Re: [PATCH] block: fix refcounting in BLKBSZSET

From: Florian Mickler
Date: Thu Feb 24 2011 - 10:20:39 EST


2011/2/24 Mike Snitzer <snitzer@xxxxxxxxxx>:
> On Thu, Feb 24, 2011 at 9:48 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>> [and lkml cc-d too]
>> This fixes bug 29202 in the 2.6.38 regression list.
> It looks like this may fix bug 29792 too.
> Mike
>> Please apply.
>> Thanks,
>> Miklos
>> ----
>> Subject: block: fix refcounting in BLKBSZSET
>> From: Miklos Szeredi <mszeredi@xxxxxxx>
>> 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().

putting a small reference to the bug reports in the changelog
(it is enough to have the bugnumber in there somewhere, grepping for 5
digit numbers doesn't turn up all too many false positives... )
helps with keeping track of the regressions and letting people know
that a fix / change was posted.

A line like "This fixes bug 29202." is sufficient.

Pasting a complete link( i.e. ) would even allow
for an automated note in the bugzilla when it hits Linus tree.

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