drivers/md/bcache/super.c: use kvmalloc

bcache_device_init uses kmalloc for small requests and vmalloc for those
which are larger than 64 pages.  This alone is a strange criterion.
Moreover kmalloc can fallback to vmalloc on the failure.  Let's simply
use kvmalloc instead as it knows how to handle the fallback properly

Link: http://lkml.kernel.org/r/20170306103327.2766-5-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/bcache/super.c

@@ -767,16 +767,12 @@ static int bcache_device_init(struct bcache_device *d, unsigned block_size,
 	}
 
 	n = d->nr_stripes * sizeof(atomic_t);
-	d->stripe_sectors_dirty = n < PAGE_SIZE << 6
-		? kzalloc(n, GFP_KERNEL)
-		: vzalloc(n);
+	d->stripe_sectors_dirty = kvzalloc(n, GFP_KERNEL);
 	if (!d->stripe_sectors_dirty)
 		return -ENOMEM;
 
 	n = BITS_TO_LONGS(d->nr_stripes) * sizeof(unsigned long);
-	d->full_dirty_stripes = n < PAGE_SIZE << 6
-		? kzalloc(n, GFP_KERNEL)
-		: vzalloc(n);
+	d->full_dirty_stripes = kvzalloc(n, GFP_KERNEL);
 	if (!d->full_dirty_stripes)
 		return -ENOMEM;