netdev - Re: [PATCH] TX_RING and packet mmap

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Message-ID: <7e0dd21a0904181438j251f4f8cnc210c6dee8ce5212@mail.gmail.com>
Date:	Sat, 18 Apr 2009 23:38:48 +0200
From:	Johann Baudy <johann.baudy@...-log.net>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>, jamal <hadi@...erus.ca>
Subject: Re: [PATCH] TX_RING and packet mmap

> I think it should only be called when shared area is about to be freed
> and not when attached skb is freed.
During skb_linearize(). shared info is memcopied and freed in
pskb_expand_head() if not enough memory is available in current head.
Then, Do you expect this new destructor to be called twice? (during
skb_linearize() and kfree_skb())

>Thus you can put your pages into
> fraglist and reuse them after the last reference to the shared area is
> gone.

If my understanding is correct, skb can be linearized without calling
skb_release_data() (if enough space is available in head). Hence, In
this case, I will not have access to original frags[] from
skb_shared_info destructor.

Thanks again,
Johann
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