Messages in this thread | | | Date | Thu, 11 Jan 2007 09:32:41 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH 0/4] Improve swap page error handling |
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Richard Purdie wrote:
>>No, not this way, I'm afraid. Sorry, I don't remember the prior >>discussion on LKML, must have flooded past when my attention was >>elsewhere. > > > I think you were cc'd on some of it but you never commented. Anyhow, > I've reworked this patch series based on your comments. The hints were > appreciated, thanks. This was the way I'd originally hoped to be able to > work things, I just couldn't find the right way to do it.
IMO it seems a bit complex for so small a benefit. Last time I was working on this, I thought it would be almost as good to do something simple like stop trying to write out the page if PG_error is set (and clear that bit in delete_from_swap_cache or try_to_unusesomewhere). This way the admin could swapoff and scan the swap device at some point.
>>Is it worth doing this at all? Probably, but I've no experience >>whatsoever of swap write errors, so it's hard for me to judge: my >>guess is that many cases would turn out to be software errors (e.g. >>lower level needing more memory to perform the write). But you'd >>be right to counter: let's assume they're hardware errors, and >>then fix up any software errors when reported. > > > I have a swap block driver where hardware write errors are more likely > and hence have a need to handle them more gracefully than IO loops. It > seems like a good idea to avoid the IO loops anyway. > > >>If it is worth doing this, then you'll need to add code to write >>back the swap header, to note the bad pages permanently: you may >>well have been waiting to see what reception the patches so far >>get, before embarking on that. > > > You can't proceed to do that until you're able to identify the bad pages > so this would be a necessary first step towards that, yes.
Agreed here, FWIW. I think that might be just as well done in userspace?
Nick
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