From: Linus Torvalds <torvalds@linux-foundation.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>,
"the arch/x86 maintainers" <x86@kernel.org>,
Song Liu <songliubraving@fb.com>,
"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] mm/vmalloc: huge vmalloc backing pages should be split rather than compound
Date: Fri, 22 Apr 2022 09:23:18 -0700 [thread overview]
Message-ID: <CAHk-=wg09h4_-g6Fc1K5UqA==Zfe1gXQhJcZ6J9Mnopp15gptg@mail.gmail.com> (raw)
In-Reply-To: <20220422060107.781512-2-npiggin@gmail.com>
On Thu, Apr 21, 2022 at 11:01 PM Nicholas Piggin <npiggin@gmail.com> wrote:
>
> Huge vmalloc higher-order backing pages were allocated with __GFP_COMP
> in order to allow the sub-pages to be refcounted by callers such as
> "remap_vmalloc_page [sic]" (remap_vmalloc_range).
>
> However a similar problem exists for other struct page fields callers
> use, for example fb_deferred_io_fault() takes a vmalloc'ed page and
> not only refcounts it but uses ->lru, ->mapping, ->index. This is not
> compatible with compound sub-pages.
>
> The correct approach is to use split high-order pages for the huge
> vmalloc backing. These allow callers to treat them in exactly the same
> way as individually-allocated order-0 pages.
This patch looks ObviouslyCorrect(tm), and you even reproduced the
fbdev problem.
Applied.
Linus
next prev parent reply other threads:[~2022-04-22 16:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-22 6:01 [PATCH 0/2] Request to test fix for "x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP)" Nicholas Piggin
2022-04-22 6:01 ` [PATCH 1/2] mm/vmalloc: huge vmalloc backing pages should be split rather than compound Nicholas Piggin
2022-04-22 16:23 ` Linus Torvalds [this message]
2022-04-22 6:01 ` [PATCH 2/2] Revert "vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP" Nicholas Piggin
2022-04-22 17:08 ` Linus Torvalds
2022-04-22 18:41 ` Linus Torvalds
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