[PATCH 5.3 044/193] mm/khugepaged: fix might_sleep() warn with CONFIG_HIGHPTE=y

[Greg Kroah-Hartman]

From: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>

commit ec649c9d454ea372dcf16cccf48250994f1d7788 upstream.

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@xxxxxxxxx
Fixes: 810e24e009cf71 ("mm/mmu_notifiers: annotate with might_sleep()")
Signed-off-by: Ville Syrjl <ville.syrjala@xxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1016,12 +1016,13 @@ 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