On Wed, Apr 23, 2014 at 11:42:47AM +0800, Qiang Huang wrote:
> From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Acked-by: Paul Clements <Paul.Clements@xxxxxxxxxxxx>
> Cc: Alex Bligh <alex@xxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> [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@xxxxxxxxxxxxxxx>
> [hq: Backported to 3.4: Adjusted context]
> Signed-off-by: Qiang Huang <h.huangqiang@xxxxxxxxxx>
Applied, thanks.
greg k-h
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html