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From: "Theodore Ts'o" <tytso@mit.edu>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
	linux-kernel@vger.kernel.org, joneslee@google.com,
	linux-mm@kvack.org
Subject: Re: [PATCH] ext4: remove superfluous check that pointer is not NULL
Date: Mon, 8 May 2023 12:14:54 -0400	[thread overview]
Message-ID: <ZFkf/oJnCLZSWgYr@mit.edu> (raw)
In-Reply-To: <20230508151337.79304-1-tudor.ambarus@linaro.org>

On Mon, May 08, 2023 at 03:13:37PM +0000, Tudor Ambarus wrote:
> If @buffer is NULL, no operation is performed for kvfree(buffer),
> remove superfluous check.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

I was looking at this just a few weeks ago, and I couldn't find any
actual *documentation* that it was safe to call vfree(NIILL) or
kvfree(NULL).  The problem is there are a lot of architecture-specific
functions, and unlike with kfree() there is no top-level "if (ptr ==
NULL) return;" in the top-level vfree() and kvfree().

So I thought about removing the NULL check for kvfree(), and
ultimately chickened out, since I was afraid that there might be
crashes for some obscure architecture or kernel CONFIG setup.

I've added linux-mm@ for their comments, and for a plea that if it
is safe to pass NULL to vfree, kvfree, kvfree_rcu, etc. that it
actually be *documented* somewhere.

						- Ted


       reply	other threads:[~2023-05-08 16:15 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20230508151337.79304-1-tudor.ambarus@linaro.org>
2023-05-08 16:14 ` Theodore Ts'o [this message]
2023-05-08 21:13   ` Matthew Wilcox
2023-05-09 18:53     ` Theodore Ts'o

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