Messages in this thread | | | Date | Wed, 30 May 2018 13:27:50 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH] mm/huge_memory.c: __split_huge_page() use atomic ClearPageDirty() |
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On Wed, May 30, 2018 at 01:50:22AM +0000, Hugh Dickins wrote: > Swapping load on huge=always tmpfs (with khugepaged tuned up to be very > eager, but I'm not sure that is relevant) soon hung uninterruptibly, > waiting for page lock in shmem_getpage_gfp()'s find_lock_entry(), most > often when "cp -a" was trying to write to a smallish file. Debug showed > that the page in question was not locked, and page->mapping NULL by now, > but page->index consistent with having been in a huge page before. > > Reproduced in minutes on a 4.15 kernel, even with 4.17's 605ca5ede764 > ("mm/huge_memory.c: reorder operations in __split_huge_page_tail()") > added in; but took hours to reproduce on a 4.17 kernel (no idea why). > > The culprit proved to be the __ClearPageDirty() on tails beyond i_size > in __split_huge_page(): the non-atomic __bitoperation may have been safe > when 4.8's baa355fd3314 ("thp: file pages support for split_huge_page()") > introduced it, but liable to erase PageWaiters after 4.10's 62906027091f > ("mm: add PageWaiters indicating tasks are waiting for a page bit"). > > Fixes: 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit") > Signed-off-by: Hugh Dickins <hughd@google.com>
Thanks for catching this.
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
-- Kirill A. Shutemov
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