From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jann Horn <jannh@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>,
Russell King <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Mark Salter <msalter@redhat.com>,
Aurelien Jacquiot <jacquiot.aurelien@gmail.com>,
linux-c6x-dev@linux-c6x.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>,
Linux-sh list <linux-sh@vger.kernel.org>
Subject: Re: [PATCH 5/5] mm/gup: Take mmap_sem in get_dump_page()
Date: Mon, 27 Apr 2020 20:50:40 -0700 [thread overview]
Message-ID: <CAHk-=wgBNSQhH1gyjo+Z2NFy4tOQnBQB4rra-jh+3XTpOjnThQ@mail.gmail.com> (raw)
In-Reply-To: <20200428032745.133556-6-jannh@google.com>
On Mon, Apr 27, 2020 at 8:28 PM Jann Horn <jannh@google.com> wrote:
>
> Properly take the mmap_sem before calling into the GUP code from
> get_dump_page(); and play nice, allowing __get_user_pages_locked() to drop
> the mmap_sem if it has to sleep.
This makes my skin crawl.
The only reason for this all is that page cache flushing.
My gut feeling is that it should be done by get_user_pages() anyway,
since all the other users presumably want it to be coherent in the
cache.
And in fact, looking at __get_user_pages(), it already does that
if (pages) {
pages[i] = page;
flush_anon_page(vma, page, start);
flush_dcache_page(page);
ctx.page_mask = 0;
}
and I think that the get_dump_page() logic is unnecessary to begin with.
Linus
next prev parent reply other threads:[~2020-04-28 3:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 3:27 [PATCH 0/5] Fix ELF / FDPIC ELF core dumping, and use mmap_sem properly in there Jann Horn
2020-04-28 3:27 ` [PATCH 1/5] binfmt_elf_fdpic: Stop using dump_emit() on user pointers on !MMU Jann Horn
2020-04-28 3:27 ` [PATCH 2/5] coredump: Fix handling of partial writes in dump_emit() Jann Horn
2020-04-28 3:35 ` Linus Torvalds
2020-04-28 5:52 ` Jann Horn
2020-04-28 16:40 ` Rob Landley
2020-04-28 16:40 ` Linus Torvalds
2020-04-28 3:27 ` [PATCH 3/5] coredump: Refactor page range dumping into common helper Jann Horn
2020-04-28 3:27 ` [PATCH 4/5] binfmt_elf, binfmt_elf_fdpic: Use a VMA list snapshot Jann Horn
2020-04-28 3:27 ` [PATCH 5/5] mm/gup: Take mmap_sem in get_dump_page() Jann Horn
2020-04-28 3:50 ` Linus Torvalds [this message]
2020-04-28 6:10 ` Jann Horn
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