From: Ville Syrjälä ville.syrjala@linux.intel.com Subject: mm/khugepaged: fix might_sleep() warn with CONFIG_HIGHPTE=y

I got some khugepaged spew on a 32bit x86:

[ 217.490026] BUG: sleeping function called from invalid context at include/linux/mmu_notifier.h:346 [ 217.492826] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 25, name: khugepaged [ 217.495589] INFO: lockdep is turned off. [ 217.498371] CPU: 1 PID: 25 Comm: khugepaged Not tainted 5.4.0-rc5-elk+ #206 [ 217.501233] Hardware name: System manufacturer P5Q-EM/P5Q-EM, BIOS 2203 07/08/2009 [ 217.501697] Call Trace: [ 217.501697] dump_stack+0x66/0x8e [ 217.501697] ___might_sleep.cold.96+0x95/0xa6 [ 217.501697] __might_sleep+0x2e/0x80 [ 217.501697] collapse_huge_page.isra.51+0x5ac/0x1360 [ 217.501697] ? __alloc_pages_nodemask+0xec/0xf80 [ 217.501697] ? __alloc_pages_nodemask+0x191/0xf80 [ 217.501697] ? trace_hardirqs_on+0x4a/0xf0 [ 217.501697] khugepaged+0x9a9/0x20f0 [ 217.501697] ? _raw_spin_unlock+0x21/0x30 [ 217.501697] ? trace_hardirqs_on+0x4a/0xf0 [ 217.501697] ? wait_woken+0xa0/0xa0 [ 217.501697] kthread+0xf5/0x110 [ 217.501697] ? collapse_pte_mapped_thp+0x3b0/0x3b0 [ 217.501697] ? kthread_create_worker_on_cpu+0x20/0x20 [ 217.501697] ret_from_fork+0x2e/0x38

Looks like it's due to CONFIG_HIGHPTE=y pte_offset_map()->kmap_atomic() vs. mmu_notifier_invalidate_range_start(). Let's do the naive approach and just reorder the two operations.

Link: http://lkml.kernel.org/r/20191029201513.GG1208@intel.com Fixes: 810e24e009cf71 ("mm/mmu_notifiers: annotate with might_sleep()") Signed-off-by: Ville Syrjl ville.syrjala@linux.intel.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: "H. Peter Anvin" hpa@zytor.com Cc: Jérôme Glisse jglisse@redhat.com Cc: Ralph Campbell rcampbell@nvidia.com Cc: Ira Weiny ira.weiny@intel.com Cc: Jason Gunthorpe jgg@mellanox.com Cc: Daniel Vetter daniel.vetter@intel.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/khugepaged.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/mm/khugepaged.c~khugepaged-might_sleep-warn-due-to-config_highpte=y +++ a/mm/khugepaged.c @@ -1028,12 +1028,13 @@ static void collapse_huge_page(struct mm

anon_vma_lock_write(vma->anon_vma);

- pte = pte_offset_map(pmd, address); - pte_ptl = pte_lockptr(mm, pmd); - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, address, address + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); + + pte = pte_offset_map(pmd, address); + pte_ptl = pte_lockptr(mm, pmd); + pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ /* * After this gup_fast can't run anymore. This also removes _