* Re: [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
2025-10-14 5:58 [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Pedro Demarchi Gomes
@ 2025-10-14 9:26 ` David Hildenbrand
2025-10-14 13:36 ` Pedro Demarchi Gomes
2025-10-14 11:40 ` [syzbot ci] " syzbot ci
1 sibling, 1 reply; 4+ messages in thread
From: David Hildenbrand @ 2025-10-14 9:26 UTC (permalink / raw)
To: Pedro Demarchi Gomes, Andrew Morton, craftfever
Cc: Xu Xin, Chengming Zhou, linux-mm, linux-kernel
On 14.10.25 07:58, Pedro Demarchi Gomes wrote:
> Currently, scan_get_next_rmap_item() walks every page address in a VMA
> to locate mergeable pages. This becomes highly inefficient when scanning
> large virtual memory areas that contain mostly unmapped regions.
>
> This patch replaces the per-address lookup with a range walk using
> walk_page_range(). The range walker allows KSM to skip over entire
> unmapped holes in a VMA, avoiding unnecessary lookups.
>
> To evaluate this change, I created a test that maps a 1 TB virtual area
> where only the first and last 10 MB are populated with identical data.
> With this patch applied, KSM scanned and merged the region approximately
> seven times faster.
>
> This problem was previously discussed in [1].
>
> [1] https://lore.kernel.org/linux-mm/423de7a3-1c62-4e72-8e79-19a6413e420c@redhat.com/
>
> Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
> ---
> mm/ksm.c | 136 ++++++++++++++++++++++++++++++++-----------------------
> 1 file changed, 79 insertions(+), 57 deletions(-)
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 3aed0478fdce..584fd987e8ae 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2455,15 +2455,80 @@ static bool should_skip_rmap_item(struct folio *folio,
> return true;
> }
>
> +struct ksm_walk_private {
> + struct page *page;
> + struct ksm_rmap_item *rmap_item;
> + struct ksm_mm_slot *mm_slot;
> +};
> +
> +static int ksm_walk_test(unsigned long addr, unsigned long next, struct mm_walk *walk)
> +{
> + struct vm_area_struct *vma = walk->vma;
> +
> + if (!vma || !(vma->vm_flags & VM_MERGEABLE))
The anon_vma check should go in here as well.
How can we possibly get !vma?
> + return 1;
> + return 0;
> +}
> +
> +static int ksm_pte_entry(pte_t *pte, unsigned long addr,
> + unsigned long end, struct mm_walk *walk)
> +{
> + struct mm_struct *mm = walk->mm;
> + struct vm_area_struct *vma = walk->vma;
> + struct ksm_walk_private *private = (struct ksm_walk_private *) walk->private;
> + struct ksm_mm_slot *mm_slot = private->mm_slot;
> + pte_t ptent = ptep_get(pte);
> + struct page *page = pfn_to_online_page(pte_pfn(ptent));
Oh no.
vm_normal_page()
> + struct ksm_rmap_item *rmap_item;
> + struct folio *folio;
> +
> + ksm_scan.address = addr;
> +
> + if (ksm_test_exit(mm))
> + return 1;
> +
> + if (!page)
> + return 0;
> +
> + folio = page_folio(page);
> + if (folio_is_zone_device(folio) || !folio_test_anon(folio))
> + return 0;
> +
> + folio_get(folio);
> +
> + flush_anon_page(vma, page, ksm_scan.address);
> + flush_dcache_page(page);
> + rmap_item = get_next_rmap_item(mm_slot,
> + ksm_scan.rmap_list, ksm_scan.address);
> + if (rmap_item) {
> + ksm_scan.rmap_list =
> + &rmap_item->rmap_list;
> +
> + if (should_skip_rmap_item(folio, rmap_item)) {
> + folio_put(folio);
> + return 0;
> + }
> + ksm_scan.address = end;
> + private->page = page;
> + } else
> + folio_put(folio);
> +
You're under PTL, get_next_rmap_item() will perform an allocation, so
that won't work.
Observe how the original code worked around that by performing all magic
outside of the PTL (folio_walk_end()).
When you switch to .pmd_entry() (see below) you will be able to handle it.
What you could also try doing is returing page+folio and letting the
caller deal with everything starting at the flush_anon_page().
> + private->rmap_item = rmap_item;
> + return 1;
> +}
> +
> +struct mm_walk_ops walk_ops = {
> + .pte_entry = ksm_pte_entry,
> + .test_walk = ksm_walk_test,
> + .walk_lock = PGWALK_RDLOCK,
> +};
It's more complicated: you'd be remapping each PMD to be mapped by PTEs
first, which is not what we want. You'll have to handle pmd_entry
instead of pte_entry.
> +
> static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
> {
> struct mm_struct *mm;
> struct ksm_mm_slot *mm_slot;
> struct mm_slot *slot;
> - struct vm_area_struct *vma;
> - struct ksm_rmap_item *rmap_item;
> - struct vma_iterator vmi;
> - int nid;
> + int nid, ret;
>
> if (list_empty(&ksm_mm_head.slot.mm_node))
> return NULL;
> @@ -2527,64 +2592,21 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
>
> slot = &mm_slot->slot;
> mm = slot->mm;
> - vma_iter_init(&vmi, mm, ksm_scan.address);
>
> mmap_read_lock(mm);
> if (ksm_test_exit(mm))
> goto no_vmas;
>
> - for_each_vma(vmi, vma) {
> - if (!(vma->vm_flags & VM_MERGEABLE))
> - continue;
> - if (ksm_scan.address < vma->vm_start)
> - ksm_scan.address = vma->vm_start;
> - if (!vma->anon_vma)
> - ksm_scan.address = vma->vm_end;
> -
> - while (ksm_scan.address < vma->vm_end) {
> - struct page *tmp_page = NULL;
> - struct folio_walk fw;
> - struct folio *folio;
> -
> - if (ksm_test_exit(mm))
> - break;
> -
> - folio = folio_walk_start(&fw, vma, ksm_scan.address, 0);
> - if (folio) {
> - if (!folio_is_zone_device(folio) &&
> - folio_test_anon(folio)) {
> - folio_get(folio);
> - tmp_page = fw.page;
> - }
> - folio_walk_end(&fw, vma);
> - }
> -
> - if (tmp_page) {
> - flush_anon_page(vma, tmp_page, ksm_scan.address);
> - flush_dcache_page(tmp_page);
> - rmap_item = get_next_rmap_item(mm_slot,
> - ksm_scan.rmap_list, ksm_scan.address);
> - if (rmap_item) {
> - ksm_scan.rmap_list =
> - &rmap_item->rmap_list;
> -
> - if (should_skip_rmap_item(folio, rmap_item)) {
> - folio_put(folio);
> - goto next_page;
> - }
> -
> - ksm_scan.address += PAGE_SIZE;
> - *page = tmp_page;
> - } else {
> - folio_put(folio);
> - }
> - mmap_read_unlock(mm);
> - return rmap_item;
> - }
> -next_page:
> - ksm_scan.address += PAGE_SIZE;
> - cond_resched();
You're dropping all cond_resched(), which will be a problem.
> - }
> + struct ksm_walk_private walk_private = {
> + .page = NULL,
> + .rmap_item = NULL,
> + .mm_slot = ksm_scan.mm_slot
> + };
empty line missing
> + ret = walk_page_range(mm, ksm_scan.address, -1, &walk_ops, (void *) &walk_private);
> + *page = walk_private.page;
> + if (ret) {
> + mmap_read_unlock(mm);
> + return walk_private.rmap_item;
> }
>
> if (ksm_test_exit(mm)) {
--
Cheers
David / dhildenb
^ permalink raw reply [flat|nested] 4+ messages in thread* [syzbot ci] Re: ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
2025-10-14 5:58 [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Pedro Demarchi Gomes
2025-10-14 9:26 ` David Hildenbrand
@ 2025-10-14 11:40 ` syzbot ci
1 sibling, 0 replies; 4+ messages in thread
From: syzbot ci @ 2025-10-14 11:40 UTC (permalink / raw)
To: akpm, chengming.zhou, craftfever, david, linux-kernel, linux-mm,
pedrodemargomes, xu.xin16
Cc: syzbot, syzkaller-bugs
syzbot ci has tested the following series
[v1] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
https://lore.kernel.org/all/20251014055828.124522-1-pedrodemargomes@gmail.com
* [PATCH] ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
and found the following issue:
possible deadlock in __pte_offset_map_lock
Full report is available here:
https://ci.syzbot.org/series/15a341dd-23e3-4627-9fb9-00b92b7bae3f
***
possible deadlock in __pte_offset_map_lock
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 0d97f2067c166eb495771fede9f7b73999c67f66
arch: amd64
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config: https://ci.syzbot.org/builds/31dfd455-a2ef-4c41-8f8d-172612e161d9/config
C repro: https://ci.syzbot.org/findings/5bddd702-c879-4aa6-b86d-5be2b4b3d0e2/c_repro
syz repro: https://ci.syzbot.org/findings/5bddd702-c879-4aa6-b86d-5be2b4b3d0e2/syz_repro
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
ksmd/41 is trying to acquire lock:
ffffffff8e245b20 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline]
ffffffff8e245b20 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4897 [inline]
ffffffff8e245b20 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:5221 [inline]
ffffffff8e245b20 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_noprof+0x45/0x6e0 mm/slub.c:5252
but task is already holding lock:
ffff888112eeb8b8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff888112eeb8b8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: __pte_offset_map_lock+0x13e/0x210 mm/pgtable-generic.c:401
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
map_pte mm/page_vma_mapped.c:72 [inline]
page_vma_mapped_walk+0xeea/0x20f0 mm/page_vma_mapped.c:291
try_to_migrate_one+0x5d8/0x34d0 mm/rmap.c:2339
rmap_walk_anon+0x553/0x730 mm/rmap.c:2855
try_to_migrate+0x319/0x3d0 mm/rmap.c:-1
migrate_folio_unmap mm/migrate.c:1319 [inline]
migrate_pages_batch+0x1432/0x35e0 mm/migrate.c:1882
migrate_pages+0x1d5a/0x2930 mm/migrate.c:2103
migrate_misplaced_folio+0x28c/0x840 mm/migrate.c:2724
do_numa_page mm/memory.c:6004 [inline]
handle_pte_fault mm/memory.c:6183 [inline]
__handle_mm_fault+0x3bab/0x5400 mm/memory.c:6318
handle_mm_fault+0x40a/0x8e0 mm/memory.c:6487
do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
__get_user_8+0x14/0x30 arch/x86/lib/getuser.S:100
rseq_get_rseq_cs_ptr_val kernel/rseq.c:248 [inline]
rseq_get_rseq_cs kernel/rseq.c:270 [inline]
rseq_ip_fixup kernel/rseq.c:390 [inline]
__rseq_handle_notify_resume+0x13d/0x1220 kernel/rseq.c:438
rseq_handle_notify_resume include/linux/rseq.h:44 [inline]
resume_user_mode_work include/linux/resume_user_mode.h:62 [inline]
exit_to_user_mode_loop+0xbf/0x130 kernel/entry/common.c:43
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (&anon_vma->rwsem){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
anon_vma_lock_write include/linux/rmap.h:122 [inline]
vma_prepare+0x25c/0x4b0 mm/vma.c:309
__split_vma+0x76e/0xa00 mm/vma.c:550
split_vma mm/vma.c:598 [inline]
vma_modify+0x13b3/0x1970 mm/vma.c:1631
vma_modify_flags+0x1e8/0x230 mm/vma.c:1649
mprotect_fixup+0x407/0x9c0 mm/mprotect.c:816
do_mprotect_pkey+0x8c5/0xcd0 mm/mprotect.c:990
__do_sys_mprotect mm/mprotect.c:1011 [inline]
__se_sys_mprotect mm/mprotect.c:1008 [inline]
__x64_sys_mprotect+0x80/0x90 mm/mprotect.c:1008
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&mapping->i_mmap_rwsem){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
i_mmap_lock_write include/linux/fs.h:548 [inline]
dma_resv_lockdep+0x2f6/0x5b0 drivers/dma-buf/dma-resv.c:797
do_one_initcall+0x236/0x820 init/main.c:1283
do_initcall_level+0x104/0x190 init/main.c:1345
do_initcalls+0x59/0xa0 init/main.c:1361
kernel_init_freeable+0x334/0x4b0 init/main.c:1593
kernel_init+0x1d/0x1d0 init/main.c:1483
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #0 (fs_reclaim){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4269 [inline]
fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4283
might_alloc include/linux/sched/mm.h:318 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x45/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
other info that might help us debug this:
Chain exists of:
fs_reclaim --> &anon_vma->rwsem --> ptlock_ptr(ptdesc)#2
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(ptlock_ptr(ptdesc)#2);
lock(&anon_vma->rwsem);
lock(ptlock_ptr(ptdesc)#2);
lock(fs_reclaim);
*** DEADLOCK ***
4 locks held by ksmd/41:
#0: ffffffff8e259b88 (ksm_thread_mutex){+.+.}-{4:4}, at: ksm_scan_thread+0xc8/0x4b0 mm/ksm.c:2703
#1: ffff8881703b9760 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:368 [inline]
#1: ffff8881703b9760 (&mm->mmap_lock){++++}-{4:4}, at: scan_get_next_rmap_item mm/ksm.c:2596 [inline]
#1: ffff8881703b9760 (&mm->mmap_lock){++++}-{4:4}, at: ksm_do_scan+0x578/0x5c10 mm/ksm.c:2681
#2: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#2: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
#2: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: ___pte_offset_map+0x29/0x250 mm/pgtable-generic.c:286
#3: ffff888112eeb8b8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
#3: ffff888112eeb8b8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: __pte_offset_map_lock+0x13e/0x210 mm/pgtable-generic.c:401
stack backtrace:
CPU: 1 UID: 0 PID: 41 Comm: ksmd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4269 [inline]
fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4283
might_alloc include/linux/sched/mm.h:318 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x45/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 41 Comm: ksmd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 41, name: ksmd
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 41 Comm: ksmd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x495/0x610 kernel/sched/core.c:8925
might_alloc include/linux/sched/mm.h:321 [inline]
slab_pre_alloc_hook mm/slub.c:4897 [inline]
slab_alloc_node mm/slub.c:5221 [inline]
kmem_cache_alloc_noprof+0x65/0x6e0 mm/slub.c:5252
alloc_rmap_item mm/ksm.c:565 [inline]
get_next_rmap_item mm/ksm.c:2378 [inline]
ksm_pte_entry+0x414/0xa60 mm/ksm.c:2501
walk_pte_range_inner+0x1ba/0x380 mm/pagewalk.c:50
walk_pte_range mm/pagewalk.c:88 [inline]
walk_pmd_range mm/pagewalk.c:155 [inline]
walk_pud_range mm/pagewalk.c:224 [inline]
walk_p4d_range mm/pagewalk.c:262 [inline]
walk_pgd_range+0x12bf/0x1d40 mm/pagewalk.c:303
__walk_page_range+0x14c/0x710 mm/pagewalk.c:410
walk_page_range_mm+0x454/0x660 mm/pagewalk.c:506
scan_get_next_rmap_item mm/ksm.c:2605 [inline]
ksm_do_scan+0x60c/0x5c10 mm/ksm.c:2681
ksm_scan_thread+0x10b/0x4b0 mm/ksm.c:2706
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@syzkaller.appspotmail.com
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.
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