linux-kernel - Re: [PATCH 2/6] idr: remove MAX_IDR_MASK and move left MAX_IDR

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Date:	Sun, 10 Feb 2013 12:52:14 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jean Delvare <khali@...ux-fr.org>, linux-i2c@...r.kernel.org,
	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	"Marciniszyn, Mike" <mike.marciniszyn@...el.com>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Or Gerlitz <ogerlitz@...lanox.com>, linux-rdma@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 2/6] idr: remove MAX_IDR_MASK and move left MAX_IDR_*
 into idr.c

On Fri, Feb 08, 2013 at 01:01:49PM -0800, Tejun Heo wrote:
> MAX_IDR_MASK is another weirdness in the idr interface.  As idr covers
> whole positive integer range, it's defined as 0x7fffffff or INT_MAX.
> 
> Its usage in idr_find(), idr_replace() and idr_remove() is bizarre.
> They basically mask off the sign bit and operate on the rest, so if
> the caller, by accident, passes in a negative number, the sign bit
> will be masked off and the remaining part will be used as if that was
> the input, which is worse than crashing.
> 
> The constant is visible in idr.h and there are several users in the
> kernel.
> 
> * drivers/i2c/i2c-core.c:i2c_add_numbered_adapter()
> 
>   Basically used to test if adap->nr is a negative number which isn't
>   -1 and returns -EINVAL if so.  idr_alloc() already has negative
>   @start checking (w/ WARN_ON_ONCE), so this can go away.
> 
> * drivers/infiniband/core/cm.c:cm_alloc_id()
>   drivers/infiniband/hw/mlx4/cm.c:id_map_alloc()
> 
>   Used to wrap cyclic @start.  Can be replaced with max(next, 0).
>   Note that this type of cyclic allocation using idr is buggy.  These
>   are prone to spurious -ENOSPC failure after the first wraparound.
> 
> * fs/super.c:get_anon_bdev()
> 
>   The ID allocated from ida is masked off before being tested whether
>   it's inside valid range.  ida allocated ID can never be a negative
>   number and the masking is unnecessary.
> 
> Update idr_*() functions to fail with -EINVAL when negative @id is
> specified and update other MAX_IDR_MASK users as described above.
> 
> This leaves MAX_IDR_MASK without any user, remove it and relocate
> other MAX_IDR_* constants to lib/idr.c.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>

For the i2c-part:

Acked-by: Wolfram Sang <wolfram@...-dreams.de>

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