linux-ext4 - Re: [PATCH] ext4: extents: Remove unnecessary ‘NULL’ values from path

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Date: Mon, 1 Apr 2024 23:55:02 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: Li zeming <zeming@...china.com>
Cc: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: extents: Remove unnecessary ‘NULL’ values from path

On Tue, Apr 02, 2024 at 10:41:40AM +0800, Li zeming wrote:
> path is assigned first, so it does not need to initialize the
> assignment.

That's technically true, but the compiler is perfectly capable of
optimizing it out.  So it's harmless, and removing it does make the
code a bit more fragile, since it needs to be set so that the cleanup
code doesn't accidentally dereference an uninitialized pointer:

out:
	up_read(&ei->i_data_sem);
	ext4_free_ext_path(path);
	return ret;

So if later on, we add code which does a "goto out" on an error,
before path gets initialized, that would be bad.  So removing the
"unnecessary" set has no upside, and it has a potential disadvantage.

	      	      	 	     - Ted