btrfs: replace BTRFS_MAX_BIO_SECTORS with BIO_MAX_VECS

It's impossible to have a btrfs bio with more than BIO_MAX_VECS vectors
anyway.

And there is only one location utilizing that macro, just replace it
with BIO_MAX_VECS.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: adam900710

fs/btrfs/bio.h

@@ -18,13 +18,6 @@ struct btrfs_inode;
 
 #define BTRFS_BIO_INLINE_CSUM_SIZE	64
 
-/*
- * Maximum number of sectors for a single bio to limit the size of the
- * checksum array.  This matches the number of bio_vecs per bio and thus the
- * I/O size for buffered I/O.
- */
-#define BTRFS_MAX_BIO_SECTORS		(256)
-
 typedef void (*btrfs_bio_end_io_t)(struct btrfs_bio *bbio);
 
 /*

fs/btrfs/direct-io.c

@@ -385,7 +385,7 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 	 * to allocate a contiguous array for the checksums.
 	 */
 	if (!write)
-		len = min_t(u64, len, fs_info->sectorsize * BTRFS_MAX_BIO_SECTORS);
+		len = min_t(u64, len, fs_info->sectorsize * BIO_MAX_VECS);
 
 	lockstart = start;
 	lockend = start + len - 1;