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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Borislav Petkov:
- Allow the compiler to optimize away unused percpu accesses and change
the local_lock_* macros back to inline functions
- A couple of fixes to static call insn patching
* tag 'locking_urgent_for_v5.18_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Revert "mm/page_alloc: mark pagesets as __maybe_unused"
Revert "locking/local_lock: Make the empty local_lock_*() function a macro."
x86/percpu: Remove volatile from arch_raw_cpu_ptr().
static_call: Remove __DEFINE_STATIC_CALL macro
static_call: Properly initialise DEFINE_STATIC_CALL_RET0()
static_call: Don't make __static_call_return0 static
x86,static_call: Fix __static_call_return0 for i386
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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.
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Commit 405cc51fc104 ("mm/list_lru: optimize memcg_reparent_list_lru_node()")
has subtle races which are proving ugly to fix. Revert the original
optimization. If quantitative testing indicates that we have a
significant problem here then other implementations can be looked at.
Fixes: 405cc51fc104 ("mm/list_lru: optimize memcg_reparent_list_lru_node()")
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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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: 42288fe366c4 ("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>
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If an mremap() syscall with old_size=0 ends up in move_page_tables(), it
will call invalidate_range_start()/invalidate_range_end() unnecessarily,
i.e. with an empty range.
This causes a WARN in KVM's mmu_notifier. In the past, empty ranges
have been diagnosed to be off-by-one bugs, hence the WARNing. Given the
low (so far) number of unique reports, the benefits of detecting more
buggy callers seem to outweigh the cost of having to fix cases such as
this one, where userspace is doing something silly. In this particular
case, an early return from move_page_tables() is enough to fix the
issue.
Link: https://lkml.kernel.org/r/20220329173155.172439-1-pbonzini@redhat.com
Reported-by: syzbot+6bde52d89cfdf9f61425@syzkaller.appspotmail.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out} check
that even slots in the tsk->kmap_ctrl.pteval are unmapped. The slots are
initialized with 0 value, but the check is done with pte_none. 0 pte
however does not necessarily mean that pte_none will return true. e.g.
on xtensa it returns false, resulting in the following runtime warnings:
WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_out+0x51/0x108
__schedule+0x71a/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
CPU: 0 PID: 101 Comm: touch Tainted: G W 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_in+0x50/0xe0
finish_task_switch$isra$0+0x1ce/0x2f8
__schedule+0x86e/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.
Link: https://lkml.kernel.org/r/20220403235159.3498065-1-jcmvbkbc@gmail.com
Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@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>
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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: d68eccad3706 ("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>
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page_mapped_in_vma() sets nr_pages to 1, which is usually correct as we
only want to know about the precise page and not about other pages in
the folio. However, hugetlbfs does want to know about the entire hpage,
and using nr_pages to get the size of the hpage is wrong. We could
change page_mapped_in_vma() to special-case hugetlbfs pages, but it's
better to ignore nr_pages in page_vma_mapped_walk() and get the size
from the VMA instead.
Fixes: 2aff7a4755bed ("mm: Convert page_vma_mapped_walk to work on PFNs")
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
[edit commit message, use hstate directly]
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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>
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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>
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Unify alloc_misplaced_dst_page() and alloc_misplaced_dst_page_thp().
Removes an assumption that compound pages are HPAGE_PMD_ORDER.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
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This removes an assumption that a large folio is HPAGE_PMD_ORDER
as well as letting us remove the call to prep_transhuge_page()
and a few hidden calls to compound_head().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
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Calling try_to_unmap() with TTU_SPLIT_HUGE_PMD and a folio that's not
mapped by a PMD causes oopses on arm64 because we now call page_folio()
on an invalid page. pmd_page() returns a valid page for non-leaf PMDs on
some architectures, so this bug escaped testing before now. Fix this bug
by delaying the call to pmd_page() until after we know the PMD is a leaf.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215804
Fixes: af28a988b313 ("mm/huge_memory: Convert __split_huge_pmd() to take a folio")
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Zorro Lang <zlang@redhat.com>
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The local_lock() is now using a proper static inline function which is
enough for llvm to accept that the variable is used.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220328145810.86783-4-bigeasy@linutronix.de
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Pull more filesystem folio updates from Matthew Wilcox:
"A mixture of odd changes that didn't quite make it into the original
pull and fixes for things that did. Also the readpages changes had to
wait for the NFS tree to be pulled first.
- Remove ->readpages infrastructure
- Remove AOP_FLAG_CONT_EXPAND
- Move read_descriptor_t to networking code
- Pass the iocb to generic_perform_write
- Minor updates to iomap, btrfs, ext4, f2fs, ntfs"
* tag 'folio-5.18d' of git://git.infradead.org/users/willy/pagecache:
btrfs: Remove a use of PAGE_SIZE in btrfs_invalidate_folio()
ntfs: Correct mark_ntfs_record_dirty() folio conversion
f2fs: Get the superblock from the mapping instead of the page
f2fs: Correct f2fs_dirty_data_folio() conversion
ext4: Correct ext4_journalled_dirty_folio() conversion
filemap: Remove AOP_FLAG_CONT_EXPAND
fs: Pass an iocb to generic_perform_write()
fs, net: Move read_descriptor_t to net.h
fs: Remove read_actor_t
iomap: Simplify is_partially_uptodate a little
readahead: Update comments
mm: remove the skip_page argument to read_pages
mm: remove the pages argument to read_pages
fs: Remove ->readpages address space operation
readahead: Remove read_cache_pages()
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In the DAMON, the minimum wait time of the schemes decides whether the
kernel wakes up 'kdamon_fn()'. But since the minimum wait time is
initialized to zero, there are corner cases against the original
objective.
For example, if we have several schemes for one target, and if the wait
time of the first scheme is zero, the minimum wait time will set zero,
which means 'kdamond_fn()' should wake up to apply this scheme.
However, in the following scheme, wait time can be set to non-zero.
Thus, the mininum wait time will be set to non-zero, which can cause
sleeping this interval for 'kdamon_fn()' due to one deactivated last
scheme.
This commit prevents making DAMON monitoring inactive state due to other
deactivated schemes.
Link: https://lkml.kernel.org/r/20220330105302.32114-1-tome01@ajou.ac.kr
Signed-off-by: Jonghyeon Kim <tome01@ajou.ac.kr>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When we use HW-tag based kasan and enable vmalloc support, we hit the
following bug. It is due to comparison between tagged object and
non-tagged pointer.
We need to reset the kasan tag when we need to compare tagged object and
non-tagged pointer.
kmemleak: [name:kmemleak&]Scan area larger than object 0xffffffe77076f440
CPU: 4 PID: 1 Comm: init Tainted: G S W 5.15.25-android13-0-g5cacf919c2bc #1
Hardware name: MT6983(ENG) (DT)
Call trace:
add_scan_area+0xc4/0x244
kmemleak_scan_area+0x40/0x9c
layout_and_allocate+0x1e8/0x288
load_module+0x2c8/0xf00
__se_sys_finit_module+0x190/0x1d0
__arm64_sys_finit_module+0x20/0x30
invoke_syscall+0x60/0x170
el0_svc_common+0xc8/0x114
do_el0_svc+0x28/0xa0
el0_svc+0x60/0xf8
el0t_64_sync_handler+0x88/0xec
el0t_64_sync+0x1b4/0x1b8
kmemleak: [name:kmemleak&]Object 0xf5ffffe77076b000 (size 32768):
kmemleak: [name:kmemleak&] comm "init", pid 1, jiffies 4294894197
kmemleak: [name:kmemleak&] min_count = 0
kmemleak: [name:kmemleak&] count = 0
kmemleak: [name:kmemleak&] flags = 0x1
kmemleak: [name:kmemleak&] checksum = 0
kmemleak: [name:kmemleak&] backtrace:
module_alloc+0x9c/0x120
move_module+0x34/0x19c
layout_and_allocate+0x1c4/0x288
load_module+0x2c8/0xf00
__se_sys_finit_module+0x190/0x1d0
__arm64_sys_finit_module+0x20/0x30
invoke_syscall+0x60/0x170
el0_svc_common+0xc8/0x114
do_el0_svc+0x28/0xa0
el0_svc+0x60/0xf8
el0t_64_sync_handler+0x88/0xec
el0t_64_sync+0x1b4/0x1b8
Link: https://lkml.kernel.org/r/20220318034051.30687-1-Kuan-Ying.Lee@mediatek.com
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Nicholas Tang <nicholas.tang@mediatek.com>
Cc: Yee Lee <yee.lee@mediatek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In some cases it appears the invalidation of a hwpoisoned page fails
because the page is still mapped in another process. This can cause a
program to be continuously restarted and die when it page faults on the
page that was not invalidated. Avoid that problem by unmapping the
hwpoisoned page when we find it.
Another issue is that sometimes we end up oopsing in finish_fault, if
the code tries to do something with the now-NULL vmf->page. I did not
hit this error when submitting the previous patch because there are
several opportunities for alloc_set_pte to bail out before accessing
vmf->page, and that apparently happened on those systems, and most of
the time on other systems, too.
However, across several million systems that error does occur a handful
of times a day. It can be avoided by returning VM_FAULT_NOPAGE which
will cause do_read_fault to return before calling finish_fault.
Link: https://lkml.kernel.org/r/20220325161428.5068d97e@imladris.surriel.com
Fixes: e53ac7374e64 ("mm: invalidate hwpoison page cache page in fault path")
Signed-off-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Tested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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If the kfence object is allocated to be used for objects vector, then
this slot of the pool eventually being occupied permanently since the
vector is never freed. The solutions could be (1) freeing vector when
the kfence object is freed or (2) allocating all vectors statically.
Since the memory consumption of object vectors is low, it is better to
chose (2) to fix the issue and it is also can reduce overhead of vectors
allocating in the future.
Link: https://lkml.kernel.org/r/20220328132843.16624-1-songmuchun@bytedance.com
Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The access to mlock_pvec is protected by disabling preemption via
get_cpu_var() or implicit by having preemption disabled by the caller
(in mlock_page_drain() case). This breaks on PREEMPT_RT since
folio_lruvec_lock_irq() acquires a sleeping lock in this section.
Create struct mlock_pvec which consits of the local_lock_t and the
pagevec. Acquire the local_lock() before accessing the per-CPU pagevec.
Replace mlock_page_drain() with a _local() version which is invoked on
the local CPU and acquires the local_lock_t and a _remote() version
which uses the pagevec from a remote CPU which offline.
Link: https://lkml.kernel.org/r/YjizWi9IY0mpvIfb@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Mike reports that LTP memcg_stat_test usually leads to
memcg_stat_test 3 TINFO: Test unevictable with MAP_LOCKED
memcg_stat_test 3 TINFO: Running memcg_process --mmap-lock1 -s 135168
memcg_stat_test 3 TINFO: Warming up pid: 3460
memcg_stat_test 3 TINFO: Process is still here after warm up: 3460
memcg_stat_test 3 TFAIL: unevictable is 122880, 135168 expected
but may also lead to
memcg_stat_test 4 TINFO: Test unevictable with mlock
memcg_stat_test 4 TINFO: Running memcg_process --mmap-lock2 -s 135168
memcg_stat_test 4 TINFO: Warming up pid: 4271
memcg_stat_test 4 TINFO: Process is still here after warm up: 4271
memcg_stat_test 4 TFAIL: unevictable is 122880, 135168 expected
or both. A wee bit flaky.
follow_page_pte() used to have an lru_add_drain() per each page mlocked,
and the test came to rely on accurate stats. The pagevec to be drained
is different now, but still covered by lru_add_drain(); and, never mind
the test, I believe it's in everyone's interest that a bulk faulting
interface like populate_vma_page_range() or faultin_vma_page_range()
should drain its local pagevecs at the end, to save others sometimes
needing the much more expensive lru_add_drain_all().
This does not absolutely guarantee exact stats - the mlocking task can
be migrated between CPUs as it proceeds - but it's good enough and the
tests pass.
Link: https://lkml.kernel.org/r/47f6d39c-a075-50cb-1cfb-26dd957a48af@google.com
Fixes: b67bf49ce7aa ("mm/munlock: delete FOLL_MLOCK and FOLL_POPULATE")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Mike Galbraith <efault@gmx.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This reverts commit 08095d6310a7 ("mm: madvise: skip unmapped vma holes
passed to process_madvise") as process_madvise() fails to return the
exact processed bytes in other cases too.
As an example: if process_madvise() hits mlocked pages after processing
some initial bytes passed in [start, end), it just returns EINVAL
although some bytes are processed. Thus making an exception only for
ENOMEM is partially fixing the problem of returning the proper advised
bytes.
Thus revert this patch and return proper bytes advised.
Link: https://lkml.kernel.org/r/e73da1304a88b6a8a11907045117cccf4c2b8374.1648046642.git.quic_charante@quicinc.com
Fixes: 08095d6310a7ce ("mm: madvise: skip unmapped vma holes passed to process_madvise")
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We can extract both the file pointer and the pos from the iocb.
This simplifies each caller as well as allowing generic_perform_write()
to see more of the iocb contents in the future.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
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- Refer to folios where appropriate, not pages (Matthew Wilcox)
- Eliminate references to the internal PG_readhead
- Use "readahead" consistently - not "read-ahead" or "read ahead"
(mostly Neil Brown)
- Clarify some sections that, on reflection, weren't very clear (Neil
Brown)
- Minor punctuation/spelling fixes (Neil Brown)
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
|
|
The skip_page argument to read_pages controls if rac->_index is
incremented before returning from the function. Just open code that in
the callers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
|
|
This is always an empty list or NULL with the removal of the ->readahead
support, so remove it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
|
|
All filesystems have now been converted to use ->readahead, so
remove the ->readpages operation and fix all the comments that
used to refer to it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
With no remaining users, remove this function and the related
infrastructure.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Pull virtio updates from Michael Tsirkin:
- vdpa generic device type support
- more virtio hardening for broken devices (but on the same theme,
revert some virtio hotplug hardening patches - they were misusing
some interrupt flags and had to be reverted)
- RSS support in virtio-net
- max device MTU support in mlx5 vdpa
- akcipher support in virtio-crypto
- shared IRQ support in ifcvf vdpa
- a minor performance improvement in vhost
- enable virtio mem for ARM64
- beginnings of advance dma support
- cleanups, fixes all over the place
* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (33 commits)
vdpa/mlx5: Avoid processing works if workqueue was destroyed
vhost: handle error while adding split ranges to iotlb
vdpa: support exposing the count of vqs to userspace
vdpa: change the type of nvqs to u32
vdpa: support exposing the config size to userspace
vdpa/mlx5: re-create forwarding rules after mac modified
virtio: pci: check bar values read from virtio config space
Revert "virtio_pci: harden MSI-X interrupts"
Revert "virtio-pci: harden INTX interrupts"
drivers/net/virtio_net: Added RSS hash report control.
drivers/net/virtio_net: Added RSS hash report.
drivers/net/virtio_net: Added basic RSS support.
drivers/net/virtio_net: Fixed padded vheader to use v1 with hash.
virtio: use virtio_device_ready() in virtio_device_restore()
tools/virtio: compile with -pthread
tools/virtio: fix after premapped buf support
virtio_ring: remove flags check for unmap packed indirect desc
virtio_ring: remove flags check for unmap split indirect desc
virtio_ring: rename vring_unmap_state_packed() to vring_unmap_extra_packed()
net/mlx5: Add support for configuring max device MTU
...
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Whenever a buddy page is found, page_is_buddy() should be called to
check its validity. Add the missing check during pageblock merge check.
Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable pageblocks with others")
Link: https://lore.kernel.org/all/20220330154208.71aca532@gandalf.local.home/
Reported-and-tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ptrace cleanups from Eric Biederman:
"This set of changes removes tracehook.h, moves modification of all of
the ptrace fields inside of siglock to remove races, adds a missing
permission check to ptrace.c
The removal of tracehook.h is quite significant as it has been a major
source of confusion in recent years. Much of that confusion was around
task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
semantics clearer).
For people who don't know tracehook.h is a vestiage of an attempt to
implement uprobes like functionality that was never fully merged, and
was later superseeded by uprobes when uprobes was merged. For many
years now we have been removing what tracehook functionaly a little
bit at a time. To the point where anything left in tracehook.h was
some weird strange thing that was difficult to understand"
* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
ptrace: Remove duplicated include in ptrace.c
ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
ptrace: Return the signal to continue with from ptrace_stop
ptrace: Move setting/clearing ptrace_message into ptrace_stop
tracehook: Remove tracehook.h
resume_user_mode: Move to resume_user_mode.h
resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
task_work: Call tracehook_notify_signal from get_signal on all architectures
task_work: Introduce task_work_pending
task_work: Remove unnecessary include from posix_timers.h
ptrace: Remove tracehook_signal_handler
ptrace: Remove arch_syscall_{enter,exit}_tracehook
ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
ptrace/arm: Rename tracehook_report_syscall report_syscall
ptrace: Move ptrace_report_syscall into ptrace.h
|
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git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull shm ucounts fix from Eric Biederman:
"The introduction of a new failure mode when the code was converted to
ucounts resulted in user_shm_lock misbehaving.
The change simplifies the code to make the code easier to follow and
removes the known misbehaviors"
* tag 'ucount-rlimit-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
mm/mlock: fix two bugs in user_shm_lock()
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Since commit b1123ea6d3b3 ("mm: balloon: use general non-lru movable page
feature"), these functions are called via balloon_aops callbacks. They're
not called directly outside this file. So make them static and clean up
the relevant code.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Link: https://lore.kernel.org/r/20220125132221.2220-1-linmiaohe@huawei.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
|
|
The objcg is not cleared and put for kfence object when it is freed,
which could lead to memory leak for struct obj_cgroup and wrong
statistics of NR_SLAB_RECLAIMABLE_B or NR_SLAB_UNRECLAIMABLE_B.
Since the last freed object's objcg is not cleared,
mem_cgroup_from_obj() could return the wrong memcg when this kfence
object, which is not charged to any objcgs, is reallocated to other
users.
A real word issue [1] is caused by this bug.
Link: https://lore.kernel.org/all/000000000000cabcb505dae9e577@google.com/ [1]
Reported-by: syzbot+f8c45ccc7d5d45fc5965@syzkaller.appspotmail.com
Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock
Pull memblock updates from Mike Rapoport:
"Test suite and a small cleanup:
- A small cleanup of unused variable in __next_mem_pfn_range_in_zone
- Initial test suite to simulate memblock behaviour in userspace"
* tag 'memblock-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock: (27 commits)
memblock tests: Add TODO and README files
memblock tests: Add memblock_alloc_try_nid tests for bottom up
memblock tests: Add memblock_alloc_try_nid tests for top down
memblock tests: Add memblock_alloc_from tests for bottom up
memblock tests: Add memblock_alloc_from tests for top down
memblock tests: Add memblock_alloc tests for bottom up
memblock tests: Add memblock_alloc tests for top down
memblock tests: Add simulation of physical memory
memblock tests: Split up reset_memblock function
memblock tests: Fix testing with 32-bit physical addresses
memblock: __next_mem_pfn_range_in_zone: remove unneeded local variable nid
memblock tests: Add memblock_free tests
memblock tests: Add memblock_add_node test
memblock tests: Add memblock_remove tests
memblock tests: Add memblock_reserve tests
memblock tests: Add memblock_add tests
memblock tests: Add memblock reset function
memblock tests: Add skeleton of the memblock simulator
tools/include: Add debugfs.h stub
tools/include: Add pfn.h stub
...
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2
Pull iomap fixlet from Andreas Gruenbacher:
"Fix buffered write page prefaulting.
I forgot to send it the previous merge window. I've only improved the
patch description since"
* tag 'write-page-prefaulting' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
fs/iomap: Fix buffered write page prefaulting
|
|
When part of the user buffer passed to generic_perform_write() or
iomap_file_buffered_write() cannot be faulted in for reading, the entire
write currently fails. The correct behavior would be to write all the
data that can be written, up to the point of failure.
Commit a6294593e8a1 ("iov_iter: Turn iov_iter_fault_in_readable into
fault_in_iov_iter_readable") gave us the information needed, so fix the
page prefaulting in generic_perform_write() and iomap_write_iter() to
only bail out when no pages could be faulted in.
We already factor in that pages that are faulted in may no longer be
resident by the time they are accessed. Paging out pages has the same
effect as not faulting in those pages in the first place, so the code
can already deal with that.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
|
|
MADV_DONTNEED historically rejects mlocked ranges, but with MLOCK_ONFAULT
and MCL_ONFAULT allowing to mlock without populating, there are valid use
cases for depopulating locked ranges as well.
Users mlock memory to protect secrets. There are allocators for secure
buffers that want in-use memory generally mlocked, but cleared and
invalidated memory to give up the physical pages. This could be done with
explicit munlock -> mlock calls on free -> alloc of course, but that adds
two unnecessary syscalls, heavy mmap_sem write locks, vma splits and
re-merges - only to get rid of the backing pages.
Users also mlockall(MCL_ONFAULT) to suppress sustained paging, but are
okay with on-demand initial population. It seems valid to selectively
free some memory during the lifetime of such a process, without having to
mess with its overall policy.
Why add a separate flag? Isn't this a pretty niche usecase?
- MADV_DONTNEED has been bailing on locked vmas forever. It's at least
conceivable that someone, somewhere is relying on mlock to protect
data from perhaps broader invalidation calls. Changing this behavior
now could lead to quiet data corruption.
- It also clarifies expectations around MADV_FREE and maybe
MADV_REMOVE. It avoids the situation where one quietly behaves
different than the others. MADV_FREE_LOCKED can be added later.
- The combination of mlock() and madvise() in the first place is
probably niche. But where it happens, I'd say that dropping pages
from a locked region once they don't contain secrets or won't page
anymore is much saner than relying on mlock to protect memory from
speculative or errant invalidation calls. It's just that we can't
change the default behavior because of the two previous points.
Given that, an explicit new flag seems to make the most sense.
[hannes@cmpxchg.org: fix mips build]
Link: https://lkml.kernel.org/r/20220304171912.305060-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Problem:
=======
Userspace might read the zero-page instead of actual data from a direct IO
read on a block device if the buffers have been called madvise(MADV_FREE)
on earlier (this is discussed below) due to a race between page reclaim on
MADV_FREE and blkdev direct IO read.
- Race condition:
==============
During page reclaim, the MADV_FREE page check in try_to_unmap_one() checks
if the page is not dirty, then discards its rmap PTE(s) (vs. remap back
if the page is dirty).
However, after try_to_unmap_one() returns to shrink_page_list(), it might
keep the page _anyway_ if page_ref_freeze() fails (it expects exactly
_one_ page reference, from the isolation for page reclaim).
Well, blkdev_direct_IO() gets references for all pages, and on READ
operations it only sets them dirty _later_.
So, if MADV_FREE'd pages (i.e., not dirty) are used as buffers for direct
IO read from block devices, and page reclaim happens during
__blkdev_direct_IO[_simple]() exactly AFTER bio_iov_iter_get_pages()
returns, but BEFORE the pages are set dirty, the situation happens.
The direct IO read eventually completes. Now, when userspace reads the
buffers, the PTE is no longer there and the page fault handler
do_anonymous_page() services that with the zero-page, NOT the data!
A synthetic reproducer is provided.
- Page faults:
===========
If page reclaim happens BEFORE bio_iov_iter_get_pages() the issue doesn't
happen, because that faults-in all pages as writeable, so
do_anonymous_page() sets up a new page/rmap/PTE, and that is used by
direct IO. The userspace reads don't fault as the PTE is there (thus
zero-page is not used/setup).
But if page reclaim happens AFTER it / BEFORE setting pages dirty, the PTE
is no longer there; the subsequent page faults can't help:
The data-read from the block device probably won't generate faults due to
DMA (no MMU) but even in the case it wouldn't use DMA, that happens on
different virtual addresses (not user-mapped addresses) because `struct
bio_vec` stores `struct page` to figure addresses out (which are different
from user-mapped addresses) for the read.
Thus userspace reads (to user-mapped addresses) still fault, then
do_anonymous_page() gets another `struct page` that would address/ map to
other memory than the `struct page` used by `struct bio_vec` for the read.
(The original `struct page` is not available, since it wasn't freed, as
page_ref_freeze() failed due to more page refs. And even if it were
available, its data cannot be trusted anymore.)
Solution:
========
One solution is to check for the expected page reference count in
try_to_unmap_one().
There should be one reference from the isolation (that is also checked in
shrink_page_list() with page_ref_freeze()) plus one or more references
from page mapping(s) (put in discard: label). Further references mean
that rmap/PTE cannot be unmapped/nuked.
(Note: there might be more than one reference from mapping due to
fork()/clone() without CLONE_VM, which use the same `struct page` for
references, until the copy-on-write page gets copied.)
So, additional page references (e.g., from direct IO read) now prevent the
rmap/PTE from being unmapped/dropped; similarly to the page is not freed
per shrink_page_list()/page_ref_freeze()).
- Races and Barriers:
==================
The new check in try_to_unmap_one() should be safe in races with
bio_iov_iter_get_pages() in get_user_pages() fast and slow paths, as it's
done under the PTE lock.
The fast path doesn't take the lock, but it checks if the PTE has changed
and if so, it drops the reference and leaves the page for the slow path
(which does take that lock).
The fast path requires synchronization w/ full memory barrier: it writes
the page reference count first then it reads the PTE later, while
try_to_unmap() writes PTE first then it reads page refcount.
And a second barrier is needed, as the page dirty flag should not be read
before the page reference count (as in __remove_mapping()). (This can be
a load memory barrier only; no writes are involved.)
Call stack/comments:
- try_to_unmap_one()
- page_vma_mapped_walk()
- map_pte() # see pte_offset_map_lock():
pte_offset_map()
spin_lock()
- ptep_get_and_clear() # write PTE
- smp_mb() # (new barrier) GUP fast path
- page_ref_count() # (new check) read refcount
- page_vma_mapped_walk_done() # see pte_unmap_unlock():
pte_unmap()
spin_unlock()
- bio_iov_iter_get_pages()
- __bio_iov_iter_get_pages()
- iov_iter_get_pages()
- get_user_pages_fast()
- internal_get_user_pages_fast()
# fast path
- lockless_pages_from_mm()
- gup_{pgd,p4d,pud,pmd,pte}_range()
ptep = pte_offset_map() # not _lock()
pte = ptep_get_lockless(ptep)
page = pte_page(pte)
try_grab_compound_head(page) # inc refcount
# (RMW/barrier
# on success)
if (pte_val(pte) != pte_val(*ptep)) # read PTE
put_compound_head(page) # dec refcount
# go slow path
# slow path
- __gup_longterm_unlocked()
- get_user_pages_unlocked()
- __get_user_pages_locked()
- __get_user_pages()
- follow_{page,p4d,pud,pmd}_mask()
- follow_page_pte()
ptep = pte_offset_map_lock()
pte = *ptep
page = vm_normal_page(pte)
try_grab_page(page) # inc refcount
pte_unmap_unlock()
- Huge Pages:
==========
Regarding transparent hugepages, that logic shouldn't change, as MADV_FREE
(aka lazyfree) pages are PageAnon() && !PageSwapBacked()
(madvise_free_pte_range() -> mark_page_lazyfree() -> lru_lazyfree_fn())
thus should reach shrink_page_list() -> split_huge_page_to_list() before
try_to_unmap[_one](), so it deals with normal pages only.
(And in case unlikely/TTU_SPLIT_HUGE_PMD/split_huge_pmd_address() happens,
which should not or be rare, the page refcount should be greater than
mapcount: the head page is referenced by tail pages. That also prevents
checking the head `page` then incorrectly call page_remove_rmap(subpage)
for a tail page, that isn't even in the shrink_page_list()'s page_list (an
effect of split huge pmd/pmvw), as it might happen today in this unlikely
scenario.)
MADV_FREE'd buffers:
===================
So, back to the "if MADV_FREE pages are used as buffers" note. The case
is arguable, and subject to multiple interpretations.
The madvise(2) manual page on the MADV_FREE advice value says:
1) 'After a successful MADV_FREE ... data will be lost when
the kernel frees the pages.'
2) 'the free operation will be canceled if the caller writes
into the page' / 'subsequent writes ... will succeed and
then [the] kernel cannot free those dirtied pages'
3) 'If there is no subsequent write, the kernel can free the
pages at any time.'
Thoughts, questions, considerations... respectively:
1) Since the kernel didn't actually free the page (page_ref_freeze()
failed), should the data not have been lost? (on userspace read.)
2) Should writes performed by the direct IO read be able to cancel
the free operation?
- Should the direct IO read be considered as 'the caller' too,
as it's been requested by 'the caller'?
- Should the bio technique to dirty pages on return to userspace
(bio_check_pages_dirty() is called/used by __blkdev_direct_IO())
be considered in another/special way here?
3) Should an upcoming write from a previously requested direct IO
read be considered as a subsequent write, so the kernel should
not free the pages? (as it's known at the time of page reclaim.)
And lastly:
Technically, the last point would seem a reasonable consideration and
balance, as the madvise(2) manual page apparently (and fairly) seem to
assume that 'writes' are memory access from the userspace process (not
explicitly considering writes from the kernel or its corner cases; again,
fairly).. plus the kernel fix implementation for the corner case of the
largely 'non-atomic write' encompassed by a direct IO read operation, is
relatively simple; and it helps.
Reproducer:
==========
@ test.c (simplified, but works)
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
int main() {
int fd, i;
char *buf;
fd = open(DEV, O_RDONLY | O_DIRECT);
buf = mmap(NULL, BUF_SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
for (i = 0; i < BUF_SIZE; i += PAGE_SIZE)
buf[i] = 1; // init to non-zero
madvise(buf, BUF_SIZE, MADV_FREE);
read(fd, buf, BUF_SIZE);
for (i = 0; i < BUF_SIZE; i += PAGE_SIZE)
printf("%p: 0x%x\n", &buf[i], buf[i]);
return 0;
}
@ block/fops.c (formerly fs/block_dev.c)
+#include <linux/swap.h>
...
... __blkdev_direct_IO[_simple](...)
{
...
+ if (!strcmp(current->comm, "good"))
+ shrink_all_memory(ULONG_MAX);
+
ret = bio_iov_iter_get_pages(...);
+
+ if (!strcmp(current->comm, "bad"))
+ shrink_all_memory(ULONG_MAX);
...
}
@ shell
# NUM_PAGES=4
# PAGE_SIZE=$(getconf PAGE_SIZE)
# yes | dd of=test.img bs=${PAGE_SIZE} count=${NUM_PAGES}
# DEV=$(losetup -f --show test.img)
# gcc -DDEV=\"$DEV\" \
-DBUF_SIZE=$((PAGE_SIZE * NUM_PAGES)) \
-DPAGE_SIZE=${PAGE_SIZE} \
test.c -o test
# od -tx1 $DEV
0000000 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a
*
0040000
# mv test good
# ./good
0x7f7c10418000: 0x79
0x7f7c10419000: 0x79
0x7f7c1041a000: 0x79
0x7f7c1041b000: 0x79
# mv good bad
# ./bad
0x7fa1b8050000: 0x0
0x7fa1b8051000: 0x0
0x7fa1b8052000: 0x0
0x7fa1b8053000: 0x0
Note: the issue is consistent on v5.17-rc3, but it's intermittent with the
support of MADV_FREE on v4.5 (60%-70% error; needs swap). [wrap
do_direct_IO() in do_blockdev_direct_IO() @ fs/direct-io.c].
- v5.17-rc3:
# for i in {1..1000}; do ./good; done \
| cut -d: -f2 | sort | uniq -c
4000 0x79
# mv good bad
# for i in {1..1000}; do ./bad; done \
| cut -d: -f2 | sort | uniq -c
4000 0x0
# free | grep Swap
Swap: 0 0 0
- v4.5:
# for i in {1..1000}; do ./good; done \
| cut -d: -f2 | sort | uniq -c
4000 0x79
# mv good bad
# for i in {1..1000}; do ./bad; done \
| cut -d: -f2 | sort | uniq -c
2702 0x0
1298 0x79
# swapoff -av
swapoff /swap
# for i in {1..1000}; do ./bad; done \
| cut -d: -f2 | sort | uniq -c
4000 0x79
Ceph/TCMalloc:
=============
For documentation purposes, the use case driving the analysis/fix is Ceph
on Ubuntu 18.04, as the TCMalloc library there still uses MADV_FREE to
release unused memory to the system from the mmap'ed page heap (might be
committed back/used again; it's not munmap'ed.) - PageHeap::DecommitSpan()
-> TCMalloc_SystemRelease() -> madvise() - PageHeap::CommitSpan() ->
TCMalloc_SystemCommit() -> do nothing.
Note: TCMalloc switched back to MADV_DONTNEED a few commits after the
release in Ubuntu 18.04 (google-perftools/gperftools 2.5), so the issue
just 'disappeared' on Ceph on later Ubuntu releases but is still present
in the kernel, and can be hit by other use cases.
The observed issue seems to be the old Ceph bug #22464 [1], where checksum
mismatches are observed (and instrumentation with buffer dumps shows
zero-pages read from mmap'ed/MADV_FREE'd page ranges).
The issue in Ceph was reasonably deemed a kernel bug (comment #50) and
mostly worked around with a retry mechanism, but other parts of Ceph could
still hit that (rocksdb). Anyway, it's less likely to be hit again as
TCMalloc switched out of MADV_FREE by default.
(Some kernel versions/reports from the Ceph bug, and relation with
the MADV_FREE introduction/changes; TCMalloc versions not checked.)
- 4.4 good
- 4.5 (madv_free: introduction)
- 4.9 bad
- 4.10 good? maybe a swapless system
- 4.12 (madv_free: no longer free instantly on swapless systems)
- 4.13 bad
[1] https://tracker.ceph.com/issues/22464
Thanks:
======
Several people contributed to analysis/discussions/tests/reproducers in
the first stages when drilling down on ceph/tcmalloc/linux kernel:
- Dan Hill
- Dan Streetman
- Dongdong Tao
- Gavin Guo
- Gerald Yang
- Heitor Alves de Siqueira
- Ioanna Alifieraki
- Jay Vosburgh
- Matthew Ruffell
- Ponnuvel Palaniyappan
Reviews, suggestions, corrections, comments:
- Minchan Kim
- Yu Zhao
- Huang, Ying
- John Hubbard
- Christoph Hellwig
[mfo@canonical.com: v4]
Link: https://lkml.kernel.org/r/20220209202659.183418-1-mfo@canonical.comLink: https://lkml.kernel.org/r/20220131230255.789059-1-mfo@canonical.com
Fixes: 802a3a92ad7a ("mm: reclaim MADV_FREE pages")
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Dan Hill <daniel.hill@canonical.com>
Cc: Dan Streetman <dan.streetman@canonical.com>
Cc: Dongdong Tao <dongdong.tao@canonical.com>
Cc: Gavin Guo <gavin.guo@canonical.com>
Cc: Gerald Yang <gerald.yang@canonical.com>
Cc: Heitor Alves de Siqueira <halves@canonical.com>
Cc: Ioanna Alifieraki <ioanna-maria.alifieraki@canonical.com>
Cc: Jay Vosburgh <jay.vosburgh@canonical.com>
Cc: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: Ponnuvel Palaniyappan <ponnuvel.palaniyappan@canonical.com>
Cc: <stable@vger.kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
ARCH_HAS_FILTER_PGPROT config has duplicate definitions on platforms that
subscribe it. Instead make it a generic config option which can be
selected on applicable platforms when required.
Link: https://lkml.kernel.org/r/1643004823-16441-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Revert 48ec833b7851 ("Revert "mm/memory.c: share the i_mmap_rwsem"") to
reinstate c8475d144abb ("mm/memory.c: share the i_mmap_rwsem"): the
unmap_mapping_range family of functions do the unmapping of user pages
(ultimately via zap_page_range_single) without modifying the interval tree
itself, and unmapping races are necessarily guarded by page table lock,
thus the i_mmap_rwsem should be shared in unmap_mapping_pages() and
unmap_mapping_folio().
Commit 48ec833b7851 was intended as a short-term measure, allowing the
other shared lock changes into 3.19 final, before investigating three
trinity crashes, one of which had been bisected to commit c8475d144ab:
[1] https://lkml.org/lkml/2014/11/14/342
https://lore.kernel.org/lkml/5466142C.60100@oracle.com/
[2] https://lkml.org/lkml/2014/12/22/213
https://lore.kernel.org/lkml/549832E2.8060609@oracle.com/
[3] https://lkml.org/lkml/2014/12/9/741
https://lore.kernel.org/lkml/5487ACC5.1010002@oracle.com/
Two of those were Bad page states: free_pages_prepare() found PG_mlocked
still set - almost certain to have been fixed by 4.4 commit b87537d9e2fe
("mm: rmap use pte lock not mmap_sem to set PageMlocked"). The NULL deref
on rwsem in [2]: unclear, only happened once, not bisected to c8475d144ab.
No change to the i_mmap_lock_write() around __unmap_hugepage_range_final()
in unmap_single_vma(): IIRC that's a special usage, helping to serialize
hugetlbfs page table sharing, not to be dabbled with lightly. No change
to other uses of i_mmap_lock_write() by hugetlbfs.
I am not aware of any significant gains from the concurrency allowed by
this commit: it is submitted more to resolve an ancient misunderstanding.
Link: https://lkml.kernel.org/r/e4a5e356-6c87-47b2-3ce8-c2a95ae84e20@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
filemap_unaccount_folio() has a WARN_ON_ONCE(folio_test_dirty(folio)). It
is good to warn of late dirtying on a persistent filesystem, but late
dirtying on tmpfs can only lose data which is expected to be thrown away;
and it's a pity if that warning comes ONCE on tmpfs, then hides others
which really matter. Make it conditional on mapping_cap_writeback().
Cleanup: then folio_account_cleaned() no longer needs to check that for
itself, and so no longer needs to know the mapping.
Link: https://lkml.kernel.org/r/b5a1106c-7226-a5c6-ad41-ad4832cae1f@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Let's remove the stale logic that was required for reuse_swap_page().
[akpm@linux-foundation.org: simplification, per Yang Shi]
Link: https://lkml.kernel.org/r/20220131162940.210846-10-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
All users are gone, let's remove it.
Link: https://lkml.kernel.org/r/20220131162940.210846-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
All users are gone, let's remove it. We'll let SWP_STABLE_WRITES stick
around for now, as it might come in handy in the near future.
Link: https://lkml.kernel.org/r/20220131162940.210846-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
reuse_swap_page() currently indicates if we can write to an anon page
without COW. A COW is required if the page is shared by multiple
processes (either already mapped or via swap entries) or if there is
concurrent writeback that cannot tolerate concurrent page modifications.
However, in the context of khugepaged we're not actually going to write to
a read-only mapped page, we'll copy the page content to our newly
allocated THP and map that THP writable. All we have to make sure is that
the read-only mapped page we're about to copy won't get reused by another
process sharing the page, otherwise, page content would get modified. But
that is already guaranteed via multiple mechanisms (e.g., holding a
reference, holding the page lock, removing the rmap after copying the
page).
The swapcache handling was introduced in commit 10359213d05a ("mm:
incorporate read-only pages into transparent huge pages") and it sounds
like it merely wanted to mimic what do_swap_page() would do when trying to
map a page obtained via the swapcache writable.
As that logic is unnecessary, let's just remove it, removing the last user
of reuse_swap_page().
Link: https://lkml.kernel.org/r/20220131162940.210846-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
We currently have a different COW logic for anon THP than we have for
ordinary anon pages in do_wp_page(): the effect is that the issue reported
in CVE-2020-29374 is currently still possible for anon THP: an unintended
information leak from the parent to the child.
Let's apply the same logic (page_count() == 1), with similar optimizations
to remove additional references first as we really want to avoid
PTE-mapping the THP and copying individual pages best we can.
If we end up with a page that has page_count() != 1, we'll have to PTE-map
the THP and fallback to do_wp_page(), which will always copy the page.
Note that KSM does not apply to THP.
I. Interaction with the swapcache and writeback
While a THP is in the swapcache, the swapcache holds one reference on each
subpage of the THP. So with PageSwapCache() set, we expect as many
additional references as we have subpages. If we manage to remove the THP
from the swapcache, all these references will be gone.
Usually, a THP is not split when entered into the swapcache and stays a
compound page. However, try_to_unmap() will PTE-map the THP and use PTE
swap entries. There are no PMD swap entries for that purpose,
consequently, we always only swapin subpages into PTEs.
Removing a page from the swapcache can fail either when there are
remaining swap entries (in which case COW is the right thing to do) or if
the page is currently under writeback.
Having a locked, R/O PMD-mapped THP that is in the swapcache seems to be
possible only in corner cases, for example, if try_to_unmap() failed after
adding the page to the swapcache. However, it's comparatively easy to
handle.
As we have to fully unmap a THP before starting writeback, and swapin is
always done on the PTE level, we shouldn't find a R/O PMD-mapped THP in
the swapcache that is under writeback. This should at least leave
writeback out of the picture.
II. Interaction with GUP references
Having a R/O PMD-mapped THP with GUP references (i.e., R/O references)
will result in PTE-mapping the THP on a write fault. Similar to ordinary
anon pages, do_wp_page() will have to copy sub-pages and result in a
disconnect between the GUP references and the pages actually mapped into
the page tables. To improve the situation in the future, we'll need
additional handling to mark anonymous pages as definitely exclusive to a
single process, only allow GUP pins on exclusive anon pages, and disallow
sharing of exclusive anon pages with GUP pins e.g., during fork().
III. Interaction with references from LRU pagevecs
There is no need to try draining the (local) LRU pagevecs in case we would
stumble over a !PageLRU() page: folio_add_lru() and friends will always
flush the affected pagevec after adding a compound page to it immediately
-- pagevec_add_and_need_flush() always returns "true" for them. Note that
the LRU pagevecs will hold a reference on the compound page for a very
short time, between adding the page to the pagevec and draining it
immediately afterwards.
IV. Interaction with speculative/temporary references
Similar to ordinary anon pages, other speculative/temporary references on
the THP, for example, from the pagecache or page migration code, will
disallow exclusive reuse of the page. We'll have to PTE-map the THP.
Link: https://lkml.kernel.org/r/20220131162940.210846-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Currently we have a different COW logic when:
* triggering a read-fault to swapin first and then trigger a write-fault
-> do_swap_page() + do_wp_page()
* triggering a write-fault to swapin
-> do_swap_page() + do_wp_page() only if we fail reuse in do_swap_page()
The COW logic in do_swap_page() is different than our reuse logic in
do_wp_page(). The COW logic in do_wp_page() -- page_count() == 1 -- makes
currently sure that we certainly don't have a remaining reference, e.g.,
via GUP, on the target page we want to reuse: if there is any unexpected
reference, we have to copy to avoid information leaks.
As do_swap_page() behaves differently, in environments with swap enabled
we can currently have an unintended information leak from the parent to
the child, similar as known from CVE-2020-29374:
1. Parent writes to anonymous page
-> Page is mapped writable and modified
2. Page is swapped out
-> Page is unmapped and replaced by swap entry
3. fork()
-> Swap entries are copied to child
4. Child pins page R/O
-> Page is mapped R/O into child
5. Child unmaps page
-> Child still holds GUP reference
6. Parent writes to page
-> Page is reused in do_swap_page()
-> Child can observe changes
Exchanging 2. and 3. should have the same effect.
Let's apply the same COW logic as in do_wp_page(), conditionally trying to
remove the page from the swapcache after freeing the swap entry, however,
before actually mapping our page. We can change the order now that we use
try_to_free_swap(), which doesn't care about the mapcount, instead of
reuse_swap_page().
To handle references from the LRU pagevecs, conditionally drain the local
LRU pagevecs when required, however, don't consider the page_count() when
deciding whether to drain to keep it simple for now.
Link: https://lkml.kernel.org/r/20220131162940.210846-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Let's make it clearer that KSM might only have to copy a page in case we
have a page in the swapcache, not if we allocated a fresh page and
bypassed the swapcache. While at it, add a comment why this is usually
necessary and merge the two swapcache conditions.
[akpm@linux-foundation.org: fix comment, per David]
Link: https://lkml.kernel.org/r/20220131162940.210846-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
For example, if a page just got swapped in via a read fault, the LRU
pagevecs might still hold a reference to the page. If we trigger a write
fault on such a page, the additional reference from the LRU pagevecs will
prohibit reusing the page.
Let's conditionally drain the local LRU pagevecs when we stumble over a
!PageLRU() page. We cannot easily drain remote LRU pagevecs and it might
not be desirable performance-wise. Consequently, this will only avoid
copying in some cases.
Add a simple "page_count(page) > 3" check first but keep the
"page_count(page) > 1 + PageSwapCache(page)" check in place, as we want to
minimize cases where we remove a page from the swapcache but won't be able
to reuse it, for example, because another process has it mapped R/O, to
not affect reclaim.
We cannot easily handle the following cases and we will always have to
copy:
(1) The page is referenced in the LRU pagevecs of other CPUs. We really
would have to drain the LRU pagevecs of all CPUs -- most probably
copying is much cheaper.
(2) The page is already PageLRU() but is getting moved between LRU
lists, for example, for activation (e.g., mark_page_accessed()),
deactivation (MADV_COLD), or lazyfree (MADV_FREE). We'd have to
drain mostly unconditionally, which might be bad performance-wise.
Most probably this won't happen too often in practice.
Note that there are other reasons why an anon page might temporarily not
be PageLRU(): for example, compaction and migration have to isolate LRU
pages from the LRU lists first (isolate_lru_page()), moving them to
temporary local lists and clearing PageLRU() and holding an additional
reference on the page. In that case, we'll always copy.
This change seems to be fairly effective with the reproducer [1] shared by
Nadav, as long as writeback is done synchronously, for example, using
zram. However, with asynchronous writeback, we'll usually fail to free
the swapcache because the page is still under writeback: something we
cannot easily optimize for, and maybe it's not really relevant in
practice.
[1] https://lkml.kernel.org/r/0480D692-D9B2-429A-9A88-9BBA1331AC3A@gmail.com
Link: https://lkml.kernel.org/r/20220131162940.210846-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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