netdev - Re: skb_splice_bits() and large chunks in pipe (was Re: xfs_file_splice_read: possible circular locking dependency detected

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Message-ID: <20160920095102.GA21088@gondor.apana.org.au>
Date:   Tue, 20 Sep 2016 17:51:02 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     torvalds@...ux-foundation.org, axboe@...nel.dk, npiggin@...il.com,
        linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
        edumazet@...gle.com
Subject: Re: skb_splice_bits() and large chunks in pipe (was Re:
 xfs_file_splice_read: possible circular locking dependency detected

Al Viro <viro@...iv.linux.org.uk> wrote:
>
>        * shoved into scatterlist, which gets fed into crypto/*.c machinery.
> No way for a pipe_buffer stuff to get there, fortunately, because I would
> be very surprised if it works correctly with compound pages and large
> ranges in those.

FWIW the crypto API has always been supposed to handle SG entries
that cross page boundaries.  There were a couple of bugs in this
area but AFAIK they've all been fixed.

Of course I cannot guarantee that every crypto driver also handles
it correctly, but at least we have a few test vectors which test
the page-crossing case specifically.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt