linux-kernel - Re: [rfc patch 4/4] splice: use do_generic_file

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Message-ID: <20080624080557.GK20851@kernel.dk>
Date:	Tue, 24 Jun 2008 10:05:57 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, torvalds@...ux-foundation.org
Subject: Re: [rfc patch 4/4] splice: use do_generic_file_read()

On Sat, Jun 21 2008, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> __generic_file_splice_read() duplicates a lot of stuff common with the
> generic page cache reading.  So reuse that code instead to simplify
> the page cache splice code.
> 
> This also fixes some corner cases which weren't properly handled in
> the splice code because of complexity issues.  In particular it fixes
> a problem when the filesystem (e.g. fuse) invalidates pages during the
> splice operation.
> 
> There might be some slight fall in performance due to the removal of
> the gang lookup for pages.  However I'm not sure if this is
> significant enough to warrant the extra complication.

This makes everything sync, it's a no go. Why don't we look into fixing
the invalidate problem that fuse sees (can you elaborate on that?)?

I tried to do a quick performance test with your patches for comparison
in the cached case, but it crashes immediately in spd_release_page()


-- 
Jens Axboe

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