bcachefs: Improve check for when bios are physically contiguous

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/compress.c

@@ -70,7 +70,7 @@ static struct bbuf __bio_map_or_bounce(struct bch_fs *c, struct bio *bio,
 
 	BUG_ON(bvec_iter_sectors(start) > c->sb.encoded_extent_max);
 
-	if (!IS_ENABLED(CONFIG_HIGHMEM) &&
+	if (!PageHighMem(bio_iter_page(bio, start)) &&
 	    bio_phys_contig(bio, start))
 		return (struct bbuf) {
 			.b = page_address(bio_iter_page(bio, start)) +