fs: add i_blocksize()

Replace all 1 << inode->i_blkbits and (1 << inode->i_blkbits) in fs
branch.

This patch also fixes multiple checkpatch warnings: WARNING: Prefer
'unsigned int' to bare use of 'unsigned'

Thanks to Andrew Morton for suggesting more appropriate function instead
of macro.

[geliangtang@gmail.com: truncate: use i_blocksize()]
  Link: http://lkml.kernel.org/r/9c8b2cd83c8f5653805d43debde9fa8817e02fc4.1484895804.git.geliangtang@gmail.com
Link: http://lkml.kernel.org/r/1481319905-10126-1-git-send-email-fabf@skynet.be
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/iomap.c b/fs/iomap.c
index d209f42..0f85f24 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -420,8 +420,8 @@
 iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
 		const struct iomap_ops *ops)
 {
-	unsigned blocksize = (1 << inode->i_blkbits);
-	unsigned off = pos & (blocksize - 1);
+	unsigned int blocksize = i_blocksize(inode);
+	unsigned int off = pos & (blocksize - 1);
 
 	/* Block boundary? Nothing to do */
 	if (!off)
@@ -735,9 +735,9 @@
 		void *data, struct iomap *iomap)
 {
 	struct iomap_dio *dio = data;
-	unsigned blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
-	unsigned fs_block_size = (1 << inode->i_blkbits), pad;
-	unsigned align = iov_iter_alignment(dio->submit.iter);
+	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
+	unsigned int fs_block_size = i_blocksize(inode), pad;
+	unsigned int align = iov_iter_alignment(dio->submit.iter);
 	struct iov_iter iter;
 	struct bio *bio;
 	bool need_zeroout = false;