[RFC 6/8] block/bdev: lift block size restrictions and use common definition

[Luis Chamberlain <mcgrof@kernel.org>]

We now can support blocksizes larger than PAGE_SIZE, so lift
the restriction up to the max supported page cache order and
just bake this into a common helper used by the block layer.

We bound ourselves to 64k, because beyond that we need more testing.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 block/bdev.c           | 5 ++---
 include/linux/blkdev.h | 6 +++++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 167d82b46781..3a5fd65f6c8e 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -157,8 +157,7 @@ int set_blocksize(struct file *file, int size)
 	struct inode *inode = file->f_mapping->host;
 	struct block_device *bdev = I_BDEV(inode);
 
-	/* Size must be a power of two, and between 512 and PAGE_SIZE */
-	if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
+	if (blk_validate_block_size(size))
 		return -EINVAL;
 
 	/* Size cannot be smaller than the size supported by the device */
@@ -185,7 +184,7 @@ int sb_set_blocksize(struct super_block *sb, int size)
 	if (set_blocksize(sb->s_bdev_file, size))
 		return 0;
 	/* If we get here, we know size is power of two
-	 * and it's value is between 512 and PAGE_SIZE */
+	 * and it's value is larger than 512 */
 	sb->s_blocksize = size;
 	sb->s_blocksize_bits = blksize_bits(size);
 	return sb->s_blocksize;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 50c3b959da28..cc9fca1fceaa 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -25,6 +25,7 @@
 #include <linux/uuid.h>
 #include <linux/xarray.h>
 #include <linux/file.h>
+#include <linux/pagemap.h>
 
 struct module;
 struct request_queue;
@@ -268,10 +269,13 @@ static inline dev_t disk_devt(struct gendisk *disk)
 	return MKDEV(disk->major, disk->first_minor);
 }
 
+/* We should strive for 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER) */
+#define BLK_MAX_BLOCK_SIZE      (SZ_64K)
+
 /* blk_validate_limits() validates bsize, so drivers don't usually need to */
 static inline int blk_validate_block_size(unsigned long bsize)
 {
-	if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
+	if (bsize < 512 || bsize > BLK_MAX_BLOCK_SIZE || !is_power_of_2(bsize))
 		return -EINVAL;
 
 	return 0;
-- 
2.43.0