Messages in this thread | | | Date | Wed, 17 Jul 2013 14:09:53 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 5/8] thp, mm: locking tail page is a bug |
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On Mon, 15 Jul 2013 13:47:51 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > > Locking head page means locking entire compound page. > If we try to lock tail page, something went wrong. > > .. > > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -639,6 +639,7 @@ void __lock_page(struct page *page) > { > DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); > > + VM_BUG_ON(PageTail(page)); > __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page, > TASK_UNINTERRUPTIBLE); > } > @@ -648,6 +649,7 @@ int __lock_page_killable(struct page *page) > { > DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); > > + VM_BUG_ON(PageTail(page)); > return __wait_on_bit_lock(page_waitqueue(page), &wait, > sleep_on_page_killable, TASK_KILLABLE); > }
lock_page() is a pretty commonly called function, and I assume quite a lot of people run with CONFIG_DEBUG_VM=y.
Is the overhead added by this patch really worthwhile?
I'm thinking I might leave it in -mm indefinitely but not send it upstream.
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