set_migratetype_isolate() does not allow isolating MIGRATE_CMA pageblocks
unless it is used for CMA allocation. isolate_single_pageblock() did not
have the same behavior when it is used together with
set_migratetype_isolate() in start_isolate_page_range(). This allows
alloc_contig_range() with migratetype other than MIGRATE_CMA, like
MIGRATE_MOVABLE (used by alloc_contig_pages()), to isolate first and last
pageblock but fail the rest. The failure leads to changing migratetype of
the first and last pageblock to MIGRATE_MOVABLE from MIGRATE_CMA,
corrupting the CMA region. This can happen during gigantic page
allocations.
Like Doug said here:
https://lore.kernel.org/linux-mm/a3363a52-883b-dcd1-b77f-f2bb378d6f2d@gmail.com/T/#u,
for gigantic page allocations, the user would notice no difference,
since the allocation on CMA region will fail as well as it did before.
But it might hurt the performance of device drivers that use CMA, since
CMA region size decreases.
Fix it by passing migratetype into isolate_single_pageblock(), so that
set_migratetype_isolate() used by isolate_single_pageblock() will prevent
the isolation happening.
Link: https://lkml.kernel.org/r/20220914023913.1855924-1-zi.yan@sent.com
Fixes: b2c9e2fbba ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: Doug Berger <opendmb@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The GHES code calls memory_failure_queue() from IRQ context to queue work
into workqueue and schedule it on the current CPU. Then the work is
processed in memory_failure_work_func() by kworker and calls
memory_failure().
When a page is already poisoned, commit a3f5d80ea4 ("mm,hwpoison: send
SIGBUS with error virutal address") make memory_failure() call
kill_accessing_process() that:
- holds mmap locking of current->mm
- does pagetable walk to find the error virtual address
- and sends SIGBUS to the current process with error info.
However, the mm of kworker is not valid, resulting in a null-pointer
dereference. So check mm when killing the accessing process.
[akpm@linux-foundation.org: remove unrelated whitespace alteration]
Link: https://lkml.kernel.org/r/20220914064935.7851-1-xueshuai@linux.alibaba.com
Fixes: a3f5d80ea4 ("mm,hwpoison: send SIGBUS with error virutal address")
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Bixuan Cui <cuibixuan@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
With gigantic pages it may not be true that struct page structures are
contiguous across the entire gigantic page. The nth_page macro is used
here in place of direct pointer arithmetic to correct for this.
Mike said:
: This error could cause addressing exceptions. However, this is only
: possible in configurations where CONFIG_SPARSEMEM &&
: !CONFIG_SPARSEMEM_VMEMMAP. Such a configuration option is rare and
: unknown to be the default anywhere.
Link: https://lkml.kernel.org/r/20220914190917.3517663-1-opendmb@gmail.com
Fixes: 8531fc6f52 ("hugetlb: add hugetlb demote page support")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
A number of drivers call page_frag_alloc() with a fragment's size >
PAGE_SIZE.
In low memory conditions, __page_frag_cache_refill() may fail the order
3 cache allocation and fall back to order 0; In this case, the cache
will be smaller than the fragment, causing memory corruptions.
Prevent this from happening by checking if the newly allocated cache is
large enough for the fragment; if not, the allocation will fail and
page_frag_alloc() will return NULL.
Link: https://lkml.kernel.org/r/20220715125013.247085-1-mlombard@redhat.com
Fixes: b63ae8ca09 ("mm/net: Rename and move page fragment handling from net/ to mm/")
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Chen Lin <chen45464546@163.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Running this test program on ARMv4 a few times (sometimes just once)
reproduces the bug.
int main()
{
unsigned i;
char paragon[SIZE];
void* ptr;
memset(paragon, 0xAA, SIZE);
ptr = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_SHARED, -1, 0);
if (ptr == MAP_FAILED) return 1;
printf("ptr = %p\n", ptr);
for (i=0;i<10000;i++){
memset(ptr, 0xAA, SIZE);
if (memcmp(ptr, paragon, SIZE)) {
printf("Unexpected bytes on iteration %u!!!\n", i);
break;
}
}
munmap(ptr, SIZE);
}
In the "ptr" buffer there appear runs of zero bytes which are aligned
by 16 and their lengths are multiple of 16.
Linux v5.11 does not have the bug, "git bisect" finds the first bad commit:
f9ce0be71d ("mm: Cleanup faultaround and finish_fault() codepaths")
Before the commit update_mmu_cache() was called during a call to
filemap_map_pages() as well as finish_fault(). After the commit
finish_fault() lacks it.
Bring back update_mmu_cache() to finish_fault() to fix the bug.
Also call update_mmu_tlb() only when returning VM_FAULT_NOPAGE to more
closely reproduce the code of alloc_set_pte() function that existed before
the commit.
On many platforms update_mmu_cache() is nop:
x86, see arch/x86/include/asm/pgtable
ARMv6+, see arch/arm/include/asm/tlbflush.h
So, it seems, few users ran into this bug.
Link: https://lkml.kernel.org/r/20220908204809.2012451-1-saproj@gmail.com
Fixes: f9ce0be71d ("mm: Cleanup faultaround and finish_fault() codepaths")
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
NULL pointer dereference is triggered when calling thp split via debugfs
on the system with offlined memory blocks. With debug option enabled, the
following kernel messages are printed out:
page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000
flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff)
raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: unmovable page
page:000000007d7ab72e is uninitialized and poisoned
page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:1248!
invalid opcode: 0000 [#1] PREEMPT SMP PTI
CPU: 16 PID: 20964 Comm: bash Tainted: G I 6.0.0-rc3-foll-numa+ #41
...
RIP: 0010:split_huge_pages_write+0xcf4/0xe30
This shows that page_to_nid() in page_zone() is unexpectedly called for an
offlined memmap.
Use pfn_to_online_page() to get struct page in PFN walker.
Link: https://lkml.kernel.org/r/20220908041150.3430269-1-naoya.horiguchi@linux.dev
Fixes: f1dd2cd13c ("mm, memory_hotplug: do not associate hotadded memory to zones until online") [visible after d0dc12e86b]
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Co-developed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org> [5.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
MADV_PAGEOUT tries to isolate non-LRU pages and gets a warning from
isolate_lru_page below.
Fix it by checking PageLRU in advance.
------------[ cut here ]------------
trying to isolate tail page
WARNING: CPU: 0 PID: 6175 at mm/folio-compat.c:158 isolate_lru_page+0x130/0x140
Modules linked in:
CPU: 0 PID: 6175 Comm: syz-executor.0 Not tainted 5.18.12 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:isolate_lru_page+0x130/0x140
Link: https://lore.kernel.org/linux-mm/485f8c33.2471b.182d5726afb.Coremail.hantianshuo@iie.ac.cn/
Link: https://lkml.kernel.org/r/20220908151204.762596-1-minchan@kernel.org
Fixes: 1a4e58cce8 ("mm: introduce MADV_PAGEOUT")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: 韩天ç` <hantianshuo@iie.ac.cn>
Suggested-by: Yang Shi <shy828301@gmail.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since general RCU GUP fast was introduced in commit 2667f50e8b ("mm:
introduce a general RCU get_user_pages_fast()"), a TLB flush is no longer
sufficient to handle concurrent GUP-fast in all cases, it only handles
traditional IPI-based GUP-fast correctly. On architectures that send an
IPI broadcast on TLB flush, it works as expected. But on the
architectures that do not use IPI to broadcast TLB flush, it may have the
below race:
CPU A CPU B
THP collapse fast GUP
gup_pmd_range() <-- see valid pmd
gup_pte_range() <-- work on pte
pmdp_collapse_flush() <-- clear pmd and flush
__collapse_huge_page_isolate()
check page pinned <-- before GUP bump refcount
pin the page
check PTE <-- no change
__collapse_huge_page_copy()
copy data to huge page
ptep_clear()
install huge pmd for the huge page
return the stale page
discard the stale page
The race can be fixed by checking whether PMD is changed or not after
taking the page pin in fast GUP, just like what it does for PTE. If the
PMD is changed it means there may be parallel THP collapse, so GUP should
back off.
Also update the stale comment about serializing against fast GUP in
khugepaged.
Link: https://lkml.kernel.org/r/20220907180144.555485-1-shy828301@gmail.com
Fixes: 2667f50e8b ("mm: introduce a general RCU get_user_pages_fast()")
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit 6c287605fd ("mm: remember exclusively mapped anonymous pages with
PG_anon_exclusive") made sure that when PageAnonExclusive() has to be
cleared during temporary unmapping of a page, that the PTE is
cleared/invalidated and that the TLB is flushed.
What we want to achieve in all cases is that we cannot end up with a pin on
an anonymous page that may be shared, because such pins would be
unreliable and could result in memory corruptions when the mapped page
and the pin go out of sync due to a write fault.
That TLB flush handling was inspired by an outdated comment in
mm/ksm.c:write_protect_page(), which similarly required the TLB flush in
the past to synchronize with GUP-fast. However, ever since general RCU GUP
fast was introduced in commit 2667f50e8b ("mm: introduce a general RCU
get_user_pages_fast()"), a TLB flush is no longer sufficient to handle
concurrent GUP-fast in all cases -- it only handles traditional IPI-based
GUP-fast correctly.
Peter Xu (thankfully) questioned whether that TLB flush is really
required. On architectures that send an IPI broadcast on TLB flush,
it works as expected. To synchronize with RCU GUP-fast properly, we're
conceptually fine, however, we have to enforce a certain memory order and
are missing memory barriers.
Let's document that, avoid the TLB flush where possible and use proper
explicit memory barriers where required. We shouldn't really care about the
additional memory barriers here, as we're not on extremely hot paths --
and we're getting rid of some TLB flushes.
We use a smp_mb() pair for handling concurrent pinning and a
smp_rmb()/smp_wmb() pair for handling the corner case of only temporary
PTE changes but permanent PageAnonExclusive changes.
One extreme example, whereby GUP-fast takes a R/O pin and KSM wants to
convert an exclusive anonymous page to a KSM page, and that page is already
mapped write-protected (-> no PTE change) would be:
Thread 0 (KSM) Thread 1 (GUP-fast)
(B1) Read the PTE
# (B2) skipped without FOLL_WRITE
(A1) Clear PTE
smp_mb()
(A2) Check pinned
(B3) Pin the mapped page
smp_mb()
(A3) Clear PageAnonExclusive
smp_wmb()
(A4) Restore PTE
(B4) Check if the PTE changed
smp_rmb()
(B5) Check PageAnonExclusive
Thread 1 will properly detect that PageAnonExclusive was cleared and
back off.
Note that we don't need a memory barrier between checking if the page is
pinned and clearing PageAnonExclusive, because stores are not
speculated.
The possible issues due to reordering are of theoretical nature so far
and attempts to reproduce the race failed.
Especially the "no PTE change" case isn't the common case, because we'd
need an exclusive anonymous page that's mapped R/O and the PTE is clean
in KSM code -- and using KSM with page pinning isn't extremely common.
Further, the clear+TLB flush we used for now implies a memory barrier.
So the problematic missing part should be the missing memory barrier
after pinning but before checking if the PTE changed.
Link: https://lkml.kernel.org/r/20220901083559.67446-1-david@redhat.com
Fixes: 6c287605fd ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Christoph von Recklinghausen <crecklin@redhat.com>
Cc: Don Dutile <ddutile@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Drop unneed comment and blank, adjust the variable, and the most important
is to delete BUG_ON(). The page passed is always buddy page into
__isolate_free_page() from compaction, page_isolation and page_reporting,
and the caller also check the return, BUG_ON() is a too drastic measure,
remove it.
Link: https://lkml.kernel.org/r/20220901015043.189276-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
No caller cares about the return value of create_object(), so make it
return void.
Link: https://lkml.kernel.org/r/20220901023007.3471887-1-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When code reaches here, invalid page would have been accessed if huge pte
is none. So this BUG_ON(huge_pte_none()) is meaningless. Remove it.
Link: https://lkml.kernel.org/r/20220901120030.63318-10-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The SetHPageVmemmapOptimized() called here seems unnecessary as it's
assumed to be set when calling this function. But it's indeed cleared
by above set_page_private(page, 0). Add a comment to avoid possible
future confusion.
Link: https://lkml.kernel.org/r/20220901120030.63318-9-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fold hugetlbfs_pagecache_page() into its sole caller to remove some
duplicated code. No functional change intended.
Link: https://lkml.kernel.org/r/20220901120030.63318-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We can pass NULL to kobj_to_hstate() directly when nid is unused to
simplify the code. No functional change intended.
Link: https://lkml.kernel.org/r/20220901120030.63318-7-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Use helper huge_pte_lock and pmd_lock to simplify the code. No functional
change intended.
Link: https://lkml.kernel.org/r/20220901120030.63318-6-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It's better to use sizeof() to get the array size instead of manual
calculation. Minor readability improvement.
Link: https://lkml.kernel.org/r/20220901120030.63318-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Use LIST_HEAD() directly to define a list head to simplify the code.
No functional change intended.
Link: https://lkml.kernel.org/r/20220901120030.63318-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Use helper macro SZ_1K to do the size conversion to make code more
consistent in this file. Minor readability improvement.
Link: https://lkml.kernel.org/r/20220901120030.63318-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "A few cleanup patches for hugetlb", v2.
This series contains a few cleanup patches to use helper functions to
simplify the codes, remove unneeded nid parameter and so on. More
details can be found in the respective changelogs.
This patch (of 10):
Make hugetlb_cma_check() static as it's only used inside mm/hugetlb.c.
Link: https://lkml.kernel.org/r/20220901120030.63318-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220901120030.63318-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
find_vmap_lowest_match() is now able to handle different roots. With
DEBUG_AUGMENT_LOWEST_MATCH_CHECK enabled as:
: --- a/mm/vmalloc.c
: +++ b/mm/vmalloc.c
: @@ -713,7 +713,7 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
: /*** Global kva allocator ***/
:
: -#define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0
: +#define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 1
compilation failed as:
mm/vmalloc.c: In function 'find_vmap_lowest_match_check':
mm/vmalloc.c:1328:32: warning: passing argument 1 of 'find_vmap_lowest_match' makes pointer from integer without a cast [-Wint-conversion]
1328 | va_1 = find_vmap_lowest_match(size, align, vstart, false);
| ^~~~
| |
| long unsigned int
mm/vmalloc.c:1236:40: note: expected 'struct rb_root *' but argument is of type 'long unsigned int'
1236 | find_vmap_lowest_match(struct rb_root *root, unsigned long size,
| ~~~~~~~~~~~~~~~~^~~~
mm/vmalloc.c:1328:9: error: too few arguments to function 'find_vmap_lowest_match'
1328 | va_1 = find_vmap_lowest_match(size, align, vstart, false);
| ^~~~~~~~~~~~~~~~~~~~~~
mm/vmalloc.c:1236:1: note: declared here
1236 | find_vmap_lowest_match(struct rb_root *root, unsigned long size,
| ^~~~~~~~~~~~~~~~~~~~~~
Extend find_vmap_lowest_match_check() and find_vmap_lowest_linear_match()
with extra arguments to fix this.
Link: https://lkml.kernel.org/r/20220906060548.1127396-1-song@kernel.org
Link: https://lkml.kernel.org/r/20220831052734.3423079-1-song@kernel.org
Fixes: f9863be493 ("mm/vmalloc: extend __alloc_vmap_area() with extra arguments")
Signed-off-by: Song Liu <song@kernel.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit ab09243aa9 ("mm/migrate.c: remove MIGRATE_PFN_LOCKED") changed
the way trylock_page() in migrate_vma_collect_pmd() works without updating
the comment. Reword the comment to be less misleading and a better
reflection of what happens.
Link: https://lkml.kernel.org/r/20220830020138.497063-1-apopple@nvidia.com
Fixes: ab09243aa9 ("mm/migrate.c: remove MIGRATE_PFN_LOCKED")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reported-by: Peter Xu <peterx@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The gfp_flags parameter is not used in rmqueue_pcplist, so directly delete
this parameter.
Link: https://lkml.kernel.org/r/20220831013404.3360714-1-zuoze1@huawei.com
Signed-off-by: zezuo <zuoze1@huawei.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We can get the hotness value from damon_hot_score() directly in
damon_pageout_score() function and improve the code readability.
Link: https://lkml.kernel.org/r/1661766366-20998-1-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The damon regions that belong to the same damon target have the same
'struct mm_struct *mm', so it's unnecessary to compare the mm and last_mm
objects among the damon regions in one damon target when checking
accesses. But the check is necessary when the target changed in
'__damon_va_check_accesses()', so we can simplify the whole operation by
using the bool 'same_target' to indicate whether the target changed.
Link: https://lkml.kernel.org/r/1661590971-20893-3-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: Simplify the damon regions access check", v2.
This patchset simplifies the operations when checking the damon regions
accesses.
This patch (of 2):
The parameter 'struct damon_ctx *ctx' isn't used in the functions
__damon_{p,v}a_check_access(), so we can remove it and simplify the
parameter passing.
Link: https://lkml.kernel.org/r/1661590971-20893-1-git-send-email-kaixuxia@tencent.com
Link: https://lkml.kernel.org/r/1661590971-20893-2-git-send-email-kaixuxia@tencent.com
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
kswapd_run/stop() will set pgdat->kswapd to NULL, which could race with
kswapd_is_running() in kcompactd(),
kswapd_run/stop() kcompactd()
kswapd_is_running()
pgdat->kswapd // error or nomal ptr
verify pgdat->kswapd
// load non-NULL
pgdat->kswapd
pgdat->kswapd = NULL
task_is_running(pgdat->kswapd)
// Null pointer derefence
KASAN reports the null-ptr-deref shown below,
vmscan: Failed to start kswapd on node 0
...
BUG: KASAN: null-ptr-deref in kcompactd+0x440/0x504
Read of size 8 at addr 0000000000000024 by task kcompactd0/37
CPU: 0 PID: 37 Comm: kcompactd0 Kdump: loaded Tainted: G OE 5.10.60 #1
Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
Call trace:
dump_backtrace+0x0/0x394
show_stack+0x34/0x4c
dump_stack+0x158/0x1e4
__kasan_report+0x138/0x140
kasan_report+0x44/0xdc
__asan_load8+0x94/0xd0
kcompactd+0x440/0x504
kthread+0x1a4/0x1f0
ret_from_fork+0x10/0x18
At present kswapd/kcompactd_run() and kswapd/kcompactd_stop() are protected
by mem_hotplug_begin/done(), but without kcompactd(). There is no need to
involve memory hotplug lock in kcompactd(), so let's add a new mutex to
protect pgdat->kswapd accesses.
Also, because the kcompactd task will check the state of kswapd task, it's
better to call kcompactd_stop() before kswapd_stop() to reduce lock
conflicts.
[akpm@linux-foundation.org: add comments]
Link: https://lkml.kernel.org/r/20220827111959.186838-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Directly check state of struct memory_block, no need a single function.
Link: https://lkml.kernel.org/r/20220827112043.187028-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
All callers of find_get_pages_contig() have been removed, so it is no
longer needed.
Link: https://lkml.kernel.org/r/20220824004023.77310-8-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: David Sterba <dsterb@suse.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Convert to filemap_get_folios_contig()", v3.
This patch series replaces find_get_pages_contig() with
filemap_get_folios_contig().
This patch (of 7):
This function is meant to replace find_get_pages_contig().
Unlike find_get_pages_contig(), filemap_get_folios_contig() no longer
takes in a target number of pages to find - It returns up to 15 contiguous
folios.
To be more consistent with filemap_get_folios(),
filemap_get_folios_contig() now also updates the start index passed in,
and takes an end index.
Link: https://lkml.kernel.org/r/20220824004023.77310-1-vishal.moola@gmail.com
Link: https://lkml.kernel.org/r/20220824004023.77310-2-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Sterba <dsterb@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Return the value cgwb_bdi_init() directly instead of storing it in another
redundant variable.
Link: https://lkml.kernel.org/r/20220826071906.252419-1-ye.xingchen@zte.com.cn
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In commit 2f1ee0913c ("Revert "mm: use early_pfn_to_nid in
page_ext_init""), we call page_ext_init() after page_alloc_init_late() to
avoid some panic problem. It seems that we cannot track early page
allocations in current kernel even if page structure has been initialized
early.
This patch introduces a new boot parameter 'early_page_ext' to resolve
this problem. If we pass it to the kernel, page_ext_init() will be moved
up and the feature 'deferred initialization of struct pages' will be
disabled to initialize the page allocator early and prevent the panic
problem above. It can help us to catch early page allocations. This is
useful especially when we find that the free memory value is not the same
right after different kernel booting.
[akpm@linux-foundation.org: fix section issue by removing __meminitdata]
Link: https://lkml.kernel.org/r/20220825102714.669-1-lizhe.67@bytedance.com
Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "memcg: optimize charge codepath", v2.
Recently Linux networking stack has moved from a very old per socket
pre-charge caching to per-cpu caching to avoid pre-charge fragmentation
and unwarranted OOMs. One impact of this change is that for network
traffic workloads, memcg charging codepath can become a bottleneck. The
kernel test robot has also reported this regression[1]. This patch series
tries to improve the memcg charging for such workloads.
This patch series implement three optimizations:
(A) Reduce atomic ops in page counter update path.
(B) Change layout of struct page_counter to eliminate false sharing
between usage and high.
(C) Increase the memcg charge batch to 64.
To evaluate the impact of these optimizations, on a 72 CPUs machine, we
ran the following workload in root memcg and then compared with scenario
where the workload is run in a three level of cgroup hierarchy with top
level having min and low setup appropriately.
$ netserver -6
# 36 instances of netperf with following params
$ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K
Results (average throughput of netperf):
1. root memcg 21694.8 Mbps
2. 6.0-rc1 10482.7 Mbps (-51.6%)
3. 6.0-rc1 + (A) 14542.5 Mbps (-32.9%)
4. 6.0-rc1 + (B) 12413.7 Mbps (-42.7%)
5. 6.0-rc1 + (C) 17063.7 Mbps (-21.3%)
6. 6.0-rc1 + (A+B+C) 20120.3 Mbps (-7.2%)
With all three optimizations, the memcg overhead of this workload has
been reduced from 51.6% to just 7.2%.
[1] https://lore.kernel.org/linux-mm/20220619150456.GB34471@xsang-OptiPlex-9020/
This patch (of 3):
For cgroups using low or min protections, the function
propagate_protected_usage() was doing an atomic xchg() operation
irrespectively. We can optimize out this atomic operation for one
specific scenario where the workload is using the protection (i.e. min >
0) and the usage is above the protection (i.e. usage > min).
This scenario is actually very common where the users want a part of their
workload to be protected against the external reclaim. Though this
optimization does introduce a race when the usage is around the protection
and concurrent charges and uncharged trip it over or under the protection.
In such cases, we might see lower effective protection but the subsequent
charge/uncharge will correct it.
To evaluate the impact of this optimization, on a 72 CPUs machine, we ran
the following workload in a three level of cgroup hierarchy with top level
having min and low setup appropriately to see if this optimization is
effective for the mentioned case.
$ netserver -6
# 36 instances of netperf with following params
$ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K
Results (average throughput of netperf):
Without (6.0-rc1) 10482.7 Mbps
With patch 14542.5 Mbps (38.7% improvement)
With the patch, the throughput improved by 38.7%
Link: https://lkml.kernel.org/r/20220825000506.239406-1-shakeelb@google.com
Link: https://lkml.kernel.org/r/20220825000506.239406-2-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Feng Tang <feng.tang@intel.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oliver Sang <oliver.sang@intel.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
zswap has been with us since 2013, and it's widely used in many products.
Link: https://lkml.kernel.org/r/20220823152033.66682-1-david@ixit.cz
Signed-off-by: David Heidelberg <david@ixit.cz>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When pinning pages with FOLL_LONGTERM check_and_migrate_movable_pages() is
called to migrate pages out of zones which should not contain any longterm
pinned pages.
When migration succeeds all pages will have been unpinned so pinning needs
to be retried. Migration can also fail, in which case the pages will also
have been unpinned but the operation should not be retried. If all pages
are in the correct zone nothing will be unpinned and no retry is required.
The logic in check_and_migrate_movable_pages() tracks unnecessary state
and the return codes for each case are difficult to follow. Refactor the
code to clean this up. No behaviour change is intended.
[akpm@linux-foundation.org: fix unused var warning]
Link: https://lkml.kernel.org/r/19583d1df07fdcb99cfa05c265588a3fa58d1902.1661317396.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
gup_flags is passed to check_and_migrate_movable_pages() so that it can
call either put_page() or unpin_user_page() to drop the page reference.
However check_and_migrate_movable_pages() is only called for
FOLL_LONGTERM, which implies FOLL_PIN so there is no need to pass
gup_flags.
Link: https://lkml.kernel.org/r/d611c65a9008ff55887307df457c6c2220ad6163.1661317396.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In page_counter_set_max, we want to make sure the new limit is not below
the concurrently-changing counter value. We read the counter and check
that the limit is not below the counter before the swap. After the swap,
we read the counter again and retry in case the counter is incremented as
this may violate the requirement. Even though the page_counter_try_charge
can see the old limit, it is guaranteed that the counter is not above the
old limit after the increment. So in case the new limit is not below the
old limit, the counter is guaranteed to be not above the new limit too.
We can skip the retry in this case to optimize a little bit.
Link: https://lkml.kernel.org/r/20220821154055.109635-1-minhquangbui99@gmail.com
Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Workingset refault stats are important and useful metrics to measure how
well reclaimer and swapping work and how healthy the services are, but
they are just available for cgroup v2. There are still plenty users with
cgroup v1, export the stats for cgroup v1.
Link: https://lkml.kernel.org/r/20220816185801.651091-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It is too slow to dump all the pages, in some usage we just want to dump a
given start pfn, for example: a CMA range or a single page.
To speed up and save time, this change allows specifying of a start pfn by
adding llseek for page_owner.
Link: https://lkml.kernel.org/r/20220818022425.31056-1-quic_yingangl@quicinc.com
Signed-off-by: Kassey Li <quic_yingangl@quicinc.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pmd_huge() is used to validate if the pmd entry is mapped by a huge page,
also including the case of non-present (migration or hwpoisoned) pmd entry
on arm64 or x86 architectures. This means that pmd_pfn() can not get the
correct pfn number for a non-present pmd entry, which will cause
damon_get_page() to get an incorrect page struct (also may be NULL by
pfn_to_online_page()), making the access statistics incorrect.
This means that the DAMON may make incorrect decision according to the
incorrect statistics, for example, DAMON may can not reclaim cold page
in time due to this cold page was regarded as accessed mistakenly if
DAMOS_PAGEOUT operation is specified.
Moreover it does not make sense that we still waste time to get the page
of the non-present entry. Just treat it as not-accessed and skip it,
which maintains consistency with non-present pte level entries.
So add pmd entry present validation to fix the above issues.
Link: https://lkml.kernel.org/r/58b1d1f5fbda7db49ca886d9ef6783e3dcbbbc98.1660805030.git.baolin.wang@linux.alibaba.com
Fixes: 3f49584b26 ("mm/damon: implement primitives for the virtual memory address spaces")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
If there is private data attached to a THP, the refcount of THP will be
increased and will prevent the THP from being split. Attempt to release
any private data attached to the THP before attempting the split to
increase the chance of splitting successfully.
There was a memory failure issue hit during HW error injection testing
with 5.18 kernel + xfs as rootfs. The test was killed and a system reboot
was required to re-run the test.
The issue was tracked down to a THP split failure caused by the memory
failure not being handled. The page dump showed:
[ 1785.433075] page:0000000025f9530b refcount:18 mapcount:0 mapping:000000008162eea7 index:0xa10 pfn:0x2f0200
[ 1785.443954] head:0000000025f9530b order:4 compound_mapcount:0 compound_pincount:0
[ 1785.452408] memcg:ff4247f2d28e9000
[ 1785.456304] aops:xfs_address_space_operations ino:8555182 dentry name:"baseos-filenames.solvx"
[ 1785.466612] flags: 0x1000000000012036(referenced|uptodate|lru|active|private|head|node=0|zone=2)
[ 1785.476514] raw: 1000000000012036 ffb9460f8bc07c08 ffb9460f8bc08408 ff4247f22e6299f8
[ 1785.485268] raw: 0000000000000a10 ff4247f194ade900 00000012ffffffff ff4247f2d28e9000
It was like the error was injected to a large folio for xfs with private
data attached.
With private data released before splitting the THP, the test case could
be run successfully many times without rebooting the system.
Link: https://lkml.kernel.org/r/20220810064907.582899-1-fengwei.yin@intel.com
Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When the pgtable is NULL in the set_huge_zero_page(), we should not
increment the count of PTE page table pages by calling mm_inc_nr_ptes().
Otherwise we may receive the following warning when the mm exits:
BUG: non-zero pgtables_bytes on freeing mm
Now we can't observe the above warning since only
do_huge_pmd_anonymous_page() invokes set_huge_zero_page() and the pgtable
can not be NULL.
Therefore, instead of moving mm_inc_nr_ptes() to the non-NULL branch of
pgtable, it is better to remove the redundant pgtable check directly.
Link: https://lkml.kernel.org/r/20220818082748.40021-1-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Open-code the page_handle_poison() into soft_offline_page() and kill
unneeded soft_offline_free_page().
Link: https://lkml.kernel.org/r/20220819033402.156519-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We can choose to copy three contiguous tail pages' content to the first
three pages instead of copying one by one to simplify the code and reduce
code size from 229 bytes to 63 bytes. The BUILD_BUG_ON() aims to avoid
out-of-bounds accesses.
Link: https://lkml.kernel.org/r/20220819035532.6189-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
