From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,TVD_SUBJ_WIPE_DEBT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C5E2C433E2 for ; Tue, 1 Sep 2020 17:46:37 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D35A9207D3 for ; Tue, 1 Sep 2020 17:46:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="vkH+jqka" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D35A9207D3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BgvdQ60YkzDqWg for ; Wed, 2 Sep 2020 03:46:34 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=infradead.org (client-ip=2001:8b0:10b:1236::1; helo=casper.infradead.org; envelope-from=willy@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4BgvXn4NV4zDqGg for ; Wed, 2 Sep 2020 03:42:33 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=b2ed4kKOHBE6qB3WmU3cuZU1WUsaY/IfPchrSUMqTzk=; b=vkH+jqkaaXHPFcoC+6AYwSwZ55 cL8pberSXUZvGfrHlSm5svroGmEItBMRukBfiGAyGWzzsFs2JlIoJET0AjGynUvzoRuuD9EsFwXSO rpu2LLzH/Z3ELTKczZYrEsmmrKwgkIGFF07QI0osyEqvGqt2ry2oIIUALpo7x08P3iueFHzVT6YIC pYcxWLqVVwPXrNAHNRJREfFmnbq9QvS2rv6Yoaw088D4/II4Uk7hMNZOVagL8M+s/W/u/VlaA4JdW aH5bnGd4XpvLHTLqX3ShGe32/Fc/7Kkn2Kf1JYKxSTTApeUToFe9GoqbqrR8NBt2Xhc9I3rGIr/M2 MWobY3sg==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDAIS-0005Yb-9R; Tue, 01 Sep 2020 17:42:16 +0000 Date: Tue, 1 Sep 2020 18:42:16 +0100 From: Matthew Wilcox To: Al Viro Subject: Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Message-ID: <20200901174216.GT14765@casper.infradead.org> References: <20200827150030.282762-1-hch@lst.de> <20200901172512.GI1236603@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200901172512.GI1236603@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-arch@vger.kernel.org, Kees Cook , x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Linus Torvalds , Christoph Hellwig Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Sep 01, 2020 at 06:25:12PM +0100, Al Viro wrote: > On Tue, Sep 01, 2020 at 07:13:00PM +0200, Christophe Leroy wrote: > > > 10.92% dd [kernel.kallsyms] [k] iov_iter_zero > > Interesting... Could you get an instruction-level profile inside iov_iter_zero(), > along with the disassembly of that sucker? Also, does [1] make any difference? Probably not since it's translating O flags into IOCB flags instead of RWF flags into IOCB flags. I wonder if there's a useful trick we can play here ... something like: static inline int iocb_flags(struct file *file) { int res = 0; if (likely(!file->f_flags & O_APPEND | O_DIRECT | O_DSYNC | __O_SYNC)) && !IS_SYNC(file->f_mapping->host)) return res; if (file->f_flags & O_APPEND) res |= IOCB_APPEND; if (file->f_flags & O_DIRECT) res |= IOCB_DIRECT; if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host)) res |= IOCB_DSYNC; if (file->f_flags & __O_SYNC) res |= IOCB_SYNC; return res; } Can we do something like force O_DSYNC to be set if the inode IS_SYNC() at the time of open? Or is setting the sync bit on the inode required to affect currently-open files? [1] https://lore.kernel.org/linux-fsdevel/95de7ce4-9254-39f1-304f-4455f66bf0f4@kernel.dk/