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Date: Thu, 5 Sep 2002 22:51:24 +0200
To: Andrew Morton <akpm@zip.com.au>
Cc: Chuck Lever <cel@citi.umich.edu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: invalidate_inode_pages in 2.5.32/3
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From: Trond Myklebust <trond.myklebust@fys.uio.no>
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>>>>> " " == Andrew Morton <akpm@zip.com.au> writes:

     > Probably, it worked OK with the global locking because nobody
     > was taking a temp ref against those pages.

But we still have global locking in that readdir by means of the
BKL. There should be no nasty races...

     > Please tell me exactly what semantics NFS needs in there.  Does
     > truncate_inode_pages() do the wrong thing?

Definitely. In most cases we *cannot* wait on I/O completion because
nfs_zap_caches() can be called directly from the 'rpciod' process by
means of a callback. Since 'rpciod' is responsible for completing all
asynchronous I/O, then truncate_inode_pages() would deadlock.

As I said: I don't believe the problem here has anything to do with
invalidate_inode_pages vs. truncate_inode_pages:
  - Pages should only be locked if they are actually being read from
    the server.
  - They should only be refcounted and/or cleared while the BKL is
    held...
There is no reason why code which worked fine under 2.2.x and 2.4.x
shouldn't work under 2.5.x.

Cheers,
  Trond
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