Messages in this thread | | | Date | Fri, 20 Mar 2015 10:04:16 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages |
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On Fri, Mar 20, 2015 at 03:32:05PM +0800, Hillf Danton wrote: > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -269,7 +269,7 @@ static inline struct page *compound_head_fast(struct page *page) > > return page; > > } > > > > -TESTPAGEFLAG(Locked, locked, ANY) > > +__PAGEFLAG(Locked, locked, NO_TAIL) > > PAGEFLAG(Error, error, ANY) TESTCLEARFLAG(Error, error, ANY) > > PAGEFLAG(Referenced, referenced, ANY) TESTCLEARFLAG(Referenced, referenced, ANY) > > __SETPAGEFLAG(Referenced, referenced, ANY) > [...] > > @@ -490,9 +481,9 @@ extern int wait_on_page_bit_killable_timeout(struct page *page, > > > > static inline int wait_on_page_locked_killable(struct page *page) > > { > > - if (PageLocked(page)) > > - return wait_on_page_bit_killable(page, PG_locked); > > - return 0; > > + if (!PageLocked(page)) > > + return 0; > > I am lost here: can we feed any page to NO_TAIL operation?
NO_TAIL triggers VM_BUG on set/clear, but not on checks. PageLocked() will look on head page.
I tried to enforce policy for checks too, but it triggers all over the kernel. We tend to check random pages.
We can try apply enforcing for *some* flags, but I didn't evaluate that.
-- Kirill A. Shutemov
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