Re: [PATCH 1/1] fs/mpage.c: forgotten WRITE_SYNC in case of data integrity write

Jan Kara
2014-03-14T14:52:22Z

On Fri 14-03-14 23:23:45, Roman Peniaev wrote:
> On Fri, Mar 14, 2014 at 11:15 PM, Jan Kara <jack@suse.cz> wrote:
> > On Fri 14-03-14 10:11:43, Tejun Heo wrote:
> >> > Also, could you please help me do understand how can I guarantee
> >> > integrity in case of block device with big volatile
> >> > cache and filesystem, which does not support REQ_FLUSH/FUA?
> >>
> >> If a device has a volatile cache but doesn't support flush, it can't
> >> guarantee integrity. There's no way for its user to determine or
> >> force whether certain data is on non-volatile media. It's an
> >> inherently broken device.
> > I think his problem was that the device does support REQ_FLUSH/FUA but
> > the filesystem on top of it doesn't issue it properly. That's a filesystem
> > problem so fix the filesystem... :) Which one is it?
>
> take any old school, e.g. ext2 or even better: fat :)
Well, for ext2, you can use ext4 kernel driver which takes care of
REQ_FLUSH properly. For fat, you'll need to fix the fs...

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR