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From: Jens Axboe <>
To: Dave Kleikamp <>
Cc: JFS Discussion <>,
	fsdevel <>,
	linux-kernel <>,
	Nick Piggin <>
Subject: Re: [PATCH: 2.6.20-rc4-mm1] JFS: Avoid deadlock introduced by explicit  I/O plugging
Date: Thu, 18 Jan 2007 10:18:47 +1100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Jan 17 2007, Dave Kleikamp wrote:
> Jens,
> Can you please take a look at this patch, and if you think it's sane,
> add it to your explicit i/o plugging patchset?  Would it make sense in
> any of these paths to use io_schedule() instead of schedule()?

I'm glad you bring that up, actually. One of the "downsides" of the new
unplugging is that it really requires anyone waiting for IO in a path
like the file system or device driver to use io_schedule() instead of
schedule() to get the blk_replug_current_nested() done to avoid
deadlocks. While it is annoying that it could introduce some deadlocks
until we get things fixed it, I do consider it a correctness fix even in
the generic kernel, as you are really waiting for IO and as such should
use io_schedule() in the first place.

Perhaps I should add a WARN_ON() check for this to catch these bugs

> I hadn't looked at your patchset until I discovered that jfs was easy to
> hang in the -mm kernel.  I think jfs may be able to add explicit
> plugging and unplugging in a couple of places, but I'd like to fix the
> hang right away and take my time with any later patches.

Can you try io_schedule() and verify that things just work?

Jens Axboe

  reply	other threads:[~2007-01-17 23:27 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-17 22:55 Dave Kleikamp
2007-01-17 23:18 ` Jens Axboe [this message]
2007-01-17 23:39   ` Dave Kleikamp
2007-01-17 23:46     ` Jens Axboe
2007-01-18  3:23       ` Dave Kleikamp
2007-01-18  6:30 ` Josef Sipek
2007-01-18 14:15   ` Dave Kleikamp

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