block: kmsan: skip bio block merging logic for KMSAN

KMSAN doesn't allow treating adjacent memory pages as such, if they were
allocated by different alloc_pages() calls.  The block layer however does
so: adjacent pages end up being used together.  To prevent this, make
page_is_mergeable() return false under KMSAN.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
Suggested-by: Eric Biggers <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Ilya Leoshkevich <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vegard Nossum <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

block/bio.c

@@ -869,6 +869,8 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
 	*same_page = ((vec_end_addr & PAGE_MASK) == page_addr);
 	if (*same_page)
 		return true;
+	else if (IS_ENABLED(CONFIG_KMSAN))
+		return false;
 	return (bv->bv_page + bv_end / PAGE_SIZE) == (page + off / PAGE_SIZE);
 }