From: Brian Foster <bfoster@redhat.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 0/4] xfs: online relabeling [RFC]
Date: Fri, 10 Jun 2016 08:19:36 -0400 [thread overview]
Message-ID: <20160610121936.GC21568@bfoster.bfoster> (raw)
In-Reply-To: <2305b486-f336-6d1e-9420-b69dc5bdc572@sandeen.net>
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
>
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next prev parent reply other threads:[~2016-06-10 12:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-09 16:36 [PATCH 0/4] xfs: online relabeling [RFC] Eric Sandeen
2016-06-09 16:38 ` [PATCH 1/4] fs: hoist [GS]ET_FSLABEL to vfs Eric Sandeen
2016-06-09 16:39 ` [PATCH 2/4] xfs: factor out secondary superblock updates Eric Sandeen
2016-06-09 16:41 ` [PATCH 3/4] xfs: implement online get/set fs label Eric Sandeen
2016-06-10 12:19 ` Brian Foster
2016-06-09 16:44 ` [PATCH 4/4] xfsprogs: add online relabel commands Eric Sandeen
2016-06-09 16:51 ` [PATCH 0/4] xfs: online relabeling [RFC] Eric Sandeen
2016-06-10 12:19 ` Brian Foster [this message]
2016-06-10 16:41 ` Darrick J. Wong
2016-06-10 18:12 ` Eric Sandeen
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