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Shutemov" To: Matthew Wilcox Cc: Josef Bacik , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: filemap_fault can lose errors Message-ID: <20190911152338.gqqgxrmqycodfocb@box> References: <20190911025158.GG29434@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190911025158.GG29434@bombadil.infradead.org> User-Agent: NeoMutt/20180716 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 Tue, Sep 10, 2019 at 07:51:58PM -0700, Matthew Wilcox wrote: > > If we encounter an error on a page, we can lose the error if we've > dropped the mmap_sem while we wait for the I/O. That can result in > taking the fault multiple times, and retrying the read multiple times. > Spotted by inspection. But does the patch make any difference? Looking into x86 code, VM_FAULT_RETRY makes it retry the fault or return to userspace before it checks for VM_FAULT_SIGBUS bit. -- Kirill A. Shutemov