Messages in this thread | | | Date | Tue, 16 Feb 2010 03:37:12 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH 2/3] mm: Implement writeback livelock avoidance using page tagging |
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On Mon, Feb 15, 2010 at 11:24:53AM -0500, Christoph Hellwig wrote: > On Tue, Feb 16, 2010 at 03:21:27AM +1100, Nick Piggin wrote: > > Also, I wonder what you think about leaving the tags dangling when > > the loop bails out early? I have a *slight* concern about this > > because previously we never have a tag set when radix_tree_delete > > is called. I actually had a bug in that code in earlier versions > > of rcu radix tree that only got found by the user test harness. > > And another slight concern that it is just a bit ugly to leave the > > tag. But I can accept that lower CPU overhead trumps ugliness :) > > The XFS inode cache calls radix_tree_delete with a tag set, and > interestingly enough we're trying to catch a very weird bug in that > area currently, which seems more or less directly related to the use > of tags. But we also had a real locking bug related to tags, so I'm > not yet sure what the issue is back until I hear back from the bug > reported and reproducer.
Upon looking at the radix_tree_delete code again, the tag clearing there seems rather simple so perhaps I misremembered some detail of that bug I had.
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