linux-kernel - Re: [RFC PATCH 28/30] Improved symbolic error names

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Message-ID: <c3a6e2d86724efd3ac4b94ca1975e23ddb26cc6f.camel@perches.com>
Date:   Thu, 01 Sep 2022 16:19:35 -0700
From:   Joe Perches <joe@...ches.com>
To:     Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org
Cc:     kent.overstreet@...ux.dev, mhocko@...e.com, vbabka@...e.cz,
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Subject: Re: [RFC PATCH 28/30] Improved symbolic error names

On Tue, 2022-08-30 at 14:49 -0700, Suren Baghdasaryan wrote:
> From: Kent Overstreet <kent.overstreet@...ux.dev>
> 
> This patch adds per-error-site error codes, with error strings that
> include their file and line number.
> 
> To use, change code that returns an error, e.g.
>     return -ENOMEM;
> to
>     return -ERR(ENOMEM);
> 
> Then, errname() will return a string that includes the file and line
> number of the ERR() call, for example
>     printk("Got error %s!\n", errname(err));
> will result in
>     Got error ENOMEM at foo.c:1234

Why? Something wrong with just using %pe ?

	printk("Got error %pe at %s:%d!\n", ERR_PTR(err), __FILE__, __LINE__);

Likely __FILE__ and __LINE__ aren't particularly useful.

And using ERR would add rather a lot of bloat as each codetag_error_code
struct would be unique.

+#define ERR(_err)							\
+({									\
+	static struct codetag_error_code				\
+	__used								\
+	__section("error_code_tags")					\
+	__aligned(8) e = {						\
+		.str	= #_err " at " __FILE__ ":" __stringify(__LINE__),\
+		.err	= _err,						\
+	};								\
+									\
+	e.err;								\
+})