From f40ed19c957e23cee2a178a688c45197aa1bc30c Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 27 Feb 2013 17:05:25 -0800 Subject: [PATCH] nbd: fsync and kill block device on shutdown commit 3a2d63f87989e01437ba994df5f297528c353d7d upstream. There are two problems with shutdown in the NBD driver. 1: Receiving the NBD_DISCONNECT ioctl does not sync the filesystem. This patch adds the sync operation into __nbd_ioctl()'s NBD_DISCONNECT handler. 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). 2: Once we clear the socket we have no guarantee that later reads will come from the same backing storage. The patch adds calls to kill_bdev() in __nbd_ioctl()'s socket clearing code so the page cache is 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. Signed-off-by: Paolo Bonzini Acked-by: Paul Clements Cc: Alex Bligh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: - Adjusted context - s/\bnbd\b/lo/ - Incorporate export of kill_bdev() from commit ff01bb483265 ('fs: move code out of buffer.c')] Signed-off-by: Ben Hutchings [hq: Backported to 3.4: Adjusted context] Signed-off-by: Qiang Huang Signed-off-by: Greg Kroah-Hartman --- drivers/block/nbd.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index d724da5..35fc569 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -584,10 +584,17 @@ 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; @@ -606,6 +613,7 @@ 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; @@ -688,6 +696,7 @@ 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); if (file) fput(file); nbd->bytesize = 0; -- 2.7.4