From: Michal Hocko <mhocko@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
hannes@cmpxchg.org, david@redhat.com, vbabka@suse.cz,
willy@infradead.org, akpm@linux-foundation.org,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH] mm/page-flags: Check enforce parameter in PF_ONLY_HEAD()
Date: Wed, 27 Mar 2019 14:15:06 +0100 [thread overview]
Message-ID: <20190327131506.GI11927@dhcp22.suse.cz> (raw)
In-Reply-To: <1553689672-28343-1-git-send-email-anshuman.khandual@arm.com>
[Cc Nick]
On Wed 27-03-19 17:57:52, Anshuman Khandual wrote:
> Just check for enforce parameter in PF_ONLY_HEAD() wrapper before calling
> VM_BUG_ON_PGFLAGS() for tail pages.
Why is this an actual fix? Only TESTPAGEFLAG doesn't enforce the check
but I suspect that Nick just wanted the check to be _always_ performed
as the name suggests. What kind of problem are you trying to solve?
> Fixes: 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit")
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> include/linux/page-flags.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 9f8712a4b1a5..82539e287bc6 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -229,7 +229,7 @@ static inline void page_init_poison(struct page *page, size_t size)
> #define PF_ANY(page, enforce) PF_POISONED_CHECK(page)
> #define PF_HEAD(page, enforce) PF_POISONED_CHECK(compound_head(page))
> #define PF_ONLY_HEAD(page, enforce) ({ \
> - VM_BUG_ON_PGFLAGS(PageTail(page), page); \
> + VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \
> PF_POISONED_CHECK(page); })
> #define PF_NO_TAIL(page, enforce) ({ \
> VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \
> --
> 2.20.1
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-03-27 13:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-27 12:27 [PATCH] mm/page-flags: Check enforce parameter in PF_ONLY_HEAD() Anshuman Khandual
2019-03-27 13:15 ` Michal Hocko [this message]
2019-03-27 13:59 ` Anshuman Khandual
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