linux-kernel - Re: [patch for-3.17] mm, thp: fix collapsing of hugepages on madvise

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Message-ID: <CA+55aFx+n_n5wXBE7d+6cL-3ObUqNsJt7ZuuthOb+tmKZYeSyw@mail.gmail.com>
Date:	Sun, 5 Oct 2014 10:15:53 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	stable <stable@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [patch for-3.17] mm, thp: fix collapsing of hugepages on madvise

On Sat, Oct 4, 2014 at 7:48 PM, David Rientjes <rientjes@...gle.com> wrote:
>
> This occurs because the madvise(2) handler for thp, hugepage_advise(),
> clears VM_NOHUGEPAGE on the stack and it isn't stored in vma->vm_flags
> until the final action of madvise_behavior().  This causes the
> khugepaged_enter_vma_merge() to be a no-op in hugepage_advise() when the
> vma had previously had VM_NOHUGEPAGE set.

So color me confused, and when I'm confused I don't apply patches. But
there's no "hugepage_advise()" in my source tree, and quite frankly, I
also don't like how you now separately pass in vm_flags that always
*should* be the same as vma->vm_flags.

Maybe this is against -mm, but it's marked for stable and sent to me,
so I'm piping up about my lack of applying this.

                Linus
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