[PATCH] fix 4K ext2fs support in 2.6 initrd's

The ramdisk_blocksize option has been broken for quite a while in 2.6.
Making an initrd with a 4K ext2 filesystem impossible to use.

After digging into this, the problem turned out to that rd.c was not
setting the hard sector size.  There were a few secondary problems like
i_blkbits was not being set, and the number KiB in uncompressed ext2 images
was not taking into account the block size.

I have also corrected the surrounding comments as they were not just
incorrect but misleading.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/block/rd.c

@@ -349,13 +349,17 @@ static int rd_open(struct inode *inode, struct file *filp)
 	if (rd_bdev[unit] == NULL) {
 		struct block_device *bdev = inode->i_bdev;
 		struct address_space *mapping;
+		unsigned bsize;
 		int gfp_mask;
 
 		inode = igrab(bdev->bd_inode);
 		rd_bdev[unit] = bdev;
 		bdev->bd_openers++;
-		bdev->bd_block_size = rd_blocksize;
-		inode->i_size = get_capacity(rd_disks[unit])<<9;
+		bsize = bdev_hardsect_size(bdev);
+		bdev->bd_block_size = bsize;
+		inode->i_blkbits = blksize_bits(bsize);
+		inode->i_size = get_capacity(bdev->bd_disk)<<9;
+
 		mapping = inode->i_mapping;
 		mapping->a_ops = &ramdisk_aops;
 		mapping->backing_dev_info = &rd_backing_dev_info;
@@ -449,6 +453,7 @@ static int __init rd_init(void)
 			goto out_queue;
 
 		blk_queue_make_request(rd_queue[i], &rd_make_request);
+		blk_queue_hardsect_size(rd_queue[i], rd_blocksize);
 
 		/* rd_size is given in kB */
 		disk->major = RAMDISK_MAJOR;

init/do_mounts_rd.c

@@ -122,7 +122,8 @@ identify_ramdisk_image(int fd, int start_block)
 		printk(KERN_NOTICE
 		       "RAMDISK: ext2 filesystem found at block %d\n",
 		       start_block);
-		nblocks = le32_to_cpu(ext2sb->s_blocks_count);
+		nblocks = le32_to_cpu(ext2sb->s_blocks_count) <<
+			le32_to_cpu(ext2sb->s_log_block_size);
 		goto done;
 	}
 
@@ -173,10 +174,15 @@ int __init rd_load_image(char *from)
 	}
 
 	/*
-	 * NOTE NOTE: nblocks suppose that the blocksize is BLOCK_SIZE, so
-	 * rd_load_image will work only with filesystem BLOCK_SIZE wide!
-	 * So make sure to use 1k blocksize while generating ext2fs
-	 * ramdisk-images.
+	 * NOTE NOTE: nblocks is not actually blocks but
+	 * the number of kibibytes of data to load into a ramdisk.
+	 * So any ramdisk block size that is a multiple of 1KiB should
+	 * work when the appropriate ramdisk_blocksize is specified
+	 * on the command line.
+	 *
+	 * The default ramdisk_blocksize is 1KiB and it is generally
+	 * silly to use anything else, so make sure to use 1KiB
+	 * blocksize while generating ext2fs ramdisk-images.
 	 */
 	if (sys_ioctl(out_fd, BLKGETSIZE, (unsigned long)&rd_blocks) < 0)
 		rd_blocks = 0;
@@ -184,7 +190,7 @@ int __init rd_load_image(char *from)
 		rd_blocks >>= 1;
 
 	if (nblocks > rd_blocks) {
-		printk("RAMDISK: image too big! (%d/%ld blocks)\n",
+		printk("RAMDISK: image too big! (%dKiB/%ldKiB)\n",
 		       nblocks, rd_blocks);
 		goto done;
 	}
@@ -211,7 +217,7 @@ int __init rd_load_image(char *from)
 		goto done;
 	}
 
-	printk(KERN_NOTICE "RAMDISK: Loading %d blocks [%ld disk%s] into ram disk... ", 
+	printk(KERN_NOTICE "RAMDISK: Loading %dKiB [%ld disk%s] into ram disk... ",
 		nblocks, ((nblocks-1)/devblocks)+1, nblocks>devblocks ? "s" : "");
 	for (i = 0, disk = 1; i < nblocks; i++) {
 		if (i && (i % devblocks == 0)) {