From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1F4D61E0DD5 for ; Mon, 6 Jan 2025 19:34:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736192057; cv=none; b=IAqcjhLa+IGFmRuHKEm/b6s5I+T98mscXQ7qAUqgI2V3LHv3D157zcOqu8s8efRFRx4VAYNlWVo8vbqgpFEIHng8QfT1Eb9Gi5cfWY6TqmHGXFiKoAu9a5a+uJiOycNC0UxiCtVAFCkYRcRR1v4pI26aawFQnMyapcG981umYGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736192057; c=relaxed/simple; bh=GB3sXo3jAtM81w79ykpn4c5FBCPRD/E0J0LJOVeLMes=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=d9x59/l2wpzGFxqDTZwFtz/rE5xwIBQQxrJTjILVXOSN6nQ/4EtTraPHKd14QSyC9w1J/FO8z/6ZTA4Tk4cuSbmICKixN9D66vCRtrFaUDqqduuqgSoWcRQFj92wePjNK7IeP+J02UtvebtwJmRVZlra0HxNDb8LTBlK/8AdRyM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=U7kYTXgJ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U7kYTXgJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736192054; 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: in-reply-to:in-reply-to:references:references; bh=WPwn/8SQnPxOYFh1+f07h1WSOgnvETMG9MM+HTA/pYY=; b=U7kYTXgJlS8Ed1lq3T34tfamyZ8u45Y8H2RAE95fFXa4okDdhMd/8OxMAHKxd2kXQefUba 0nD85IoNOCh9ZRuPLVsR4qZUUuCHDFMN1wIIC+xbBWrelO4MgbuK+khRsu8sRbQL6Q8i1+ uyLAj9JmbXauxex9tmYRJbAFKySwHdg= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-180-1S819-6uM7CS8FErvQe9vw-1; Mon, 06 Jan 2025 14:34:08 -0500 X-MC-Unique: 1S819-6uM7CS8FErvQe9vw-1 X-Mimecast-MFC-AGG-ID: 1S819-6uM7CS8FErvQe9vw Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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 mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 197761955F42; Mon, 6 Jan 2025 19:34:06 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.102]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 64F8B1956053; Mon, 6 Jan 2025 19:34:03 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 6 Jan 2025 20:33:40 +0100 (CET) Date: Mon, 6 Jan 2025 20:33:37 +0100 From: Oleg Nesterov To: Linus Torvalds Cc: Manfred Spraul , Christian Brauner , David Howells , WangYuli , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: wakeup_pipe_readers/writers() && pipe_poll() Message-ID: <20250106193336.GH7233@redhat.com> References: <20241229135737.GA3293@redhat.com> <20250102163320.GA17691@redhat.com> <20250106163038.GE7233@redhat.com> <20250106183646.GG7233@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250106183646.GG7233@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Damn ;) It is amazing how much unnecessary spam I added to these discussions. But let me ask 2 more questions, hopefully no more. 1. pipe_read() says * But when we do wake up writers, we do so using a sync wakeup * (WF_SYNC), because we want them to get going and generate more * data for us. OK, WF_SYNC makes sense if pipe_read() or pipe_write() is going to do wait_event() after wake_up(). But wake_up_interruptible_sync_poll() looks at bit misleading if we are going to wakeup the writer or next_reader before return. 2. I can't understand this code in pipe_write() if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) { int err = file_update_time(filp); if (err) ret = err; sb_end_write(file_inode(filp)->i_sb); } - it only makes sense in the "fifo" case, right? When i_sb->s_magic != PIPEFS_MAGIC... - why should we propogate the error code if "ret > 0" but file_update_time() fails? Oleg.