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 0547343DED9 for ; Fri, 11 Sep 2026 07:17:03 +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=1789111034; cv=none; b=k3Wm8yAGf5ckjJQNsb5pe5VfvUGm00UOMQF7f3Op8iBW7XKJ43rOUZhzSVUHM3/fnMhxKWpgeohws70AaLY37HJMKg4H+IFHWpkghLExZbxmnyvjFs61ZcSS9lDApheuQen4u03HQkbZ8AkYgw+SsnbtXvc1Tke3vZZrNZHQ/cM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789111034; c=relaxed/simple; bh=6sM511Yghy0FHDLvevziRdPvpQEZD+8AKouYt7mgOik=; h=From:In-Reply-To:References:To:Cc:Subject:MIME-Version: Content-Type:Date:Message-ID; b=TUJ3G+4NJMBtXDPEubfQ7kIRtonTHTCSXttYJ8dmpDEibpTquOQo9lgRtC0J9p2zWFzxC5rQ4bCaijMR8CiyFUTMZEeI5hn07GWSqgXmOsUe9ljlYOQfqa/ETjGs+egxGx4Jl0f91llV3xytnYcnZEDJOdci/VIjBQ546SmQrck= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=eM8ZyH0f; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="eM8ZyH0f" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1789111020; 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=VuQgHOd1pJjLYwSa9FuLfTu/u2Cf9iOR7RKv6iApg+w=; b=eM8ZyH0fShQYRLUzalCry11X4devxwuuyrl5dLBMjFYAn/raMVViq68+yucJfYDeVahi+F 4lxRRHTXGUFPJ0Oncw2KW31sNih9SrVu3VWg/0kECAhVWVVKxw+bIx/CBIJJQ69sHifCbY cDWbT2tuKD87K4RNHy0XoZsbfpN9geM= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-612-7tEUIbcYPEuyro1qP9-SsA-1; Fri, 11 Sep 2026 03:16:55 -0400 X-MC-Unique: 7tEUIbcYPEuyro1qP9-SsA-1 X-Mimecast-MFC-AGG-ID: 7tEUIbcYPEuyro1qP9-SsA_1789111013 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C92F218005B2; Fri, 11 Sep 2026 07:16:52 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.44.32.54]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 038F618004D4; Fri, 11 Sep 2026 07:16:47 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: To: Michael Mulqueen Cc: dhowells@redhat.com, ericvh@kernel.org, lucho@ionkov.net, asmadeus@codewreck.org, pc@manguebit.org, linux_oss@crudebyte.com, v9fs@lists.linux.dev, netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, regressions@lists.linux.dev Subject: Re: PROBLEM: [REGRESSION 7.1-rc4 -> 7.1-rc5] 9p: silent NUL corruption of file data on cache modes with CACHE_WRITEBACK Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <2208515.1789111006.1@warthog.procyon.org.uk> Date: Fri, 11 Sep 2026 08:16:46 +0100 Message-ID: <2208516.1789111006@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Michael Mulqueen wrote: > A 9p mount returns NULs in place of file contents the server holds, and can > write those NULs back over the server's copy. Nothing reports an error - the > read succeeds and the file is the correct length. Affects CACHE_WRITEBACK > modes - mmap, loose and fscache - but not none or readahead. Are you actually using this with a cache? Or just enabling the "use a cache" options? David