linux.git/mm/migrate.c, branch v5.6

mm: pagewalk: add 'depth' parameter to pte_hole

2020-02-04T03:05:25+00:00

The pte_hole() callback is called at multiple levels of the page tables.
Code dumping the kernel page tables needs to know what at what depth the
missing entry is.  Add this is an extra parameter to pte_hole().  When the
depth isn't know (e.g.  processing a vma) then -1 is passed.

The depth that is reported is the actual level where the entry is missing
(ignoring any folding that is in place), i.e.  any levels where
PTRS_PER_P?D is set to 1 are ignored.

Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their
natural numbers as levels 2/3/4.

Link: http://lkml.kernel.org/r/20191218162402.45610-16-steven.price@arm.com
Signed-off-by: Steven Price 
Tested-by: Zong Li 
Cc: Albert Ou 
Cc: Alexandre Ghiti 
Cc: Andy Lutomirski 
Cc: Ard Biesheuvel 
Cc: Arnd Bergmann 
Cc: Benjamin Herrenschmidt 
Cc: Borislav Petkov 
Cc: Catalin Marinas 
Cc: Christian Borntraeger 
Cc: Dave Hansen 
Cc: David S. Miller 
Cc: Heiko Carstens 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: James Hogan 
Cc: James Morse 
Cc: Jerome Glisse 
Cc: "Liang, Kan" 
Cc: Mark Rutland 
Cc: Michael Ellerman 
Cc: Paul Burton 
Cc: Paul Mackerras 
Cc: Paul Walmsley 
Cc: Peter Zijlstra 
Cc: Ralf Baechle 
Cc: Russell King 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Vineet Gupta 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate: add stable check in migrate_vma_insert_page()

2020-01-31T18:30:39+00:00

migrate_vma_insert_page() closely follows the code in:
  __handle_mm_fault()
    handle_pte_fault()
      do_anonymous_page()

Add a call to check_stable_address_space() after locking the page table
entry before inserting a ZONE_DEVICE private zero page mapping similar
to page faulting a new anonymous page.

Link: http://lkml.kernel.org/r/20200107211208.24595-4-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell 
Reviewed-by: Christoph Hellwig 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Jason Gunthorpe 
Cc: Bharata B Rao 
Cc: Michal Hocko 
Cc: Chris Down 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate: clean up some minor coding style

2020-01-31T18:30:39+00:00

Fix some comment typos and coding style clean up in preparation for the
next patch.  No functional changes.

Link: http://lkml.kernel.org/r/20200107211208.24595-3-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell 
Acked-by: Chris Down 
Reviewed-by: Christoph Hellwig 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Jason Gunthorpe 
Cc: Bharata B Rao 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate: remove useless mask of start address

2020-01-31T18:30:39+00:00

Addresses passed to walk_page_range() callback functions are already
page aligned and don't need to be masked with PAGE_MASK.

Link: http://lkml.kernel.org/r/20200107211208.24595-2-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell 
Reviewed-by: Christoph Hellwig 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Jason Gunthorpe 
Cc: Bharata B Rao 
Cc: Michal Hocko 
Cc: Chris Down 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move_pages: report the number of non-attempted pages

2020-01-31T18:30:36+00:00

Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"), the
semantic of move_pages() has changed to return the number of
non-migrated pages if they were result of a non-fatal reasons (usually a
busy page).

This was an unintentional change that hasn't been noticed except for LTP
tests which checked for the documented behavior.

There are two ways to go around this change.  We can even get back to
the original behavior and return -EAGAIN whenever migrate_pages is not
able to migrate pages due to non-fatal reasons.  Another option would be
to simply continue with the changed semantic and extend move_pages
documentation to clarify that -errno is returned on an invalid input or
when migration simply cannot succeed (e.g.  -ENOMEM, -EBUSY) or the
number of pages that couldn't have been migrated due to ephemeral
reasons (e.g.  page is pinned or locked for other reasons).

This patch implements the second option because this behavior is in
place for some time without anybody complaining and possibly new users
depending on it.  Also it allows to have a slightly easier error
handling as the caller knows that it is worth to retry when err > 0.

But since the new semantic would be aborted immediately if migration is
failed due to ephemeral reasons, need include the number of
non-attempted pages in the return value too.

Link: http://lkml.kernel.org/r/1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
Signed-off-by: Yang Shi 
Suggested-by: Michal Hocko 
Acked-by: Michal Hocko 
Reviewed-by: Wei Yang 
Cc:     [4.17+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: also overwrite error when it is bigger than zero

2020-01-31T18:30:36+00:00

If we get here after successfully adding page to list, err would be 1 to
indicate the page is queued in the list.

Current code has two problems:

  * on success, 0 is not returned
  * on error, if add_page_for_migratioin() return 1, and the following err1
    from do_move_pages_to_node() is set, the err1 is not returned since err
    is 1

And these behaviors break the user interface.

Link: http://lkml.kernel.org/r/20200119065753.21694-1-richardw.yang@linux.intel.com
Fixes: e0153fc2c760 ("mm: move_pages: return valid node id in status if the page is already on the target node").
Signed-off-by: Wei Yang 
Acked-by: Yang Shi 
Cc: John Hubbard 
Cc: Vlastimil Babka 
Cc: Christoph Lameter 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move_pages: return valid node id in status if the page is already on the target node

2020-01-04T21:55:09+00:00

Felix Abecassis reports move_pages() would return random status if the
pages are already on the target node by the below test program:

  int main(void)
  {
	const long node_id = 1;
	const long page_size = sysconf(_SC_PAGESIZE);
	const int64_t num_pages = 8;

	unsigned long nodemask =  1 << node_id;
	long ret = set_mempolicy(MPOL_BIND, &nodemask, sizeof(nodemask));
	if (ret < 0)
		return (EXIT_FAILURE);

	void **pages = malloc(sizeof(void*) * num_pages);
	for (int i = 0; i < num_pages; ++i) {
		pages[i] = mmap(NULL, page_size, PROT_WRITE | PROT_READ,
				MAP_PRIVATE | MAP_POPULATE | MAP_ANONYMOUS,
				-1, 0);
		if (pages[i] == MAP_FAILED)
			return (EXIT_FAILURE);
	}

	ret = set_mempolicy(MPOL_DEFAULT, NULL, 0);
	if (ret < 0)
		return (EXIT_FAILURE);

	int *nodes = malloc(sizeof(int) * num_pages);
	int *status = malloc(sizeof(int) * num_pages);
	for (int i = 0; i < num_pages; ++i) {
		nodes[i] = node_id;
		status[i] = 0xd0; /* simulate garbage values */
	}

	ret = move_pages(0, num_pages, pages, nodes, status, MPOL_MF_MOVE);
	printf("move_pages: %ld\n", ret);
	for (int i = 0; i < num_pages; ++i)
		printf("status[%d] = %d\n", i, status[i]);
  }

Then running the program would return nonsense status values:

  $ ./move_pages_bug
  move_pages: 0
  status[0] = 208
  status[1] = 208
  status[2] = 208
  status[3] = 208
  status[4] = 208
  status[5] = 208
  status[6] = 208
  status[7] = 208

This is because the status is not set if the page is already on the
target node, but move_pages() should return valid status as long as it
succeeds.  The valid status may be errno or node id.

We can't simply initialize status array to zero since the pages may be
not on node 0.  Fix it by updating status with node id which the page is
already on.

Link: http://lkml.kernel.org/r/1575584353-125392-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
Signed-off-by: Yang Shi 
Reported-by: Felix Abecassis 
Tested-by: Felix Abecassis 
Suggested-by: Michal Hocko 
Reviewed-by: John Hubbard 
Acked-by: Christoph Lameter 
Acked-by: Michal Hocko 
Reviewed-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: 	[4.17+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

autonuma: fix watermark checking in migrate_balanced_pgdat()

2019-12-01T20:59:09+00:00

When zone_watermark_ok() is called in migrate_balanced_pgdat() to check
migration target node, the parameter classzone_idx (for requested zone)
is specified as 0 (ZONE_DMA).  But when allocating memory for autonuma
in alloc_misplaced_dst_page(), the requested zone from GFP flags is
ZONE_MOVABLE.  That is, the requested zone is different.  The size of
lowmem_reserve for the different requested zone is different.  And this
may cause some issues.

For example, in the zoneinfo of a test machine as below,

Node 0, zone    DMA32
  pages free     61592
        min      29
        low      454
        high     879
        spanned  1044480
        present  442306
        managed  425921
        protection: (0, 0, 62457, 62457, 62457)

The free page number of ZONE_DMA32 is greater than "high watermark +
lowmem_reserve[ZONE_DMA]", but less than "high watermark +
lowmem_reserve[ZONE_MOVABLE]".  And because __alloc_pages_node() in
alloc_misplaced_dst_page() requests ZONE_MOVABLE, the
zone_watermark_ok() on ZONE_DMA32 in migrate_balanced_pgdat() may always
return true.  So, autonuma may not stop even when memory pressure in
node 0 is heavy.

To fix the issue, ZONE_MOVABLE is used as parameter to call
zone_watermark_ok() in migrate_balanced_pgdat().  This makes it same as
requested zone in alloc_misplaced_dst_page().  So that
migrate_balanced_pgdat() returns false when memory pressure is heavy.

Link: http://lkml.kernel.org/r/20191101075727.26683-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" 
Acked-by: Mel Gorman 
Cc: Michal Hocko 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Dave Hansen 
Cc: Dan Williams 
Cc: Fengguang Wu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/migrate.c: handle freed page at the first place

2019-12-01T20:59:09+00:00

When doing migration if the freed page is met, we just return without
migrating it since it is pointless to migrate a freed page.  But, the
current code allocates target page unconditionally before handling freed
page, if the page is freed, the newly allocated will be just freed.  It
doesn't make too much sense and is just a waste of time although
migrating freed page is rare.

So, handle freed page at the before that to avoid unnecessary page
allocation and free.

Link: http://lkml.kernel.org/r/1573755869-106954-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Cc: Mel Gorman 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: untag user pointers passed to memory syscalls

2019-09-26T00:51:41+00:00

This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.

This patch allows tagged pointers to be passed to the following memory
syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
mremap, msync, munlock, move_pages.

The mmap and mremap syscalls do not currently accept tagged addresses.
Architectures may interpret the tag as a background colour for the
corresponding vma.

Link: http://lkml.kernel.org/r/aaf0c0969d46b2feb9017f3e1b3ef3970b633d91.1563904656.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov 
Reviewed-by: Khalid Aziz 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Catalin Marinas 
Reviewed-by: Kees Cook 
Cc: Al Viro 
Cc: Dave Hansen 
Cc: Eric Auger 
Cc: Felix Kuehling 
Cc: Jens Wiklander 
Cc: Mauro Carvalho Chehab 
Cc: Mike Rapoport 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds