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 0E302442390 for ; Fri, 11 Sep 2026 07:17:02 +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=1789111029; cv=none; b=VHvk/LyrJunJj47ksbWz0JpQ7Xtw1HK7hQEDZU880n+tEnA5HnfbC/jLAfcBIHdxMYnRrFZf+Z2iCRhkRJ8Ru00p2VolDPfJFlsUjazIeHJcZ4bTQenGPdM9bbUJaThD6TrakDtShX3XH2dVY2RkV+0nO8G5ERh0hadUT+z4prw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789111029; c=relaxed/simple; bh=6sM511Yghy0FHDLvevziRdPvpQEZD+8AKouYt7mgOik=; h=From:In-Reply-To:References:To:Cc:Subject:MIME-Version:Date: Message-ID:Content-Type; b=uxudQ+rocMboSg0CKVlHdLiEOn33lbUoz0vTDGClg5pfkO4TLGQR9Wd137K1yduZ0ZEHNMgLM36Lt1OU7nklmCiBOiejmth8F10gO6aO6QAVSXJW1mWsDHKAgEr7NLfClQVX3F2ihVoEx9dr6Dt7dQwxMqYlhdIbwS9mebtdLkE= 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=bxyETBR6; 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="bxyETBR6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1789111019; 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=bxyETBR6wwSquzKLLbiEPguZ32HogAFX1d2Pigsz2CTSt7+SdobQkz8OT1JqnG49v4AuPo AUHMzZP76O4mhxfh3whA8jBpvcMen6Z27rAjLdwh1vqxhcBoiXX6Sg7Kde+pC+7/RifP6y p0xdRrkPiVMCyD7eq+Mn6Q+cxhAjasM= 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: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 X-Mimecast-MFC-PROC-ID: kVlX_WL7ELjn6C8k4mIzTGCMf08fXtzgqaTY9n0U93M_1789111013 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-ID: <2208515.1789111006.1@warthog.procyon.org.uk> 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