set_blocksize: Allow to set a larger block size than PAGE_SIZE

set_blocksize is changed to allow to specify a blocksize larger than a
page. If that occurs then we switch the device to use compound pages.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 fs/block_dev.c |   50 +++++++++++++++++++++++++++++++++++++++++++-------
 fs/buffer.c    |    2 +-
 fs/inode.c     |    1 +
 3 files changed, 45 insertions(+), 8 deletions(-)

Index: vps/fs/block_dev.c
===================================================================
--- vps.orig/fs/block_dev.c	2007-06-11 15:56:36.000000000 -0700
+++ vps/fs/block_dev.c	2007-06-12 20:31:53.000000000 -0700
@@ -65,12 +65,41 @@ static void kill_bdev(struct block_devic
 		return;
 	invalidate_bh_lrus();
 	truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
-}	
+}
+
+#ifdef CONFIG_LARGE_BLOCKSIZE
+
+static int page_cache_min_order = 0;
+static int page_cache_max_order = 4;	/* 64k */
+
+static int __init setup_page_cache_min_order(char *str)
+{
+	get_option (&str, &page_cache_min_order);
+	return 1;
+}
+
+__setup("page_cache_min_order=", setup_page_cache_min_order);
+
+static int __init setup_page_cache_max_order(char *str)
+{
+	get_option (&str, &page_cache_max_order);
+	return 1;
+}
+
+__setup("page_cache_max_order=", setup_page_cache_max_order);
+#else
+
+#define page_cache_min_order 0
+#define page_cache_max_order 0
+
+#endif
 
 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))
+	if (size < 512 || !is_power_of_2(size))
+		return -EINVAL;
+
+	if (!page_cache_valid_blocksize(size))
 		return -EINVAL;
 
 	/* Size cannot be smaller than the size supported by the device */
@@ -79,10 +108,15 @@ int set_blocksize(struct block_device *b
 
 	/* Don't change the size if it is same as current */
 	if (bdev->bd_block_size != size) {
+		int bits = blksize_bits(size);
+		struct address_space *mapping =
+			bdev->bd_inode->i_mapping;
+
 		sync_blockdev(bdev);
-		bdev->bd_block_size = size;
-		bdev->bd_inode->i_blkbits = blksize_bits(size);
 		kill_bdev(bdev);
+		bdev->bd_block_size = size;
+		bdev->bd_inode->i_blkbits = bits;
+		set_mapping_bits(mapping, bits);
 	}
 	return 0;
 }
@@ -93,8 +127,10 @@ int sb_set_blocksize(struct super_block 
 {
 	if (set_blocksize(sb->s_bdev, 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 power of two
+	 * and it's value is valid for the page cache
+	 */
 	sb->s_blocksize = size;
 	sb->s_blocksize_bits = blksize_bits(size);
 	return sb->s_blocksize;
Index: vps/fs/buffer.c
===================================================================
--- vps.orig/fs/buffer.c	2007-06-12 18:59:28.000000000 -0700
+++ vps/fs/buffer.c	2007-06-12 20:26:23.000000000 -0700
@@ -1097,7 +1097,7 @@ __getblk_slow(struct block_device *bdev,
 {
 	/* Size must be multiple of hard sectorsize */
 	if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
-			(size < 512 || size > PAGE_SIZE))) {
+		!page_cache_valid_blocksize(size))) {
 		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
 					size);
 		printk(KERN_ERR "hardsect size: %d\n",
Index: vps/fs/inode.c
===================================================================
--- vps.orig/fs/inode.c	2007-06-11 15:56:36.000000000 -0700
+++ vps/fs/inode.c	2007-06-12 20:26:53.000000000 -0700
@@ -146,6 +146,7 @@ static struct inode *alloc_inode(struct 
  		mapping->host = inode;
 		mapping->flags = 0;
 		mapping_set_gfp_mask(mapping, GFP_HIGHUSER_PAGECACHE);
+		set_mapping_bits(mapping, inode->i_blkbits);
 		mapping->assoc_mapping = NULL;
 		mapping->backing_dev_info = &default_backing_dev_info;