Re: [PATCH v2] fs: namespace: suppress 'may be used uninitialized' warnings

From: Al Viro
Date: Thu Aug 28 2014 - 10:32:49 EST

On Thu, Aug 28, 2014 at 07:55:49AM -0600, rtg.canonical@xxxxxxxxx wrote:
> From: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
> The gcc version 4.9.1 compiler complains even though it isn't possible for
> these variables to not get initialized before they are used.

Sigh... The root cause of that shite is that copy_mount_string() is too
convoluted for gcc (piss-poor) detection of uninitialized variables. And
yes, it is somewhat overcomplicated - it returns 0 or -E... *and* in former
case it returns NULL or a string as well, via a char ** argument.

The usual convention for such suckers is "return a pointer, using
ERR_PTR(-E...) to indicate an error". We have all of 4 (four) callers,
all in fs/*.c (and nobody else could see that function, unless they manually
included fs/internal.h).

So let's turn that into
char *copy_mount_string(const void __user *data)
return data ? strndup_user(data, PAGE_SIZE) : NULL;

and uses of that thing into
kernel_type = copy_mount_string(type);
ret = PTR_ERR(kernel_type);
if (IS_ERR(kernel_type))
goto out_type;
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