mm: enumerate all gfp flags

Introduce GFP bits enumeration to let compiler track the number of used
bits (which depends on the config options) instead of hardcoding them. 
That simplifies __GFP_BITS_SHIFT calculation.

Link: https://lkml.kernel.org/r/20240224015800.2569851-1-surenb@google.com
Suggested-by: Petr Tesařík <petr@tesarici.cz>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Petr Tesarik <petr@tesarici.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/gfp_types.h

@@ -21,44 +21,78 @@ typedef unsigned int __bitwise gfp_t;
  * include/trace/events/mmflags.h and tools/perf/builtin-kmem.c
  */
 
+enum {
+	___GFP_DMA_BIT,
+	___GFP_HIGHMEM_BIT,
+	___GFP_DMA32_BIT,
+	___GFP_MOVABLE_BIT,
+	___GFP_RECLAIMABLE_BIT,
+	___GFP_HIGH_BIT,
+	___GFP_IO_BIT,
+	___GFP_FS_BIT,
+	___GFP_ZERO_BIT,
+	___GFP_UNUSED_BIT,	/* 0x200u unused */
+	___GFP_DIRECT_RECLAIM_BIT,
+	___GFP_KSWAPD_RECLAIM_BIT,
+	___GFP_WRITE_BIT,
+	___GFP_NOWARN_BIT,
+	___GFP_RETRY_MAYFAIL_BIT,
+	___GFP_NOFAIL_BIT,
+	___GFP_NORETRY_BIT,
+	___GFP_MEMALLOC_BIT,
+	___GFP_COMP_BIT,
+	___GFP_NOMEMALLOC_BIT,
+	___GFP_HARDWALL_BIT,
+	___GFP_THISNODE_BIT,
+	___GFP_ACCOUNT_BIT,
+	___GFP_ZEROTAGS_BIT,
+#ifdef CONFIG_KASAN_HW_TAGS
+	___GFP_SKIP_ZERO_BIT,
+	___GFP_SKIP_KASAN_BIT,
+#endif
+#ifdef CONFIG_LOCKDEP
+	___GFP_NOLOCKDEP_BIT,
+#endif
+	___GFP_LAST_BIT
+};
+
 /* Plain integer GFP bitmasks. Do not use this directly. */
-#define ___GFP_DMA		0x01u
-#define ___GFP_HIGHMEM		0x02u
-#define ___GFP_DMA32		0x04u
-#define ___GFP_MOVABLE		0x08u
-#define ___GFP_RECLAIMABLE	0x10u
-#define ___GFP_HIGH		0x20u
-#define ___GFP_IO		0x40u
-#define ___GFP_FS		0x80u
-#define ___GFP_ZERO		0x100u
+#define ___GFP_DMA		BIT(___GFP_DMA_BIT)
+#define ___GFP_HIGHMEM		BIT(___GFP_HIGHMEM_BIT)
+#define ___GFP_DMA32		BIT(___GFP_DMA32_BIT)
+#define ___GFP_MOVABLE		BIT(___GFP_MOVABLE_BIT)
+#define ___GFP_RECLAIMABLE	BIT(___GFP_RECLAIMABLE_BIT)
+#define ___GFP_HIGH		BIT(___GFP_HIGH_BIT)
+#define ___GFP_IO		BIT(___GFP_IO_BIT)
+#define ___GFP_FS		BIT(___GFP_FS_BIT)
+#define ___GFP_ZERO		BIT(___GFP_ZERO_BIT)
 /* 0x200u unused */
-#define ___GFP_DIRECT_RECLAIM	0x400u
-#define ___GFP_KSWAPD_RECLAIM	0x800u
-#define ___GFP_WRITE		0x1000u
-#define ___GFP_NOWARN		0x2000u
-#define ___GFP_RETRY_MAYFAIL	0x4000u
-#define ___GFP_NOFAIL		0x8000u
-#define ___GFP_NORETRY		0x10000u
-#define ___GFP_MEMALLOC		0x20000u
-#define ___GFP_COMP		0x40000u
-#define ___GFP_NOMEMALLOC	0x80000u
-#define ___GFP_HARDWALL		0x100000u
-#define ___GFP_THISNODE		0x200000u
-#define ___GFP_ACCOUNT		0x400000u
-#define ___GFP_ZEROTAGS		0x800000u
+#define ___GFP_DIRECT_RECLAIM	BIT(___GFP_DIRECT_RECLAIM_BIT)
+#define ___GFP_KSWAPD_RECLAIM	BIT(___GFP_KSWAPD_RECLAIM_BIT)
+#define ___GFP_WRITE		BIT(___GFP_WRITE_BIT)
+#define ___GFP_NOWARN		BIT(___GFP_NOWARN_BIT)
+#define ___GFP_RETRY_MAYFAIL	BIT(___GFP_RETRY_MAYFAIL_BIT)
+#define ___GFP_NOFAIL		BIT(___GFP_NOFAIL_BIT)
+#define ___GFP_NORETRY		BIT(___GFP_NORETRY_BIT)
+#define ___GFP_MEMALLOC		BIT(___GFP_MEMALLOC_BIT)
+#define ___GFP_COMP		BIT(___GFP_COMP_BIT)
+#define ___GFP_NOMEMALLOC	BIT(___GFP_NOMEMALLOC_BIT)
+#define ___GFP_HARDWALL		BIT(___GFP_HARDWALL_BIT)
+#define ___GFP_THISNODE		BIT(___GFP_THISNODE_BIT)
+#define ___GFP_ACCOUNT		BIT(___GFP_ACCOUNT_BIT)
+#define ___GFP_ZEROTAGS		BIT(___GFP_ZEROTAGS_BIT)
 #ifdef CONFIG_KASAN_HW_TAGS
-#define ___GFP_SKIP_ZERO	0x1000000u
-#define ___GFP_SKIP_KASAN	0x2000000u
+#define ___GFP_SKIP_ZERO	BIT(___GFP_SKIP_ZERO_BIT)
+#define ___GFP_SKIP_KASAN	BIT(___GFP_SKIP_KASAN_BIT)
 #else
 #define ___GFP_SKIP_ZERO	0
 #define ___GFP_SKIP_KASAN	0
 #endif
 #ifdef CONFIG_LOCKDEP
-#define ___GFP_NOLOCKDEP	0x4000000u
+#define ___GFP_NOLOCKDEP	BIT(___GFP_NOLOCKDEP_BIT)
 #else
 #define ___GFP_NOLOCKDEP	0
 #endif
-/* If the above are modified, __GFP_BITS_SHIFT may need updating */
 
 /*
  * Physical address zone modifiers (see linux/mmzone.h - low four bits)
@@ -249,7 +283,7 @@ typedef unsigned int __bitwise gfp_t;
 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
 
 /* Room for N __GFP_FOO bits */
-#define __GFP_BITS_SHIFT (26 + IS_ENABLED(CONFIG_LOCKDEP))
+#define __GFP_BITS_SHIFT ___GFP_LAST_BIT
 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
 
 /**