On (09/23/15 16:22), Kirill A. Shutemov wrote: [..] > khugepaged does swap in during collapse under anon_vma lock. It causes > complain from lockdep. The trace below shows following scenario: > > - khugepaged tries to swap in a page under mmap_sem and anon_vma lock; > - do_swap_page() calls swapin_readahead() with GFP_HIGHUSER_MOVABLE; > - __read_swap_cache_async() tries to allocate the page for swap in; > - lockdep_trace_alloc() in __alloc_pages_nodemask() notices that with > given gfp_mask we could end up in direct relaim. > - Lockdep already knows that reclaim sometimes (e.g. in case of > split_huge_page()) wants to take anon_vma lock on its own. > > Therefore deadlock is possible. [..] Gave it some testing on my box. Works fine on my side. I guess you can add (if needed) Tested-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> -ss > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Reported-by: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> > --- > mm/huge_memory.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index dd58ecfcafe6..06c8f6d8fee2 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2725,10 +2725,10 @@ static void collapse_huge_page(struct mm_struct *mm, > goto out; > } > > - anon_vma_lock_write(vma->anon_vma); > - > __collapse_huge_page_swapin(mm, vma, address, pmd); > > + anon_vma_lock_write(vma->anon_vma); > + > pte = pte_offset_map(pmd, address); > pte_ptl = pte_lockptr(mm, pmd); > > -- > Kirill A. Shutemov > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>