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authorPaolo Bonzini <pbonzini@redhat.com>2013-02-28 05:05:25 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-28 07:10:22 +0400
commit3a2d63f87989e01437ba994df5f297528c353d7d (patch)
tree1630fdaef77fab8baedb15f0318c680654c78068 /drivers
parent75f187aba5e7a3eea259041f85099029774a4c5b (diff)
downloadlinux-3a2d63f87989e01437ba994df5f297528c353d7d.tar.xz
nbd: fsync and kill block device on shutdown
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 <pbonzini@redhat.com> Acked-by: Paul Clements <Paul.Clements@steeleye.com> Cc: Alex Bligh <alex@alex.org.uk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/block/nbd.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 695c68fedd32..869861a87f40 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);