[RFC v2 03/10] bdev: increase bdev max blocksize depending on the aops used

[Luis Chamberlain <mcgrof@kernel.org>]

While buffer-heads is stuck at order 0, so PAGE_SIZE, iomap support is
currently capped at MAX_PAGECACHE_ORDER as that is the cap also set on
readahead. We match parity for the max allowed block size when using
iomap.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 block/bdev.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 63b4d7dd8075..0d685270cd34 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -143,10 +143,17 @@ static void set_init_blocksize(struct block_device *bdev)
 	}
 }
 
+static int bdev_bsize_limit(struct block_device *bdev)
+{
+	if (bdev->bd_inode->i_data.a_ops == &def_blk_aops_iomap)
+		return 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER);
+	return PAGE_SIZE;
+}
+
 int set_blocksize(struct block_device *bdev, int size)
 {
-	/* Size must be a power of two, and between 512 and PAGE_SIZE */
-	if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
+	/* Size must be a power of two, and between 512 and supported order */
+	if (size > bdev_bsize_limit(bdev) || size < 512 || !is_power_of_2(size))
 		return -EINVAL;
 
 	/* Size cannot be smaller than the size supported by the device */
-- 
2.39.2