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[2620:137:e000::1:20]) by mx.google.com with ESMTP id n18-20020a170902d2d200b001a04ed06ea0si13727602plc.419.2023.04.18.19.19.03; Tue, 18 Apr 2023 19:19:14 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@manguebit.com header.s=dkim header.b=prf48Ijv; arc=pass (i=1); spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=manguebit.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231496AbjDSCQ7 (ORCPT + 99 others); Tue, 18 Apr 2023 22:16:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231159AbjDSCQ5 (ORCPT ); Tue, 18 Apr 2023 22:16:57 -0400 Received: from mx.manguebit.com (mx.manguebit.com [167.235.159.17]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3609D2681; Tue, 18 Apr 2023 19:16:53 -0700 (PDT) Message-ID: <03d46708ca8adaf2fe98689e04c98541.pc@manguebit.com> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=manguebit.com; s=dkim; t=1681870610; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xwuO365E3uWJjHSCA6WvcUrrebXU0puVdAVof+NAIBk=; b=prf48IjvaTQG15ExjQ/iMTOUBexRi1XKhmRMZWqjIfwDnPeBw5B81xfseexaew9Q1TfKtv eZ7CljqWYTnugydnfn9aUtYvvl4dW7wIIMUqgg8FUbfW/POzf1ryjQVdJv/hyQTNM63Ag6 ygygP9aIImvP6OGEv2/oykEvw1zfpSozjFkrMzbjkPxkqkLXg8N6E6P2Kr3QvwyiksAk04 UBDW0NpTKc2dSAk8v6Tb1Gy5gadJbU92BgsZB35Ha+IiknBdwXWO4hq6aclO4eMZP97hvS IYmnhZvSmxbclMK9UxJDPCsoS0j2j/1iVwaby70TV941cWK4HmWrs68ouhQuUA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=manguebit.com; s=dkim; t=1681870610; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xwuO365E3uWJjHSCA6WvcUrrebXU0puVdAVof+NAIBk=; b=CuhbOYftU+3lzams5OIgKou8sm6usykvy8iEAiiO0vhMDTt40Tb+feXmEV3jyMFTNwm2Zi rN0tcEhXYzdcBGbXc8P8Ug+KR2iqjVIY+noKPYBvEO2A+71B/uowYCBCfTBTsVpKuM5a9D cCCpF1OwGULVDgT3Y3ti78l9gFJ3643mL27/8Ym/sAMeEBFuUaOJ/bylZKD/j5Vb16rz7U zWp2BefO4C/kFClXizk/HLhmTPPIPjQ6xubcRRhjMOD/fzCyq8nKeyDnKx8FZlYvw1T41e eb4RAQXYRqtsI3Zv7zvSpnKWQAjtnPpSoyTpcZAqVcPJKEmcphOR0ThdaHYHww== ARC-Authentication-Results: i=1; ORIGINATING; auth=pass smtp.auth=pc@manguebit.com smtp.mailfrom=pc@manguebit.com ARC-Seal: i=1; s=dkim; d=manguebit.com; t=1681870610; a=rsa-sha256; cv=none; b=izNevIs0sGaspWAvKtlZKGm8XHoRXRhjpwxfC36SVd//nNpIKJlJoUrHAeapwgyQRFjwe0 Itnk5ePF+56GcN6KX9YTvzM93EDVCnIzUiKlvn5QZTSO25tcr3XTNvOiA6CLRMdeayYoDJ 3JYPFWXWqhjYAuQtRMSEizFY/t+CY0MAvLmevReQvXBIDUUMPY7jz7f92FSu+4FhYMWwbs 8RYspDbxN5vmhXiAJ/yxQwD3hafu49ledalfHUg+4EiK+sOVVzKC3OVZyU2fKUpQVLHiwj UXiwn7LTGgNwMMrLRngmF26yVWrATDyzKu6NoHGEILMYssC5yzG51ArwZ7PH3A== From: Paulo Alcantara To: David Howells , Steve French Cc: dhowells@redhat.com, =?utf-8?B?SsOpcsO0bWU=?= Glisse , Long Li , Enzo Matsumiya , Shyam Prasad N , Rohith Surabattula , Jeff Layton , linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cifs: Fix unbuffered read In-Reply-To: <1692048.1681857607@warthog.procyon.org.uk> References: <1692048.1681857607@warthog.procyon.org.uk> Date: Tue, 18 Apr 2023 23:16:45 -0300 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Howells writes: > If read() is done in an unbuffered manner, such that, say, > cifs_strict_readv() goes through cifs_user_readv() and thence > __cifs_readv(), it doesn't recognise the EOF and keeps indicating to > userspace that it returning full buffers of data. > > This is due to ctx->iter being advanced in cifs_send_async_read() as the > buffer is split up amongst a number of rdata objects. The iterator count > is then used in collect_uncached_read_data() in the non-DIO case to set t= he > total length read - and thus the return value of sys_read(). But since t= he > iterator normally gets used up completely during splitting, ctx->total_len > gets overridden to the full amount. > > However, prior to that in collect_uncached_read_data(), we've gone through > the list of rdatas and added up the amount of data we actually received > (which we then throw away). > > Fix this by removing the bit that overrides the amount read in the non-DIO > case and just going with the total added up in the aforementioned loop. > > This was observed by mounting a cifs share with multiple channels, e.g.: > > mount //192.168.6.1/test /test/ -o user=3Dshares,pass=3D...,max_channels= =3D6 > > and then reading a 1MiB file on the share: > > strace cat /xfstest.test/1M >/dev/null > > Through strace, the same data can be seen being read again and again. >=20=20=20=20=20 > Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rathe= r than a page list") > Signed-off-by: David Howells > cc: Steve French > cc: Paulo Alcantara > cc: J=C3=A9r=C3=B4me Glisse > cc: Long Li > cc: Enzo Matsumiya > cc: Shyam Prasad N > cc: Rohith Surabattula > cc: Jeff Layton > cc: linux-cifs@vger.kernel.org > --- > fs/cifs/file.c | 4 ---- > 1 file changed, 4 deletions(-) Acked-by: Paulo Alcantara (SUSE)