[RFC v2 09/11] block/bdev: lift block size restrictions and use common definition

Luis Chamberlain
2024-12-14T03:11:04Z

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 as a sensible limit. The hard limit,
however is 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER).

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
block/bdev.c | 5 ++---
include/linux/blkdev.h | 11 ++++++++++-
2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 167d82b46781..b57dc4bff81b 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 its 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 08a727b40816..a7303a55ed2a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -269,10 +269,19 @@ static inline dev_t disk_devt(struct gendisk *disk)
return MKDEV(disk->major, disk->first_minor);
}

+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+/*
+ * The hard limit is (1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER).
+ */
+#define BLK_MAX_BLOCK_SIZE (SZ_64K)
+#else
+#define BLK_MAX_BLOCK_SIZE (PAGE_SIZE)
+#endif
+
/* 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