On Sat, Dec 28, 2013 at 08:45:04PM -0500, Sasha Levin wrote: > Check if the flag is already set before setting it, and vice versa > for clearing. > > Obviously setting or clearing a flag twice isn't a problem on it's > own, but it implies that there's an issue where some piece of code > assumed an opposite state of the flag.
BUG() is overkill. WARN_ONCE is more then enough. And I don't think this kind of checks make sense for all flags. Have you seen any obviously broken case which these checks could catch? > Signed-off-by: Sasha Levin <[email protected]> > --- > include/linux/page-flags.h | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index d1fe1a7..36b0bef 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -130,6 +130,12 @@ enum pageflags { > > #ifndef __GENERATING_BOUNDS_H > > +#ifdef CONFIG_DEBUG_VM_PAGE_FLAGS > +#define VM_ASSERT_FLAG(assert, page) VM_BUG_ON_PAGE(assert, page) > +#else > +#define VM_ASSERT_FLAG(assert, page) do { } while (0) > +#endif > + > /* > * Macros to create function definitions for page flags > */ > @@ -139,11 +145,13 @@ static inline int Page##uname(const struct page *page) > \ > > #define SETPAGEFLAG(uname, lname) \ > static inline void SetPage##uname(struct page *page) \ > - { set_bit(PG_##lname, &page->flags); } > + { VM_ASSERT_FLAG(Page##uname(page), page); \ > + set_bit(PG_##lname, &page->flags); } > > #define CLEARPAGEFLAG(uname, lname) \ > static inline void ClearPage##uname(struct page *page) > \ > - { clear_bit(PG_##lname, &page->flags); } > + { VM_ASSERT_FLAG(!Page##uname(page), page); \ > + clear_bit(PG_##lname, &page->flags); } > > #define __SETPAGEFLAG(uname, lname) \ > static inline void __SetPage##uname(struct page *page) > \ > -- > 1.8.3.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
