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Date:   Sat, 7 May 2022 12:37:28 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Vasily Averin <vvs@openvz.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, kernel@openvz.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH mm] tracing: incorrect gfp_t conversion
Message-Id: <20220507123728.f20d977eba9fbb66bddee722@linux-foundation.org>
In-Reply-To: <331d88fe-f4f7-657c-02a2-d977f15fbff6@openvz.org>
References: <e1c09bbb-2c58-a986-c704-1db538da905a@openvz.org>
        <331d88fe-f4f7-657c-02a2-d977f15fbff6@openvz.org>
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On Sat, 7 May 2022 22:02:05 +0300 Vasily Averin <vvs@openvz.org> wrote:

> Fixes the following sparse warnings:
> 
> include/trace/events/*: sparse: cast to restricted gfp_t
> include/trace/events/*: sparse: restricted gfp_t degrades to integer
> 
> gfp_t type is bitwise and requires __force attributes for any casts.
> 
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -14,43 +14,43 @@
>   */
>  
>  #define __def_gfpflag_names						\
> -	{(unsigned long)GFP_TRANSHUGE,		"GFP_TRANSHUGE"},	\
> -	{(unsigned long)GFP_TRANSHUGE_LIGHT,	"GFP_TRANSHUGE_LIGHT"}, \
> -	{(unsigned long)GFP_HIGHUSER_MOVABLE,	"GFP_HIGHUSER_MOVABLE"},\
> -	{(unsigned long)GFP_HIGHUSER,		"GFP_HIGHUSER"},	\
> -	{(unsigned long)GFP_USER,		"GFP_USER"},		\
> -	{(unsigned long)GFP_KERNEL_ACCOUNT,	"GFP_KERNEL_ACCOUNT"},	\
> -	{(unsigned long)__GFP_SKIP_KASAN_POISON,"__GFP_SKIP_KASAN_POISON"}\
>
> ...
>
> +	{(__force unsigned long)GFP_TRANSHUGE,		"GFP_TRANSHUGE"},	\
> +	{(__force unsigned long)GFP_TRANSHUGE_LIGHT,	"GFP_TRANSHUGE_LIGHT"}, \
> +	{(__force unsigned long)GFP_HIGHUSER_MOVABLE,	"GFP_HIGHUSER_MOVABLE"},\
> +	{(__force unsigned long)GFP_HIGHUSER,		"GFP_HIGHUSER"},	\
> +	{(__force unsigned long)GFP_USER,		"GFP_USER"},		\
> +	{(__force unsigned long)GFP_KERNEL_ACCOUNT,	"GFP_KERNEL_ACCOUNT"},	\
> +	{(__force unsigned long)GFP_KERNEL,		"GFP_KERNEL"},		\
> +	{(__force unsigned long)GFP_NOFS,		"GFP_NOFS"},		\

This got all repetitive, line-wrappy and ugly :(

What do we think of something silly like this?


--- a/include/trace/events/mmflags.h~tracing-incorrect-gfp_t-conversion-fix
+++ a/include/trace/events/mmflags.h
@@ -13,53 +13,57 @@
  * Thus most bits set go first.
  */
 
+#define FUL __force unsigned long
+
 #define __def_gfpflag_names						\
-	{(__force unsigned long)GFP_TRANSHUGE,		"GFP_TRANSHUGE"},	\
-	{(__force unsigned long)GFP_TRANSHUGE_LIGHT,	"GFP_TRANSHUGE_LIGHT"}, \
-	{(__force unsigned long)GFP_HIGHUSER_MOVABLE,	"GFP_HIGHUSER_MOVABLE"},\
-	{(__force unsigned long)GFP_HIGHUSER,		"GFP_HIGHUSER"},	\
-	{(__force unsigned long)GFP_USER,		"GFP_USER"},		\
-	{(__force unsigned long)GFP_KERNEL_ACCOUNT,	"GFP_KERNEL_ACCOUNT"},	\
-	{(__force unsigned long)GFP_KERNEL,		"GFP_KERNEL"},		\
-	{(__force unsigned long)GFP_NOFS,		"GFP_NOFS"},		\
-	{(__force unsigned long)GFP_ATOMIC,		"GFP_ATOMIC"},		\
-	{(__force unsigned long)GFP_NOIO,		"GFP_NOIO"},		\
-	{(__force unsigned long)GFP_NOWAIT,		"GFP_NOWAIT"},		\
-	{(__force unsigned long)GFP_DMA,		"GFP_DMA"},		\
-	{(__force unsigned long)__GFP_HIGHMEM,		"__GFP_HIGHMEM"},	\
-	{(__force unsigned long)GFP_DMA32,		"GFP_DMA32"},		\
-	{(__force unsigned long)__GFP_HIGH,		"__GFP_HIGH"},		\
-	{(__force unsigned long)__GFP_ATOMIC,		"__GFP_ATOMIC"},	\
-	{(__force unsigned long)__GFP_IO,		"__GFP_IO"},		\
-	{(__force unsigned long)__GFP_FS,		"__GFP_FS"},		\
-	{(__force unsigned long)__GFP_NOWARN,		"__GFP_NOWARN"},	\
-	{(__force unsigned long)__GFP_RETRY_MAYFAIL,	"__GFP_RETRY_MAYFAIL"},	\
-	{(__force unsigned long)__GFP_NOFAIL,		"__GFP_NOFAIL"},	\
-	{(__force unsigned long)__GFP_NORETRY,		"__GFP_NORETRY"},	\
-	{(__force unsigned long)__GFP_COMP,		"__GFP_COMP"},		\
-	{(__force unsigned long)__GFP_ZERO,		"__GFP_ZERO"},		\
-	{(__force unsigned long)__GFP_NOMEMALLOC,	"__GFP_NOMEMALLOC"},	\
-	{(__force unsigned long)__GFP_MEMALLOC,		"__GFP_MEMALLOC"},	\
-	{(__force unsigned long)__GFP_HARDWALL,		"__GFP_HARDWALL"},	\
-	{(__force unsigned long)__GFP_THISNODE,		"__GFP_THISNODE"},	\
-	{(__force unsigned long)__GFP_RECLAIMABLE,	"__GFP_RECLAIMABLE"},	\
-	{(__force unsigned long)__GFP_MOVABLE,		"__GFP_MOVABLE"},	\
-	{(__force unsigned long)__GFP_ACCOUNT,		"__GFP_ACCOUNT"},	\
-	{(__force unsigned long)__GFP_WRITE,		"__GFP_WRITE"},		\
-	{(__force unsigned long)__GFP_RECLAIM,		"__GFP_RECLAIM"},	\
-	{(__force unsigned long)__GFP_DIRECT_RECLAIM,	"__GFP_DIRECT_RECLAIM"},\
-	{(__force unsigned long)__GFP_KSWAPD_RECLAIM,	"__GFP_KSWAPD_RECLAIM"},\
-	{(__force unsigned long)__GFP_ZEROTAGS,		"__GFP_ZEROTAGS"}	\
+	{(FUL)GFP_TRANSHUGE,		"GFP_TRANSHUGE"},	\
+	{(FUL)GFP_TRANSHUGE_LIGHT,	"GFP_TRANSHUGE_LIGHT"}, \
+	{(FUL)GFP_HIGHUSER_MOVABLE,	"GFP_HIGHUSER_MOVABLE"},\
+	{(FUL)GFP_HIGHUSER,		"GFP_HIGHUSER"},	\
+	{(FUL)GFP_USER,		"GFP_USER"},		\
+	{(FUL)GFP_KERNEL_ACCOUNT,	"GFP_KERNEL_ACCOUNT"},	\
+	{(FUL)GFP_KERNEL,		"GFP_KERNEL"},		\
+	{(FUL)GFP_NOFS,		"GFP_NOFS"},		\
+	{(FUL)GFP_ATOMIC,		"GFP_ATOMIC"},		\
+	{(FUL)GFP_NOIO,		"GFP_NOIO"},		\
+	{(FUL)GFP_NOWAIT,		"GFP_NOWAIT"},		\
+	{(FUL)GFP_DMA,		"GFP_DMA"},		\
+	{(FUL)__GFP_HIGHMEM,		"__GFP_HIGHMEM"},	\
+	{(FUL)GFP_DMA32,		"GFP_DMA32"},		\
+	{(FUL)__GFP_HIGH,		"__GFP_HIGH"},		\
+	{(FUL)__GFP_ATOMIC,		"__GFP_ATOMIC"},	\
+	{(FUL)__GFP_IO,		"__GFP_IO"},		\
+	{(FUL)__GFP_FS,		"__GFP_FS"},		\
+	{(FUL)__GFP_NOWARN,		"__GFP_NOWARN"},	\
+	{(FUL)__GFP_RETRY_MAYFAIL,	"__GFP_RETRY_MAYFAIL"},	\
+	{(FUL)__GFP_NOFAIL,		"__GFP_NOFAIL"},	\
+	{(FUL)__GFP_NORETRY,		"__GFP_NORETRY"},	\
+	{(FUL)__GFP_COMP,		"__GFP_COMP"},		\
+	{(FUL)__GFP_ZERO,		"__GFP_ZERO"},		\
+	{(FUL)__GFP_NOMEMALLOC,	"__GFP_NOMEMALLOC"},	\
+	{(FUL)__GFP_MEMALLOC,		"__GFP_MEMALLOC"},	\
+	{(FUL)__GFP_HARDWALL,		"__GFP_HARDWALL"},	\
+	{(FUL)__GFP_THISNODE,		"__GFP_THISNODE"},	\
+	{(FUL)__GFP_RECLAIMABLE,	"__GFP_RECLAIMABLE"},	\
+	{(FUL)__GFP_MOVABLE,		"__GFP_MOVABLE"},	\
+	{(FUL)__GFP_ACCOUNT,		"__GFP_ACCOUNT"},	\
+	{(FUL)__GFP_WRITE,		"__GFP_WRITE"},		\
+	{(FUL)__GFP_RECLAIM,		"__GFP_RECLAIM"},	\
+	{(FUL)__GFP_DIRECT_RECLAIM,	"__GFP_DIRECT_RECLAIM"},\
+	{(FUL)__GFP_KSWAPD_RECLAIM,	"__GFP_KSWAPD_RECLAIM"},\
+	{(FUL)__GFP_ZEROTAGS,		"__GFP_ZEROTAGS"}	\
 
 #ifdef CONFIG_KASAN_HW_TAGS
 #define __def_gfpflag_names_kasan ,					       \
-	{(__force unsigned long)__GFP_SKIP_ZERO,	   "__GFP_SKIP_ZERO"},	       \
-	{(__force unsigned long)__GFP_SKIP_KASAN_POISON,   "__GFP_SKIP_KASAN_POISON"}, \
-	{(__force unsigned long)__GFP_SKIP_KASAN_UNPOISON, "__GFP_SKIP_KASAN_UNPOISON"}
+	{(FUL)__GFP_SKIP_ZERO,	   "__GFP_SKIP_ZERO"},	       \
+	{(FUL)__GFP_SKIP_KASAN_POISON,   "__GFP_SKIP_KASAN_POISON"}, \
+	{(FUL)__GFP_SKIP_KASAN_UNPOISON, "__GFP_SKIP_KASAN_UNPOISON"}
 #else
 #define __def_gfpflag_names_kasan
 #endif
 
+#undef FUL
+
 #define show_gfp_flags(flags)						\
 	(flags) ? __print_flags(flags, "|",				\
 	__def_gfpflag_names __def_gfpflag_names_kasan			\
_