diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2013-02-27 17:05:25 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-03-06 03:24:17 +0000 |
| commit | 4189aa4ceebb1cd2b216d88980e35399e299c8c5 (patch) | |
| tree | 98a8596f41272b75dd4cbc2c4fa83d2eece89281 /fs | |
| parent | 0ba15a927d8cf09cab753066736c87831a735987 (diff) | |
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 <pbonzini@redhat.com>
Acked-by: Paul Clements <Paul.Clements@steeleye.com>
Cc: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[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 <ben@decadent.org.uk>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/block_dev.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c index 5db58fc60c0..613edd8822d 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -82,13 +82,14 @@ sector_t blkdev_max_block(struct block_device *bdev) } /* Kill _all_ buffers and pagecache , dirty or not.. */ -static void kill_bdev(struct block_device *bdev) +void kill_bdev(struct block_device *bdev) { if (bdev->bd_inode->i_mapping->nrpages == 0) return; invalidate_bh_lrus(); truncate_inode_pages(bdev->bd_inode->i_mapping, 0); } +EXPORT_SYMBOL(kill_bdev); int set_blocksize(struct block_device *bdev, int size) { |