[patch 02/15] mm/mmap.c: close race between munmap() and expand_upwards()/downwards()

[patch 02/15] mm/mmap.c: close race between munmap() and expand_upwards()/downwards()

[Andrew Morton]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: mm/mmap.c: close race between munmap() and expand_upwards()/downwards()

VMA with VM_GROWSDOWN or VM_GROWSUP flag set can change their size under
mmap_read_lock().  It can lead to race with __do_munmap():

	Thread A			Thread B
__do_munmap()
  detach_vmas_to_be_unmapped()
  mmap_write_downgrade()
				expand_downwards()
				  vma->vm_start = address;
				  // The VMA now overlaps with
				  // VMAs detached by the Thread A
				// page fault populates expanded part
				// of the VMA
  unmap_region()
    // Zaps pagetables partly
    // populated by Thread B

Similar race exists for expand_upwards().

The fix is to avoid downgrading mmap_lock in __do_munmap() if detached
VMAs are next to VM_GROWSDOWN or VM_GROWSUP VMA.

[akpm@linux-foundation.org: s/mmap_sem/mmap_lock/ in comment]
Link: http://lkml.kernel.org/r/20200709105309.42495-1-kirill.shutemov@linux.intel.com
Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Jann Horn <jannh@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.20+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

--- a/mm/mmap.c~mm-close-race-between-munmap-and-expand_upwards-downwards
+++ a/mm/mmap.c
@@ -2620,7 +2620,7 @@ static void unmap_region(struct mm_struc
  * Create a list of vma's touched by the unmap, removing them from the mm's
  * vma list as we go..
  */
-static void
+static bool
 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
 	struct vm_area_struct *prev, unsigned long end)
 {
@@ -2645,6 +2645,17 @@ detach_vmas_to_be_unmapped(struct mm_str
 
 	/* Kill the cache */
 	vmacache_invalidate(mm);
+
+	/*
+	 * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
+	 * VM_GROWSUP VMA. Such VMAs can change their size under
+	 * down_read(mmap_lock) and collide with the VMA we are about to unmap.
+	 */
+	if (vma && (vma->vm_flags & VM_GROWSDOWN))
+		return false;
+	if (prev && (prev->vm_flags & VM_GROWSUP))
+		return false;
+	return true;
 }
 
 /*
@@ -2825,7 +2836,8 @@ int __do_munmap(struct mm_struct *mm, un
 	}
 
 	/* Detach vmas from rbtree */
-	detach_vmas_to_be_unmapped(mm, vma, prev, end);
+	if (!detach_vmas_to_be_unmapped(mm, vma, prev, end))
+		downgrade = false;
 
 	if (downgrade)
 		mmap_write_downgrade(mm);
_

[patch 03/15] vfs/xattr: mm/shmem: kernfs: release simple xattr entry in a right way

[Andrew Morton]

From: Chengguang Xu <cgxu519@mykernel.net>
Subject: vfs/xattr: mm/shmem: kernfs: release simple xattr entry in a right way

After commit fdc85222d58e ("kernfs: kvmalloc xattr value instead of
kmalloc"), simple xattr entry is allocated with kvmalloc() instead of
kmalloc(), so we should release it with kvfree() instead of kfree().

Link: http://lkml.kernel.org/r/20200704051608.15043-1-cgxu519@mykernel.net
Fixes: fdc85222d58e ("kernfs: kvmalloc xattr value instead of kmalloc")
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Daniel Xu <dxu@dxuuu.xyz>
Cc: Chris Down <chris@chrisdown.name>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>	[5.7]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/xattr.h |    3 ++-
 mm/shmem.c            |    2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

--- a/include/linux/xattr.h~vfs-xattr-mm-shmem-kernfs-release-simple-xattr-entry-in-a-right-way
+++ a/include/linux/xattr.h
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/spinlock.h>
+#include <linux/mm.h>
 #include <uapi/linux/xattr.h>
 
 struct inode;
@@ -94,7 +95,7 @@ static inline void simple_xattrs_free(st
 
 	list_for_each_entry_safe(xattr, node, &xattrs->head, list) {
 		kfree(xattr->name);
-		kfree(xattr);
+		kvfree(xattr);
 	}
 }
 
--- a/mm/shmem.c~vfs-xattr-mm-shmem-kernfs-release-simple-xattr-entry-in-a-right-way
+++ a/mm/shmem.c
@@ -3178,7 +3178,7 @@ static int shmem_initxattrs(struct inode
 		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
 					  GFP_KERNEL);
 		if (!new_xattr->name) {
-			kfree(new_xattr);
+			kvfree(new_xattr);
 			return -ENOMEM;
 		}
 
_

[patch 06/15] mm/memcg: fix refcount error while moving and swapping

[Andrew Morton]

From: Hugh Dickins <hughd@google.com>
Subject: mm/memcg: fix refcount error while moving and swapping

It was hard to keep a test running, moving tasks between memcgs with
move_charge_at_immigrate, while swapping: mem_cgroup_id_get_many()'s
refcount is discovered to be 0 (supposedly impossible), so it is then
forced to REFCOUNT_SATURATED, and after thousands of warnings in quick
succession, the test is at last put out of misery by being OOM killed.

This is because of the way moved_swap accounting was saved up until the
task move gets completed in __mem_cgroup_clear_mc(), deferred from when
mem_cgroup_move_swap_account() actually exchanged old and new ids. 
Concurrent activity can free up swap quicker than the task is scanned,
bringing id refcount down 0 (which should only be possible when
offlining).

Just skip that optimization: do that part of the accounting immediately.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils
Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-fix-refcount-error-while-moving-and-swapping
+++ a/mm/memcontrol.c
@@ -5669,7 +5669,6 @@ static void __mem_cgroup_clear_mc(void)
 		if (!mem_cgroup_is_root(mc.to))
 			page_counter_uncharge(&mc.to->memory, mc.moved_swap);
 
-		mem_cgroup_id_get_many(mc.to, mc.moved_swap);
 		css_put_many(&mc.to->css, mc.moved_swap);
 
 		mc.moved_swap = 0;
@@ -5860,7 +5859,8 @@ put:			/* get_mctgt_type() gets the page
 			ent = target.ent;
 			if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) {
 				mc.precharge--;
-				/* we fixup refcnts and charges later. */
+				mem_cgroup_id_get_many(mc.to, 1);
+				/* we fixup other refcnts and charges later. */
 				mc.moved_swap++;
 			}
 			break;
_

[patch 07/15] mm: memcg/slab: fix memory leak at non-root kmem_cache destroy

[Andrew Morton]

From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: memcg/slab: fix memory leak at non-root kmem_cache destroy

If the kmem_cache refcount is greater than one, we should not mark the
root kmem_cache as dying.  If we mark the root kmem_cache dying
incorrectly, the non-root kmem_cache can never be destroyed.  It resulted
in memory leak when memcg was destroyed.  We can use the following steps
to reproduce.

  1) Use kmem_cache_create() to create a new kmem_cache named A.
  2) Coincidentally, the kmem_cache A is an alias for kmem_cache B,
     so the refcount of B is just increased.
  3) Use kmem_cache_destroy() to destroy the kmem_cache A, just
     decrease the B's refcount but mark the B as dying.
  4) Create a new memory cgroup and alloc memory from the kmem_cache
     B. It leads to create a non-root kmem_cache for allocating memory.
  5) When destroy the memory cgroup created in the step 4), the
     non-root kmem_cache can never be destroyed.

If we repeat steps 4) and 5), this will cause a lot of memory leak.  So
only when refcount reach zero, we mark the root kmem_cache as dying.

Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@bytedance.com
Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slab_common.c |   35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

--- a/mm/slab_common.c~mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy
+++ a/mm/slab_common.c
@@ -326,6 +326,14 @@ int slab_unmergeable(struct kmem_cache *
 	if (s->refcount < 0)
 		return 1;
 
+#ifdef CONFIG_MEMCG_KMEM
+	/*
+	 * Skip the dying kmem_cache.
+	 */
+	if (s->memcg_params.dying)
+		return 1;
+#endif
+
 	return 0;
 }
 
@@ -886,12 +894,15 @@ static int shutdown_memcg_caches(struct
 	return 0;
 }
 
-static void flush_memcg_workqueue(struct kmem_cache *s)
+static void memcg_set_kmem_cache_dying(struct kmem_cache *s)
 {
 	spin_lock_irq(&memcg_kmem_wq_lock);
 	s->memcg_params.dying = true;
 	spin_unlock_irq(&memcg_kmem_wq_lock);
+}
 
+static void flush_memcg_workqueue(struct kmem_cache *s)
+{
 	/*
 	 * SLAB and SLUB deactivate the kmem_caches through call_rcu. Make
 	 * sure all registered rcu callbacks have been invoked.
@@ -923,10 +934,6 @@ static inline int shutdown_memcg_caches(
 {
 	return 0;
 }
-
-static inline void flush_memcg_workqueue(struct kmem_cache *s)
-{
-}
 #endif /* CONFIG_MEMCG_KMEM */
 
 void slab_kmem_cache_release(struct kmem_cache *s)
@@ -944,8 +951,6 @@ void kmem_cache_destroy(struct kmem_cach
 	if (unlikely(!s))
 		return;
 
-	flush_memcg_workqueue(s);
-
 	get_online_cpus();
 	get_online_mems();
 
@@ -955,6 +960,22 @@ void kmem_cache_destroy(struct kmem_cach
 	if (s->refcount)
 		goto out_unlock;
 
+#ifdef CONFIG_MEMCG_KMEM
+	memcg_set_kmem_cache_dying(s);
+
+	mutex_unlock(&slab_mutex);
+
+	put_online_mems();
+	put_online_cpus();
+
+	flush_memcg_workqueue(s);
+
+	get_online_cpus();
+	get_online_mems();
+
+	mutex_lock(&slab_mutex);
+#endif
+
 	err = shutdown_memcg_caches(s);
 	if (!err)
 		err = shutdown_cache(s);
_

[patch 08/15] mm/hugetlb: avoid hardcoding while checking if cma is enabled

[Andrew Morton]

From: Barry Song <song.bao.hua@hisilicon.com>
Subject: mm/hugetlb: avoid hardcoding while checking if cma is enabled

hugetlb_cma[0] can be NULL due to various reasons, for example, node0 has
no memory.  so NULL hugetlb_cma[0] doesn't necessarily mean cma is not
enabled.  gigantic pages might have been reserved on other nodes.  This
patch fixes possible double reservation and CMA leak.

[akpm@linux-foundation.org: fix CONFIG_CMA=n warning]
[sfr@canb.auug.org.au: better checks before using hugetlb_cma]
  Link: http://lkml.kernel.org/r/20200721205716.6dbaa56b@canb.auug.org.au
Link: http://lkml.kernel.org/r/20200710005726.36068-1-song.bao.hua@hisilicon.com
Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-avoid-hardcoding-while-checking-if-cma-is-enabled
+++ a/mm/hugetlb.c
@@ -45,7 +45,10 @@ int hugetlb_max_hstate __read_mostly;
 unsigned int default_hstate_idx;
 struct hstate hstates[HUGE_MAX_HSTATE];
 
+#ifdef CONFIG_CMA
 static struct cma *hugetlb_cma[MAX_NUMNODES];
+#endif
+static unsigned long hugetlb_cma_size __initdata;
 
 /*
  * Minimum page order among possible hugepage sizes, set to a proper value
@@ -1235,9 +1238,10 @@ static void free_gigantic_page(struct pa
 	 * If the page isn't allocated using the cma allocator,
 	 * cma_release() returns false.
 	 */
-	if (IS_ENABLED(CONFIG_CMA) &&
-	    cma_release(hugetlb_cma[page_to_nid(page)], page, 1 << order))
+#ifdef CONFIG_CMA
+	if (cma_release(hugetlb_cma[page_to_nid(page)], page, 1 << order))
 		return;
+#endif
 
 	free_contig_range(page_to_pfn(page), 1 << order);
 }
@@ -1248,7 +1252,8 @@ static struct page *alloc_gigantic_page(
 {
 	unsigned long nr_pages = 1UL << huge_page_order(h);
 
-	if (IS_ENABLED(CONFIG_CMA)) {
+#ifdef CONFIG_CMA
+	{
 		struct page *page;
 		int node;
 
@@ -1262,6 +1267,7 @@ static struct page *alloc_gigantic_page(
 				return page;
 		}
 	}
+#endif
 
 	return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
 }
@@ -2571,7 +2577,7 @@ static void __init hugetlb_hstate_alloc_
 
 	for (i = 0; i < h->max_huge_pages; ++i) {
 		if (hstate_is_gigantic(h)) {
-			if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) {
+			if (hugetlb_cma_size) {
 				pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
 				break;
 			}
@@ -5654,7 +5660,6 @@ void move_hugetlb_state(struct page *old
 }
 
 #ifdef CONFIG_CMA
-static unsigned long hugetlb_cma_size __initdata;
 static bool cma_reserve_called __initdata;
 
 static int __init cmdline_parse_hugetlb_cma(char *p)
_

[patch 09/15] khugepaged: fix null-pointer dereference due to race

[Andrew Morton]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: khugepaged: fix null-pointer dereference due to race

khugepaged has to drop mmap lock several times while collapsing a page. 
The situation can change while the lock is dropped and we need to
re-validate that the VMA is still in place and the PMD is still subject
for collapse.

But we miss one corner case: while collapsing an anonymous pages the VMA
could be replaced with file VMA. If the file VMA doesn't have any
private pages we get NULL pointer dereference:

	general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
	KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
	anon_vma_lock_write include/linux/rmap.h:120 [inline]
	collapse_huge_page mm/khugepaged.c:1110 [inline]
	khugepaged_scan_pmd mm/khugepaged.c:1349 [inline]
	khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline]
	khugepaged_do_scan mm/khugepaged.c:2193 [inline]
	khugepaged+0x3bba/0x5a10 mm/khugepaged.c:2238

The fix is to make sure that the VMA is anonymous in
hugepage_vma_revalidate().  The helper is only used for collapsing
anonymous pages.

Link: http://lkml.kernel.org/r/20200722121439.44328-1-kirill.shutemov@linux.intel.com
Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: syzbot+ed318e8b790ca72c5ad0@syzkaller.appspotmail.com
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/khugepaged.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/khugepaged.c~khugepaged-fix-null-pointer-dereference-due-to-race
+++ a/mm/khugepaged.c
@@ -958,6 +958,9 @@ static int hugepage_vma_revalidate(struc
 		return SCAN_ADDRESS_RANGE;
 	if (!hugepage_vma_check(vma, vma->vm_flags))
 		return SCAN_VMA_CHECK;
+	/* Anon VMA expected */
+	if (!vma->anon_vma || vma->vm_ops)
+		return SCAN_VMA_CHECK;
 	return 0;
 }
 
_

[patch 13/15] io-mapping: indicate mapping failure

[Andrew Morton]

From: "Michael J. Ruhl" <michael.j.ruhl@intel.com>
Subject: io-mapping: indicate mapping failure

The !ATOMIC_IOMAP version of io_maping_init_wc will always return success,
even when the ioremap fails.

Since the ATOMIC_IOMAP version returns NULL when the init fails, and
callers check for a NULL return on error this is unexpected.

During a device probe, where the ioremap failed, a crash can look
like this:

BUG: unable to handle page fault for address: 0000000000210000
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 Oops: 0002 [#1] PREEMPT SMP
 CPU: 0 PID: 177 Comm:
 RIP: 0010:fill_page_dma [i915]
  gen8_ppgtt_create [i915]
  i915_ppgtt_create [i915]
  intel_gt_init [i915]
  i915_gem_init [i915]
  i915_driver_probe [i915]
  pci_device_probe
  really_probe
  driver_probe_device

The remap failure occurred much earlier in the probe.  If it had
been propagated, the driver would have exited with an error.

Return NULL on ioremap failure.

[akpm@linux-foundation.org: detect ioremap_wc() errors earlier]
Link: http://lkml.kernel.org/r/20200721171936.81563-1-michael.j.ruhl@intel.com
Fixes: cafaf14a5d8f ("io-mapping: Always create a struct to hold metadata about the io-mapping")
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/io-mapping.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/io-mapping.h~io-mapping-indicate-mapping-failure
+++ a/include/linux/io-mapping.h
@@ -107,9 +107,12 @@ io_mapping_init_wc(struct io_mapping *io
 		   resource_size_t base,
 		   unsigned long size)
 {
+	iomap->iomem = ioremap_wc(base, size);
+	if (!iomap->iomem)
+		return NULL;
+
 	iomap->base = base;
 	iomap->size = size;
-	iomap->iomem = ioremap_wc(base, size);
 #if defined(pgprot_noncached_wc) /* archs can't agree on a name ... */
 	iomap->prot = pgprot_noncached_wc(PAGE_KERNEL);
 #elif defined(pgprot_writecombine)
_

Re: [patch 06/15] mm/memcg: fix refcount error while moving and swapping

[Alex Shi]

在 2020/7/24 下午12:15, Andrew Morton 写道:
> From: Hugh Dickins <hughd@google.com>
> Subject: mm/memcg: fix refcount error while moving and swapping
> 
> It was hard to keep a test running, moving tasks between memcgs with
> move_charge_at_immigrate, while swapping: mem_cgroup_id_get_many()'s
> refcount is discovered to be 0 (supposedly impossible), so it is then
> forced to REFCOUNT_SATURATED, and after thousands of warnings in quick
> succession, the test is at last put out of misery by being OOM killed.
> 
> This is because of the way moved_swap accounting was saved up until the
> task move gets completed in __mem_cgroup_clear_mc(), deferred from when
> mem_cgroup_move_swap_account() actually exchanged old and new ids. 
> Concurrent activity can free up swap quicker than the task is scanned,
> bringing id refcount down 0 (which should only be possible when
> offlining).
> 
> Just skip that optimization: do that part of the accounting immediately.
> 
> Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils
> Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Alex Shi <alex.shi@linux.alibaba.com>
> Cc: Shakeel Butt <shakeelb@google.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---

Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>

> 
>  mm/memcontrol.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/mm/memcontrol.c~mm-memcg-fix-refcount-error-while-moving-and-swapping
> +++ a/mm/memcontrol.c
> @@ -5669,7 +5669,6 @@ static void __mem_cgroup_clear_mc(void)
>  		if (!mem_cgroup_is_root(mc.to))
>  			page_counter_uncharge(&mc.to->memory, mc.moved_swap);
>  
> -		mem_cgroup_id_get_many(mc.to, mc.moved_swap);
>  		css_put_many(&mc.to->css, mc.moved_swap);
>  
>  		mc.moved_swap = 0;
> @@ -5860,7 +5859,8 @@ put:			/* get_mctgt_type() gets the page
>  			ent = target.ent;
>  			if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) {
>  				mc.precharge--;
> -				/* we fixup refcnts and charges later. */
> +				mem_cgroup_id_get_many(mc.to, 1);
> +				/* we fixup other refcnts and charges later. */
>  				mc.moved_swap++;
>  			}
>  			break;
> _
> 

+ mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch added to -mm tree

[Andrew Morton]

The patch titled
     Subject: mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible
has been added to the -mm tree.  Its filename is
     mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Peter Xu <peterx@redhat.com>
Subject: mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible

This is found by code observation only.

Firstly, the worst case scenario should assume the whole range was covered
by pmd sharing.  The old algorithm might not work as expected for ranges
like (1g-2m, 1g+2m), where the adjusted range should be (0, 1g+2m) but the
expected range should be (0, 2g).

Since at it, remove the loop since it should not be required.  With that,
the new code should be faster too when the invalidating range is huge.

Mike said:

: With range (1g-2m, 1g+2m) within a vma (0, 2g) the existing code will only
: adjust to (0, 1g+2m) which is incorrect.
: 
: We should cc stable.  The original reason for adjusting the range was to
: prevent data corruption (getting wrong page).  Since the range is not
: always adjusted correctly, the potential for corruption still exists.
: 
: However, I am fairly confident that adjust_range_if_pmd_sharing_possible
: is only gong to be called in two cases:
: 
: 1) for a single page
: 2) for range == entire vma
: 
: In those cases, the current code should produce the correct results.
: 
: To be safe, let's just cc stable.

Link: http://lkml.kernel.org/r/20200730201636.74778-1-peterx@redhat.com
Fixes: 017b1660df89 ("mm: migration: fix migration of huge PMD shared pages")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |   24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible
+++ a/mm/hugetlb.c
@@ -5314,25 +5314,21 @@ static bool vma_shareable(struct vm_area
 void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
 				unsigned long *start, unsigned long *end)
 {
-	unsigned long check_addr;
+	unsigned long a_start, a_end;
 
 	if (!(vma->vm_flags & VM_MAYSHARE))
 		return;
 
-	for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
-		unsigned long a_start = check_addr & PUD_MASK;
-		unsigned long a_end = a_start + PUD_SIZE;
+	/* Extend the range to be PUD aligned for a worst case scenario */
+	a_start = ALIGN_DOWN(*start, PUD_SIZE);
+	a_end = ALIGN(*end, PUD_SIZE);
 
-		/*
-		 * If sharing is possible, adjust start/end if necessary.
-		 */
-		if (range_in_vma(vma, a_start, a_end)) {
-			if (a_start < *start)
-				*start = a_start;
-			if (a_end > *end)
-				*end = a_end;
-		}
-	}
+	/*
+	 * Intersect the range with the vma range, since pmd sharing won't be
+	 * across vma after all
+	 */
+	*start = max(vma->vm_start, a_start);
+	*end = min(vma->vm_end, a_end);
 }
 
 /*
_

Patches currently in -mm which might be from peterx@redhat.com are

mm-hugetlb-fix-calculation-of-adjust_range_if_pmd_sharing_possible.patch
mm-do-page-fault-accounting-in-handle_mm_fault.patch
mm-alpha-use-general-page-fault-accounting.patch
mm-arc-use-general-page-fault-accounting.patch
mm-arm-use-general-page-fault-accounting.patch
mm-arm64-use-general-page-fault-accounting.patch
mm-csky-use-general-page-fault-accounting.patch
mm-hexagon-use-general-page-fault-accounting.patch
mm-ia64-use-general-page-fault-accounting.patch
mm-m68k-use-general-page-fault-accounting.patch
mm-microblaze-use-general-page-fault-accounting.patch
mm-mips-use-general-page-fault-accounting.patch
mm-nds32-use-general-page-fault-accounting.patch
mm-nios2-use-general-page-fault-accounting.patch
mm-openrisc-use-general-page-fault-accounting.patch
mm-parisc-use-general-page-fault-accounting.patch
mm-powerpc-use-general-page-fault-accounting.patch
mm-riscv-use-general-page-fault-accounting.patch
mm-s390-use-general-page-fault-accounting.patch
mm-sh-use-general-page-fault-accounting.patch
mm-sparc32-use-general-page-fault-accounting.patch
mm-sparc64-use-general-page-fault-accounting.patch
mm-x86-use-general-page-fault-accounting.patch
mm-xtensa-use-general-page-fault-accounting.patch
mm-clean-up-the-last-pieces-of-page-fault-accountings.patch
mm-gup-remove-task_struct-pointer-for-all-gup-code.patch

+ cma-dont-quit-at-first-error-when-activating-reserved-areas.patch added to -mm tree

[Andrew Morton]

The patch titled
     Subject: cma: don't quit at first error when activating reserved areas
has been added to the -mm tree.  Its filename is
     cma-dont-quit-at-first-error-when-activating-reserved-areas.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/cma-dont-quit-at-first-error-when-activating-reserved-areas.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/cma-dont-quit-at-first-error-when-activating-reserved-areas.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Mike Kravetz <mike.kravetz@oracle.com>
Subject: cma: don't quit at first error when activating reserved areas

The routine cma_init_reserved_areas is designed to activate all
reserved cma areas.  It quits when it first encounters an error.
This can leave some areas in a state where they are reserved but
not activated.  There is no feedback to code which performed the
reservation.  Attempting to allocate memory from areas in such a
state will result in a BUG.

Modify cma_init_reserved_areas to always attempt to activate all
areas.  The called routine, cma_activate_area is responsible for
leaving the area in a valid state.  No one is making active use
of returned error codes, so change the routine to void.

How to reproduce:  This example uses kernelcore, hugetlb and cma
as an easy way to reproduce.  However, this is a more general cma
issue.

Two node x86 VM 16GB total, 8GB per node
Kernel command line parameters, kernelcore=4G hugetlb_cma=8G
Related boot time messages,
  hugetlb_cma: reserve 8192 MiB, up to 4096 MiB per node
  cma: Reserved 4096 MiB at 0x0000000100000000
  hugetlb_cma: reserved 4096 MiB on node 0
  cma: Reserved 4096 MiB at 0x0000000300000000
  hugetlb_cma: reserved 4096 MiB on node 1
  cma: CMA area hugetlb could not be activated

 # echo 8 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  ...
  Call Trace:
    bitmap_find_next_zero_area_off+0x51/0x90
    cma_alloc+0x1a5/0x310
    alloc_fresh_huge_page+0x78/0x1a0
    alloc_pool_huge_page+0x6f/0xf0
    set_max_huge_pages+0x10c/0x250
    nr_hugepages_store_common+0x92/0x120
    ? __kmalloc+0x171/0x270
    kernfs_fop_write+0xc1/0x1a0
    vfs_write+0xc7/0x1f0
    ksys_write+0x5f/0xe0
    do_syscall_64+0x4d/0x90
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

Link: http://lkml.kernel.org/r/20200730163123.6451-1-mike.kravetz@oracle.com
Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Barry Song <song.bao.hua@hisilicon.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/cma.c |   23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

--- a/mm/cma.c~cma-dont-quit-at-first-error-when-activating-reserved-areas
+++ a/mm/cma.c
@@ -93,17 +93,15 @@ static void cma_clear_bitmap(struct cma
 	mutex_unlock(&cma->lock);
 }
 
-static int __init cma_activate_area(struct cma *cma)
+static void __init cma_activate_area(struct cma *cma)
 {
 	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
 	unsigned i = cma->count >> pageblock_order;
 	struct zone *zone;
 
 	cma->bitmap = bitmap_zalloc(cma_bitmap_maxno(cma), GFP_KERNEL);
-	if (!cma->bitmap) {
-		cma->count = 0;
-		return -ENOMEM;
-	}
+	if (!cma->bitmap)
+		goto out_error;
 
 	WARN_ON_ONCE(!pfn_valid(pfn));
 	zone = page_zone(pfn_to_page(pfn));
@@ -133,25 +131,22 @@ static int __init cma_activate_area(stru
 	spin_lock_init(&cma->mem_head_lock);
 #endif
 
-	return 0;
+	return;
 
 not_in_zone:
-	pr_err("CMA area %s could not be activated\n", cma->name);
 	bitmap_free(cma->bitmap);
+out_error:
 	cma->count = 0;
-	return -EINVAL;
+	pr_err("CMA area %s could not be activated\n", cma->name);
+	return;
 }
 
 static int __init cma_init_reserved_areas(void)
 {
 	int i;
 
-	for (i = 0; i < cma_area_count; i++) {
-		int ret = cma_activate_area(&cma_areas[i]);
-
-		if (ret)
-			return ret;
-	}
+	for (i = 0; i < cma_area_count; i++)
+		cma_activate_area(&cma_areas[i]);
 
 	return 0;
 }
_

Patches currently in -mm which might be from mike.kravetz@oracle.com are

hugetlbfs-prevent-filesystem-stacking-of-hugetlbfs.patch
cma-dont-quit-at-first-error-when-activating-reserved-areas.patch