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From: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>
Reply-To: vda@port.imtp.ilyichevsk.odessa.ua
To: Joe Thornber <joe@fib011235813.fsnet.co.uk>
Subject: Re: [PATCH] dm.c  -  device-mapper I/O path fixes
Date: Wed, 11 Dec 2002 16:19:07 -0200
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Cc: Kevin Corry <corryk@us.ibm.com>, Linus Torvalds <torvalds@transmeta.com>,
       Kernel Mailing List <linux-kernel@vger.kernel.org>,
       lvm-devel@sistina.com
References: <02121016034706.02220@boiler> <20021211121749.GA20782@reti> <20021211121915.GB20782@reti>
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On 11 December 2002 10:19, Joe Thornber wrote:
> dec_pending(): only bother spin locking if io->error is going to be
> updated. [Kevin Corry]
>
> --- diff/drivers/md/dm.c	2002-12-11 12:00:29.000000000 +0000
> +++ source/drivers/md/dm.c	2002-12-11 12:00:34.000000000 +0000
> @@ -238,10 +238,11 @@
>  	static spinlock_t _uptodate_lock = SPIN_LOCK_UNLOCKED;
>  	unsigned long flags;
>
> -	spin_lock_irqsave(&_uptodate_lock, flags);
> -	if (error)
> +	if (error) {
> +		spin_lock_irqsave(&_uptodate_lock, flags);
>  		io->error = error;
> -	spin_unlock_irqrestore(&_uptodate_lock, flags);
> +		spin_unlock_irqrestore(&_uptodate_lock, flags);
> +	}
>
>  	if (atomic_dec_and_test(&io->io_count)) {
>  		if (atomic_dec_and_test(&io->md->pending))

This seems pointless, end result:

	spin_lock_irqsave(&_uptodate_lock, flags);
 	io->error = error;
	spin_unlock_irqrestore(&_uptodate_lock, flags);


BTW, the function we are looking at:

static inline void dec_pending(struct dm_io *io, int error)
       ^^^^^^
is too big for inlining.
--
vda
-
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