Messages in this thread | | | Date | Fri, 9 Feb 2007 11:32:58 +0100 | From | Nick Piggin <> | Subject | Re: [rfc][patch 0/3] a faster buffered write deadlock fix? |
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On Fri, Feb 09, 2007 at 02:09:54AM -0800, Andrew Morton wrote: > On Fri, 9 Feb 2007 10:54:05 +0100 Nick Piggin <npiggin@suse.de> wrote: > > > > > That's still got a deadlock, > > It does?
Yes, PG_lock vs mm->mmap_sem.
> > and also it doesn't work if we want to lock > > the page when performing a minor fault (which I want to fix fault vs > > invalidate), > > It's hard to discuss this without a description of what you want to fix > there, and a description of how you plan to fix it.
http://marc.theaimsgroup.com/?l=linux-mm&m=116865911432667&w=2
> > and also assumes nobody's ->nopage locks the page or > > requires any resources that are held by prepare_write (something not > > immediately clear to me with the cluster filesystems, at least). > > The nopage handler is filemap_nopage(). Are there any exceptions to that?
OCFS2 and GFS2.
> > But that all becomes legacy path, so do we really care? Supposing fs > > maintainers like perform_write, then after the main ones have implementations > > we could switch over to the slow-but-correct prepare_write legacy path. > > Or we could leave it, or we could use Linus's slightly-less-buggy scheme... > > by that point I expect I'd be sick of arguing about it ;) > > It's worth "arguing" about. This is write(). What matters more??
That's the legacy path that uses prepare/commit (ie. supposing that all major filesystems did get converted to perform_write).
Of course I would still want my correct-but-slow version in that case, but I just wouldn't care to argue if you still wanted to keep it fast.
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