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Message-ID: <20070612112950.GA16477@2ka.mipt.ru> Date: Tue, 12 Jun 2007 15:29:51 +0400 From: Evgeniy Polyakov <johnpol@....mipt.ru> To: Jens Axboe <jens.axboe@...cle.com> Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: [PATCH][RFC] network splice receive On Sat, Jun 09, 2007 at 08:36:09AM +0200, Jens Axboe (jens.axboe@...cle.com) wrote: > On Fri, Jun 08 2007, Evgeniy Polyakov wrote: > > On Fri, Jun 08, 2007 at 06:57:25PM +0400, Evgeniy Polyakov (johnpol@....mipt.ru) wrote: > > > I will try some things for the nearest 30-60 minutes, and then will move to > > > canoe trip until thuesday, so will not be able to work on this idea. > > > > Ok, replacing in fs/splice.c every page_cache_release() with > > static void splice_page_release(struct page *p) > > { > > if (!PageSlab(p)) > > page_cache_release(p); > > } > > Ehm, I don't see why that should be necessary. Except in > splice_to_pipe(), I have considered that we need to pass in a release > function if mapping fails at some point. But it's probably best to do > that in the caller, since they have the knowledge of how to release the > pages. > > The rest of the PageSlab() tests are bogus. I had a crashdump, where page was released via splice_to_pipe() indeed, I did not investigate if it is possible to release provided page in other places. I think if in future there will other slab usage cases except networking receiving, that might be useful, but as is it is not needed. > > and putting cloned skb into private field instead of > > original on in spd_fill_page() ends up without kernel hung. > > Why? Seems pointless to allocate a clone just to hold on to the skb, a > reference should be equally good. I would not be opposed to doing it > this way, I just don't see what a clone buys us as compared to just > holding that reference to the skb. Receiving code does not expect shared skbs - too many fields are changed with assumptions that it is a private copy. > > I'm not sure it is correct, that page can be released in fs/splice.c > > without calling any callback from network code, when network data is > > being processed. > > Please explain! I had a crashdump, where page was attempted to be released in fs/splice.c:splice_to_pipe(), I do not have details handy, but the best solution would be to provide a release callback and use that instead of page_cache_release(). -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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