On 6/10/16 11:41 AM, Darrick J. Wong wrote: > On Fri, Jun 10, 2016 at 08:19:36AM -0400, Brian Foster wrote: >> 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. > > Trouble is, I bet blkid prints LABEL=foo here and not LABEL=derp as > the admin is probably expecting. exactly. And FWIW, when btrfs does it, it *is* visible. > /me wonders if invalidate_inode_pages2_range here would help? Um, not sure. Calling that against metadata from xfs feels a bit bizarre... -Eric _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
