.c, branch v3.14.38

mm: close PageTail race

2014-03-04T15:55:47+00:00

Commit bf6bddf1924e ("mm: introduce compaction and migration for
ballooned pages") introduces page_count(page) into memory compaction
which dereferences page->first_page if PageTail(page).

This results in a very rare NULL pointer dereference on the
aforementioned page_count(page).  Indeed, anything that does
compound_head(), including page_count() is susceptible to racing with
prep_compound_page() and seeing a NULL or dangling page->first_page
pointer.

This patch uses Andrea's implementation of compound_trans_head() that
deals with such a race and makes it the default compound_head()
implementation.  This includes a read memory barrier that ensures that
if PageTail(head) is true that we return a head page that is neither
NULL nor dangling.  The patch then adds a store memory barrier to
prep_compound_page() to ensure page->first_page is set.

This is the safest way to ensure we see the head page that we are
expecting, PageTail(page) is already in the unlikely() path and the
memory barriers are unfortunately required.

Hugetlbfs is the exception, we don't enforce a store memory barrier
during init since no race is possible.

Signed-off-by: David Rientjes 
Cc: Holger Kiehl 
Cc: Christoph Lameter 
Cc: Rafael Aquini 
Cc: Vlastimil Babka 
Cc: Michal Hocko 
Cc: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: Rik van Riel 
Cc: "Kirill A. Shutemov" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: audit/fix non-modular users of module_init in core code

2014-01-24T00:36:52+00:00

Code that is obj-y (always built-in) or dependent on a bool Kconfig
(built-in or absent) can never be modular.  So using module_init as an
alias for __initcall can be somewhat misleading.

Fix these up now, so that we can relocate module_init from init.h into
module.h in the future.  If we don't do this, we'd have to add module.h
to obviously non-modular code, and that would be a worse thing.

The audit targets the following module_init users for change:
 mm/ksm.c                       bool KSM
 mm/mmap.c                      bool MMU
 mm/huge_memory.c               bool TRANSPARENT_HUGEPAGE
 mm/mmu_notifier.c              bool MMU_NOTIFIER

Note that direct use of __initcall is discouraged, vs.  one of the
priority categorized subgroups.  As __initcall gets mapped onto
device_initcall, our use of subsys_initcall (which makes sense for these
files) will thus change this registration from level 6-device to level
4-subsys (i.e.  slightly earlier).

However no observable impact of that difference has been observed during
testing.

One might think that core_initcall (l2) or postcore_initcall (l3) would
be more appropriate for anything in mm/ but if we look at some actual
init functions themselves, we see things like:

mm/huge_memory.c --> hugepage_init     --> hugepage_init_sysfs
mm/mmap.c        --> init_user_reserve --> sysctl_user_reserve_kbytes
mm/ksm.c         --> ksm_init          --> sysfs_create_group

and hence the choice of subsys_initcall (l4) seems reasonable, and at
the same time minimizes the risk of changing the priority too
drastically all at once.  We can adjust further in the future.

Also, several instances of missing ";" at EOL are fixed.

Signed-off-by: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE

2014-01-24T00:36:50+00:00

Most of the VM_BUG_ON assertions are performed on a page.  Usually, when
one of these assertions fails we'll get a BUG_ON with a call stack and
the registers.

I've recently noticed based on the requests to add a small piece of code
that dumps the page to various VM_BUG_ON sites that the page dump is
quite useful to people debugging issues in mm.

This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what
VM_BUG_ON() does, also dumps the page before executing the actual
BUG_ON.

[akpm@linux-foundation.org: fix up includes]
Signed-off-by: Sasha Levin 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/rmap: use rmap_walk() in page_referenced()

2014-01-22T00:19:45+00:00

Now, we have an infrastructure in rmap_walk() to handle difference from
variants of rmap traversing functions.

So, just use it in page_referenced().

In this patch, I change following things.

1. remove some variants of rmap traversing functions.
	cf> page_referenced_ksm, page_referenced_anon,
	page_referenced_file

2. introduce new struct page_referenced_arg and pass it to
   page_referenced_one(), main function of rmap_walk, in order to count
   reference, to store vm_flags and to check finish condition.

3. mechanical change to use rmap_walk() in page_referenced().

[liwanp@linux.vnet.ibm.com: fix BUG at rmap_walk]
Signed-off-by: Joonsoo Kim 
Reviewed-by: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Ingo Molnar 
Cc: Hillf Danton 
Signed-off-by: Wanpeng Li 
Cc: Sasha Levin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/rmap: use rmap_walk() in try_to_munlock()

2014-01-22T00:19:45+00:00

Now, we have an infrastructure in rmap_walk() to handle difference from
variants of rmap traversing functions.

So, just use it in try_to_munlock().

In this patch, I change following things.

1. remove some variants of rmap traversing functions.
	cf> try_to_unmap_ksm, try_to_unmap_anon, try_to_unmap_file
2. mechanical change to use rmap_walk() in try_to_munlock().
3. copy and paste comments.

Signed-off-by: Joonsoo Kim 
Reviewed-by: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Ingo Molnar 
Cc: Hillf Danton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/rmap: use rmap_walk() in try_to_unmap()

2014-01-22T00:19:45+00:00

Now, we have an infrastructure in rmap_walk() to handle difference from
variants of rmap traversing functions.

So, just use it in try_to_unmap().

In this patch, I change following things.

1. enable rmap_walk() if !CONFIG_MIGRATION.
2. mechanical change to use rmap_walk() in try_to_unmap().

Signed-off-by: Joonsoo Kim 
Reviewed-by: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Ingo Molnar 
Cc: Hillf Danton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/rmap: extend rmap_walk_xxx() to cope with different cases

2014-01-22T00:19:45+00:00

There are a lot of common parts in traversing functions, but there are
also a little of uncommon parts in it.  By assigning proper function
pointer on each rmap_walker_control, we can handle these difference
correctly.

Following are differences we should handle.

1. difference of lock function in anon mapping case
2. nonlinear handling in file mapping case
3. prechecked condition:
	checking memcg in page_referenced(),
	checking VM_SHARE in page_mkclean()
	checking temporary vma in try_to_unmap()
4. exit condition:
	checking page_mapped() in try_to_unmap()

So, in this patch, I introduce 4 function pointers to handle above
differences.

Signed-off-by: Joonsoo Kim 
Cc: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Ingo Molnar 
Cc: Hillf Danton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/rmap: make rmap_walk to get the rmap_walk_control argument

2014-01-22T00:19:45+00:00

In each rmap traverse case, there is some difference so that we need
function pointers and arguments to them in order to handle these

For this purpose, struct rmap_walk_control is introduced in this patch,
and will be extended in following patch.  Introducing and extending are
separate, because it clarify changes.

Signed-off-by: Joonsoo Kim 
Reviewed-by: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Ingo Molnar 
Cc: Hillf Danton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ksm: remove redundant __GFP_ZERO from kcalloc

2013-11-13T03:09:02+00:00

kcalloc returns zeroed memory.  There's no need to use this flag.

Signed-off-by: Joe Perches 
Reviewed-by: Wanpeng Li 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: replace strict_strtoul() with kstrtoul()

2013-09-11T22:57:11+00:00

The use of strict_strtoul() is not preferred, because strict_strtoul() is
obsolete.  Thus, kstrtoul() should be used.

Signed-off-by: Jingoo Han 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds