linux.git/mm/migrate.c, branch v2.6.37

mm/migrate.c: fix compilation error

2010-12-23T03:43:34+00:00

GCC complained about update_mmu_cache() not being defined in migrate.c.
Including  seems to solve the problem.

Signed-off-by: Michal Nazarewicz 
Signed-off-by: Kyungmin Park 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix error reporting in move_pages() syscall

2010-10-26T23:52:11+00:00

The vma returned by find_vma does not necessarily include the target
address.  If this happens the code tries to follow a page outside of any
vma and returns ENOENT instead of EFAULT.

Signed-off-by: Gleb Natapov 
Acked-by: Christoph Lameter 
Cc: Minchan Kim 
Cc: KAMEZAWA Hiroyuki 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: compaction: fix COMPACTPAGEFAILED counting

2010-10-26T23:52:06+00:00

Presently update_nr_listpages() doesn't have a role.  That's because lists
passed is always empty just after calling migrate_pages.  The
migrate_pages cleans up page list which have failed to migrate before
returning by aaa994b3.

 [PATCH] page migration: handle freeing of pages in migrate_pages()

 Do not leave pages on the lists passed to migrate_pages().  Seems that we will
 not need any postprocessing of pages.  This will simplify the handling of
 pages by the callers of migrate_pages().

At that time, we thought we don't need any postprocessing of pages.  But
the situation is changed.  The compaction need to know the number of
failed to migrate for COMPACTPAGEFAILED stat

This patch makes new rule for caller of migrate_pages to call
putback_lru_pages.  So caller need to clean up the lists so it has a
chance to postprocess the pages.  [suggested by Christoph Lameter]

Signed-off-by: Minchan Kim 
Cc: Hugh Dickins 
Cc: Andi Kleen 
Reviewed-by: Mel Gorman 
Reviewed-by: Wu Fengguang 
Acked-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

writeback: remove nonblocking/encountered_congestion references

2010-10-26T23:52:05+00:00

This removes more dead code that was somehow missed by commit 0d99519efef
(writeback: remove unused nonblocking and congestion checks).  There are
no behavior change except for the removal of two entries from one of the
ext4 tracing interface.

The nonblocking checks in ->writepages are no longer used because the
flusher now prefer to block on get_request_wait() than to skip inodes on
IO congestion.  The latter will lead to more seeky IO.

The nonblocking checks in ->writepage are no longer used because it's
redundant with the WB_SYNC_NONE check.

We no long set ->nonblocking in VM page out and page migration, because
a) it's effectively redundant with WB_SYNC_NONE in current code
b) it's old semantic of "Don't get stuck on request queues" is mis-behavior:
   that would skip some dirty inodes on congestion and page out others, which
   is unfair in terms of LRU age.

Inspired by Christoph Hellwig. Thanks!

Signed-off-by: Wu Fengguang 
Cc: Theodore Ts'o 
Cc: David Howells 
Cc: Sage Weil 
Cc: Steve French 
Cc: Chris Mason 
Cc: Jens Axboe 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix migration.c compilation on s390

2010-10-11T14:57:39+00:00

31bit s390 doesn't have huge pages and failed with:

> mm/migrate.c: In function 'remove_migration_pte':
> mm/migrate.c:143:3: error: implicit declaration of function 'pte_mkhuge'
> mm/migrate.c:143:7: error: incompatible types when assigning to type 'pte_t' from type 'int'

Put that code into a ifdef.

Reported by Heiko Carstens

Signed-off-by: Andi Kleen

hugetlb: hugepage migration core

2010-10-08T07:32:45+00:00

This patch extends page migration code to support hugepage migration.
One of the potential users of this feature is soft offlining which
is triggered by memory corrected errors (added by the next patch.)

Todo:
- there are other users of page migration such as memory policy,
  memory hotplug and memocy compaction.
  They are not ready for hugepage support for now.

ChangeLog since v4:
- define migrate_huge_pages()
- remove changes on isolation/putback_lru_page()

ChangeLog since v2:
- refactor isolate/putback_lru_page() to handle hugepage
- add comment about race on unmap_and_move_huge_page()

ChangeLog since v1:
- divide migration code path for hugepage
- define routine checking migration swap entry for hugetlb
- replace "goto" with "if/else" in remove_migration_pte()

Signed-off-by: Naoya Horiguchi 
Signed-off-by: Jun'ichi Nomura 
Acked-by: Mel Gorman 
Signed-off-by: Andi Kleen

mm: extend KSM refcounts to the anon_vma root

2010-08-10T03:44:55+00:00

KSM reference counts can cause an anon_vma to exist after the processe it
belongs to have already exited.  Because the anon_vma lock now lives in
the root anon_vma, we need to ensure that the root anon_vma stays around
until after all the "child" anon_vmas have been freed.

The obvious way to do this is to have a "child" anon_vma take a reference
to the root in anon_vma_fork.  When the anon_vma is freed at munmap or
process exit, we drop the refcount in anon_vma_unlink and possibly free
the root anon_vma.

The KSM anon_vma reference count function also needs to be modified to
deal with the possibility of freeing 2 levels of anon_vma.  The easiest
way to do this is to break out the KSM magic and make it generic.

When compiling without CONFIG_KSM, this code is compiled out.

Signed-off-by: Rik van Riel 
Tested-by: Larry Woodman 
Acked-by: Larry Woodman 
Reviewed-by: Minchan Kim 
Cc: KAMEZAWA Hiroyuki 
Acked-by: Mel Gorman 
Acked-by: Linus Torvalds 
Tested-by: Dave Young 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: always lock the root (oldest) anon_vma

2010-08-10T03:44:55+00:00

Always (and only) lock the root (oldest) anon_vma whenever we do something
in an anon_vma.  The recently introduced anon_vma scalability is due to
the rmap code scanning only the VMAs that need to be scanned.  Many common
operations still took the anon_vma lock on the root anon_vma, so always
taking that lock is not expected to introduce any scalability issues.

However, always taking the same lock does mean we only need to take one
lock, which means rmap_walk on pages from any anon_vma in the vma is
excluded from occurring during an munmap, expand_stack or other operation
that needs to exclude rmap_walk and similar functions.

Also add the proper locking to vma_adjust.

Signed-off-by: Rik van Riel 
Tested-by: Larry Woodman 
Acked-by: Larry Woodman 
Reviewed-by: Minchan Kim 
Reviewed-by: KAMEZAWA Hiroyuki 
Acked-by: Mel Gorman 
Acked-by: Linus Torvalds 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: change direct call of spin_lock(anon_vma->lock) to inline function

2010-08-10T03:44:55+00:00

Subsitute a direct call of spin_lock(anon_vma->lock) with an inline
function doing exactly the same.

This makes it easier to do the substitution to the root anon_vma lock in a
following patch.

We will deal with the handful of special locks (nested, dec_and_lock, etc)
separately.

Signed-off-by: Rik van Riel 
Acked-by: Mel Gorman 
Acked-by: KAMEZAWA Hiroyuki 
Tested-by: Larry Woodman 
Acked-by: Larry Woodman 
Reviewed-by: Minchan Kim 
Acked-by: Linus Torvalds 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: fix mis-accounting of file mapped racy with migration

2010-05-27T16:12:44+00:00

FILE_MAPPED per memcg of migrated file cache is not properly updated,
because our hook in page_add_file_rmap() can't know to which memcg
FILE_MAPPED should be counted.

Basically, this patch is for fixing the bug but includes some big changes
to fix up other messes.

Now, at migrating mapped file, events happen in following sequence.

 1. allocate a new page.
 2. get memcg of an old page.
 3. charge ageinst a new page before migration. But at this point,
    no changes to new page's page_cgroup, no commit for the charge.
    (IOW, PCG_USED bit is not set.)
 4. page migration replaces radix-tree, old-page and new-page.
 5. page migration remaps the new page if the old page was mapped.
 6. Here, the new page is unlocked.
 7. memcg commits the charge for newpage, Mark the new page's page_cgroup
    as PCG_USED.

Because "commit" happens after page-remap, we can count FILE_MAPPED
at "5", because we should avoid to trust page_cgroup->mem_cgroup.
if PCG_USED bit is unset.
(Note: memcg's LRU removal code does that but LRU-isolation logic is used
 for helping it. When we overwrite page_cgroup->mem_cgroup, page_cgroup is
 not on LRU or page_cgroup->mem_cgroup is NULL.)

We can lose file_mapped accounting information at 5 because FILE_MAPPED
is updated only when mapcount changes 0->1. So we should catch it.

BTW, historically, above implemntation comes from migration-failure
of anonymous page. Because we charge both of old page and new page
with mapcount=0, we can't catch
  - the page is really freed before remap.
  - migration fails but it's freed before remap
or .....corner cases.

New migration sequence with memcg is:

 1. allocate a new page.
 2. mark PageCgroupMigration to the old page.
 3. charge against a new page onto the old page's memcg. (here, new page's pc
    is marked as PageCgroupUsed.)
 4. page migration replaces radix-tree, page table, etc...
 5. At remapping, new page's page_cgroup is now makrked as "USED"
    We can catch 0->1 event and FILE_MAPPED will be properly updated.

    And we can catch SWAPOUT event after unlock this and freeing this
    page by unmap() can be caught.

 7. Clear PageCgroupMigration of the old page.

So, FILE_MAPPED will be correctly updated.

Then, for what MIGRATION flag is ?
  Without it, at migration failure, we may have to charge old page again
  because it may be fully unmapped. "charge" means that we have to dive into
  memory reclaim or something complated. So, it's better to avoid
  charge it again. Before this patch, __commit_charge() was working for
  both of the old/new page and fixed up all. But this technique has some
  racy condtion around FILE_MAPPED and SWAPOUT etc...
  Now, the kernel use MIGRATION flag and don't uncharge old page until
  the end of migration.

I hope this change will make memcg's page migration much simpler.  This
page migration has caused several troubles.  Worth to add a flag for
simplification.

Reviewed-by: Daisuke Nishimura 
Tested-by: Daisuke Nishimura 
Reported-by: Daisuke Nishimura 
Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: Christoph Lameter 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds