/*
 * ramdisk.c - Multiple RAM disk driver - gzip-loading version - v. 0.8 beta.
 * 
 * (C) Chad Page, Theodore Ts'o, et. al, 1995. 
 *
 * This RAM disk is designed to have filesystems created on it and mounted
 * just like a regular floppy disk.  
 *  
 * It also does something suggested by Linus: use the buffer cache as the
 * RAM disk data.  This makes it possible to dynamically allocate the RAM disk
 * buffer - with some consequences I have to deal with as I write this. 
 * 
 * This code is based on the original ramdisk.c, written mostly by
 * Theodore Ts'o (TYT) in 1991.  The code was largely rewritten by
 * Chad Page to use the buffer cache to store the RAM disk data in
 * 1995; Theodore then took over the driver again, and cleaned it up
 * for inclusion in the mainline kernel.
 *
 * The original CRAMDISK code was written by Richard Lyons, and
 * adapted by Chad Page to use the new RAM disk interface.  Theodore
 * Ts'o rewrote it so that both the compressed RAM disk loader and the
 * kernel decompressor uses the same inflate.c codebase.  The RAM disk
 * loader now also loads into a dynamic (buffer cache based) RAM disk,
 * not the old static RAM disk.  Support for the old static RAM disk has
 * been completely removed.
 *
 * Loadable module support added by Tom Dyas.
 *
 * Further cleanups by Chad Page (page0588@sundance.sjsu.edu):
 *	Cosmetic changes in #ifdef MODULE, code movement, etc.
 * 	When the RAM disk module is removed, free the protected buffers
 * 	Default RAM disk size changed to 2.88 MB
 *
 *  Added initrd: Werner Almesberger & Hans Lermen, Feb '96
 *
 * 4/25/96 : Made RAM disk size a parameter (default is now 4 MB) 
 *		- Chad Page
 *
 * Add support for fs images split across >1 disk, Paul Gortmaker, Mar '98
 *
 * Make block size and block size shift for RAM disks a global macro
 * and set blk_size for -ENOSPC,     Werner Fink <werner@suse.de>, Apr '99
 */

#include <linux/config.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <asm/atomic.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include <linux/genhd.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>		/* for invalidate_bdev() */
#include <linux/backing-dev.h>
#include <linux/blkpg.h>
#include <asm/uaccess.h>

/* The RAM disk size is now a parameter */
#define NUM_RAMDISKS 16		/* This cannot be overridden (yet) */ 

/* Various static variables go here.  Most are used only in the RAM disk code.
 */

static struct gendisk *rd_disks[NUM_RAMDISKS];
static struct block_device *rd_bdev[NUM_RAMDISKS];/* Protected device data */
static struct request_queue *rd_queue;

/*
 * Parameters for the boot-loading of the RAM disk.  These are set by
 * init/main.c (from arguments to the kernel command line) or from the
 * architecture-specific setup routine (from the stored boot sector
 * information). 
 */
int rd_size = CONFIG_BLK_DEV_RAM_SIZE;		/* Size of the RAM disks */
/*
 * It would be very desirable to have a soft-blocksize (that in the case
 * of the ramdisk driver is also the hardblocksize ;) of PAGE_SIZE because
 * doing that we'll achieve a far better MM footprint. Using a rd_blocksize of
 * BLOCK_SIZE in the worst case we'll make PAGE_SIZE/BLOCK_SIZE buffer-pages
 * unfreeable. With a rd_blocksize of PAGE_SIZE instead we are sure that only
 * 1 page will be protected. Depending on the size of the ramdisk you
 * may want to change the ramdisk blocksize to achieve a better or worse MM
 * behaviour. The default is still BLOCK_SIZE (needed by rd_load_image that
 * supposes the filesystem in the image uses a BLOCK_SIZE blocksize).
 */
int rd_blocksize = BLOCK_SIZE;			/* blocksize of the RAM disks */

/*
 * Copyright (C) 2000 Linus Torvalds.
 *               2000 Transmeta Corp.
 * aops copied from ramfs.
 */
static int ramdisk_readpage(struct file *file, struct page * page)
{
	if (!PageUptodate(page)) {
		void *kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr, 0, PAGE_CACHE_SIZE);
		flush_dcache_page(page);
		kunmap_atomic(kaddr, KM_USER0);
		SetPageUptodate(page);
	}
	unlock_page(page);
	return 0;
}

static int ramdisk_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
	if (!PageUptodate(page)) {
		void *kaddr = kmap_atomic(page, KM_USER0);

		memset(kaddr, 0, PAGE_CACHE_SIZE);
		flush_dcache_page(page);
		kunmap_atomic(kaddr, KM_USER0);
		SetPageUptodate(page);
	}
	SetPageDirty(page);
	return 0;
}

static int ramdisk_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
	return 0;
}

static struct address_space_operations ramdisk_aops = {
	.readpage = ramdisk_readpage,
	.prepare_write = ramdisk_prepare_write,
	.commit_write = ramdisk_commit_write,
};

static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
				struct address_space *mapping)
{
	unsigned long index = sector >> (PAGE_CACHE_SHIFT - 9);
	unsigned int vec_offset = vec->bv_offset;
	int offset = (sector << 9) & ~PAGE_CACHE_MASK;
	int size = vec->bv_len;
	int err = 0;

	do {
		int count;
		struct page * page;
		char * src, * dst;
		int unlock = 0;

		count = PAGE_CACHE_SIZE - offset;
		if (count > size)
			count = size;
		size -= count;

		page = find_get_page(mapping, index);
		if (!page) {
			page = grab_cache_page(mapping, index);
			err = -ENOMEM;
			if (!page)
				goto out;
			err = 0;

			if (!PageUptodate(page)) {
				void *kaddr = kmap_atomic(page, KM_USER0);

				memset(kaddr, 0, PAGE_CACHE_SIZE);
				flush_dcache_page(page);
				kunmap_atomic(kaddr, KM_USER0);
				SetPageUptodate(page);
			}

			unlock = 1;
		}

		index++;

		if (rw == READ) {
			src = kmap(page) + offset;
			dst = kmap(vec->bv_page) + vec_offset;
		} else {
			dst = kmap(page) + offset;
			src = kmap(vec->bv_page) + vec_offset;
		}
		offset = 0;
		vec_offset += count;

		memcpy(dst, src, count);

		kunmap(page);
		kunmap(vec->bv_page);

		if (rw == READ) {
			flush_dcache_page(vec->bv_page);
		} else {
			SetPageDirty(page);
		}
		if (unlock)
			unlock_page(page);
		__free_page(page);
	} while (size);

 out:
	return err;
}

/*
 *  Basically, my strategy here is to set up a buffer-head which can't be
 *  deleted, and make that my Ramdisk.  If the request is outside of the
 *  allocated size, we must get rid of it...
 *
 * 19-JAN-1998  Richard Gooch <rgooch@atnf.csiro.au>  Added devfs support
 *
 */
static int rd_make_request(request_queue_t * q, struct bio *bio)
{
	struct block_device *bdev = bio->bi_bdev;
	struct address_space * mapping = bdev->bd_inode->i_mapping;
	sector_t sector = bio->bi_sector;
	unsigned long len = bio->bi_size >> 9;
	int rw = bio_data_dir(bio);
	struct bio_vec *bvec;
	int ret = 0, i;

	if (sector + len > get_capacity(bdev->bd_disk))
		goto fail;

	if (rw==READA)
		rw=READ;

	bio_for_each_segment(bvec, bio, i) {
		ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping);
		sector += bvec->bv_len >> 9;
	}
	if (ret)
		goto fail;

	bio_endio(bio, bio->bi_size, 0);
	return 0;
fail:
	bio_io_error(bio, bio->bi_size);
	return 0;
} 

static int rd_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
	int error;

	if (cmd != BLKFLSBUF)
		return -EINVAL;

	/* special: we want to release the ramdisk memory,
	   it's not like with the other blockdevices where
	   this ioctl only flushes away the buffer cache. */
	error = -EBUSY;
	down(&inode->i_bdev->bd_sem);
	if (inode->i_bdev->bd_openers <= 2) {
		truncate_inode_pages(inode->i_mapping, 0);
		error = 0;
	}
	up(&inode->i_bdev->bd_sem);
	return error;
}

static struct backing_dev_info rd_backing_dev_info = {
	.ra_pages	= 0,	/* No readahead */
	.memory_backed	= 1,	/* Does not contribute to dirty memory */
};

static int rd_open(struct inode * inode, struct file * filp)
{
	unsigned unit = minor(inode->i_rdev);

	/*
	 * Immunize device against invalidate_buffers() and prune_icache().
	 */
	if (rd_bdev[unit] == NULL) {
		struct block_device *bdev = inode->i_bdev;
		atomic_inc(&bdev->bd_count);
		rd_bdev[unit] = bdev;
		bdev->bd_openers++;
		bdev->bd_block_size = rd_blocksize;
		bdev->bd_inode->i_size = get_capacity(rd_disks[unit])<<9;
		inode->i_mapping->a_ops = &ramdisk_aops;
		inode->i_mapping->backing_dev_info = &rd_backing_dev_info;
	}

	return 0;
}

static struct block_device_operations rd_bd_op = {
	.owner =	THIS_MODULE,
	.open =		rd_open,
	.ioctl =	rd_ioctl,
};

/* Before freeing the module, invalidate all of the protected buffers! */
static void __exit rd_cleanup (void)
{
	int i;

	for (i = 0 ; i < NUM_RAMDISKS; i++) {
		struct block_device *bdev = rd_bdev[i];
		rd_bdev[i] = NULL;
		if (bdev) {
			invalidate_bdev(bdev, 1);
			blkdev_put(bdev, BDEV_FILE);
		}
		del_gendisk(rd_disks[i]);
		put_disk(rd_disks[i]);
	}
	kfree(rd_queue);
	devfs_remove("rd");
	unregister_blkdev(RAMDISK_MAJOR, "ramdisk" );
}

/* This is the registration and initialization section of the RAM disk driver */
static int __init rd_init (void)
{
	int i;
	int err = -ENOMEM;

	if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 ||
	    (rd_blocksize & (rd_blocksize-1))) {
		printk("RAMDISK: wrong blocksize %d, reverting to defaults\n",
		       rd_blocksize);
		rd_blocksize = BLOCK_SIZE;
	}

	for (i = 0; i < NUM_RAMDISKS; i++) {
		rd_disks[i] = alloc_disk(1);
		if (!rd_disks[i])
			goto out;
	}

	rd_queue = kmalloc(NUM_RAMDISKS * sizeof(struct request_queue),
			     GFP_KERNEL);
	if (!rd_queue)
		goto out;
	memset(rd_queue, 0, NUM_RAMDISKS * sizeof(struct request_queue));
	if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) {
		err = -EIO;
		goto out_queue;
	}

	devfs_mk_dir("rd");

	for (i = 0; i < NUM_RAMDISKS; i++) {
		struct gendisk *disk = rd_disks[i];

		blk_queue_make_request(&rd_queue[i], &rd_make_request);

		/* rd_size is given in kB */
		disk->major = RAMDISK_MAJOR;
		disk->first_minor = i;
		disk->fops = &rd_bd_op;
		disk->queue = &rd_queue[i];
		sprintf(disk->disk_name, "ram%d", i);
		sprintf(disk->devfs_name, "rd/%d", i);
		set_capacity(disk, rd_size * 2);
		add_disk(rd_disks[i]);
	}

	/* rd_size is given in kB */
	printk("RAMDISK driver initialized: "
	       "%d RAM disks of %dK size %d blocksize\n",
	       NUM_RAMDISKS, rd_size, rd_blocksize);

	return 0;
out_queue:
	kfree(rd_queue);
out:
	while (i--)
		put_disk(rd_disks[i]);
	return err;
}

module_init(rd_init);
module_exit(rd_cleanup);

/* options - nonmodular */
#ifndef MODULE
static int __init ramdisk_size(char *str)
{
	rd_size = simple_strtol(str,NULL,0);
	return 1;
}
static int __init ramdisk_size2(char *str)	/* kludge */
{
	return ramdisk_size(str);
}
static int __init ramdisk_blocksize(char *str)
{
	rd_blocksize = simple_strtol(str,NULL,0);
	return 1;
}
__setup("ramdisk=", ramdisk_size);
__setup("ramdisk_size=", ramdisk_size2);
__setup("ramdisk_blocksize=", ramdisk_blocksize);
#endif

/* options - modular */
MODULE_PARM     (rd_size, "1i");
MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
MODULE_PARM     (rd_blocksize, "i");
MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes.");

MODULE_LICENSE("GPL");
