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  1. 23 Nov, 2022 18 commits
    • Marco Elver's avatar
      kfence: fix stack trace pruning · 747c0f35
      Marco Elver authored 
      Commit b1405135 ("mm/sl[au]b: generalize kmalloc subsystem")
refactored large parts of the kmalloc subsystem, resulting in the stack
trace pruning logic done by KFENCE to no longer work.

While b1405135 attempted to fix the situation by including
'__kmem_cache_free' in the list of functions KFENCE should skip through,
this only works when the compiler actually optimized the tail call from
kfree() to __kmem_cache_free() into a jump (and thus kfree() _not_
appearing in the full stack trace to begin with).

In some configurations, the compiler no longer optimizes the tail call
into a jump, and __kmem_cache_free() appears in the stack trace.  This
means that the pruned stack trace shown by KFENCE would include kfree()
which is not intended - for example:

 | BUG: KFENCE: invalid free in kfree+0x7c/0x120
 |
 | Invalid free of 0xffff8883ed8fefe0 (in kfence-#126):
 |  kfree+0x7c/0x120
 |  test_double_free+0x116/0x1a9
 |  kunit_try_run_case+0x90/0xd0
 | [...]

Fix it by moving __kmem_cache_free() to the list of functions that may be
tail called by an allocator entry function, making the pruning logic work
in both the optimized and unoptimized tail call cases.

Link: https://lkml.kernel.org/r/20221118152216.3914899-1-elver@google.com
Fixes: b1405135 ("mm/sl[au]b: generalize kmalloc subsystem")
Signed-off-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarAlexander Potapenko <glider@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Feng Tang <feng.tang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      747c0f35
    • Yosry Ahmed's avatar
      proc/meminfo: fix spacing in SecPageTables · f850c849
      Yosry Ahmed authored 
      SecPageTables has a tab after it instead of a space, this can break
fragile parsers that depend on spaces after the stat names.

Link: https://lkml.kernel.org/r/20221117043247.133294-1-yosryahmed@google.com
Fixes: ebc97a52 ("mm: add NR_SECONDARY_PAGETABLE to count secondary page table uses.")
Signed-off-by: default avatarYosry Ahmed <yosryahmed@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      f850c849
    • Yu Zhao's avatar
      mm: multi-gen LRU: retry folios written back while isolated · 359a5e14
      Yu Zhao authored 
      The page reclaim isolates a batch of folios from the tail of one of the
LRU lists and works on those folios one by one.  For a suitable
swap-backed folio, if the swap device is async, it queues that folio for
writeback.  After the page reclaim finishes an entire batch, it puts back
the folios it queued for writeback to the head of the original LRU list.

In the meantime, the page writeback flushes the queued folios also by
batches.  Its batching logic is independent from that of the page reclaim.
For each of the folios it writes back, the page writeback calls
folio_rotate_reclaimable() which tries to rotate a folio to the tail.

folio_rotate_reclaimable() only works for a folio after the page reclaim
has put it back.  If an async swap device is fast enough, the page
writeback can finish with that folio while the page reclaim is still
working on the rest of the batch containing it.  In this case, that folio
will remain at the head and the page reclaim will not retry it before
reaching there.

This patch adds a retry to evict_folios().  After evict_folios() has
finished an entire batch and before it puts back folios it cannot free
immediately, it retries those that may have missed the rotation.

Before this patch, ~60% of folios swapped to an Intel Optane missed
folio_rotate_reclaimable().  After this patch, ~99% of missed folios were
reclaimed upon retry.

This problem affects relatively slow async swap devices like Samsung 980
Pro much less and does not affect sync swap devices like zram or zswap at
all.

Link: https://lkml.kernel.org/r/20221116013808.3995280-1-yuzhao@google.com
Fixes: ac35a490 ("mm: multi-gen LRU: minimal implementation")
Signed-off-by: default avatarYu Zhao <yuzhao@google.com>
Cc: "Yin, Fengwei" <fengwei.yin@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      359a5e14
    • Satya Priya's avatar
      mailmap: update email address for Satya Priya · 47123d7f
      Satya Priya authored 
      Add and also update email address, skakit@codeaurora.org is no longer
active.

Link: https://lkml.kernel.org/r/20221116105017.3018971-1-quic_c_skakit@quicinc.comSigned-off-by: default avatarSatya Priya <quic_c_skakit@quicinc.com>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      47123d7f
    • Alistair Popple's avatar
      mm/migrate_device: return number of migrating pages in args->cpages · 44af0b45
      Alistair Popple authored 
      migrate_vma->cpages originally contained a count of the number of pages
migrating including non-present pages which can be populated directly on
the target.

Commit 241f6885 ("mm/migrate_device.c: refactor migrate_vma and
migrate_device_coherent_page()") inadvertantly changed this to contain
just the number of pages that were unmapped.  Usage of migrate_vma->cpages
isn't documented, but most drivers use it to see if all the requested
addresses can be migrated so restore the original behaviour.

Link: https://lkml.kernel.org/r/20221111005135.1344004-1-apopple@nvidia.com
Fixes: 241f6885 ("mm/migrate_device.c: refactor migrate_vma and migrate_deivce_coherent_page()")
Signed-off-by: default avatarAlistair Popple <apopple@nvidia.com>
Reported-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Reviewed-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      44af0b45
    • Sam James's avatar
      kbuild: fix -Wimplicit-function-declaration in license_is_gpl_compatible · 50c69721
      Sam James authored 
      Add missing <linux/string.h> include for strcmp.

Clang 16 makes -Wimplicit-function-declaration an error by default. 
Unfortunately, out of tree modules may use this in configure scripts,
which means failure might cause silent miscompilation or misconfiguration.

For more information, see LWN.net [0] or LLVM's Discourse [1], gentoo-dev@ [2],
or the (new) c-std-porting mailing list [3].

[0] https://lwn.net/Articles/913505/
[1] https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213
[2] https://archives.gentoo.org/gentoo-dev/message/dd9f2d3082b8b6f8dfbccb0639e6e240
[3] hosted at lists.linux.dev.

[akpm@linux-foundation.org: remember "linux/"]
Link: https://lkml.kernel.org/r/20221116182634.2823136-1-sam@gentoo.orgSigned-off-by: default avatarSam James <sam@gentoo.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      50c69721
    • Alex Hung's avatar
      MAINTAINERS: update Alex Hung's email address · db8e0998
      Alex Hung authored 
      Use my personal email address.

Link: https://lkml.kernel.org/r/20221114001302.671897-2-alex.hung@amd.comSigned-off-by: default avatarAlex Hung <alexhung@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      db8e0998
    • Alex Hung's avatar
      mailmap: update Alex Hung's email address · d39e2ad6
      Alex Hung authored 
      I am no longer at Canonical and add entry of my personal email address.

Link: https://lkml.kernel.org/r/20221114001302.671897-1-alex.hung@amd.comSigned-off-by: default avatarAlex Hung <alexhung@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      d39e2ad6
    • Ian Cowan's avatar
      mm: mmap: fix documentation for vma_mas_szero · 4a423440
      Ian Cowan authored 
      When the struct_mm input, mm, was changed to a struct ma_state, mas, the
documentation for the function was never updated.  This updates that
documentation reference.

Link: https://lkml.kernel.org/r/20221114003349.41235-1-ian@linux.cowan.aeroSigned-off-by: default avatarIan Cowan <ian@linux.cowan.aero>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      4a423440
    • SeongJae Park's avatar
      mm/damon/sysfs-schemes: skip stats update if the scheme directory is removed · 8468b486
      SeongJae Park authored 
      A DAMON sysfs interface user can start DAMON with a scheme, remove the
sysfs directory for the scheme, and then ask update of the scheme's stats.
Because the schemes stats update logic isn't aware of the situation, it
results in an invalid memory access.  Fix the bug by checking if the
scheme sysfs directory exists.

Link: https://lkml.kernel.org/r/20221114175552.1951-1-sj@kernel.org
Fixes: 0ac32b8a ("mm/damon/sysfs: support DAMOS stats")
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[v5.18]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      8468b486
    • Alistair Popple's avatar
      mm/memory: return vm_fault_t result from migrate_to_ram() callback · 4a955bed
      Alistair Popple authored 
      The migrate_to_ram() callback should always succeed, but in rare cases can
fail usually returning VM_FAULT_SIGBUS.  Commit 16ce101d
("mm/memory.c: fix race when faulting a device private page") incorrectly
stopped passing the return code up the stack.  Fix this by setting the ret
variable, restoring the previous behaviour on migrate_to_ram() failure.

Link: https://lkml.kernel.org/r/20221114115537.727371-1-apopple@nvidia.com
Fixes: 16ce101d ("mm/memory.c: fix race when faulting a device private page")
Signed-off-by: default avatarAlistair Popple <apopple@nvidia.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarFelix Kuehling <Felix.Kuehling@amd.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      4a955bed
    • Li Liguang's avatar
      mm: correctly charge compressed memory to its memcg · cd08d80e
      Li Liguang authored 
      Kswapd will reclaim memory when memory pressure is high, the annonymous
memory will be compressed and stored in the zpool if zswap is enabled. 
The memcg_kmem_bypass() in get_obj_cgroup_from_page() will bypass the
kernel thread and cause the compressed memory not be charged to its memory
cgroup.

Remove the memcg_kmem_bypass() call and properly charge compressed memory
to its corresponding memory cgroup.

Link: https://lore.kernel.org/linux-mm/CALvZod4nnn8BHYqAM4xtcR0Ddo2-Wr8uKm9h_CHWUaXw7g_DCg@mail.gmail.com/
Link: https://lkml.kernel.org/r/20221114194828.100822-1-hannes@cmpxchg.org
Fixes: f4840ccf ("zswap: memcg accounting")
Signed-off-by: default avatarLi Liguang <liliguang@baidu.com>
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: <stable@vger.kernel.org>	[5.19+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      cd08d80e
    • Mike Kravetz's avatar
      ipc/shm: call underlying open/close vm_ops · b6305049
      Mike Kravetz authored 
      Shared memory segments can be created that are backed by hugetlb pages. 
When this happens, the vmas associated with any mappings (shmat) are
marked VM_HUGETLB, yet the vm_ops for such mappings are provided by
ipc/shm (shm_vm_ops).  There is a mechanism to call the underlying hugetlb
vm_ops, and this is done for most operations.  However, it is not done for
open and close.

This was not an issue until the introduction of the hugetlb vma_lock. 
This lock structure is pointed to by vm_private_data and the open/close
vm_ops help maintain this structure.  The special hugetlb routine called
at fork took care of structure updates at fork time.  However,
vma_splitting is not properly handled for ipc shared memory mappings
backed by hugetlb pages.  This can result in a "kernel NULL pointer
dereference" BUG or use after free as two vmas point to the same lock
structure.

Update the shm open and close routines to always call the underlying open
and close routines.

Link: https://lkml.kernel.org/r/20221114210018.49346-1-mike.kravetz@oracle.com
Fixes: 8d9bfb26 ("hugetlb: add vma based lock for pmd sharing")
Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Reported-by: default avatarDoug Nelson <doug.nelson@intel.com>
Reported-by: <syzbot+83b4134621b7c326d950@syzkaller.appspotmail.com>
Cc: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      b6305049
    • Mukesh Ojha's avatar
      gcov: clang: fix the buffer overflow issue · a6f810ef
      Mukesh Ojha authored 
      Currently, in clang version of gcov code when module is getting removed
gcov_info_add() incorrectly adds the sfn_ptr->counter to all the
dst->functions and it result in the kernel panic in below crash report. 
Fix this by properly handling it.

[    8.899094][  T599] Unable to handle kernel write to read-only memory at virtual address ffffff80461cc000
[    8.899100][  T599] Mem abort info:
[    8.899102][  T599]   ESR = 0x9600004f
[    8.899103][  T599]   EC = 0x25: DABT (current EL), IL = 32 bits
[    8.899105][  T599]   SET = 0, FnV = 0
[    8.899107][  T599]   EA = 0, S1PTW = 0
[    8.899108][  T599]   FSC = 0x0f: level 3 permission fault
[    8.899110][  T599] Data abort info:
[    8.899111][  T599]   ISV = 0, ISS = 0x0000004f
[    8.899113][  T599]   CM = 0, WnR = 1
[    8.899114][  T599] swapper pgtable: 4k pages, 39-bit VAs, pgdp=00000000ab8de000
[    8.899116][  T599] [ffffff80461cc000] pgd=18000009ffcde003, p4d=18000009ffcde003, pud=18000009ffcde003, pmd=18000009ffcad003, pte=00600000c61cc787
[    8.899124][  T599] Internal error: Oops: 9600004f [#1] PREEMPT SMP
[    8.899265][  T599] Skip md ftrace buffer dump for: 0x1609e0
....
..,
[    8.899544][  T599] CPU: 7 PID: 599 Comm: modprobe Tainted: G S         OE     5.15.41-android13-8-g38e9b1af6bce #1
[    8.899547][  T599] Hardware name: XXX (DT)
[    8.899549][  T599] pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
[    8.899551][  T599] pc : gcov_info_add+0x9c/0xb8
[    8.899557][  T599] lr : gcov_event+0x28c/0x6b8
[    8.899559][  T599] sp : ffffffc00e733b00
[    8.899560][  T599] x29: ffffffc00e733b00 x28: ffffffc00e733d30 x27: ffffffe8dc297470
[    8.899563][  T599] x26: ffffffe8dc297000 x25: ffffffe8dc297000 x24: ffffffe8dc297000
[    8.899566][  T599] x23: ffffffe8dc0a6200 x22: ffffff880f68bf20 x21: 0000000000000000
[    8.899569][  T599] x20: ffffff880f68bf00 x19: ffffff8801babc00 x18: ffffffc00d7f9058
[    8.899572][  T599] x17: 0000000000088793 x16: ffffff80461cbe00 x15: 9100052952800785
[    8.899575][  T599] x14: 0000000000000200 x13: 0000000000000041 x12: 9100052952800785
[    8.899577][  T599] x11: ffffffe8dc297000 x10: ffffffe8dc297000 x9 : ffffff80461cbc80
[    8.899580][  T599] x8 : ffffff8801babe80 x7 : ffffffe8dc2ec000 x6 : ffffffe8dc2ed000
[    8.899583][  T599] x5 : 000000008020001f x4 : fffffffe2006eae0 x3 : 000000008020001f
[    8.899586][  T599] x2 : ffffff8027c49200 x1 : ffffff8801babc20 x0 : ffffff80461cb3a0
[    8.899589][  T599] Call trace:
[    8.899590][  T599]  gcov_info_add+0x9c/0xb8
[    8.899592][  T599]  gcov_module_notifier+0xbc/0x120
[    8.899595][  T599]  blocking_notifier_call_chain+0xa0/0x11c
[    8.899598][  T599]  do_init_module+0x2a8/0x33c
[    8.899600][  T599]  load_module+0x23cc/0x261c
[    8.899602][  T599]  __arm64_sys_finit_module+0x158/0x194
[    8.899604][  T599]  invoke_syscall+0x94/0x2bc
[    8.899607][  T599]  el0_svc_common+0x1d8/0x34c
[    8.899609][  T599]  do_el0_svc+0x40/0x54
[    8.899611][  T599]  el0_svc+0x94/0x2f0
[    8.899613][  T599]  el0t_64_sync_handler+0x88/0xec
[    8.899615][  T599]  el0t_64_sync+0x1b4/0x1b8
[    8.899618][  T599] Code: f905f56c f86e69ec f86e6a0f 8b0c01ec (f82e6a0c)
[    8.899620][  T599] ---[ end trace ed5218e9e5b6e2e6 ]---

Link: https://lkml.kernel.org/r/1668020497-13142-1-git-send-email-quic_mojha@quicinc.com
Fixes: e178a5be ("gcov: clang support")
Signed-off-by: default avatarMukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: default avatarPeter Oberparleiter <oberpar@linux.ibm.com>
Tested-by: default avatarPeter Oberparleiter <oberpar@linux.ibm.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: <stable@vger.kernel.org>	[5.2+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      a6f810ef
    • Gautam Menghani's avatar
      mm/khugepaged: refactor mm_khugepaged_scan_file tracepoint to remove filename from function call · 045634ff
      Gautam Menghani authored 
      Refactor the mm_khugepaged_scan_file tracepoint to move filename
dereference to the tracepoint definition, to maintain consistency with
other tracepoints[1].

[1]:lore.kernel.org/lkml/20221024111621.3ba17e2c@gandalf.local.home/

Link: https://lkml.kernel.org/r/20221026044524.54793-1-gautammenghani201@gmail.com
Fixes: d41fd201 ("mm/khugepaged: add tracepoint to hpage_collapse_scan_file()")
Signed-off-by: default avatarGautam Menghani <gautammenghani201@gmail.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Reviewed-by: default avatarZach O'Keefe <zokeefe@google.com>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      045634ff
    • Charan Teja Kalla's avatar
      mm/page_exit: fix kernel doc warning in page_ext_put() · ed86b748
      Charan Teja Kalla authored 
      Fix the below compiler warnings reported with 'make W=1 mm/'. 
mm/page_ext.c:178: warning: Function parameter or member 'page_ext' not
described in 'page_ext_put'.

[quic_pkondeti@quicinc.com: better patch title]
Link: https://lkml.kernel.org/r/1667884582-2465-1-git-send-email-quic_charante@quicinc.com
Fixes: b1d5488a ("mm: fix use-after free of page_ext after race with memory-offline")
Signed-off-by: default avatarCharan Teja Kalla <quic_charante@quicinc.com>
Reported-by: default avatarVlastimil Babka <vbabka@suse.cz>
Tested-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Pavan Kondeti <quic_pkondeti@quicinc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      ed86b748
    • Yang Shi's avatar
      mm: khugepaged: allow page allocation fallback to eligible nodes · e031ff96
      Yang Shi authored 
      Syzbot reported the below splat:

WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 __alloc_pages_node include/linux/gfp.h:221 [inline]
WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 hpage_collapse_alloc_page mm/khugepaged.c:807 [inline]
WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963
Modules linked in:
CPU: 1 PID: 3646 Comm: syz-executor210 Not tainted 6.1.0-rc1-syzkaller-00454-ga7038524 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
RIP: 0010:__alloc_pages_node include/linux/gfp.h:221 [inline]
RIP: 0010:hpage_collapse_alloc_page mm/khugepaged.c:807 [inline]
RIP: 0010:alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963
Code: e5 01 4c 89 ee e8 6e f9 ae ff 4d 85 ed 0f 84 28 fc ff ff e8 70 fc ae ff 48 8d 6b ff 4c 8d 63 07 e9 16 fc ff ff e8 5e fc ae ff <0f> 0b e9 96 fa ff ff 41 bc 1a 00 00 00 e9 86 fd ff ff e8 47 fc ae
RSP: 0018:ffffc90003fdf7d8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888077f457c0 RSI: ffffffff81cd8f42 RDI: 0000000000000001
RBP: ffff888079388c0c R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f6b48ccf700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6b48a819f0 CR3: 00000000171e7000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 collapse_file+0x1ca/0x5780 mm/khugepaged.c:1715
 hpage_collapse_scan_file+0xd6c/0x17a0 mm/khugepaged.c:2156
 madvise_collapse+0x53a/0xb40 mm/khugepaged.c:2611
 madvise_vma_behavior+0xd0a/0x1cc0 mm/madvise.c:1066
 madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1240
 do_madvise.part.0+0x24a/0x340 mm/madvise.c:1419
 do_madvise mm/madvise.c:1432 [inline]
 __do_sys_madvise mm/madvise.c:1432 [inline]
 __se_sys_madvise mm/madvise.c:1430 [inline]
 __x64_sys_madvise+0x113/0x150 mm/madvise.c:1430
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f6b48a4eef9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6b48ccf318 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f6b48af0048 RCX: 00007f6b48a4eef9
RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000000020000000
RBP: 00007f6b48af0040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b48aa53a4
R13: 00007f6b48bffcbf R14: 00007f6b48ccf400 R15: 0000000000022000
 </TASK>

The khugepaged code would pick up the node with the most hit as the preferred
node, and also tries to do some balance if several nodes have the same
hit record.  Basically it does conceptually:
    * If the target_node <= last_target_node, then iterate from
last_target_node + 1 to MAX_NUMNODES (1024 on default config)
    * If the max_value == node_load[nid], then target_node = nid

But there is a corner case, paritucularly for MADV_COLLAPSE, that the
non-existing node may be returned as preferred node.

Assuming the system has 2 nodes, the target_node is 0 and the
last_target_node is 1, if MADV_COLLAPSE path is hit, the max_value may
be 0, then it may return 2 for target_node, but it is actually not
existing (offline), so the warn is triggered.

The node balance was introduced by commit 9f1b868a ("mm: thp:
khugepaged: add policy for finding target node") to satisfy
"numactl --interleave=all".  But interleaving is a mere hint rather than
something that has hard requirements.

So use nodemask to record the nodes which have the same hit record, the
hugepage allocation could fallback to those nodes.  And remove
__GFP_THISNODE since it does disallow fallback.  And if the nodemask
just has one node set, it means there is one single node has the most
hit record, the nodemask approach actually behaves like __GFP_THISNODE.

Link: https://lkml.kernel.org/r/20221108184357.55614-2-shy828301@gmail.com
Fixes: 7d8faaf1 ("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse")
Signed-off-by: default avatarYang Shi <shy828301@gmail.com>
Suggested-by: default avatarZach O'Keefe <zokeefe@google.com>
Suggested-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarZach O'Keefe <zokeefe@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reported-by: <syzbot+0044b22d177870ee974f@syzkaller.appspotmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      e031ff96
    • Johannes Weiner's avatar
      mm: vmscan: fix extreme overreclaim and swap floods · f53af428
      Johannes Weiner authored 
      During proactive reclaim, we sometimes observe severe overreclaim, with
several thousand times more pages reclaimed than requested.

This trace was obtained from shrink_lruvec() during such an instance:

    prio:0 anon_cost:1141521 file_cost:7767
    nr_reclaimed:4387406 nr_to_reclaim:1047 (or_factor:4190)
    nr=[7161123 345 578 1111]

While he reclaimer requested 4M, vmscan reclaimed close to 16G, most of it
by swapping.  These requests take over a minute, during which the write()
to memory.reclaim is unkillably stuck inside the kernel.

Digging into the source, this is caused by the proportional reclaim
bailout logic.  This code tries to resolve a fundamental conflict: to
reclaim roughly what was requested, while also aging all LRUs fairly and
in accordance to their size, swappiness, refault rates etc.  The way it
attempts fairness is that once the reclaim goal has been reached, it stops
scanning the LRUs with the smaller remaining scan targets, and adjusts the
remainder of the bigger LRUs according to how much of the smaller LRUs was
scanned.  It then finishes scanning that remainder regardless of the
reclaim goal.

This works fine if priority levels are low and the LRU lists are
comparable in size.  However, in this instance, the cgroup that is
targeted by proactive reclaim has almost no files left - they've already
been squeezed out by proactive reclaim earlier - and the remaining anon
pages are hot.  Anon rotations cause the priority level to drop to 0,
which results in reclaim targeting all of anon (a lot) and all of file
(almost nothing).  By the time reclaim decides to bail, it has scanned
most or all of the file target, and therefor must also scan most or all of
the enormous anon target.  This target is thousands of times larger than
the reclaim goal, thus causing the overreclaim.

The bailout code hasn't changed in years, why is this failing now?  The
most likely explanations are two other recent changes in anon reclaim:

1. Before the series starting with commit 5df74196 ("mm: fix LRU
   balancing effect of new transparent huge pages"), the VM was
   overall relatively reluctant to swap at all, even if swap was
   configured. This means the LRU balancing code didn't come into play
   as often as it does now, and mostly in high pressure situations
   where pronounced swap activity wouldn't be as surprising.

2. For historic reasons, shrink_lruvec() loops on the scan targets of
   all LRU lists except the active anon one, meaning it would bail if
   the only remaining pages to scan were active anon - even if there
   were a lot of them.

   Before the series starting with commit ccc5dc67 ("mm/vmscan:
   make active/inactive ratio as 1:1 for anon lru"), most anon pages
   would live on the active LRU; the inactive one would contain only a
   handful of preselected reclaim candidates. After the series, anon
   gets aged similarly to file, and the inactive list is the default
   for new anon pages as well, making it often the much bigger list.

   As a result, the VM is now more likely to actually finish large
   anon targets than before.

Change the code such that only one SWAP_CLUSTER_MAX-sized nudge toward the
larger LRU lists is made before bailing out on a met reclaim goal.

This fixes the extreme overreclaim problem.

Fairness is more subtle and harder to evaluate.  No obvious misbehavior
was observed on the test workload, in any case.  Conceptually, fairness
should primarily be a cumulative effect from regular, lower priority
scans.  Once the VM is in trouble and needs to escalate scan targets to
make forward progress, fairness needs to take a backseat.  This is also
acknowledged by the myriad exceptions in get_scan_count().  This patch
makes fairness decrease gradually, as it keeps fairness work static over
increasing priority levels with growing scan targets.  This should make
more sense - although we may have to re-visit the exact values.

Link: https://lkml.kernel.org/r/20220802162811.39216-1-hannes@cmpxchg.orgSigned-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarRik van Riel <riel@surriel.com>
Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      f53af428
  3. 08 Nov, 2022 22 commits
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