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Date:   Sat, 27 Aug 2022 01:23:17 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     NeilBrown <neilb@suse.de>, Daire Byrne <daire@dneg.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Chuck Lever <chuck.lever@oracle.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/10] VFS: support parallel updates in the one directory.
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On Fri, Aug 26, 2022 at 05:13:38PM -0700, Linus Torvalds wrote:

> So I feel like if the VFS code cannot rely on locking *anyway* in the
> general case, and should work without it, then we really shouldn't
> have any locking around any of the VFS operations.

That's a really big if.  There's a bunch of places where we rely upon
->i_rwsem on directories and _not_ to provide exclusion for fs methods.
I'm still halfway through the Neil's patchset, but verifying correctness
won't be easy and I'm not optimistic about getting rid of those uses...