Messages in this thread | | | Date | Wed, 11 Oct 2006 18:57:18 +0200 | From | Nick Piggin <> | Subject | Re: SPAM: Re: [patch 2/5] mm: fault vs invalidate/truncate race fix |
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On Wed, Oct 11, 2006 at 09:21:16AM -0700, Linus Torvalds wrote: > > > On Tue, 10 Oct 2006, Andrew Morton wrote: > > > > On Wed, 11 Oct 2006 15:39:22 +1000 > > Nick Piggin <nickpiggin@yahoo.com.au> wrote: > > > > > But I see that it does read twice. Do you want that behaviour retained? It > > > seems like at this level it would be logical to read it once and let lower > > > layers take care of any retries? > > > > argh. Linus has good-sounding reasons for retrying the pagefault-path's > > read a single time, but I forget what they are. Something to do with > > networked filesystems? (adds cc) > > Indeed. We _have_ to re-try a failed IO that we didn't start ourselves. > > The original IO could have been started by a person who didn't have > permissions to actually carry it out successfully, so if you enter with > the page locked (because somebody else started the IO), and you wait for > the page and it's not up-to-date afterwards, you absolutely _have_ to try > the IO, and can only return a real IO error after your _own_ IO has > failed.
Sure, but we currently try to read _twice_, don't we?
> There is another issue too: even if the page was marked as having an error > when we entered (and no longer locked - maybe the IO failed last time > around), we should _still_ re-try. It might be a temporary error that has > since gone away, and if we don't re-try, we can end up in the totally > untenable situation where the kernel makes a soft error into a hard one.
Yes, and in that case I think the page should be !Uptodate, so no problem there. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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