On Thu, Jun 09, 2016 at 11:51:12AM -0500, Eric Sandeen wrote:
>
>
> On 6/9/16 11:36 AM, Eric Sandeen wrote:
> > Ok, this more or less works; not really up to snuff
> > for submission or merging, just sketching it out, but some
> > questions first:
> >
> > 1) Is there really any point to this? :) We did have one
> > request, and btrfs can do it ...
> >
Seems reasonable to me. Any details on the use case for the request?
> > 2) Is using m_growlock horrible? growfs is the only other
> > thing that writes all supers, so I grabbed it. We don't
> > want multiple relabels stepping on each other.
> >
> > 3) Is there some way to actually force the primary to disk?
> > Right now the label change isn't actually visible on the
> > primary until unmount, which defeats the purpose. I'm not
> > sure if there's a straightforward/safe way to make it
> > visible...
>
> Oh, sorry - I guess it is getting written out, but it's only
> available via an O_DIRECT read from userspace; it's not
> invalidating the cache.
>
> # io/xfs_io -c "label derp" /mnt/test
> label = "derp"
>
> # dd if=/dev/sdb2 bs=512 count=1 | hexdump -C
> ...
> 00000060 00 00 0a 00 b4 e5 02 00 02 00 00 08 66 6f 6f 00 |............foo.|
> ...
>
> # dd if=/dev/sdb2 iflag=direct bs=512 count=1 | hexdump -C
> ...
> 00000060 00 00 0a 00 b4 e5 02 00 02 00 00 08 64 65 72 70 |............derp|
> ...
>
> # dd if=/dev/sdb2 bs=512 count=1 | hexdump -C
> ...
> 00000060 00 00 0a 00 b4 e5 02 00 02 00 00 08 66 6f 6f 00 |............foo.|
> ...
>
> Guess I need to think about this some more.
>
Isn't this to be expected? You're directly accessing the block device of
a mounted filesystem. I would think this is expected behavior, so long
as the set/get interfaces through the fs are consistent.
Brian
> -Eric
>
> _______________________________________________
> xfs mailing list
> xfs@xxxxxxxxxxx
> http://oss.sgi.com/mailman/listinfo/xfs
|