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Mon, 31 Jul 2023 13:34:23 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 31 Jul 2023 22:34:21 +0200 To: Lorenzo Stoakes Cc: David Hildenbrand , 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: X-Rspamd-Queue-Id: 1472340015 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: pmywfw64ecjs8dczpg71wmf55gnzqbca X-HE-Tag: 1690835665-564816 X-HE-Meta: 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 Gm86guIf CYc3Jf+ksJraQcmQfqqMFVXvxmqX20N/BkwS9tqD54XeSN8mKQHgIMN8p0Qz92QrRzQel9NqOjR+oz8NVZWKScF0B4qyL1/xlrVi+53JNo0LgXtfydXD7ILHmIGPWkklopbSUBc+OaQUXr6n+Xb2rnuT3fvFdhDUoeegewBX+BmLD3f9rE3vO+lYO5/VNlR43E/3yT+AitIYR6fIJBKn2gwl8XAxi/AWk8LjJKKZ7g+AMhMJNEUK/Ra5cV/ulDg6QBJQ3urDRoR7YEbSgK9E5YHHcXl+hc8n4eQgBBWAtkefqqUPSiea2OB/E6dzFAOY5w30zukCc94HnVBx8zpzsKNoWAxBmrvWdAuCtoRGBRuEC+S/+j8xo4Xpz5gcIXNzytNw7FuSD40ATBOYFQbnVLJkv48zH0mceZMv2VogfGgUymrueLIVr7ItTsT3zU359ldLMLDBAcRiTMU4aHBkNjdHvBb9yegRT1UTGbSuj7AMWZVo= 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 08:40:24PM +0100, Lorenzo Stoakes wrote: > 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... I see the issue on x86 > > 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? yes, I used to revert all 4 patches I did quick check and had to revert 2 more patches to get clean revert 38b138abc355 Revert "fs/proc/kcore: avoid bounce buffer for ktext data" e2c3b418d365 Revert "fs/proc/kcore: convert read_kcore() to read_kcore_iter()" d8bc432cb314 Revert "iov_iter: add copy_page_to_iter_nofault()" bf2c6799f68c Revert "iov_iter: Kill ITER_PIPE" ccf4b2c5c5ce Revert "mm: vmalloc: convert vread() to vread_iter()" de400d383a7e Revert "mm/vmalloc: replace the ternary conditional operator with min()" jirka