From: Matthew Wilcox <willy@infradead.org>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>,
zuoze <zuoze1@huawei.com>,
gustavoars@kernel.org, akpm@linux-foundation.org,
linux-hardening@vger.kernel.org, linux-mm@kvack.org,
keescook@chromium.org
Subject: Re: [PATCH -next] mm: usercopy: add a debugfs interface to bypass the vmalloc check.
Date: Tue, 3 Dec 2024 19:56:34 +0000 [thread overview]
Message-ID: <Z09icnP7QuaLg4Qv@casper.infradead.org> (raw)
In-Reply-To: <Z09VwuhfQbbro-gA@pc638.lan>
On Tue, Dec 03, 2024 at 08:02:26PM +0100, Uladzislau Rezki wrote:
I think there are a few other things we can try here.
First, if the copy is small (and I still don't have an answer to that
...), we can skip the vmalloc lookup if the copy doesn't cross a page
boundary.
Second, we could try storing this in a maple tree rather than an rbtree.
That gives us RCU protected lookups rather than under a spinlock.
It might even be worth going to a rwlock first, in case the problem is
that there's severe lock contention.
But I've asked for data on spinlock contention and not received an
answer on that either, so I don't know what to suggest.
Anyway, NACK to the original patch; that's just a horrible idea.
next prev parent reply other threads:[~2024-12-03 19:56 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-03 2:31 Ze Zuo
2024-12-03 4:11 ` Matthew Wilcox
2024-12-03 11:23 ` zuoze
2024-12-03 12:39 ` Uladzislau Rezki
2024-12-03 13:10 ` zuoze
2024-12-03 13:25 ` Uladzislau Rezki
2024-12-03 13:30 ` Kefeng Wang
2024-12-03 13:39 ` Uladzislau Rezki
2024-12-03 13:45 ` Kefeng Wang
2024-12-03 13:51 ` Uladzislau Rezki
2024-12-03 14:10 ` Kefeng Wang
2024-12-03 14:20 ` Uladzislau Rezki
2024-12-03 19:02 ` Uladzislau Rezki
2024-12-03 19:56 ` Matthew Wilcox [this message]
2024-12-04 1:38 ` zuoze
2024-12-04 4:43 ` Kees Cook
2024-12-04 7:55 ` Uladzislau Rezki
2024-12-04 9:21 ` zuoze
2024-12-04 9:27 ` Uladzislau Rezki
2024-12-04 8:51 ` Uladzislau Rezki
2024-12-16 4:24 ` Matthew Wilcox
2024-12-16 19:18 ` Uladzislau Rezki
2024-12-04 1:21 ` zuoze
2024-12-03 6:12 ` Uladzislau Rezki
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