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Thu, 22 Oct 2020 19:26:21 +1100 (AEDT) Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2ABFB2065D; Thu, 22 Oct 2020 08:26:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603355177; bh=dmCNgDGTpNmF+8O2fjJO2XplnMkrwwsAXNmOMHG4kDE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=zDx/QVbNU8SimNSxRnLGamZjzaL0aYk8447/KE6GRihUCtWhJ6Z86tE/3/Weg2vwC GiWZsECpqwLisbFLZe5yubGxrkvnswusVy8o3gK7vn/eUfbf4ADoW/+TTZixBrP7Y/ ZuwgVCa1BoOMrly/6gJ13uZ1QxD/B6i974xOGQS0= Date: Thu, 22 Oct 2020 10:26:54 +0200 From: Greg KH To: Al Viro , Nick Desaulniers Subject: Re: Buggy commit tracked to: "Re: [PATCH 2/9] iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c" Message-ID: <20201022082654.GA1477657@kroah.com> References: <20200925045146.1283714-1-hch@lst.de> <20200925045146.1283714-3-hch@lst.de> <20201021161301.GA1196312@kroah.com> <20201021233914.GR3576660@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201021233914.GR3576660@ZenIV.linux.org.uk> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, linux-mips@vger.kernel.org, David Howells , linux-mm@kvack.org, keyrings@vger.kernel.org, sparclinux@vger.kernel.org, Christoph Hellwig , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, kernel-team@android.com, Arnd Bergmann , linux-block@vger.kernel.org, io-uring@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jens Axboe , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, David Laight , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote: > On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote: > > On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote: > > > From: David Laight > > > > > > This lets the compiler inline it into import_iovec() generating > > > much better code. > > > > > > Signed-off-by: David Laight > > > Signed-off-by: Christoph Hellwig > > > --- > > > fs/read_write.c | 179 ------------------------------------------------ > > > lib/iov_iter.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++ > > > 2 files changed, 176 insertions(+), 179 deletions(-) > > > > Strangely, this commit causes a regression in Linus's tree right now. > > > > I can't really figure out what the regression is, only that this commit > > triggers a "large Android system binary" from working properly. There's > > no kernel log messages anywhere, and I don't have any way to strace the > > thing in the testing framework, so any hints that people can provide > > would be most appreciated. > > It's a pure move - modulo changed line breaks in the argument lists > the functions involved are identical before and after that (just checked > that directly, by checking out the trees before and after, extracting two > functions in question from fs/read_write.c and lib/iov_iter.c (before and > after, resp.) and checking the diff between those. > > How certain is your bisection? The bisection is very reproducable. But, this looks now to be a compiler bug. I'm using the latest version of clang and if I put "noinline" at the front of the function, everything works. Nick, any ideas here as to who I should report this to? I'll work on a fixup patch for the Android kernel tree to see if I can work around it there, but others will hit this in Linus's tree sooner or later... thanks, greg k-h