From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933317Ab3BLQGi (ORCPT ); Tue, 12 Feb 2013 11:06:38 -0500 Received: from mail-vc0-f176.google.com ([209.85.220.176]:54564 "EHLO mail-vc0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933270Ab3BLQGf (ORCPT ); Tue, 12 Feb 2013 11:06:35 -0500 From: Paolo Bonzini To: linux-kernel@vger.kernel.org Cc: , , Paul Clements , Andrew Morton Subject: [PATCH 2/3] nbd: fsync and kill block device on shutdown Date: Tue, 12 Feb 2013 17:06:10 +0100 Message-Id: <1360685171-3792-3-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1360685171-3792-1-git-send-email-pbonzini@redhat.com> References: <1360685171-3792-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are two problems with shutdown in the NBD driver. The first is that receiving the NBD_DISCONNECT ioctl does not sync the filesystem; this is useful because BLKFLSBUF is restricted to processes that have CAP_SYS_ADMIN, and the NBD client may not possess it (fsync of the block device does not sync the filesystem, either). The second is that once we clear the socket we have no guarantee that later reads will come from the same backing storage. Thus the page cache must be cleaned, lest reads that hit on the page cache will return stale data from the previously-accessible disk. Example: # qemu-nbd -r -c/dev/nbd0 /dev/sr0 # file -s /dev/nbd0 /dev/stdin: # UDF filesystem data (version 1.5) etc. # qemu-nbd -d /dev/nbd0 # qemu-nbd -r -c/dev/nbd0 /dev/sda # file -s /dev/nbd0 /dev/stdin: # UDF filesystem data (version 1.5) etc. While /dev/sda has: # file -s /dev/sda /dev/sda: x86 boot sector; etc. Cc: Cc: Cc: Paul Clements Cc: Andrew Morton Signed-off-by: Paolo Bonzini --- drivers/block/nbd.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 5603765..a9c5c7a 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -608,12 +608,20 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, struct request sreq; dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n"); + if (!nbd->sock) + return -EINVAL; + mutex_unlock(&nbd->tx_lock); + fsync_bdev(bdev); + mutex_lock(&nbd->tx_lock); blk_rq_init(NULL, &sreq); sreq.cmd_type = REQ_TYPE_SPECIAL; nbd_cmd(&sreq) = NBD_CMD_DISC; + + /* Check again after getting mutex back. */ if (!nbd->sock) return -EINVAL; + nbd_send_req(nbd, &sreq); return 0; } @@ -627,6 +635,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, nbd_clear_que(nbd); BUG_ON(!list_empty(&nbd->queue_head)); BUG_ON(!list_empty(&nbd->waiting_queue)); + kill_bdev(bdev); if (file) fput(file); return 0; @@ -719,6 +728,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, nbd->file = NULL; nbd_clear_que(nbd); dev_warn(disk_to_dev(nbd->disk), "queue cleared\n"); + kill_bdev(bdev); queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue); if (file) fput(file); -- 1.7.1