linux-stable.git/mm/page_alloc.c, branch v5.1.2

mm/page_alloc.c: fix never set ALLOC_NOFRAGMENT flag

2019-04-26T16:18:05+00:00

Commit 0a79cdad5eb2 ("mm: use alloc_flags to record if kswapd can wake")
removed setting of the ALLOC_NOFRAGMENT flag.  Bring it back.

The runtime effect is that ALLOC_NOFRAGMENT behaviour is restored so
that allocations are spread across local zones to avoid fragmentation
due to mixing pageblocks as long as possible.

Link: http://lkml.kernel.org/r/20190423120806.3503-2-aryabinin@virtuozzo.com
Fixes: 0a79cdad5eb2 ("mm: use alloc_flags to record if kswapd can wake")
Signed-off-by: Andrey Ryabinin 
Acked-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page_alloc.c: avoid potential NULL pointer dereference

2019-04-26T16:18:05+00:00

ac.preferred_zoneref->zone passed to alloc_flags_nofragment() can be NULL.
'zone' pointer unconditionally derefernced in alloc_flags_nofragment().
Bail out on NULL zone to avoid potential crash.  Currently we don't see
any crashes only because alloc_flags_nofragment() has another bug which
allows compiler to optimize away all accesses to 'zone'.

Link: http://lkml.kernel.org/r/20190423120806.3503-1-aryabinin@virtuozzo.com
Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
Signed-off-by: Andrey Ryabinin 
Acked-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, page_alloc: always use a captured page regardless of compaction result

2019-04-26T16:18:05+00:00

During the development of commit 5e1f0f098b46 ("mm, compaction: capture
a page under direct compaction"), a paranoid check was added to ensure
that if a captured page was available after compaction that it was
consistent with the final state of compaction.  The intent was to catch
serious programming bugs such as using a stale page pointer and causing
corruption problems.

However, it is possible to get a captured page even if compaction was
unsuccessful if an interrupt triggered and happened to free pages in
interrupt context that got merged into a suitable high-order page.  It's
highly unlikely but Li Wang did report the following warning on s390
occuring when testing OOM handling.  Note that the warning is slightly
edited for clarity.

  WARNING: CPU: 0 PID: 9783 at mm/page_alloc.c:3777 __alloc_pages_direct_compact+0x182/0x190
  Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs
    lockd grace fscache sunrpc pkey ghash_s390 prng xts aes_s390
    des_s390 des_generic sha512_s390 zcrypt_cex4 zcrypt vmur binfmt_misc
    ip_tables xfs libcrc32c dasd_fba_mod qeth_l2 dasd_eckd_mod dasd_mod
    qeth qdio lcs ctcm ccwgroup fsm dm_mirror dm_region_hash dm_log
    dm_mod
  CPU: 0 PID: 9783 Comm: copy.sh Kdump: loaded Not tainted 5.1.0-rc 5 #1

This patch simply removes the check entirely instead of trying to be
clever about pages freed from interrupt context.  If a serious
programming error was introduced, it is highly likely to be caught by
prep_new_page() instead.

Link: http://lkml.kernel.org/r/20190419085133.GH18914@techsingularity.net
Fixes: 5e1f0f098b46 ("mm, compaction: capture a page under direct compaction")
Signed-off-by: Mel Gorman 
Reported-by: Li Wang 
Acked-by: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model

2019-04-26T16:18:05+00:00

Mikulas Patocka reported that commit 1c30844d2dfe ("mm: reclaim small
amounts of memory when an external fragmentation event occurs") "broke"
memory management on parisc.

The machine is not NUMA but the DISCONTIG model creates three pgdats
even though it's a UMA machine for the following ranges

        0) Start 0x0000000000000000 End 0x000000003fffffff Size   1024 MB
        1) Start 0x0000000100000000 End 0x00000001bfdfffff Size   3070 MB
        2) Start 0x0000004040000000 End 0x00000040ffffffff Size   3072 MB

Mikulas reported:

	With the patch 1c30844d2, the kernel will incorrectly reclaim the
	first zone when it fills up, ignoring the fact that there are two
	completely free zones. Basiscally, it limits cache size to 1GiB.

	For example, if I run:
	# dd if=/dev/sda of=/dev/null bs=1M count=2048

	- with the proper kernel, there should be "Buffers - 2GiB"
	when this command finishes. With the patch 1c30844d2, buffers
	will consume just 1GiB or slightly more, because the kernel was
	incorrectly reclaiming them.

The page allocator and reclaim makes assumptions that pgdats really
represent NUMA nodes and zones represent ranges and makes decisions on
that basis.  Watermark boosting for small pgdats leads to unexpected
results even though this would have behaved reasonably on SPARSEMEM.

DISCONTIG is essentially deprecated and even parisc plans to move to
SPARSEMEM so there is no need to be fancy, this patch simply disables
watermark boosting by default on DISCONTIGMEM.

Link: http://lkml.kernel.org/r/20190419094335.GJ18914@techsingularity.net
Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
Signed-off-by: Mel Gorman 
Reported-by: Mikulas Patocka 
Tested-by: Mikulas Patocka 
Acked-by: Vlastimil Babka 
Cc: James Bottomley 
Cc: Matthew Wilcox 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hotplug: treat CMA pages as unmovable

2019-04-19T16:46:05+00:00

has_unmovable_pages() is used by allocating CMA and gigantic pages as
well as the memory hotplug.  The later doesn't know how to offline CMA
pool properly now, but if an unused (free) CMA page is encountered, then
has_unmovable_pages() happily considers it as a free memory and
propagates this up the call chain.  Memory offlining code then frees the
page without a proper CMA tear down which leads to an accounting issues.
Moreover if the same memory range is onlined again then the memory never
gets back to the CMA pool.

State after memory offline:

 # grep cma /proc/vmstat
 nr_free_cma 205824

 # cat /sys/kernel/debug/cma/cma-kvm_cma/count
 209920

Also, kmemleak still think those memory address are reserved below but
have already been used by the buddy allocator after onlining.  This
patch fixes the situation by treating CMA pageblocks as unmovable except
when has_unmovable_pages() is called as part of CMA allocation.

  Offlined Pages 4096
  kmemleak: Cannot insert 0xc000201f7d040008 into the object search tree (overlaps existing)
  Call Trace:
    dump_stack+0xb0/0xf4 (unreliable)
    create_object+0x344/0x380
    __kmalloc_node+0x3ec/0x860
    kvmalloc_node+0x58/0x110
    seq_read+0x41c/0x620
    __vfs_read+0x3c/0x70
    vfs_read+0xbc/0x1a0
    ksys_read+0x7c/0x140
    system_call+0x5c/0x70
  kmemleak: Kernel memory leak detector disabled
  kmemleak: Object 0xc000201cc8000000 (size 13757317120):
  kmemleak:   comm "swapper/0", pid 0, jiffies 4294937297
  kmemleak:   min_count = -1
  kmemleak:   count = 0
  kmemleak:   flags = 0x5
  kmemleak:   checksum = 0
  kmemleak:   backtrace:
       cma_declare_contiguous+0x2a4/0x3b0
       kvm_cma_reserve+0x11c/0x134
       setup_arch+0x300/0x3f8
       start_kernel+0x9c/0x6e8
       start_here_common+0x1c/0x4b0
  kmemleak: Automatic memory scanning thread ended

[cai@lca.pw: use is_migrate_cma_page() and update commit log]
  Link: http://lkml.kernel.org/r/20190416170510.20048-1-cai@lca.pw
Link: http://lkml.kernel.org/r/20190413002623.8967-1-cai@lca.pw
Signed-off-by: Qian Cai 
Acked-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Reviewed-by: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hotplug: fix offline undo_isolate_page_range()

2019-03-29T17:01:37+00:00

Commit f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded
memory to zones until online") introduced move_pfn_range_to_zone() which
calls memmap_init_zone() during onlining a memory block.
memmap_init_zone() will reset pagetype flags and makes migrate type to
be MOVABLE.

However, in __offline_pages(), it also call undo_isolate_page_range()
after offline_isolated_pages() to do the same thing.  Due to commit
2ce13640b3f4 ("mm: __first_valid_page skip over offline pages") changed
__first_valid_page() to skip offline pages, undo_isolate_page_range()
here just waste CPU cycles looping around the offlining PFN range while
doing nothing, because __first_valid_page() will return NULL as
offline_isolated_pages() has already marked all memory sections within
the pfn range as offline via offline_mem_sections().

Also, after calling the "useless" undo_isolate_page_range() here, it
reaches the point of no returning by notifying MEM_OFFLINE.  Those pages
will be marked as MIGRATE_MOVABLE again once onlining.  The only thing
left to do is to decrease the number of isolated pageblocks zone counter
which would make some paths of the page allocation slower that the above
commit introduced.

Even if alloc_contig_range() can be used to isolate 16GB-hugetlb pages
on ppc64, an "int" should still be enough to represent the number of
pageblocks there.  Fix an incorrect comment along the way.

[cai@lca.pw: v4]
  Link: http://lkml.kernel.org/r/20190314150641.59358-1-cai@lca.pw
Link: http://lkml.kernel.org/r/20190313143133.46200-1-cai@lca.pw
Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
Signed-off-by: Qian Cai 
Acked-by: Michal Hocko 
Reviewed-by: Oscar Salvador 
Cc: Vlastimil Babka 
Cc: 	[4.13+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memblock: drop memblock_alloc_*_nopanic() variants

2019-03-12T17:04:02+00:00

As all the memblock allocation functions return NULL in case of error
rather than panic(), the duplicates with _nopanic suffix can be removed.

Link: http://lkml.kernel.org/r/1548057848-15136-22-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport 
Acked-by: Greg Kroah-Hartman 
Reviewed-by: Petr Mladek 		[printk]
Cc: Catalin Marinas 
Cc: Christophe Leroy 
Cc: Christoph Hellwig 
Cc: "David S. Miller" 
Cc: Dennis Zhou 
Cc: Geert Uytterhoeven 
Cc: Greentime Hu 
Cc: Guan Xuetao 
Cc: Guo Ren 
Cc: Guo Ren 				[c-sky]
Cc: Heiko Carstens 
Cc: Juergen Gross 			[Xen]
Cc: Mark Salter 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Paul Burton 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Rob Herring 
Cc: Rob Herring 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Tony Luck 
Cc: Vineet Gupta 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: unexport free_reserved_area

2019-03-06T05:07:20+00:00

This function is only used by built-in code, which makes perfect sense
given the purpose of it.

Link: http://lkml.kernel.org/r/20190213174621.29297-2-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

docs/core-api/mm: fix return value descriptions in mm/

2019-03-06T05:07:20+00:00

Many kernel-doc comments in mm/ have the return value descriptions
either misformatted or omitted at all which makes kernel-doc script
unhappy:

$ make V=1 htmldocs
...
./mm/util.c:36: info: Scanning doc for kstrdup
./mm/util.c:41: warning: No description found for return value of 'kstrdup'
./mm/util.c:57: info: Scanning doc for kstrdup_const
./mm/util.c:66: warning: No description found for return value of 'kstrdup_const'
./mm/util.c:75: info: Scanning doc for kstrndup
./mm/util.c:83: warning: No description found for return value of 'kstrndup'
...

Fixing the formatting and adding the missing return value descriptions
eliminates ~100 such warnings.

Link: http://lkml.kernel.org/r/1549549644-4903-4-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport 
Reviewed-by: Andrew Morton 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

numa: make "nr_online_nodes" unsigned int

2019-03-06T05:07:20+00:00

Number of online NUMA nodes can't be negative as well.  This doesn't
save space as the variable is used only in 32-bit context, but do it
anyway for consistency.

Link: http://lkml.kernel.org/r/20190201223151.GB15820@avx2
Signed-off-by: Alexey Dobriyan 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds