Re: MPSAFE VFS -- List of upcoming actions

From: Alexander Kabaev <kabaev_at_gmail.com>
Date: Mon, 2 Jul 2012 11:03:40 -0400
On Mon, Jul 02, 2012 at 02:12:20AM -0400, Christoph Hellwig wrote:
> On Sun, Jul 01, 2012 at 03:52:05PM +0200, Attilio Rao wrote:
> > anything by SoC involved people about NTFS and certainly I don't see a
> > plan to get XFS locked.
> 
> Stupid question, but what amount of locking does XFS in FreeBSD still
> need?  I'm one of the maintainer of XFS on Linux, and while I know
> FreeBSD imported a really old version compared to the current one the
> codebases on IRIX and later Linux never relied on any global Giant-style
> locking.  So if there is anything to fix it would be the in the small
> bits of FreeBSD-specific code.
> 

When I stopped being interested in XFS, I left is marked as non-MPSAFE
entirely because of the lack of proper testing and because VFS locking
was still evolving, there was no officially proper way of locking the
FS and no other FS in the tree was MPSAFE. At that time the only
problematic area was around inode instantiation, but sereval other
lockingi changes have made it into the tree since then, namely ones that
deal with insmntque and also VOP_LOOKUP changes. To mark XFS MPSAFE, one
needs to simply audit the code and make sure it still makse sense for today's
VFS, which is not a huge amount of work. One step further woule be to take
most of the XFS from under the exclusive vnode locking to improve the
performance.

And there is a third option - just let current XFS port die and start with
newer version.

-- 
Alexander Kabaev

Received on Mon Jul 02 2012 - 13:03:45 UTC

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