mm, kasan: fix __GFP_BITS_SHIFT definition breaking LOCKDEP

From: Andrey Konovalov <[email protected]>
Subject: mm, kasan: fix __GFP_BITS_SHIFT definition breaking LOCKDEP

KASAN changes that added new GFP flags mistakenly updated __GFP_BITS_SHIFT as the total number of GFP bits instead of as a shift used to define __GFP_BITS_MASK.

This broke LOCKDEP, as __GFP_BITS_MASK now gets the 25th bit enabled instead of the 28th for __GFP_NOLOCKDEP.

Update __GFP_BITS_SHIFT to always count KASAN GFP bits.

In the future, we could handle all combinations of KASAN and LOCKDEP to occupy as few bits as possible. For now, we have enough GFP bits to be inefficient in this quick fix.

---

 include/linux/gfp.h |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

@@ -264,9 +264,7 @@ struct vm_area_struct;
 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
 
 /* Room for N __GFP_FOO bits */
-#define __GFP_BITS_SHIFT (24 +						\
-			  3 * IS_ENABLED(CONFIG_KASAN_HW_TAGS) +	\
-			  IS_ENABLED(CONFIG_LOCKDEP))
+#define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP))
 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
 
 /**

_