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Biederman" , Oleg Nesterov , Russell King , Linux ARM , Mark Salter , Aurelien Jacquiot , linux-c6x-dev@linux-c6x.org, Yoshinori Sato , Rich Felker , Linux-sh list References: <20200428032745.133556-1-jannh@google.com> <20200428032745.133556-3-jannh@google.com> From: Rob Landley Message-ID: <94141fbb-9559-1851-54c1-cdc5fc529a1a@landley.net> Date: Tue, 28 Apr 2020 11:40:47 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 4/27/20 10:35 PM, Linus Torvalds wrote: > On Mon, Apr 27, 2020 at 8:28 PM Jann Horn wrote: >> >> After a partial write, we have to update the input buffer pointer. > > Interesting. It seems this partial write case never triggers (except > for actually killing the core-dump). > > Or did you find a case where it actually matters? > > Your fix is obviously correct, but it also makes me go "that function > clearly never actually worked for partial writes, maybe we shouldn't > even bother?" Writes to a local filesystem should never be short unless disk full/error. Once upon a time this was yet another thing that NFS could break that no other filesystem would break, but I dunno about now? (I think the page cache collates it and defers the flush until the error can't be reported back anyway?) Rob