Re: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page()

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page()
Date	2016-02-01 15:30 +0100
Message-ID	<qXnEm-45e-5@gated-at.bofh.it> (permalink)
References	<qXmIi-3oo-13@gated-at.bofh.it> <qXmIj-3oo-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Mon 01-02-16 16:26:08, Kirill A. Shutemov wrote:
> We don't care if there's a tail pages which is not on LRU. We are not
> going to isolate them anyway.

yes we are not going to isolate them but calling this function on a
tail page is wrong in principle, no? PageLRU check is racy outside of
lru_lock so what if we are racing here. I know, highly unlikely but not
impossible. So I am not really sure this is an improvement. When would
we hit this VM_BUG_ON and it wouldn't be a bug or at least suspicious
usage?
-- 
Michal Hocko
SUSE Labs

Thread

[PATCH 0/2] Fix another VM_BUG_ON_PAGE(PageTail(page)) on mbind(2) "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-01 14:30 +0100
  [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-01 14:30 +0100
    Re: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page() Michal Hocko <mhocko@kernel.org> - 2016-02-01 15:30 +0100
      Re: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page() "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-02-01 15:40 +0100
        Re: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page() Michal Hocko <mhocko@kernel.org> - 2016-02-02 14:30 +0100
  [PATCH 2/2] mempolicy: do not try to queue pages from !vma_migratable() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-01 14:30 +0100
    Re: [PATCH 2/2] mempolicy: do not try to queue pages from  !vma_migratable() Andrew Morton <akpm@linux-foundation.org> - 2016-02-01 23:30 +0100

csiph-web