From: Jens Axboe <axboe@suse.de>
To: "M. Edward Borasky" <znmeb@cesmail.net>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Negative "ios_in_flight" in the 2.4 kernel
Date: Wed, 22 Dec 2004 12:16:43 +0100 [thread overview]
Message-ID: <20041222111642.GD12463@suse.de> (raw)
In-Reply-To: <1103691937.23157.14.camel@DreamGate>
On Tue, Dec 21 2004, M. Edward Borasky wrote:
> I've been looking at some "iostat" data from a 2.4.26 machine. The
> device utilizations are 100 percent, even when the disk is idle, which
> is mathematically impossible. By doing some digging, I discovered this
> is a kernel bug, caused by "hd->ios_in_flight" going negative. The
> relevant code appears to my untrained eyes to be in
> drivers/block/ll_rw_blk.c, specifically
>
>
> static inline void down_ios(struct hd_struct *hd)
> {
> disk_round_stats(hd);
> --hd->ios_in_flight;
> }
>
> static inline void up_ios(struct hd_struct *hd)
> {
> disk_round_stats(hd);
> ++hd->ios_in_flight;
> }
>
> Question: wouldn't a simple refusal to decrement ios_in_flight in
> "down_ios" if it's zero fix this, or am I missing something?
That would paper over the real bug, but it will work for you.
--
Jens Axboe
next prev parent reply other threads:[~2004-12-22 11:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-22 5:05 Negative "ios_in_flight" in the 2.4 kernel M. Edward Borasky
2004-12-22 11:16 ` Jens Axboe [this message]
2004-12-22 15:19 ` M. Edward Borasky
2004-12-22 15:58 ` Marcelo Tosatti
2004-12-23 8:08 ` Jens Axboe
2004-12-23 15:30 ` M. Edward Borasky
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