[PATCH v3 7/8] block/bdev: lift block size restrictions to 64k

[Luis Chamberlain <mcgrof@kernel.org>]

We now can support blocksizes larger than PAGE_SIZE, so in theory
we should be able to lift the restriction up to the max supported page
cache order. However bound ourselves to what we can currently validate
and test. Through blktests and fstest we can validate up to 64k today.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 block/bdev.c           | 3 +--
 include/linux/blkdev.h | 8 +++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 8aadf1f23cb4..22806ce11e1d 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -183,8 +183,7 @@ 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 */
+	/* If we get here, we know size is validated */
 	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 248416ecd01c..a97428e8bbbe 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -267,10 +267,16 @@ 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)
+ * however we constrain this to what we can validate and test.
+ */
+#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;
-- 
2.47.2