Commit ec649c9d authored Nov 05, 2019 by Ville Syrjälä Committed by Linus Torvalds Nov 06, 2019

mm/khugepaged: fix might_sleep() warn with CONFIG_HIGHPTE=y

I got some khugepaged spew on a 32bit x86:

  BUG: sleeping function called from invalid context at include/linux/mmu_notifier.h:346
  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 25, name: khugepaged
  INFO: lockdep is turned off.
  CPU: 1 PID: 25 Comm: khugepaged Not tainted 5.4.0-rc5-elk+ #206
  Hardware name: System manufacturer P5Q-EM/P5Q-EM, BIOS 2203    07/08/2009
  Call Trace:
   dump_stack+0x66/0x8e
   ___might_sleep.cold.96+0x95/0xa6
   __might_sleep+0x2e/0x80
   collapse_huge_page.isra.51+0x5ac/0x1360
   khugepaged+0x9a9/0x20f0
   kthread+0xf5/0x110
   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: 810e24e0 ("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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 93b3a674

mm/khugepaged.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1028,12 +1028,13 @@ static void collapse_huge_page(struct mm_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

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