linux-kernel - Re: [PATCH] block: fix refcounting in BLKBSZSET

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Message-ID: <20110224145438.GO7840@htj.dyndns.org>
Date:	Thu, 24 Feb 2011 15:54:38 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	kovariadam@...il.com, florian@...kler.org, rjw@...k.pl,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: fix refcounting in BLKBSZSET

On Thu, Feb 24, 2011 at 03:48:33PM +0100, Miklos Szeredi wrote:
> [and lkml cc-d too]
> 
> This fixes bug 29202 in the 2.6.38 regression list.
> 
> Please apply.
> 
> Thanks,
> Miklos
> 
> ----
> Subject: block: fix refcounting in BLKBSZSET
> 
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> Adam Kovari and others reported that disconnecting an USB drive with
> an ntfs-3g filesystem would cause "kernel BUG at fs/inode.c:1421!" to
> be triggered.
> 
> The BUG could be traced back to ioctl(BLKBSZSET), which would
> erroneously decrement the refcount on the bdev.  This is because
> blkdev_get() expects the refcount to be already incremented and either
> returns success or decrements the refcount and returns an error.
> 
> The bug was introduced by e525fd89 (block: make blkdev_get/put()
> handle exclusive access), which didn't take into account this behavior
> of blkdev_get().
> 
> Reported-by: Adam Kovari <kovariadam@...il.com>
> CC: Tejun Heo <tj@...nel.org>
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>

Ah, it was me after all.  Sorry about that.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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