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Date:   Tue, 12 Dec 2023 14:49:10 +0300
From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     Brian Gerst <brgerst@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>, x86@kernel.org
Subject: cast inside __pcpu_cast_1 macro
Message-ID: <c107538b-4e4a-4698-aca2-327eacdc15b2@p183>
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Hi, Brian.

You've added the following macros in

	commit 6865dc3ae93b9acb336ca48bd7b2db3446d89370
	x86/percpu: Introduce size abstraction macros

+#define __pcpu_cast_1(val) ((u8)(((unsigned long) val) & 0xff))
+#define __pcpu_cast_2(val) ((u16)(((unsigned long) val) & 0xffff))
+#define __pcpu_cast_4(val) ((u32)(((unsigned long) val) & 0xffffffff))
+#define __pcpu_cast_8(val) ((u64)(val))

They break complation if "val" is something complex like

	this_cpu_write(pcp, *x = 1);

Only __pcpu_cast_8() is correct in this regard.
"val" should be in parenthesis at least.

Is there a reason for casts to "unsigned long"?

Why not just

	#define __pcpu_cast_1(val)	((u8)(val))