block: always define BIO_MAX_PAGES as 256

Now multi-page bvec can cover CONFIG_THP_SWAP, so we don't need to
increase BIO_MAX_PAGES for it.

CONFIG_THP_SWAP needs to split one THP into normal pages and adds
them all to one bio. With multipage-bvec, it just takes one bvec to
hold them all.

Reviewed-by: Omar Sandoval <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: Ming Lei

include/linux/bio.h

@@ -34,15 +34,7 @@
 #define BIO_BUG_ON
 #endif
 
-#ifdef CONFIG_THP_SWAP
-#if HPAGE_PMD_NR > 256
-#define BIO_MAX_PAGES		HPAGE_PMD_NR
-#else
 #define BIO_MAX_PAGES		256
-#endif
-#else
-#define BIO_MAX_PAGES		256
-#endif
 
 #define bio_prio(bio)			(bio)->bi_ioprio
 #define bio_set_prio(bio, prio)		((bio)->bi_ioprio = prio)