Re: [aarcange@redhat.com: [PATCH] fork vs gup(-fast) fix]

[Andrea Arcangeli <aarcange@redhat.com>]

On Mon, Mar 16, 2009 at 11:14:59AM -0700, Linus Torvalds wrote:
> You may think that the lock isn't particularly "elegant", but I can only 
> say "f*ck that, look at the number of lines of code, and the simplicity".

I'm sorry but the number of lines that you're reading in the
direct_io_worker patch, aren't representative of what it takes to fix
it with a mm wide lock. It may be conceptually simpler to fix it
outside GUP, on that I can certainly agree (with the downside of
leaving splice broken etc..), but I can't see how that small patch can
fix anything as releasing the semaphore after direct_io_worker returns
with O_DIRECT mixed with async-io. Before claiming that the outer lock
results in less number of lines of code, I'd wait to see a fix that
works with O_DIRECT+async-io too as well as mine and Nick's do.

> Your "elegant" argument is total and utter sh*t, in other words. The lock 
> approach is tons more elegant, considering that it solves the problem much 
> more cleanly, and with _much_ less crap.

I guess elegant is relative, but the size argument is objective, and
that should be possible to compare if somebody writes a full fix that
doesn't fall apart if return value of direct_io_worker is -EIOCBQUEUED.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>