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Thu, 14 Apr 2022 15:24:42 +0000 Received: by hermes--canary-production-gq1-cc54c7bb9-9gfh6 (VZM Hermes SMTP Server) with ESMTPA ID 70fcc1be1711c5a35768f5595215e0c4; Thu, 14 Apr 2022 15:24:38 +0000 (UTC) Date: Thu, 14 Apr 2022 11:24:35 -0400 From: "Alex Xu (Hello71)" Subject: Re: [PATCH] mm/smaps_rollup: return empty file for kthreads instead of ESRCH To: Alexey Dobriyan Cc: Matthew Wilcox , Andrew Morton , Daniel Colascione , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka References: <20220413211357.26938-1-alex_y_xu.ref@yahoo.ca> <20220413211357.26938-1-alex_y_xu@yahoo.ca> <20220413142748.a5796e31e567a6205c850ae7@linux-foundation.org> <1649886492.rqei1nn3vm.none@localhost> <20220413160613.385269bf45a9ebb2f7223ca8@linux-foundation.org> In-Reply-To: MIME-Version: 1.0 Message-Id: <1649949601.z8rr7ed5qb.none@localhost> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Mailer: WebService/1.1.20001 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Alexey Dobriyan's message of April 14, 2022 2:55 am: > Returning ESRCH is better so that programs don't waste time reading and > closing empty files and instantiating useless inodes. Yes, except ESRCH is not returned for open, it is returned for read. > Of course it is different if this patch was sent as response to a regress= ion. I'm not sure I would classify it as a regression; I don't have an=20 existing program which broke, it is a new program which happens to use=20 some functionality which worked with a previous kernel. It is=20 theoretically possible that some program exists that currently uses=20 4.14, and will break if upgraded to 4.19+, but it is also possible that=20 some program exists that currently uses 4.19+ and will break if this=20 patch is applied. Cheers, Alex.