rewrite rd

S:	Maintained

F:	drivers/net/wireless/rt2x00/

RAMDISK RAM BLOCK DEVICE DRIVER

P:	Nick Piggin

M:	npiggin@suse.de

S:	Maintained

RANDOM NUMBER DRIVER

P:	Matt Mackall

M:	mpm@selenic.com

	  If unsure, say N.

config BLK_DEV_RAM

	tristate "RAM disk support"

	tristate "RAM block device support"

	---help---

	  Saying Y here will allow you to use a portion of your RAM memory as

	  a block device, so that you can make file systems on it, read and

	  The default value is 4096 kilobytes. Only change this if you know

	  what you are doing.

config BLK_DEV_RAM_BLOCKSIZE

	int "Default RAM disk block size (bytes)"

	depends on BLK_DEV_RAM

	default "1024"

	help

	  The default value is 1024 bytes.  PAGE_SIZE is a much more

	  efficient choice however.  The default is kept to ensure initrd

	  setups function - apparently needed by the rd_load_image routine

	  that supposes the filesystem in the image uses a 1024 blocksize.

config CDROM_PKTCDVD

	tristate "Packet writing on CD/DVD media"

	depends on !UML

obj-$(CONFIG_PS3_DISK)		+= ps3disk.o

obj-$(CONFIG_ATARI_FLOPPY)	+= ataflop.o

obj-$(CONFIG_AMIGA_Z2RAM)	+= z2ram.o

obj-$(CONFIG_BLK_DEV_RAM)	+= rd.o

obj-$(CONFIG_BLK_DEV_RAM)	+= brd.o

obj-$(CONFIG_BLK_DEV_LOOP)	+= loop.o

obj-$(CONFIG_BLK_DEV_PS2)	+= ps2esdi.o

obj-$(CONFIG_BLK_DEV_XD)	+= xd.o

/*

 * Ram backed block device driver.

 *

 * Copyright (C) 2007 Nick Piggin

 * Copyright (C) 2007 Novell Inc.

 *

 * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright

 * of their respective owners.

 */

#include <linux/init.h>

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/major.h>

#include <linux/blkdev.h>

#include <linux/bio.h>

#include <linux/highmem.h>

#include <linux/gfp.h>

#include <linux/radix-tree.h>

#include <linux/buffer_head.h> /* invalidate_bh_lrus() */

#include <asm/uaccess.h>

#define SECTOR_SHIFT		9

#define PAGE_SECTORS_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)

#define PAGE_SECTORS		(1 << PAGE_SECTORS_SHIFT)

/*

 * Each block ramdisk device has a radix_tree brd_pages of pages that stores

 * the pages containing the block device's contents. A brd page's ->index is

 * its offset in PAGE_SIZE units. This is similar to, but in no way connected

 * with, the kernel's pagecache or buffer cache (which sit above our block

 * device).

 */

struct brd_device {

	int		brd_number;

	int		brd_refcnt;

	loff_t		brd_offset;

	loff_t		brd_sizelimit;

	unsigned	brd_blocksize;

	struct request_queue	*brd_queue;

	struct gendisk		*brd_disk;

	struct list_head	brd_list;

	/*

	 * Backing store of pages and lock to protect it. This is the contents

	 * of the block device.

	 */

	spinlock_t		brd_lock;

	struct radix_tree_root	brd_pages;

};

/*

 * Look up and return a brd's page for a given sector.

 */

static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)

{

	pgoff_t idx;

	struct page *page;

	/*

	 * The page lifetime is protected by the fact that we have opened the

	 * device node -- brd pages will never be deleted under us, so we

	 * don't need any further locking or refcounting.

	 *

	 * This is strictly true for the radix-tree nodes as well (ie. we

	 * don't actually need the rcu_read_lock()), however that is not a

	 * documented feature of the radix-tree API so it is better to be

	 * safe here (we don't have total exclusion from radix tree updates

	 * here, only deletes).

	 */

	rcu_read_lock();

	idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */

	page = radix_tree_lookup(&brd->brd_pages, idx);

	rcu_read_unlock();

	BUG_ON(page && page->index != idx);

	return page;

}

/*

 * Look up and return a brd's page for a given sector.

 * If one does not exist, allocate an empty page, and insert that. Then

 * return it.

 */

static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)

{

	pgoff_t idx;

	struct page *page;

	page = brd_lookup_page(brd, sector);

	if (page)

		return page;

	/*

	 * Must use NOIO because we don't want to recurse back into the

	 * block or filesystem layers from page reclaim.

	 */

	page = alloc_page(GFP_NOIO | __GFP_HIGHMEM | __GFP_ZERO);

	if (!page)

		return NULL;

	if (radix_tree_preload(GFP_NOIO)) {

		__free_page(page);

		return NULL;

	}

	spin_lock(&brd->brd_lock);

	idx = sector >> PAGE_SECTORS_SHIFT;

	if (radix_tree_insert(&brd->brd_pages, idx, page)) {

		__free_page(page);

		page = radix_tree_lookup(&brd->brd_pages, idx);

		BUG_ON(!page);

		BUG_ON(page->index != idx);

	} else

		page->index = idx;

	spin_unlock(&brd->brd_lock);

	radix_tree_preload_end();

	return page;

}

/*

 * Free all backing store pages and radix tree. This must only be called when

 * there are no other users of the device.

 */

#define FREE_BATCH 16

static void brd_free_pages(struct brd_device *brd)

{

	unsigned long pos = 0;

	struct page *pages[FREE_BATCH];

	int nr_pages;

	do {

		int i;

		nr_pages = radix_tree_gang_lookup(&brd->brd_pages,

				(void **)pages, pos, FREE_BATCH);

		for (i = 0; i < nr_pages; i++) {

			void *ret;

			BUG_ON(pages[i]->index < pos);

			pos = pages[i]->index;

			ret = radix_tree_delete(&brd->brd_pages, pos);

			BUG_ON(!ret || ret != pages[i]);

			__free_page(pages[i]);

		}

		pos++;

		/*

		 * This assumes radix_tree_gang_lookup always returns as

		 * many pages as possible. If the radix-tree code changes,

		 * so will this have to.

		 */

	} while (nr_pages == FREE_BATCH);

}

/*

 * copy_to_brd_setup must be called before copy_to_brd. It may sleep.

 */

static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)

{

	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;

	size_t copy;

	copy = min_t(size_t, n, PAGE_SIZE - offset);

	if (!brd_insert_page(brd, sector))

		return -ENOMEM;

	if (copy < n) {

		sector += copy >> SECTOR_SHIFT;

		if (!brd_insert_page(brd, sector))

			return -ENOMEM;

	}

	return 0;

}

/*

 * Copy n bytes from src to the brd starting at sector. Does not sleep.

 */

static void copy_to_brd(struct brd_device *brd, const void *src,

			sector_t sector, size_t n)

{

	struct page *page;

	void *dst;

	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;

	size_t copy;

	copy = min_t(size_t, n, PAGE_SIZE - offset);

	page = brd_lookup_page(brd, sector);

	BUG_ON(!page);

	dst = kmap_atomic(page, KM_USER1);

	memcpy(dst + offset, src, copy);

	kunmap_atomic(dst, KM_USER1);

	if (copy < n) {

		src += copy;

		sector += copy >> SECTOR_SHIFT;

		copy = n - copy;

		page = brd_lookup_page(brd, sector);

		BUG_ON(!page);

		dst = kmap_atomic(page, KM_USER1);

		memcpy(dst, src, copy);

		kunmap_atomic(dst, KM_USER1);

	}

}

/*

 * Copy n bytes to dst from the brd starting at sector. Does not sleep.

 */

static void copy_from_brd(void *dst, struct brd_device *brd,

			sector_t sector, size_t n)

{

	struct page *page;

	void *src;

	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;

	size_t copy;

	copy = min_t(size_t, n, PAGE_SIZE - offset);

	page = brd_lookup_page(brd, sector);

	if (page) {

		src = kmap_atomic(page, KM_USER1);

		memcpy(dst, src + offset, copy);

		kunmap_atomic(src, KM_USER1);

	} else

		memset(dst, 0, copy);

	if (copy < n) {

		dst += copy;

		sector += copy >> SECTOR_SHIFT;

		copy = n - copy;

		page = brd_lookup_page(brd, sector);

		if (page) {

			src = kmap_atomic(page, KM_USER1);

			memcpy(dst, src, copy);

			kunmap_atomic(src, KM_USER1);

		} else

			memset(dst, 0, copy);

	}

}

/*

 * Process a single bvec of a bio.

 */

static int brd_do_bvec(struct brd_device *brd, struct page *page,

			unsigned int len, unsigned int off, int rw,

			sector_t sector)

{

	void *mem;

	int err = 0;

	if (rw != READ) {

		err = copy_to_brd_setup(brd, sector, len);

		if (err)

			goto out;

	}

	mem = kmap_atomic(page, KM_USER0);

	if (rw == READ) {

		copy_from_brd(mem + off, brd, sector, len);

		flush_dcache_page(page);

	} else

		copy_to_brd(brd, mem + off, sector, len);

	kunmap_atomic(mem, KM_USER0);

out:

	return err;

}

static int brd_make_request(struct request_queue *q, struct bio *bio)

{

	struct block_device *bdev = bio->bi_bdev;

	struct brd_device *brd = bdev->bd_disk->private_data;

	int rw;

	struct bio_vec *bvec;

	sector_t sector;

	int i;

	int err = -EIO;

	sector = bio->bi_sector;

	if (sector + (bio->bi_size >> SECTOR_SHIFT) >

						get_capacity(bdev->bd_disk))

		goto out;

	rw = bio_rw(bio);

	if (rw == READA)

		rw = READ;

	bio_for_each_segment(bvec, bio, i) {

		unsigned int len = bvec->bv_len;

		err = brd_do_bvec(brd, bvec->bv_page, len,

					bvec->bv_offset, rw, sector);

		if (err)

			break;

		sector += len >> SECTOR_SHIFT;

	}

out:

	bio_endio(bio, err);

	return 0;

}

static int brd_ioctl(struct inode *inode, struct file *file,

			unsigned int cmd, unsigned long arg)

{

	int error;

	struct block_device *bdev = inode->i_bdev;

	struct brd_device *brd = bdev->bd_disk->private_data;

	if (cmd != BLKFLSBUF)

		return -ENOTTY;

	/*

	 * ram device BLKFLSBUF has special semantics, we want to actually

	 * release and destroy the ramdisk data.

	 */

	mutex_lock(&bdev->bd_mutex);

	error = -EBUSY;

	if (bdev->bd_openers <= 1) {

		/*

		 * Invalidate the cache first, so it isn't written

		 * back to the device.

		 *

		 * Another thread might instantiate more buffercache here,

		 * but there is not much we can do to close that race.

		 */

		invalidate_bh_lrus();

		truncate_inode_pages(bdev->bd_inode->i_mapping, 0);

		brd_free_pages(brd);

		error = 0;

	}

	mutex_unlock(&bdev->bd_mutex);

	return error;

}

static struct block_device_operations brd_fops = {

	.owner =	THIS_MODULE,

	.ioctl =	brd_ioctl,

};

/*

 * And now the modules code and kernel interface.

 */

static int rd_nr;

int rd_size = CONFIG_BLK_DEV_RAM_SIZE;

module_param(rd_nr, int, 0);

MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");

module_param(rd_size, int, 0);

MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");

MODULE_LICENSE("GPL");

MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);

#ifndef MODULE

/* Legacy boot options - nonmodular */

static int __init ramdisk_size(char *str)

{

	rd_size = simple_strtol(str, NULL, 0);

	return 1;

}

static int __init ramdisk_size2(char *str)

{

	return ramdisk_size(str);

}

__setup("ramdisk=", ramdisk_size);

__setup("ramdisk_size=", ramdisk_size2);

#endif

/*

 * The device scheme is derived from loop.c. Keep them in synch where possible

 * (should share code eventually).

 */

static LIST_HEAD(brd_devices);

static DEFINE_MUTEX(brd_devices_mutex);

static struct brd_device *brd_alloc(int i)

{

	struct brd_device *brd;

	struct gendisk *disk;

	brd = kzalloc(sizeof(*brd), GFP_KERNEL);

	if (!brd)

		goto out;

	brd->brd_number		= i;

	spin_lock_init(&brd->brd_lock);

	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);

	brd->brd_queue = blk_alloc_queue(GFP_KERNEL);

	if (!brd->brd_queue)

		goto out_free_dev;

	blk_queue_make_request(brd->brd_queue, brd_make_request);

	blk_queue_max_sectors(brd->brd_queue, 1024);

	blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);

	disk = brd->brd_disk = alloc_disk(1);

	if (!disk)

		goto out_free_queue;

	disk->major		= RAMDISK_MAJOR;

	disk->first_minor	= i;

	disk->fops		= &brd_fops;

	disk->private_data	= brd;

	disk->queue		= brd->brd_queue;

	sprintf(disk->disk_name, "ram%d", i);

	set_capacity(disk, rd_size * 2);

	return brd;

out_free_queue:

	blk_cleanup_queue(brd->brd_queue);

out_free_dev:

	kfree(brd);

out:

	return NULL;

}

static void brd_free(struct brd_device *brd)

{

	put_disk(brd->brd_disk);

	blk_cleanup_queue(brd->brd_queue);

	brd_free_pages(brd);

	kfree(brd);

}

static struct brd_device *brd_init_one(int i)

{

	struct brd_device *brd;

	list_for_each_entry(brd, &brd_devices, brd_list) {

		if (brd->brd_number == i)

			goto out;

	}

	brd = brd_alloc(i);

	if (brd) {

		add_disk(brd->brd_disk);

		list_add_tail(&brd->brd_list, &brd_devices);

	}

out:

	return brd;

}

static void brd_del_one(struct brd_device *brd)

{

	list_del(&brd->brd_list);

	del_gendisk(brd->brd_disk);

	brd_free(brd);

}

static struct kobject *brd_probe(dev_t dev, int *part, void *data)

{

	struct brd_device *brd;

	struct kobject *kobj;

	mutex_lock(&brd_devices_mutex);

	brd = brd_init_one(dev & MINORMASK);

	kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);

	mutex_unlock(&brd_devices_mutex);

	*part = 0;

	return kobj;

}

static int __init brd_init(void)

{

	int i, nr;

	unsigned long range;

	struct brd_device *brd, *next;

	/*

	 * brd module now has a feature to instantiate underlying device

	 * structure on-demand, provided that there is an access dev node.

	 * However, this will not work well with user space tool that doesn't

	 * know about such "feature".  In order to not break any existing

	 * tool, we do the following:

	 *

	 * (1) if rd_nr is specified, create that many upfront, and this

	 *     also becomes a hard limit.

	 * (2) if rd_nr is not specified, create 1 rd device on module

	 *     load, user can further extend brd device by create dev node

	 *     themselves and have kernel automatically instantiate actual

	 *     device on-demand.

	 */

	if (rd_nr > 1UL << MINORBITS)

		return -EINVAL;

	if (rd_nr) {

		nr = rd_nr;

		range = rd_nr;

	} else {

		nr = CONFIG_BLK_DEV_RAM_COUNT;

		range = 1UL << MINORBITS;

	}

	if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))

		return -EIO;

	for (i = 0; i < nr; i++) {

		brd = brd_alloc(i);

		if (!brd)

			goto out_free;

		list_add_tail(&brd->brd_list, &brd_devices);

	}

	/* point of no return */

	list_for_each_entry(brd, &brd_devices, brd_list)

		add_disk(brd->brd_disk);

	blk_register_region(MKDEV(RAMDISK_MAJOR, 0), range,

				  THIS_MODULE, brd_probe, NULL, NULL);

	printk(KERN_INFO "brd: module loaded\n");

	return 0;

out_free:

	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {

		list_del(&brd->brd_list);

		brd_free(brd);

	}

	unregister_blkdev(RAMDISK_MAJOR, "brd");

	return -ENOMEM;

}

static void __exit brd_exit(void)

{

	unsigned long range;

	struct brd_device *brd, *next;

	range = rd_nr ? rd_nr :  1UL << MINORBITS;

	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)

		brd_del_one(brd);

	blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);

	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

}

module_init(brd_init);

module_exit(brd_exit);