Commit Graph

504 Commits

Author SHA1 Message Date
David Hildenbrand
1ef488edd6 mm/mprotect: drop pgprot_t parameter from change_protection()
Being able to provide a custom protection opens the door for
inconsistencies and BUGs: for example, accidentally allowing for more
permissions than desired by other mechanisms (e.g., softdirty tracking). 
vma->vm_page_prot should be the single source of truth.

Only PROT_NUMA is special: there is no way we can erroneously allow
for more permissions when removing all permissions. Special-case using
the MM_CP_PROT_NUMA flag.

[david@redhat.com: PAGE_NONE might not be defined without CONFIG_NUMA_BALANCING]  
  Link: https://lkml.kernel.org/r/5084ff1c-ebb3-f918-6a60-bacabf550a88@redhat.com
Link: https://lkml.kernel.org/r/20221223155616.297723-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-18 17:12:50 -08:00
Michal Hocko
e976936cfc mm/mempolicy: do not duplicate policy if it is not applicable for set_mempolicy_home_node
set_mempolicy_home_node tries to duplicate a memory policy before checking
it whether it is applicable for the operation.  There is no real reason
for doing that and it might actually be a pointless memory allocation and
deallocation exercise for MPOL_INTERLEAVE.

Not a big problem but we can do better. Simply check the policy before
acting on it.

Link: https://lkml.kernel.org/r/20221216194537.238047-2-mathieu.desnoyers@efficios.com
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-18 17:12:41 -08:00
Mathieu Desnoyers
38ce7c9bdf mm/mempolicy: fix memory leak in set_mempolicy_home_node system call
When encountering any vma in the range with policy other than MPOL_BIND or
MPOL_PREFERRED_MANY, an error is returned without issuing a mpol_put on
the policy just allocated with mpol_dup().

This allows arbitrary users to leak kernel memory.

Link: https://lkml.kernel.org/r/20221215194621.202816-1-mathieu.desnoyers@efficios.com
Fixes: c6018b4b25 ("mm/mempolicy: add set_mempolicy_home_node syscall")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: <stable@vger.kernel.org>	[5.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-12-21 14:31:51 -08:00
Liam Howlett
7329e3ebe3 mm/mempolicy: fix mbind_range() arguments to vma_merge()
Fuzzing produced an invalid argument to vma_merge() which was caught by
the newly added verification of the number of VMAs being removed on
process exit.  Analyzing the failure eventually resulted in finding an
issue with the search of a VMA that started at address 0, which caused an
underflow and thus the loss of many VMAs being tracked in the tree.  Fix
the underflow by changing the search of the maple tree to use the start
address directly.

Link: https://lkml.kernel.org/r/20221015021135.2816178-1-Liam.Howlett@oracle.com
Fixes: 66850be55e ("mm/mempolicy: use vma iterator & maple state instead of vma linked list")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
  Link: https://lore.kernel.org/r/202210052318.5ad10912-oliver.sang@intel.com
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-10-20 21:27:21 -07:00
ze zuo
aaa31e058d mm/mempolicy: use PAGE_ALIGN instead of open-coding it
Replace the simple calculation with PAGE_ALIGN.

Link: https://lkml.kernel.org/r/20220913015505.1998958-1-zuoze1@huawei.com
Signed-off-by: ze zuo <zuoze1@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-10-03 14:03:15 -07:00
Liam R. Howlett
66850be55e mm/mempolicy: use vma iterator & maple state instead of vma linked list
Reworked the way mbind_range() finds the first VMA to reuse the maple
state and limit the number of tree walks needed.

Note, this drops the VM_BUG_ON(!vma) call, which would catch a start
address higher than the last VMA.  The code was written in a way that
allowed no VMA updates to occur and still return success.  There should be
no functional change to this scenario with the new code.

Link: https://lkml.kernel.org/r/20220906194824.2110408-57-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-26 19:46:24 -07:00
Feng Tang
d2226ebd54 mm/hugetlb: add dedicated func to get 'allowed' nodemask for current process
Muchun Song found that after MPOL_PREFERRED_MANY policy was introduced in
commit b27abaccf8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple
preferred nodes"), the policy_nodemask_current()'s semantics for this new
policy has been changed, which returns 'preferred' nodes instead of
'allowed' nodes.

With the changed semantic of policy_nodemask_current, a task with
MPOL_PREFERRED_MANY policy could fail to get its reservation even though
it can fall back to other nodes (either defined by cpusets or all online
nodes) for that reservation failing mmap calles unnecessarily early.

The fix is to not consider MPOL_PREFERRED_MANY for reservations at all
because they, unlike MPOL_MBIND, do not pose any actual hard constrain.

Michal suggested the policy_nodemask_current() is only used by hugetlb,
and could be moved to hugetlb code with more explicit name to enforce the
'allowed' semantics for which only MPOL_BIND policy matters.

apply_policy_zone() is made extern to be called in hugetlb code and its
return value is changed to bool.

[1]. https://lore.kernel.org/lkml/20220801084207.39086-1-songmuchun@bytedance.com/t/

Link: https://lkml.kernel.org/r/20220805005903.95563-1-feng.tang@intel.com
Fixes: b27abaccf8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes")
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reported-by: Muchun Song <songmuchun@bytedance.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ben Widawsky <bwidawsk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-11 20:25:50 -07:00
Abel Wu
12c1dc8e74 mm/mempolicy: fix lock contention on mems_allowed
The mems_allowed field can be modified by other tasks, so it isn't safe to
access it with alloc_lock unlocked even in the current process context.

Say there are two tasks: A from cpusetA is performing set_mempolicy(2),
and B is changing cpusetA's cpuset.mems:

  A (set_mempolicy)		B (echo xx > cpuset.mems)
  -------------------------------------------------------
  pol = mpol_new();
				update_tasks_nodemask(cpusetA) {
				  foreach t in cpusetA {
				    cpuset_change_task_nodemask(t) {
  mpol_set_nodemask(pol) {
				      task_lock(t); // t could be A
    new = f(A->mems_allowed);
				      update t->mems_allowed;
    pol.create(pol, new);
				      task_unlock(t);
  }
				    }
				  }
				}
  task_lock(A);
  A->mempolicy = pol;
  task_unlock(A);

In this case A's pol->nodes is computed by old mems_allowed, and could
be inconsistent with A's new mems_allowed.

While it is different when replacing vmas' policy: the pol->nodes is
gone wild only when current_cpuset_is_being_rebound():

  A (mbind)			B (echo xx > cpuset.mems)
  -------------------------------------------------------
  pol = mpol_new();
  mmap_write_lock(A->mm);
				cpuset_being_rebound = cpusetA;
				update_tasks_nodemask(cpusetA) {
				  foreach t in cpusetA {
				    cpuset_change_task_nodemask(t) {
  mpol_set_nodemask(pol) {
				      task_lock(t); // t could be A
    mask = f(A->mems_allowed);
				      update t->mems_allowed;
    pol.create(pol, mask);
				      task_unlock(t);
  }
				    }
  foreach v in A->mm {
    if (cpuset_being_rebound == cpusetA)
      pol.rebind(pol, cpuset.mems);
    v->vma_policy = pol;
  }
  mmap_write_unlock(A->mm);
				    mmap_write_lock(t->mm);
				    mpol_rebind_mm(t->mm);
				    mmap_write_unlock(t->mm);
				  }
				}
				cpuset_being_rebound = NULL;

In this case, the cpuset.mems, which has already done updating, is finally
used for calculating pol->nodes, rather than A->mems_allowed.  So it is OK
to call mpol_set_nodemask() with alloc_lock unlocked when doing mbind(2).

Link: https://lkml.kernel.org/r/20220811124157.74888-1-wuyun.abel@bytedance.com
Fixes: 78b132e9ba ("mm/mempolicy: remove or narrow the lock on current")
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-11 20:25:50 -07:00
Miaohe Lin
6d97cf88dd mm/mempolicy: remove unneeded out label
We can use unlock label to unlock ptl and return ret directly to remove
the unneeded out label and reduce the size of mempolicy.o.  No functional
change intended.

[Before]
   text	   data	    bss	    dec	    hex	filename
  26702	   3972	   6168	  36842	   8fea	mm/mempolicy.o

[After]
   text	   data	    bss	    dec	    hex	filename
  26662	   3972	   6168	  36802	   8fc2	mm/mempolicy.o

Link: https://lkml.kernel.org/r/20220719115233.6706-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-07-29 18:07:16 -07:00
Alex Sierra
3218f8712d mm: handling Non-LRU pages returned by vm_normal_pages
With DEVICE_COHERENT, we'll soon have vm_normal_pages() return
device-managed anonymous pages that are not LRU pages.  Although they
behave like normal pages for purposes of mapping in CPU page, and for COW.
They do not support LRU lists, NUMA migration or THP.

Callers to follow_page() currently don't expect ZONE_DEVICE pages,
however, with DEVICE_COHERENT we might now return ZONE_DEVICE.  Check for
ZONE_DEVICE pages in applicable users of follow_page() as well.

Link: https://lkml.kernel.org/r/20220715150521.18165-5-alex.sierra@amd.com
Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>	[v2]
Reviewed-by: Alistair Popple <apopple@nvidia.com>	[v6]
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-07-17 17:14:28 -07:00
Tianyu Li
000eca5d04 mm/mempolicy: fix get_nodes out of bound access
When user specified more nodes than supported, get_nodes will access nmask
array out of bounds.

Link: https://lkml.kernel.org/r/20220601093211.2970565-1-tianyu.li@arm.com
Fixes: e130242dc3 ("mm: simplify compat numa syscalls")
Signed-off-by: Tianyu Li <tianyu.li@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-07-03 18:08:39 -07:00
Miaohe Lin
7ce82f4c3f mm/migration: return errno when isolate_huge_page failed
We might fail to isolate huge page due to e.g.  the page is under
migration which cleared HPageMigratable.  We should return errno in this
case rather than always return 1 which could confuse the user, i.e.  the
caller might think all of the memory is migrated while the hugetlb page is
left behind.  We make the prototype of isolate_huge_page consistent with
isolate_lru_page as suggested by Huang Ying and rename isolate_huge_page
to isolate_hugetlb as suggested by Muchun to improve the readability.

Link: https://lkml.kernel.org/r/20220530113016.16663-4-linmiaohe@huawei.com
Fixes: e8db67eb0d ("mm: migrate: move_pages() supports thp migration")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: Huang Ying <ying.huang@intel.com>
Reported-by: kernel test robot <lkp@intel.com> (build error)
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-07-03 18:08:37 -07:00
Wang Cheng
018160ad31 mm/mempolicy: fix uninit-value in mpol_rebind_policy()
mpol_set_nodemask()(mm/mempolicy.c) does not set up nodemask when
pol->mode is MPOL_LOCAL.  Check pol->mode before access
pol->w.cpuset_mems_allowed in mpol_rebind_policy()(mm/mempolicy.c).

BUG: KMSAN: uninit-value in mpol_rebind_policy mm/mempolicy.c:352 [inline]
BUG: KMSAN: uninit-value in mpol_rebind_task+0x2ac/0x2c0 mm/mempolicy.c:368
 mpol_rebind_policy mm/mempolicy.c:352 [inline]
 mpol_rebind_task+0x2ac/0x2c0 mm/mempolicy.c:368
 cpuset_change_task_nodemask kernel/cgroup/cpuset.c:1711 [inline]
 cpuset_attach+0x787/0x15e0 kernel/cgroup/cpuset.c:2278
 cgroup_migrate_execute+0x1023/0x1d20 kernel/cgroup/cgroup.c:2515
 cgroup_migrate kernel/cgroup/cgroup.c:2771 [inline]
 cgroup_attach_task+0x540/0x8b0 kernel/cgroup/cgroup.c:2804
 __cgroup1_procs_write+0x5cc/0x7a0 kernel/cgroup/cgroup-v1.c:520
 cgroup1_tasks_write+0x94/0xb0 kernel/cgroup/cgroup-v1.c:539
 cgroup_file_write+0x4c2/0x9e0 kernel/cgroup/cgroup.c:3852
 kernfs_fop_write_iter+0x66a/0x9f0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2162 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x1318/0x2030 fs/read_write.c:590
 ksys_write+0x28b/0x510 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0xdb/0x120 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 slab_alloc mm/slub.c:3259 [inline]
 kmem_cache_alloc+0x902/0x11c0 mm/slub.c:3264
 mpol_new mm/mempolicy.c:293 [inline]
 do_set_mempolicy+0x421/0xb70 mm/mempolicy.c:853
 kernel_set_mempolicy mm/mempolicy.c:1504 [inline]
 __do_sys_set_mempolicy mm/mempolicy.c:1510 [inline]
 __se_sys_set_mempolicy+0x44c/0xb60 mm/mempolicy.c:1507
 __x64_sys_set_mempolicy+0xd8/0x110 mm/mempolicy.c:1507
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

KMSAN: uninit-value in mpol_rebind_task (2)
https://syzkaller.appspot.com/bug?id=d6eb90f952c2a5de9ea718a1b873c55cb13b59dc

This patch seems to fix below bug too.
KMSAN: uninit-value in mpol_rebind_mm (2)
https://syzkaller.appspot.com/bug?id=f2fecd0d7013f54ec4162f60743a2b28df40926b

The uninit-value is pol->w.cpuset_mems_allowed in mpol_rebind_policy().
When syzkaller reproducer runs to the beginning of mpol_new(),

	    mpol_new() mm/mempolicy.c
	  do_mbind() mm/mempolicy.c
	kernel_mbind() mm/mempolicy.c

`mode` is 1(MPOL_PREFERRED), nodes_empty(*nodes) is `true` and `flags`
is 0. Then

	mode = MPOL_LOCAL;
	...
	policy->mode = mode;
	policy->flags = flags;

will be executed. So in mpol_set_nodemask(),

	    mpol_set_nodemask() mm/mempolicy.c
	  do_mbind()
	kernel_mbind()

pol->mode is 4 (MPOL_LOCAL), that `nodemask` in `pol` is not initialized,
which will be accessed in mpol_rebind_policy().

Link: https://lkml.kernel.org/r/20220512123428.fq3wofedp6oiotd4@ppc.localdomain
Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
Reported-by: <syzbot+217f792c92599518a2ab@syzkaller.appspotmail.com>
Tested-by: <syzbot+217f792c92599518a2ab@syzkaller.appspotmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-05-19 14:08:54 -07:00
Matthew Wilcox (Oracle)
adf88aa8ea mm: remove alloc_pages_vma()
All callers have now been converted to use vma_alloc_folio(), so convert
the body of alloc_pages_vma() to allocate folios instead.

Link: https://lkml.kernel.org/r/20220504182857.4013401-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-05-13 07:20:15 -07:00
Nadav Amit
4a18419f71 mm/mprotect: use mmu_gather
Patch series "mm/mprotect: avoid unnecessary TLB flushes", v6.

This patchset is intended to remove unnecessary TLB flushes during
mprotect() syscalls.  Once this patch-set make it through, similar and
further optimizations for MADV_COLD and userfaultfd would be possible.

Basically, there are 3 optimizations in this patch-set:

1. Use TLB batching infrastructure to batch flushes across VMAs and do
   better/fewer flushes.  This would also be handy for later userfaultfd
   enhancements.

2. Avoid unnecessary TLB flushes.  This optimization is the one that
   provides most of the performance benefits.  Unlike previous versions,
   we now only avoid flushes that would not result in spurious
   page-faults.

3. Avoiding TLB flushes on change_huge_pmd() that are only needed to
   prevent the A/D bits from changing.

Andrew asked for some benchmark numbers.  I do not have an easy
determinate macrobenchmark in which it is easy to show benefit.  I
therefore ran a microbenchmark: a loop that does the following on
anonymous memory, just as a sanity check to see that time is saved by
avoiding TLB flushes.  The loop goes:

	mprotect(p, PAGE_SIZE, PROT_READ)
	mprotect(p, PAGE_SIZE, PROT_READ|PROT_WRITE)
	*p = 0; // make the page writable

The test was run in KVM guest with 1 or 2 threads (the second thread was
busy-looping).  I measured the time (cycles) of each operation:

		1 thread		2 threads
		mmots	+patch		mmots	+patch
PROT_READ	3494	2725 (-22%)	8630	7788 (-10%)
PROT_READ|WRITE	3952	2724 (-31%)	9075	2865 (-68%)

[ mmots = v5.17-rc6-mmots-2022-03-06-20-38 ]

The exact numbers are really meaningless, but the benefit is clear.  There
are 2 interesting results though.  

(1) PROT_READ is cheaper, while one can expect it not to be affected. 
This is presumably due to TLB miss that is saved

(2) Without memory access (*p = 0), the speedup of the patch is even
greater.  In that scenario mprotect(PROT_READ) also avoids the TLB flush. 
As a result both operations on the patched kernel take roughly ~1500
cycles (with either 1 or 2 threads), whereas on mmotm their cost is as
high as presented in the table.


This patch (of 3):

change_pXX_range() currently does not use mmu_gather, but instead
implements its own deferred TLB flushes scheme.  This both complicates the
code, as developers need to be aware of different invalidation schemes,
and prevents opportunities to avoid TLB flushes or perform them in finer
granularity.

The use of mmu_gather for modified PTEs has benefits in various scenarios
even if pages are not released.  For instance, if only a single page needs
to be flushed out of a range of many pages, only that page would be
flushed.  If a THP page is flushed, on x86 a single TLB invlpg instruction
can be used instead of 512 instructions (or a full TLB flush, which would
Linux would actually use by default).  mprotect() over multiple VMAs
requires a single flush.

Use mmu_gather in change_pXX_range().  As the pages are not released, only
record the flushed range using tlb_flush_pXX_range().

Handle THP similarly and get rid of flush_cache_range() which becomes
redundant since tlb_start_vma() calls it when needed.

Link: https://lkml.kernel.org/r/20220401180821.1986781-1-namit@vmware.com
Link: https://lkml.kernel.org/r/20220401180821.1986781-2-namit@vmware.com
Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-05-13 07:20:05 -07:00
Miaohe Lin
bc78b5ed9f mm/mempolicy: clean up the code logic in queue_pages_pte_range
Since commit e5947d23ed ("mm: mempolicy: don't have to split pmd for
huge zero page"), THP is never splited in queue_pages_pmd.  Thus 2 is
never returned now.  We can remove such unnecessary ret != 2 check and
clean up the relevant comment.  Minor improvements in readability.

Link: https://lkml.kernel.org/r/20220419122234.45083-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-04-28 23:16:06 -07:00
Linus Torvalds
911b2b9516 Merge branch 'akpm' (patches from Andrew)
Merge fixes from Andrew Morton:
 "9 patches.

  Subsystems affected by this patch series: mm (migration, highmem,
  sparsemem, mremap, mempolicy, and memcg), lz4, mailmap, and
  MAINTAINERS"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  MAINTAINERS: add Tom as clang reviewer
  mm/list_lru.c: revert "mm/list_lru: optimize memcg_reparent_list_lru_node()"
  mailmap: update Vasily Averin's email address
  mm/mempolicy: fix mpol_new leak in shared_policy_replace
  mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0)
  mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
  lz4: fix LZ4_decompress_safe_partial read out of bound
  highmem: fix checks in __kmap_local_sched_{in,out}
  mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation.
2022-04-08 14:31:41 -10:00
Miaohe Lin
4ad099559b mm/mempolicy: fix mpol_new leak in shared_policy_replace
If mpol_new is allocated but not used in restart loop, mpol_new will be
freed via mpol_put before returning to the caller.  But refcnt is not
initialized yet, so mpol_put could not do the right things and might
leak the unused mpol_new.  This would happen if mempolicy was updated on
the shared shmem file while the sp->lock has been dropped during the
memory allocation.

This issue could be triggered easily with the below code snippet if
there are many processes doing the below work at the same time:

  shmid = shmget((key_t)5566, 1024 * PAGE_SIZE, 0666|IPC_CREAT);
  shm = shmat(shmid, 0, 0);
  loop many times {
    mbind(shm, 1024 * PAGE_SIZE, MPOL_LOCAL, mask, maxnode, 0);
    mbind(shm + 128 * PAGE_SIZE, 128 * PAGE_SIZE, MPOL_DEFAULT, mask,
          maxnode, 0);
  }

Link: https://lkml.kernel.org/r/20220329111416.27954-1-linmiaohe@huawei.com
Fixes: 42288fe366 ("mm: mempolicy: Convert shared_policy mutex to spinlock")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>	[3.8]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-04-08 14:20:36 -10:00
Zi Yan
a04cd1600b mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation.
Fix a VM_BUG_ON_FOLIO(folio_nr_pages(old) != nr_pages) crash.

With folios support, it is possible to have other than HPAGE_PMD_ORDER
THPs, in the form of folios, in the system.  Use thp_order() to correctly
determine the source page order during migration.

Link: https://lkml.kernel.org/r/20220404165325.1883267-1-zi.yan@sent.com
Link: https://lore.kernel.org/linux-mm/20220404132908.GA785673@u2004/
Fixes: d68eccad37 ("mm/filemap: Allow large folios to be added to the page cache")
Reported-by: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-04-08 14:20:36 -10:00
Matthew Wilcox (Oracle)
ec4858e07e mm/mempolicy: Use vma_alloc_folio() in new_page()
Simplify new_page() by unifying the THP and base page cases, and
handle orders other than 0 and HPAGE_PMD_ORDER correctly.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
2022-04-07 09:43:41 -04:00
Matthew Wilcox (Oracle)
f584b68005 mm: Add vma_alloc_folio()
This wrapper around alloc_pages_vma() calls prep_transhuge_page(),
removing the obligation from the caller.  This is in the same spirit
as __folio_alloc().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
2022-04-07 09:43:41 -04:00
Hugh Dickins
4e0906008c mempolicy: mbind_range() set_policy() after vma_merge()
v2.6.34 commit 9d8cebd4bc ("mm: fix mbind vma merge problem") introduced
vma_merge() to mbind_range(); but unlike madvise, mlock and mprotect, it
put a "continue" to next vma where its precedents go to update flags on
current vma before advancing: that left vma with the wrong setting in the
infamous vma_merge() case 8.

v3.10 commit 1444f92c84 ("mm: merging memory blocks resets mempolicy")
tried to fix that in vma_adjust(), without fully understanding the issue.

v3.11 commit 3964acd0db ("mm: mempolicy: fix mbind_range() &&
vma_adjust() interaction") reverted that, and went about the fix in the
right way, but chose to optimize out an unnecessary mpol_dup() with a
prior mpol_equal() test.  But on tmpfs, that also pessimized out the vital
call to its ->set_policy(), leaving the new mbind unenforced.

The user visible effect was that the pages got allocated on the local
node (happened to be 0), after the mbind() caller had specifically
asked for them to be allocated on node 1.  There was not any page
migration involved in the case reported: the pages simply got allocated
on the wrong node.

Just delete that optimization now (though it could be made conditional on
vma not having a set_policy).  Also remove the "next" variable: it turned
out to be blameless, but also pointless.

Link: https://lkml.kernel.org/r/319e4db9-64ae-4bca-92f0-ade85d342ff@google.com
Fixes: 3964acd0db ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:09 -07:00
John Hubbard
f728b9c48d mm: change lookup_node() to use get_user_pages_fast()
The purpose of calling get_user_pages_locked() from lookup_node() was to
allow for unlocking the mmap_lock when reading a page from the disk
during a page fault (hidden behind VM_FAULT_RETRY).  The idea was to
reduce contention on the heavily-used mmap_lock.  (Thanks to Jan Kara
for clearly pointing that out, and in fact I've used some of his wording
here.)

However, it is unlikely for lookup_node() to take a page fault.  With
that in mind, change over to calling get_user_pages_fast().  This
simplifies the code, runs a little faster in the expected case, and
allows removing get_user_pages_locked() entirely, in a subsequent patch.

Link: https://lkml.kernel.org/r/20220204020010.68930-5-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:01 -07:00
Suren Baghdasaryan
5c26f6ac94 mm: refactor vm_area_struct::anon_vma_name usage code
Avoid mixing strings and their anon_vma_name referenced pointers by
using struct anon_vma_name whenever possible.  This simplifies the code
and allows easier sharing of anon_vma_name structures when they
represent the same name.

[surenb@google.com: fix comment]

Link: https://lkml.kernel.org/r/20220223153613.835563-1-surenb@google.com
Link: https://lkml.kernel.org/r/20220224231834.1481408-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Colin Cross <ccross@google.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Chris Hyser <chris.hyser@oracle.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Xiaofeng Cao <caoxiaofeng@yulong.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-05 11:08:32 -08:00
Randy Dunlap
dad5b02329 mm/mempolicy: fix all kernel-doc warnings
Fix kernel-doc warnings in mempolicy.c:

  mempolicy.c:139: warning: No description found for return value of 'numa_map_to_online_node'
  mempolicy.c:2165: warning: Excess function parameter 'node' description in 'alloc_pages_vma'
  mempolicy.c:2973: warning: No description found for return value of 'mpol_parse_str'

Link: https://lkml.kernel.org/r/20211213233216.5477-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:30 +02:00
Aneesh Kumar K.V
c6018b4b25 mm/mempolicy: add set_mempolicy_home_node syscall
This syscall can be used to set a home node for the MPOL_BIND and
MPOL_PREFERRED_MANY memory policy.  Users should use this syscall after
setting up a memory policy for the specified range as shown below.

  mbind(p, nr_pages * page_size, MPOL_BIND, new_nodes->maskp,
        new_nodes->size + 1, 0);
  sys_set_mempolicy_home_node((unsigned long)p, nr_pages * page_size,
				home_node, 0);

The syscall allows specifying a home node/preferred node from which
kernel will fulfill memory allocation requests first.

For address range with MPOL_BIND memory policy, if nodemask specifies
more than one node, page allocations will come from the node in the
nodemask with sufficient free memory that is closest to the home
node/preferred node.

For MPOL_PREFERRED_MANY if the nodemask specifies more than one node,
page allocation will come from the node in the nodemask with sufficient
free memory that is closest to the home node/preferred node.  If there
is not enough memory in all the nodes specified in the nodemask, the
allocation will be attempted from the closest numa node to the home node
in the system.

This helps applications to hint at a memory allocation preference node
and fallback to _only_ a set of nodes if the memory is not available on
the preferred node.  Fallback allocation is attempted from the node
which is nearest to the preferred node.

This helps applications to have control on memory allocation numa nodes
and avoids default fallback to slow memory NUMA nodes.  For example a
system with NUMA nodes 1,2 and 3 with DRAM memory and 10, 11 and 12 of
slow memory

 new_nodes = numa_bitmask_alloc(nr_nodes);

 numa_bitmask_setbit(new_nodes, 1);
 numa_bitmask_setbit(new_nodes, 2);
 numa_bitmask_setbit(new_nodes, 3);

 p = mmap(NULL, nr_pages * page_size, protflag, mapflag, -1, 0);
 mbind(p, nr_pages * page_size, MPOL_BIND, new_nodes->maskp,  new_nodes->size + 1, 0);

 sys_set_mempolicy_home_node(p, nr_pages * page_size, 2, 0);

This will allocate from nodes closer to node 2 and will make sure the
kernel will only allocate from nodes 1, 2, and 3.  Memory will not be
allocated from slow memory nodes 10, 11, and 12.  This differs from
default MPOL_BIND behavior in that with default MPOL_BIND the allocation
will be attempted from node closer to the local node.  One of the
reasons to specify a home node is to allow allocations from cpu less
NUMA node and its nearby NUMA nodes.

With MPOL_PREFERRED_MANY on the other hand will first try to allocate
from the closest node to node 2 from the node list 1, 2 and 3.  If those
nodes don't have enough memory, kernel will allocate from slow memory
node 10, 11 and 12 which ever is closer to node 2.

Link: https://lkml.kernel.org/r/20211202123810.267175-3-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:30 +02:00
Aneesh Kumar K.V
c045511621 mm/mempolicy: use policy_node helper with MPOL_PREFERRED_MANY
Patch series "mm: add new syscall set_mempolicy_home_node", v6.

This patch (of 3):

A followup patch will enable setting a home node with
MPOL_PREFERRED_MANY memory policy.  To facilitate that switch to using
policy_node helper.  There is no functional change in this patch.

Link: https://lkml.kernel.org/r/20211202123810.267175-1-aneesh.kumar@linux.ibm.com
Link: https://lkml.kernel.org/r/20211202123810.267175-2-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:30 +02:00
Michal Hocko
be1a13eb51 mm: drop node from alloc_pages_vma
alloc_pages_vma is meant to allocate a page with a vma specific memory
policy.  The initial node parameter is always a local node so it is
pointless to waste a function argument for this.  Drop the parameter.

Link: https://lkml.kernel.org/r/YaSnlv4QpryEpesG@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:29 +02:00
Colin Cross
9a10064f56 mm: add a field to store names for private anonymous memory
In many userspace applications, and especially in VM based applications
like Android uses heavily, there are multiple different allocators in
use.  At a minimum there is libc malloc and the stack, and in many cases
there are libc malloc, the stack, direct syscalls to mmap anonymous
memory, and multiple VM heaps (one for small objects, one for big
objects, etc.).  Each of these layers usually has its own tools to
inspect its usage; malloc by compiling a debug version, the VM through
heap inspection tools, and for direct syscalls there is usually no way
to track them.

On Android we heavily use a set of tools that use an extended version of
the logic covered in Documentation/vm/pagemap.txt to walk all pages
mapped in userspace and slice their usage by process, shared (COW) vs.
unique mappings, backing, etc.  This can account for real physical
memory usage even in cases like fork without exec (which Android uses
heavily to share as many private COW pages as possible between
processes), Kernel SamePage Merging, and clean zero pages.  It produces
a measurement of the pages that only exist in that process (USS, for
unique), and a measurement of the physical memory usage of that process
with the cost of shared pages being evenly split between processes that
share them (PSS).

If all anonymous memory is indistinguishable then figuring out the real
physical memory usage (PSS) of each heap requires either a pagemap
walking tool that can understand the heap debugging of every layer, or
for every layer's heap debugging tools to implement the pagemap walking
logic, in which case it is hard to get a consistent view of memory
across the whole system.

Tracking the information in userspace leads to all sorts of problems.
It either needs to be stored inside the process, which means every
process has to have an API to export its current heap information upon
request, or it has to be stored externally in a filesystem that somebody
needs to clean up on crashes.  It needs to be readable while the process
is still running, so it has to have some sort of synchronization with
every layer of userspace.  Efficiently tracking the ranges requires
reimplementing something like the kernel vma trees, and linking to it
from every layer of userspace.  It requires more memory, more syscalls,
more runtime cost, and more complexity to separately track regions that
the kernel is already tracking.

This patch adds a field to /proc/pid/maps and /proc/pid/smaps to show a
userspace-provided name for anonymous vmas.  The names of named
anonymous vmas are shown in /proc/pid/maps and /proc/pid/smaps as
[anon:<name>].

Userspace can set the name for a region of memory by calling

   prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name)

Setting the name to NULL clears it.  The name length limit is 80 bytes
including NUL-terminator and is checked to contain only printable ascii
characters (including space), except '[',']','\','$' and '`'.

Ascii strings are being used to have a descriptive identifiers for vmas,
which can be understood by the users reading /proc/pid/maps or
/proc/pid/smaps.  Names can be standardized for a given system and they
can include some variable parts such as the name of the allocator or a
library, tid of the thread using it, etc.

The name is stored in a pointer in the shared union in vm_area_struct
that points to a null terminated string.  Anonymous vmas with the same
name (equivalent strings) and are otherwise mergeable will be merged.
The name pointers are not shared between vmas even if they contain the
same name.  The name pointer is stored in a union with fields that are
only used on file-backed mappings, so it does not increase memory usage.

CONFIG_ANON_VMA_NAME kernel configuration is introduced to enable this
feature.  It keeps the feature disabled by default to prevent any
additional memory overhead and to avoid confusing procfs parsers on
systems which are not ready to support named anonymous vmas.

The patch is based on the original patch developed by Colin Cross, more
specifically on its latest version [1] posted upstream by Sumit Semwal.
It used a userspace pointer to store vma names.  In that design, name
pointers could be shared between vmas.  However during the last
upstreaming attempt, Kees Cook raised concerns [2] about this approach
and suggested to copy the name into kernel memory space, perform
validity checks [3] and store as a string referenced from
vm_area_struct.

One big concern is about fork() performance which would need to strdup
anonymous vma names.  Dave Hansen suggested experimenting with
worst-case scenario of forking a process with 64k vmas having longest
possible names [4].  I ran this experiment on an ARM64 Android device
and recorded a worst-case regression of almost 40% when forking such a
process.

This regression is addressed in the followup patch which replaces the
pointer to a name with a refcounted structure that allows sharing the
name pointer between vmas of the same name.  Instead of duplicating the
string during fork() or when splitting a vma it increments the refcount.

[1] https://lore.kernel.org/linux-mm/20200901161459.11772-4-sumit.semwal@linaro.org/
[2] https://lore.kernel.org/linux-mm/202009031031.D32EF57ED@keescook/
[3] https://lore.kernel.org/linux-mm/202009031022.3834F692@keescook/
[4] https://lore.kernel.org/linux-mm/5d0358ab-8c47-2f5f-8e43-23b89d6a8e95@intel.com/

Changes for prctl(2) manual page (in the options section):

PR_SET_VMA
	Sets an attribute specified in arg2 for virtual memory areas
	starting from the address specified in arg3 and spanning the
	size specified	in arg4. arg5 specifies the value of the attribute
	to be set. Note that assigning an attribute to a virtual memory
	area might prevent it from being merged with adjacent virtual
	memory areas due to the difference in that attribute's value.

	Currently, arg2 must be one of:

	PR_SET_VMA_ANON_NAME
		Set a name for anonymous virtual memory areas. arg5 should
		be a pointer to a null-terminated string containing the
		name. The name length including null byte cannot exceed
		80 bytes. If arg5 is NULL, the name of the appropriate
		anonymous virtual memory areas will be reset. The name
		can contain only printable ascii characters (including
                space), except '[',']','\','$' and '`'.

                This feature is available only if the kernel is built with
                the CONFIG_ANON_VMA_NAME option enabled.

[surenb@google.com: docs: proc.rst: /proc/PID/maps: fix malformed table]
  Link: https://lkml.kernel.org/r/20211123185928.2513763-1-surenb@google.com
[surenb: rebased over v5.15-rc6, replaced userpointer with a kernel copy,
 added input sanitization and CONFIG_ANON_VMA_NAME config. The bulk of the
 work here was done by Colin Cross, therefore, with his permission, keeping
 him as the author]

Link: https://lkml.kernel.org/r/20211019215511.3771969-2-surenb@google.com
Signed-off-by: Colin Cross <ccross@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Glauber <jan.glauber@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Landley <rob@landley.net>
Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Cc: Shaohua Li <shli@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:27 +02:00
Andrey Ryabinin
3386353406 mm: mempolicy: fix THP allocations escaping mempolicy restrictions
alloc_pages_vma() may try to allocate THP page on the local NUMA node
first:

	page = __alloc_pages_node(hpage_node,
		gfp | __GFP_THISNODE | __GFP_NORETRY, order);

And if the allocation fails it retries allowing remote memory:

	if (!page && (gfp & __GFP_DIRECT_RECLAIM))
    		page = __alloc_pages_node(hpage_node,
					gfp, order);

However, this retry allocation completely ignores memory policy nodemask
allowing allocation to escape restrictions.

The first appearance of this bug seems to be the commit ac5b2c1891
("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings").

The bug disappeared later in the commit 89c83fb539 ("mm, thp:
consolidate THP gfp handling into alloc_hugepage_direct_gfpmask") and
reappeared again in slightly different form in the commit 76e654cc91
("mm, page_alloc: allow hugepage fallback to remote nodes when
madvised")

Fix this by passing correct nodemask to the __alloc_pages() call.

The demonstration/reproducer of the problem:

    $ mount -oremount,size=4G,huge=always /dev/shm/
    $ echo always > /sys/kernel/mm/transparent_hugepage/defrag
    $ cat mbind_thp.c
    #include <unistd.h>
    #include <sys/mman.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <assert.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <numaif.h>

    #define SIZE 2ULL << 30
    int main(int argc, char **argv)
    {
        int fd;
        unsigned long long i;
        char *addr;
        pid_t pid;
        char buf[100];
        unsigned long nodemask = 1;

        fd = open("/dev/shm/test", O_RDWR|O_CREAT);
        assert(fd > 0);
        assert(ftruncate(fd, SIZE) == 0);

        addr = mmap(NULL, SIZE, PROT_READ|PROT_WRITE,
                           MAP_SHARED, fd, 0);

        assert(mbind(addr, SIZE, MPOL_BIND, &nodemask, 2, MPOL_MF_STRICT|MPOL_MF_MOVE)==0);
        for (i = 0; i < SIZE; i+=4096) {
          addr[i] = 1;
        }
        pid = getpid();
        snprintf(buf, sizeof(buf), "grep shm /proc/%d/numa_maps", pid);
        system(buf);
        sleep(10000);

        return 0;
    }
    $ gcc mbind_thp.c -o mbind_thp -lnuma
    $ numactl -H
    available: 2 nodes (0-1)
    node 0 cpus: 0 2
    node 0 size: 1918 MB
    node 0 free: 1595 MB
    node 1 cpus: 1 3
    node 1 size: 2014 MB
    node 1 free: 1731 MB
    node distances:
    node   0   1
      0:  10  20
      1:  20  10
    $ rm -f /dev/shm/test; taskset -c 0 ./mbind_thp
    7fd970a00000 bind:0 file=/dev/shm/test dirty=524288 active=0 N0=396800 N1=127488 kernelpagesize_kB=4

Link: https://lkml.kernel.org/r/20211208165343.22349-1-arbn@yandex-team.com
Fixes: ac5b2c1891 ("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-12-25 12:20:55 -08:00
Linus Torvalds
512b7931ad Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton:
 "257 patches.

  Subsystems affected by this patch series: scripts, ocfs2, vfs, and
  mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
  gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
  pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
  memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
  vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
  cleanups, kfence, and damon)"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
  mm/damon: remove return value from before_terminate callback
  mm/damon: fix a few spelling mistakes in comments and a pr_debug message
  mm/damon: simplify stop mechanism
  Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
  Docs/admin-guide/mm/damon/start: simplify the content
  Docs/admin-guide/mm/damon/start: fix a wrong link
  Docs/admin-guide/mm/damon/start: fix wrong example commands
  mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
  mm/damon: remove unnecessary variable initialization
  Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
  mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
  selftests/damon: support watermarks
  mm/damon/dbgfs: support watermarks
  mm/damon/schemes: activate schemes based on a watermarks mechanism
  tools/selftests/damon: update for regions prioritization of schemes
  mm/damon/dbgfs: support prioritization weights
  mm/damon/vaddr,paddr: support pageout prioritization
  mm/damon/schemes: prioritize regions within the quotas
  mm/damon/selftests: support schemes quotas
  mm/damon/dbgfs: support quotas of schemes
  ...
2021-11-06 14:08:17 -07:00
Yang Shi
20f9ba4f99 mm: migrate: make demotion knob depend on migration
The memory demotion needs to call migrate_pages() to do the jobs.  And
it is controlled by a knob, however, the knob doesn't depend on
CONFIG_MIGRATION.  The knob could be truned on even though MIGRATION is
disabled, this will not cause any crash since migrate_pages() would just
return -ENOSYS.  But it is definitely not optimal to go through demotion
path then retry regular swap every time.

And it doesn't make too much sense to have the knob visible to the users
when !MIGRATION.  Move the related code from mempolicy.[h|c] to
migrate.[h|c].

Link: https://lkml.kernel.org/r/20211015005559.246709-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:41 -07:00
Chen Wandun
c00b6b9610 mm/vmalloc: introduce alloc_pages_bulk_array_mempolicy to accelerate memory allocation
Commit ffb29b1c25 ("mm/vmalloc: fix numa spreading for large hash
tables") can cause significant performance regressions in some
situations as Andrew mentioned in [1].  The main situation is vmalloc,
vmalloc will allocate pages with NUMA_NO_NODE by default, that will
result in alloc page one by one;

In order to solve this, __alloc_pages_bulk and mempolicy should be
considered at the same time.

1) If node is specified in memory allocation request, it will alloc all
   pages by __alloc_pages_bulk.

2) If interleaving allocate memory, it will cauculate how many pages
   should be allocated in each node, and use __alloc_pages_bulk to alloc
   pages in each node.

[1]: https://lore.kernel.org/lkml/CALvZod4G3SzP3kWxQYn0fj+VgG-G3yWXz=gz17+3N57ru1iajw@mail.gmail.com/t/#m750c8e3231206134293b089feaa090590afa0f60

[akpm@linux-foundation.org: coding style fixes]
[akpm@linux-foundation.org: make two functions static]
[akpm@linux-foundation.org: fix CONFIG_NUMA=n build]

Link: https://lkml.kernel.org/r/20211021080744.874701-3-chenwandun@huawei.com
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:37 -07:00
Linus Torvalds
49f8275c7d Memory folios
Add memory folios, a new type to represent either order-0 pages or
 the head page of a compound page.  This should be enough infrastructure
 to support filesystems converting from pages to folios.
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Merge tag 'folio-5.16' of git://git.infradead.org/users/willy/pagecache

Pull memory folios from Matthew Wilcox:
 "Add memory folios, a new type to represent either order-0 pages or the
  head page of a compound page. This should be enough infrastructure to
  support filesystems converting from pages to folios.

  The point of all this churn is to allow filesystems and the page cache
  to manage memory in larger chunks than PAGE_SIZE. The original plan
  was to use compound pages like THP does, but I ran into problems with
  some functions expecting only a head page while others expect the
  precise page containing a particular byte.

  The folio type allows a function to declare that it's expecting only a
  head page. Almost incidentally, this allows us to remove various calls
  to VM_BUG_ON(PageTail(page)) and compound_head().

  This converts just parts of the core MM and the page cache. For 5.17,
  we intend to convert various filesystems (XFS and AFS are ready; other
  filesystems may make it) and also convert more of the MM and page
  cache to folios. For 5.18, multi-page folios should be ready.

  The multi-page folios offer some improvement to some workloads. The
  80% win is real, but appears to be an artificial benchmark (postgres
  startup, which isn't a serious workload). Real workloads (eg building
  the kernel, running postgres in a steady state, etc) seem to benefit
  between 0-10%. I haven't heard of any performance losses as a result
  of this series. Nobody has done any serious performance tuning; I
  imagine that tweaking the readahead algorithm could provide some more
  interesting wins. There are also other places where we could choose to
  create large folios and currently do not, such as writes that are
  larger than PAGE_SIZE.

  I'd like to thank all my reviewers who've offered review/ack tags:
  Christoph Hellwig, David Howells, Jan Kara, Jeff Layton, Johannes
  Weiner, Kirill A. Shutemov, Michal Hocko, Mike Rapoport, Vlastimil
  Babka, William Kucharski, Yu Zhao and Zi Yan.

  I'd also like to thank those who gave feedback I incorporated but
  haven't offered up review tags for this part of the series: Nick
  Piggin, Mel Gorman, Ming Lei, Darrick Wong, Ted Ts'o, John Hubbard,
  Hugh Dickins, and probably a few others who I forget"

* tag 'folio-5.16' of git://git.infradead.org/users/willy/pagecache: (90 commits)
  mm/writeback: Add folio_write_one
  mm/filemap: Add FGP_STABLE
  mm/filemap: Add filemap_get_folio
  mm/filemap: Convert mapping_get_entry to return a folio
  mm/filemap: Add filemap_add_folio()
  mm/filemap: Add filemap_alloc_folio
  mm/page_alloc: Add folio allocation functions
  mm/lru: Add folio_add_lru()
  mm/lru: Convert __pagevec_lru_add_fn to take a folio
  mm: Add folio_evictable()
  mm/workingset: Convert workingset_refault() to take a folio
  mm/filemap: Add readahead_folio()
  mm/filemap: Add folio_mkwrite_check_truncate()
  mm/filemap: Add i_blocks_per_folio()
  mm/writeback: Add folio_redirty_for_writepage()
  mm/writeback: Add folio_account_redirty()
  mm/writeback: Add folio_clear_dirty_for_io()
  mm/writeback: Add folio_cancel_dirty()
  mm/writeback: Add folio_account_cleaned()
  mm/writeback: Add filemap_dirty_folio()
  ...
2021-11-01 08:47:59 -07:00
Eric Dumazet
6d2aec9e12 mm/mempolicy: do not allow illegal MPOL_F_NUMA_BALANCING | MPOL_LOCAL in mbind()
syzbot reported access to unitialized memory in mbind() [1]

Issue came with commit bda420b985 ("numa balancing: migrate on fault
among multiple bound nodes")

This commit added a new bit in MPOL_MODE_FLAGS, but only checked valid
combination (MPOL_F_NUMA_BALANCING can only be used with MPOL_BIND) in
do_set_mempolicy()

This patch moves the check in sanitize_mpol_flags() so that it is also
used by mbind()

  [1]
  BUG: KMSAN: uninit-value in __mpol_equal+0x567/0x590 mm/mempolicy.c:2260
   __mpol_equal+0x567/0x590 mm/mempolicy.c:2260
   mpol_equal include/linux/mempolicy.h:105 [inline]
   vma_merge+0x4a1/0x1e60 mm/mmap.c:1190
   mbind_range+0xcc8/0x1e80 mm/mempolicy.c:811
   do_mbind+0xf42/0x15f0 mm/mempolicy.c:1333
   kernel_mbind mm/mempolicy.c:1483 [inline]
   __do_sys_mbind mm/mempolicy.c:1490 [inline]
   __se_sys_mbind+0x437/0xb80 mm/mempolicy.c:1486
   __x64_sys_mbind+0x19d/0x200 mm/mempolicy.c:1486
   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
   do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
   entry_SYSCALL_64_after_hwframe+0x44/0xae

  Uninit was created at:
   slab_alloc_node mm/slub.c:3221 [inline]
   slab_alloc mm/slub.c:3230 [inline]
   kmem_cache_alloc+0x751/0xff0 mm/slub.c:3235
   mpol_new mm/mempolicy.c:293 [inline]
   do_mbind+0x912/0x15f0 mm/mempolicy.c:1289
   kernel_mbind mm/mempolicy.c:1483 [inline]
   __do_sys_mbind mm/mempolicy.c:1490 [inline]
   __se_sys_mbind+0x437/0xb80 mm/mempolicy.c:1486
   __x64_sys_mbind+0x19d/0x200 mm/mempolicy.c:1486
   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
   do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
   entry_SYSCALL_64_after_hwframe+0x44/0xae
  =====================================================
  Kernel panic - not syncing: panic_on_kmsan set ...
  CPU: 0 PID: 15049 Comm: syz-executor.0 Tainted: G    B             5.15.0-rc2-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  Call Trace:
   __dump_stack lib/dump_stack.c:88 [inline]
   dump_stack_lvl+0x1ff/0x28e lib/dump_stack.c:106
   dump_stack+0x25/0x28 lib/dump_stack.c:113
   panic+0x44f/0xdeb kernel/panic.c:232
   kmsan_report+0x2ee/0x300 mm/kmsan/report.c:186
   __msan_warning+0xd7/0x150 mm/kmsan/instrumentation.c:208
   __mpol_equal+0x567/0x590 mm/mempolicy.c:2260
   mpol_equal include/linux/mempolicy.h:105 [inline]
   vma_merge+0x4a1/0x1e60 mm/mmap.c:1190
   mbind_range+0xcc8/0x1e80 mm/mempolicy.c:811
   do_mbind+0xf42/0x15f0 mm/mempolicy.c:1333
   kernel_mbind mm/mempolicy.c:1483 [inline]
   __do_sys_mbind mm/mempolicy.c:1490 [inline]
   __se_sys_mbind+0x437/0xb80 mm/mempolicy.c:1486
   __x64_sys_mbind+0x19d/0x200 mm/mempolicy.c:1486
   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
   do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Link: https://lkml.kernel.org/r/20211001215630.810592-1-eric.dumazet@gmail.com
Fixes: bda420b985 ("numa balancing: migrate on fault among multiple bound nodes")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Matthew Wilcox (Oracle)
cc09cb1341 mm/page_alloc: Add folio allocation functions
The __folio_alloc(), __folio_alloc_node() and folio_alloc() functions
are mostly for type safety, but they also ensure that the page allocator
allocates a compound page and initialises the deferred list if the page
is large enough to have one.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
2021-10-18 07:49:40 -04:00
Linus Torvalds
a3fa7a101d Merge branches 'akpm' and 'akpm-hotfixes' (patches from Andrew)
Merge yet more updates and hotfixes from Andrew Morton:
 "Post-linux-next material, based upon latest upstream to catch the
  now-merged dependencies:

   - 10 patches.

     Subsystems affected by this patch series: mm (vmstat and migration)
     and compat.

  And bunch of hotfixes, mostly cc:stable:

   - 8 patches.

     Subsystems affected by this patch series: mm (hmm, hugetlb, vmscan,
     pagealloc, pagemap, kmemleak, mempolicy, and memblock)"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  arch: remove compat_alloc_user_space
  compat: remove some compat entry points
  mm: simplify compat numa syscalls
  mm: simplify compat_sys_move_pages
  kexec: avoid compat_alloc_user_space
  kexec: move locking into do_kexec_load
  mm: migrate: change to use bool type for 'page_was_mapped'
  mm: migrate: fix the incorrect function name in comments
  mm: migrate: introduce a local variable to get the number of pages
  mm/vmstat: protect per cpu variables with preempt disable on RT

* emailed hotfixes from Andrew Morton <akpm@linux-foundation.org>:
  nds32/setup: remove unused memblock_region variable in setup_memory()
  mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
  mm/kmemleak: allow __GFP_NOLOCKDEP passed to kmemleak's gfp
  mmap_lock: change trace and locking order
  mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype
  mm,vmscan: fix divide by zero in get_scan_count
  mm/hugetlb: initialize hugetlb_usage in mm_init
  mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled
2021-09-08 18:52:05 -07:00
yanghui
276aeee1c5 mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
Servers happened below panic:

  Kernel version:5.4.56
  BUG: unable to handle page fault for address: 0000000000002c48
  RIP: 0010:__next_zones_zonelist+0x1d/0x40
  Call Trace:
    __alloc_pages_nodemask+0x277/0x310
    alloc_page_interleave+0x13/0x70
    handle_mm_fault+0xf99/0x1390
    __do_page_fault+0x288/0x500
    do_page_fault+0x30/0x110
    page_fault+0x3e/0x50

The reason for the panic is that MAX_NUMNODES is passed in the third
parameter in __alloc_pages_nodemask(preferred_nid).  So access to
zonelist->zoneref->zone_idx in __next_zones_zonelist will cause a panic.

In offset_il_node(), first_node() returns nid from pol->v.nodes, after
this other threads may chang pol->v.nodes before next_node().  This race
condition will let next_node return MAX_NUMNODES.  So put pol->nodes in
a local variable.

The race condition is between offset_il_node and cpuset_change_task_nodemask:

  CPU0:                                     CPU1:
  alloc_pages_vma()
    interleave_nid(pol,)
      offset_il_node(pol,)
        first_node(pol->v.nodes)            cpuset_change_task_nodemask
                        //nodes==0xc          mpol_rebind_task
                                                mpol_rebind_policy
                                                  mpol_rebind_nodemask(pol,nodes)
                        //nodes==0x3
        next_node(nid, pol->v.nodes)//return MAX_NUMNODES

Link: https://lkml.kernel.org/r/20210906034658.48721-1-yanghui.def@bytedance.com
Signed-off-by: yanghui <yanghui.def@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 18:45:53 -07:00
Arnd Bergmann
59ab844eed compat: remove some compat entry points
These are all handled correctly when calling the native system call entry
point, so remove the special cases.

Link: https://lkml.kernel.org/r/20210727144859.4150043-6-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 15:32:35 -07:00
Arnd Bergmann
e130242dc3 mm: simplify compat numa syscalls
The compat implementations for mbind, get_mempolicy, set_mempolicy and
migrate_pages are just there to handle the subtly different layout of
bitmaps on 32-bit hosts.

The compat implementation however lacks some of the checks that are
present in the native one, in particular for checking that the extra bits
are all zero when user space has a larger mask size than the kernel.
Worse, those extra bits do not get cleared when copying in or out of the
kernel, which can lead to incorrect data as well.

Unify the implementation to handle the compat bitmap layout directly in
the get_nodes() and copy_nodes_to_user() helpers.  Splitting out the
get_bitmap() helper from get_nodes() also helps readability of the native
case.

On x86, two additional problems are addressed by this: compat tasks can
pass a bitmap at the end of a mapping, causing a fault when reading across
the page boundary for a 64-bit word.  x32 tasks might also run into
problems with get_mempolicy corrupting data when an odd number of 32-bit
words gets passed.

On parisc the migrate_pages() system call apparently had the wrong calling
convention, as big-endian architectures expect the words inside of a
bitmap to be swapped.  This is not a problem though since parisc has no
NUMA support.

[arnd@arndb.de: fix mempolicy crash]
  Link: https://lkml.kernel.org/r/20210730143417.3700653-1-arnd@kernel.org
  Link: https://lore.kernel.org/lkml/YQPLG20V3dmOfq3a@osiris/

Link: https://lkml.kernel.org/r/20210727144859.4150043-5-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 15:32:35 -07:00
Vasily Averin
38b031dd4d mm/mempolicy.c: use in_task() in mempolicy_slab_node()
Obsoleted in_intrrupt() include task context with disabled BH, it's better
to use in_task() instead.

Link: https://lkml.kernel.org/r/984ee771-4834-21da-801f-c15c18ddf4d1@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Feng Tang
be897d48a9 mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies
As they all do the same thing: sanity check and save nodemask info, create
one mpol_new_nodemask() to reduce redundancy.

Link: https://lkml.kernel.org/r/1627970362-61305-6-git-send-email-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Ben Widawsky
a38a59fdfa mm/mempolicy: advertise new MPOL_PREFERRED_MANY
Adds a new mode to the existing mempolicy modes, MPOL_PREFERRED_MANY.

MPOL_PREFERRED_MANY will be adequately documented in the internal
admin-guide with this patch.  Eventually, the man pages for mbind(2),
get_mempolicy(2), set_mempolicy(2) and numactl(8) will also have text
about this mode.  Those shall contain the canonical reference.

NUMA systems continue to become more prevalent.  New technologies like
PMEM make finer grain control over memory access patterns increasingly
desirable.  MPOL_PREFERRED_MANY allows userspace to specify a set of nodes
that will be tried first when performing allocations.  If those
allocations fail, all remaining nodes will be tried.  It's a straight
forward API which solves many of the presumptive needs of system
administrators wanting to optimize workloads on such machines.  The mode
will work either per VMA, or per thread.

[Michal Hocko: refine kernel doc for MPOL_PREFERRED_MANY]

Link: https://lore.kernel.org/r/20200630212517.308045-13-ben.widawsky@intel.com
Link: https://lkml.kernel.org/r/1627970362-61305-5-git-send-email-feng.tang@intel.com
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Feng Tang
4c54d94908 mm/memplicy: add page allocation function for MPOL_PREFERRED_MANY policy
The semantics of MPOL_PREFERRED_MANY is similar to MPOL_PREFERRED, that it
will first try to allocate memory from the preferred node(s), and fallback
to all nodes in system when first try fails.

Add a dedicated function alloc_pages_preferred_many() for it just like for
'interleave' policy, which will be used by 2 general memoory allocation
APIs: alloc_pages() and alloc_pages_vma()

Link: https://lore.kernel.org/r/20200630212517.308045-9-ben.widawsky@intel.com
Link: https://lkml.kernel.org/r/1627970362-61305-3-git-send-email-feng.tang@intel.com
Suggested-by: Michal Hocko <mhocko@suse.com>
Originally-by: Ben Widawsky <ben.widawsky@intel.com>
Co-developed-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Dave Hansen
b27abaccf8 mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes
Patch series "Introduce multi-preference mempolicy", v7.

This patch series introduces the concept of the MPOL_PREFERRED_MANY
mempolicy.  This mempolicy mode can be used with either the
set_mempolicy(2) or mbind(2) interfaces.  Like the MPOL_PREFERRED
interface, it allows an application to set a preference for nodes which
will fulfil memory allocation requests.  Unlike the MPOL_PREFERRED mode,
it takes a set of nodes.  Like the MPOL_BIND interface, it works over a
set of nodes.  Unlike MPOL_BIND, it will not cause a SIGSEGV or invoke the
OOM killer if those preferred nodes are not available.

Along with these patches are patches for libnuma, numactl, numademo, and
memhog.  They still need some polish, but can be found here:
https://gitlab.com/bwidawsk/numactl/-/tree/prefer-many It allows new
usage: `numactl -P 0,3,4`

The goal of the new mode is to enable some use-cases when using tiered memory
usage models which I've lovingly named.

1a. The Hare - The interconnect is fast enough to meet bandwidth and
    latency requirements allowing preference to be given to all nodes with
    "fast" memory.
1b. The Indiscriminate Hare - An application knows it wants fast
    memory (or perhaps slow memory), but doesn't care which node it runs
    on.  The application can prefer a set of nodes and then xpu bind to
    the local node (cpu, accelerator, etc).  This reverses the nodes are
    chosen today where the kernel attempts to use local memory to the CPU
    whenever possible.  This will attempt to use the local accelerator to
    the memory.
2.  The Tortoise - The administrator (or the application itself) is
    aware it only needs slow memory, and so can prefer that.

Much of this is almost achievable with the bind interface, but the bind
interface suffers from an inability to fallback to another set of nodes if
binding fails to all nodes in the nodemask.

Like MPOL_BIND a nodemask is given. Inherently this removes ordering from the
preference.

> /* Set first two nodes as preferred in an 8 node system. */
> const unsigned long nodes = 0x3
> set_mempolicy(MPOL_PREFER_MANY, &nodes, 8);

> /* Mimic interleave policy, but have fallback *.
> const unsigned long nodes = 0xaa
> set_mempolicy(MPOL_PREFER_MANY, &nodes, 8);

Some internal discussion took place around the interface. There are two
alternatives which we have discussed, plus one I stuck in:

1. Ordered list of nodes.  Currently it's believed that the added
   complexity is nod needed for expected usecases.
2. A flag for bind to allow falling back to other nodes.  This
   confuses the notion of binding and is less flexible than the current
   solution.
3. Create flags or new modes that helps with some ordering.  This
   offers both a friendlier API as well as a solution for more customized
   usage.  It's unknown if it's worth the complexity to support this.
   Here is sample code for how this might work:

> // Prefer specific nodes for some something wacky
> set_mempolicy(MPOL_PREFER_MANY, 0x17c, 1024);
>
> // Default
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_SOCKET, NULL, 0);
> // which is the same as
> set_mempolicy(MPOL_DEFAULT, NULL, 0);
>
> // The Hare
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE, NULL, 0);
>
> // The Tortoise
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE_REV, NULL, 0);
>
> // Prefer the fast memory of the first two sockets
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE, -1, 2);
>

This patch (of 5):

The NUMA APIs currently allow passing in a "preferred node" as a single
bit set in a nodemask.  If more than one bit it set, bits after the first
are ignored.

This single node is generally OK for location-based NUMA where memory
being allocated will eventually be operated on by a single CPU.  However,
in systems with multiple memory types, folks want to target a *type* of
memory instead of a location.  For instance, someone might want some
high-bandwidth memory but do not care about the CPU next to which it is
allocated.  Or, they want a cheap, high capacity allocation and want to
target all NUMA nodes which have persistent memory in volatile mode.  In
both of these cases, the application wants to target a *set* of nodes, but
does not want strict MPOL_BIND behavior as that could lead to OOM killer
or SIGSEGV.

So add MPOL_PREFERRED_MANY policy to support the multiple preferred nodes
requirement.  This is not a pie-in-the-sky dream for an API.  This was a
response to a specific ask of more than one group at Intel.  Specifically:

1. There are existing libraries that target memory types such as
   https://github.com/memkind/memkind.  These are known to suffer from
   SIGSEGV's when memory is low on targeted memory "kinds" that span more
   than one node.  The MCDRAM on a Xeon Phi in "Cluster on Die" mode is an
   example of this.

2. Volatile-use persistent memory users want to have a memory policy
   which is targeted at either "cheap and slow" (PMEM) or "expensive and
   fast" (DRAM).  However, they do not want to experience allocation
   failures when the targeted type is unavailable.

3. Allocate-then-run.  Generally, we let the process scheduler decide
   on which physical CPU to run a task.  That location provides a default
   allocation policy, and memory availability is not generally considered
   when placing tasks.  For situations where memory is valuable and
   constrained, some users want to allocate memory first, *then* allocate
   close compute resources to the allocation.  This is the reverse of the
   normal (CPU) model.  Accelerators such as GPUs that operate on
   core-mm-managed memory are interested in this model.

A check is added in sanitize_mpol_flags() to not permit 'prefer_many'
policy to be used for now, and will be removed in later patch after all
implementations for 'prefer_many' are ready, as suggested by Michal Hocko.

[mhocko@kernel.org: suggest to refine policy_node/policy_nodemask handling]

Link: https://lkml.kernel.org/r/1627970362-61305-1-git-send-email-feng.tang@intel.com
Link: https://lore.kernel.org/r/20200630212517.308045-4-ben.widawsky@intel.com
Link: https://lkml.kernel.org/r/1627970362-61305-2-git-send-email-feng.tang@intel.com
Co-developed-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>b
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Baolin Wang
062db29358 mm/mempolicy: use readable NUMA_NO_NODE macro instead of magic number
The caller of mpol_misplaced() already use NUMA_NO_NODE to check whether
current page node is misplaced, thus using NUMA_NO_NODE in
mpol_misplaced() instead of magic number is more readable.

Link: https://lkml.kernel.org/r/1b77c0ce21183fa86f4db250b115cf5e27396528.1627558356.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:17 -07:00
Huang Ying
20b51af15e mm/migrate: add sysfs interface to enable reclaim migration
Some method is obviously needed to enable reclaim-based migration.

Just like traditional autonuma, there will be some workloads that will
benefit like workloads with more "static" configurations where hot pages
stay hot and cold pages stay cold.  If pages come and go from the hot and
cold sets, the benefits of this approach will be more limited.

The benefits are truly workload-based and *not* hardware-based.  We do not
believe that there is a viable threshold where certain hardware
configurations should have this mechanism enabled while others do not.

To be conservative, earlier work defaulted to disable reclaim- based
migration and did not include a mechanism to enable it.  This proposes add
a new sysfs file

  /sys/kernel/mm/numa/demotion_enabled

as a method to enable it.

We are open to any alternative that allows end users to enable this
mechanism or disable it if workload harm is detected (just like
traditional autonuma).

Once this is enabled page demotion may move data to a NUMA node that does
not fall into the cpuset of the allocating process.  This could be
construed to violate the guarantees of cpusets.  However, since this is an
opt-in mechanism, the assumption is that anyone enabling it is content to
relax the guarantees.

Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.com
Signed-off-by: Huang Ying <ying.huang@intel.com>
Originally-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:16 -07:00
Yang Shi
5ac95884a7 mm/migrate: enable returning precise migrate_pages() success count
Under normal circumstances, migrate_pages() returns the number of pages
migrated.  In error conditions, it returns an error code.  When returning
an error code, there is no way to know how many pages were migrated or not
migrated.

Make migrate_pages() return how many pages are demoted successfully for
all cases, including when encountering errors.  Page reclaim behavior will
depend on this in subsequent patches.

Link: https://lkml.kernel.org/r/20210721063926.3024591-3-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-4-ying.huang@intel.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Oscar Salvador <osalvador@suse.de> [optional parameter]
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03 09:58:16 -07:00
Ben Widawsky
269fbe72cd mm/mempolicy: use unified 'nodes' for bind/interleave/prefer policies
Current structure 'mempolicy' uses a union to store the node info for
bind/interleave/perfer policies.

	union {
		short 		 preferred_node; /* preferred */
		nodemask_t	 nodes;		/* interleave/bind */
		/* undefined for default */
	} v;

Since preferred node can also be represented by a nodemask_t with only ont
bit set, unify these policies with using one nodemask_t 'nodes', which can
remove a union, simplify the code and make it easier to support future's
new policy's node info.

Link: https://lore.kernel.org/r/20200630212517.308045-7-ben.widawsky@intel.com
Link: https://lkml.kernel.org/r/1623399825-75651-1-git-send-email-feng.tang@intel.com
Co-developed-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-06-30 20:47:29 -07:00
Yang Shi
e5947d23ed mm: mempolicy: don't have to split pmd for huge zero page
When trying to migrate pages to obey mempolicy, the huge zero page is
split by inserting base zero pfn to all PTEs, then the page table walk
fallback to PTE level and just skips zero page.  Skipping zero page for
mempolicy has been the behavior of kernel since v2.6.16 due to commit
f4598c8b36 ("[PATCH] migration: make sure there is no attempt to migrate
reserved pages.").  So it seems pointless to split huge zero page, it
could be just skipped like base zero page.

Set ACTION_CONTINUE to prevent the walk_page_range() split the pmd for
this case.

Link: https://lkml.kernel.org/r/20210609172146.3594-1-shy828301@gmail.com
Link: https://lkml.kernel.org/r/20210604203513.240709-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-06-30 20:47:29 -07:00