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Mon, 31 Jul 2023 12:40:24 -0700 (PDT) Date: Mon, 31 Jul 2023 20:40:24 +0100 From: Lorenzo Stoakes To: David Hildenbrand Cc: Baoquan He , Jiri Olsa , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Uladzislau Rezki , Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro Subject: Re: [PATCH v8 1/4] fs/proc/kcore: avoid bounce buffer for ktext data Message-ID: References: <86fd0ccb-f460-651f-8048-1026d905a2d6@redhat.com> <32b8c5e4-c8e3-0244-1b1a-ca33bd44f38a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32b8c5e4-c8e3-0244-1b1a-ca33bd44f38a@redhat.com> X-Rspamd-Queue-Id: E2EB612000F X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 3hq9hy6c83mcgxokid98pokochwdf9ms X-HE-Tag: 1690832426-290698 X-HE-Meta: U2FsdGVkX19fi0K5hs+tIthNQ8zIkgWVozd/LhHVU2b4KgknE+ddY9Q+k+HBJH5Mpir7wZjN9DuYmesLdXY941LZBJLJDxamL616LXWjEeZKNNhun+GEGgLLzm5/xqKHkjx2WSmcrbHvFXBD4GMDemDVbh3tNxpv/YTS7qn3bsDfI63CHn7HVmgLtqXzLljW182SAqT5+q+ZxhPutUcU9dAonnIEnykbxk6MiAQFO6bVrf4OeLOvy8sgKSYJdzSfqvcwH5G29Xi25Oo3uWSJdMxgNkV4ddyfWyt5+o208dNQQZkEYtT0fSYybQt2TVuOVmG4iarxHGwQK7bpvN9tB7XNy/rDFAYVd5BzzXSp43SJ4JRAnQBKNlcv6c82eCqkV3DJ1jw4z9Qmaa39SHBhXaQfaDWdA8CDwNrdMNRsC75dyjPqtghPl6GSgC130mlaxKFuknDc45+PqmmKEuGDP8NIaFO/y3Qya337c/TXzTZK52SO/x7O8taLn61fR38fgGkPblso79sHaq9TERlfEH1MCZRV6ZQBYtTKfqS16/Nd2LQpkxRzYTNRLKd+M4H+IgiMFkBzWwSSVeJn3BnIqXBJ7MmN+M2XMIyUgkqkGLp4/iu/w+WeBjL8PY1o9uF7sv+ArQnzM3APreaCaPbvU0rGsHid/jlZH9tFQJkWWT99ArMu4pzneiAQ+JDzC+lUCKGyreXz/o3fgfoAHUoK715IHB+7h+cJlZiZrg7TAOFn8RdYK6eAAbWD56E2gMqoYjKeBJ2+sfJDzy/qx6wJBWQVRcc1OQxF9J9o1Txhnrl6LnAk0dJMXwndi28Acq80kUbhbhUL7dGOFxzDwwyixyVDAQCKnud2rgrIhcLBqrcjMufXGLJ1OEGXK1rnJzhFqH+hQpv9oFPoMo0xj01J0T+mAm3i9atdRJpb7FTj/+1NMy8z6BQUL5+J9fWxz+kPEEUUa/506SAVq+LMM1u dJv4+Aa3 Q60pphRT39Zp3OiLcdsk8QjLKQn2RIXwKkNpTQJLbf6Q4qVFLiqnkPqNsdbmG+RzK/UjT5dXbb4w21QA4e2lLF/tVNLD1Akc9yBzE5SZYzmxqE61A1BmyY7CbpuUD9K1QjQgbhAK3ji0lFYWZfcHdpuig2H0qfHnWlGx7SZsGPzq8Q/1IH/PUe8vNvYZUd0H6hFFbNFs7L/9+UR1OZgGi6xrnlviuQnUc58dJoYzTPizXD8T3Jv0fmz2N9BTlrtCG1OgYHuoVhJFU85otwrs3pckL1+nP/z8ZE1RLmDJCUpi2P849u+Hh5UlFfvMy4L1BkLmDRKI3jjxxDkUjTrGPVxwd69pBopKV/S6ZgWtluszqoLZI6Yhl6+DUAJrIqVHzRfGSeY4e6LKw6TK64rLkH+HUXl8oRrfmEppo+gSTiboC66TPIONm9b26qQZhr0iXFkj7qadWjl5xd6U= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 31, 2023 at 09:24:50PM +0200, David Hildenbrand wrote: > On 31.07.23 21:21, Lorenzo Stoakes wrote: > > On Mon, Jul 24, 2023 at 08:23:55AM +0200, David Hildenbrand wrote: > > > Hi, > > > > > > > > > > > I met this too when I executed below command to trigger a kcore reading. > > > > I wanted to do a simple testing during system running and got this. > > > > > > > > makedumpfile --mem-usage /proc/kcore > > > > > > > > Later I tried your above objdump testing, it corrupted system too. > > > > > > > > > > What do you mean with "corrupted system too" -- did it not only fail to > > > dump the system, but also actually harmed the system? > > > > > > @Lorenzo do you plan on reproduce + fix, or should we consider reverting > > > that change? > > > > > > -- > > > Cheers, > > > > > > David / dhildenb > > > > > > > Apologies I mised this, I have been very busy lately not least with book :) > > > > Concerning, I will take a look as I get a chance. I think the whole series > > would have to be reverted which would be... depressing... as other patches > > in series eliminates the bounce buffer altogether. > > > > I spotted > > https://lkml.kernel.org/r/069dd40aa71e634b414d07039d72467d051fb486.camel@gmx.de > Find that slightly confusing, they talk about just reveritng the patch but then also add a kern_addr_valid()? I'm also confused about people talking about just reverting the patch, as 4c91c07c93bb drops the bounce buffer altogether... presumably they mean reverting both? Clearly this is an arm64 thing (obviously), I have some arm64 hardware let me see if I can repro... Baoquan, Jiri - are you reverting more than just the one commit? And does doing this go from not working -> working? Or from not working (worst case oops) -> error? > today, maybe that's related. > > -- > Cheers, > > David / dhildenb >