[deliverable/linux.git] / drivers / block / brd.c

/*
 * 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/mutex.h>
#include <linux/radix-tree.h>
#include <linux/fs.h>
#include <linux/slab.h>
#ifdef CONFIG_BLK_DEV_RAM_DAX
#include <linux/pfn_t.h>
#endif

#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;

	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 DEFINE_MUTEX(brd_mutex);
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;
	gfp_t gfp_flags;

	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.
	 *
	 * Cannot support DAX and highmem, because our ->direct_access
	 * routine for DAX must return memory that is always addressable.
	 * If DAX was reworked to use pfns and kmap throughout, this
	 * restriction might be able to be lifted.
	 */
	gfp_flags = GFP_NOIO | __GFP_ZERO;
#ifndef CONFIG_BLK_DEV_RAM_DAX
	gfp_flags |= __GFP_HIGHMEM;
#endif
	page = alloc_page(gfp_flags);
	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;
	page->index = idx;
	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);
	}
	spin_unlock(&brd->brd_lock);

	radix_tree_preload_end();

	return page;
}

static void brd_free_page(struct brd_device *brd, sector_t sector)
{
	struct page *page;
	pgoff_t idx;

	spin_lock(&brd->brd_lock);
	idx = sector >> PAGE_SECTORS_SHIFT;
	page = radix_tree_delete(&brd->brd_pages, idx);
	spin_unlock(&brd->brd_lock);
	if (page)
		__free_page(page);
}

static void brd_zero_page(struct brd_device *brd, sector_t sector)
{
	struct page *page;

	page = brd_lookup_page(brd, sector);
	if (page)
		clear_highpage(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 -ENOSPC;
	if (copy < n) {
		sector += copy >> SECTOR_SHIFT;
		if (!brd_insert_page(brd, sector))
			return -ENOSPC;
	}
	return 0;
}

static void discard_from_brd(struct brd_device *brd,
			sector_t sector, size_t n)
{
	while (n >= PAGE_SIZE) {
		/*
		 * Don't want to actually discard pages here because
		 * re-allocating the pages can result in writeback
		 * deadlocks under heavy load.
		 */
		if (0)
			brd_free_page(brd, sector);
		else
			brd_zero_page(brd, sector);
		sector += PAGE_SIZE >> SECTOR_SHIFT;
		n -= PAGE_SIZE;
	}
}

/*
 * 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);
	memcpy(dst + offset, src, copy);
	kunmap_atomic(dst);

	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);
		memcpy(dst, src, copy);
		kunmap_atomic(dst);
	}
}

/*
 * 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);
		memcpy(dst, src + offset, copy);
		kunmap_atomic(src);
	} 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);
			memcpy(dst, src, copy);
			kunmap_atomic(src);
		} 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);
	if (rw == READ) {
		copy_from_brd(mem + off, brd, sector, len);
		flush_dcache_page(page);
	} else {
		flush_dcache_page(page);
		copy_to_brd(brd, mem + off, sector, len);
	}
	kunmap_atomic(mem);

out:
	return err;
}

static blk_qc_t 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;
	struct bvec_iter iter;

	sector = bio->bi_iter.bi_sector;
	if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
		goto io_error;

	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
		if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) ||
		    bio->bi_iter.bi_size & ~PAGE_MASK)
			goto io_error;
		discard_from_brd(brd, sector, bio->bi_iter.bi_size);
		goto out;
	}

	rw = bio_rw(bio);
	if (rw == READA)
		rw = READ;

	bio_for_each_segment(bvec, bio, iter) {
		unsigned int len = bvec.bv_len;
		int err;

		err = brd_do_bvec(brd, bvec.bv_page, len,
					bvec.bv_offset, rw, sector);
		if (err)
			goto io_error;
		sector += len >> SECTOR_SHIFT;
	}

out:
	bio_endio(bio);
	return BLK_QC_T_NONE;
io_error:
	bio_io_error(bio);
	return BLK_QC_T_NONE;
}

static int brd_rw_page(struct block_device *bdev, sector_t sector,
		       struct page *page, int rw)
{
	struct brd_device *brd = bdev->bd_disk->private_data;
	int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, rw, sector);
	page_endio(page, rw & WRITE, err);
	return err;
}

#ifdef CONFIG_BLK_DEV_RAM_DAX
static long brd_direct_access(struct block_device *bdev, sector_t sector,
			void __pmem **kaddr, pfn_t *pfn)
{
	struct brd_device *brd = bdev->bd_disk->private_data;
	struct page *page;

	if (!brd)
		return -ENODEV;
	page = brd_insert_page(brd, sector);
	if (!page)
		return -ENOSPC;
	*kaddr = (void __pmem *)page_address(page);
	*pfn = page_to_pfn_t(page);

	return PAGE_SIZE;
}
#else
#define brd_direct_access NULL
#endif

static int brd_ioctl(struct block_device *bdev, fmode_t mode,
			unsigned int cmd, unsigned long arg)
{
	int error;
	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(&brd_mutex);
	mutex_lock(&bdev->bd_mutex);
	error = -EBUSY;
	if (bdev->bd_openers <= 1) {
		/*
		 * Kill 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.
		 */
		kill_bdev(bdev);
		brd_free_pages(brd);
		error = 0;
	}
	mutex_unlock(&bdev->bd_mutex);
	mutex_unlock(&brd_mutex);

	return error;
}

static const struct block_device_operations brd_fops = {
	.owner =		THIS_MODULE,
	.rw_page =		brd_rw_page,
	.ioctl =		brd_ioctl,
	.direct_access =	brd_direct_access,
};

/*
 * And now the modules code and kernel interface.
 */
static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
module_param(rd_nr, int, S_IRUGO);
MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");

int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
module_param(rd_size, int, S_IRUGO);
MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");

static int max_part = 1;
module_param(max_part, int, S_IRUGO);
MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");

MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
MODULE_ALIAS("rd");

#ifndef MODULE
/* Legacy boot options - nonmodular */
static int __init ramdisk_size(char *str)
{
	rd_size = simple_strtol(str, NULL, 0);
	return 1;
}
__setup("ramdisk_size=", ramdisk_size);
#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_hw_sectors(brd->brd_queue, 1024);
	blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);

	/* This is so fdisk will align partitions on 4k, because of
	 * direct_access API needing 4k alignment, returning a PFN
	 * (This is only a problem on very small devices <= 4M,
	 *  otherwise fdisk will align on 1M. Regardless this call
	 *  is harmless)
	 */
	blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);

	brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
	blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
	brd->brd_queue->limits.discard_zeroes_data = 1;
	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);

	disk = brd->brd_disk = alloc_disk(max_part);
	if (!disk)
		goto out_free_queue;
	disk->major		= RAMDISK_MAJOR;
	disk->first_minor	= i * max_part;
	disk->fops		= &brd_fops;
	disk->private_data	= brd;
	disk->queue		= brd->brd_queue;
	disk->flags		= GENHD_FL_EXT_DEVT;
	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, bool *new)
{
	struct brd_device *brd;

	*new = false;
	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);
	}
	*new = true;
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;
	bool new;

	mutex_lock(&brd_devices_mutex);
	brd = brd_init_one(MINOR(dev) / max_part, &new);
	kobj = brd ? get_disk(brd->brd_disk) : NULL;
	mutex_unlock(&brd_devices_mutex);

	if (new)
		*part = 0;

	return kobj;
}

static int __init brd_init(void)
{
	struct brd_device *brd, *next;
	int i;

	/*
	 * brd module now has a feature to instantiate underlying device
	 * structure on-demand, provided that there is an access dev node.
	 *
	 * (1) if rd_nr is specified, create that many upfront. else
	 *     it defaults to CONFIG_BLK_DEV_RAM_COUNT
	 * (2) User can further extend brd devices by create dev node themselves
	 *     and have kernel automatically instantiate actual device
	 *     on-demand. Example:
	 *		mknod /path/devnod_name b 1 X	# 1 is the rd major
	 *		fdisk -l /path/devnod_name
	 *	If (X / max_part) was not already created it will be created
	 *	dynamically.
	 */

	if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
		return -EIO;

	if (unlikely(!max_part))
		max_part = 1;

	for (i = 0; i < rd_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), 1UL << MINORBITS,
				  THIS_MODULE, brd_probe, NULL, NULL);

	pr_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, "ramdisk");

	pr_info("brd: module NOT loaded !!!\n");
	return -ENOMEM;
}

static void __exit brd_exit(void)
{
	struct brd_device *brd, *next;

	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
		brd_del_one(brd);

	blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS);
	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

	pr_info("brd: module unloaded\n");
}

module_init(brd_init);
module_exit(brd_exit);
Commit	Line	Data
9db5579b NP	1	/*
	2	* Ram backed block device driver.
	3	*
	4	* Copyright (C) 2007 Nick Piggin
	5	* Copyright (C) 2007 Novell Inc.
	6	*
	7	* Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
	8	* of their respective owners.
	9	*/
	10
	11	#include <linux/init.h>
	12	#include <linux/module.h>
	13	#include <linux/moduleparam.h>
	14	#include <linux/major.h>
	15	#include <linux/blkdev.h>
	16	#include <linux/bio.h>
	17	#include <linux/highmem.h>
2a48fc0a	18	#include <linux/mutex.h>
9db5579b	19	#include <linux/radix-tree.h>
ff01bb48	20	#include <linux/fs.h>
5a0e3ad6	21	#include <linux/slab.h>
34c0fd54 DW	22	#ifdef CONFIG_BLK_DEV_RAM_DAX
	23	#include <linux/pfn_t.h>
	24	#endif
9db5579b NP	25
	26	#include <asm/uaccess.h>
	27
	28	#define SECTOR_SHIFT 9
	29	#define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
	30	#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
	31
	32	/*
	33	* Each block ramdisk device has a radix_tree brd_pages of pages that stores
	34	* the pages containing the block device's contents. A brd page's ->index is
	35	* its offset in PAGE_SIZE units. This is similar to, but in no way connected
	36	* with, the kernel's pagecache or buffer cache (which sit above our block
	37	* device).
	38	*/
	39	struct brd_device {
	40	int brd_number;
9db5579b NP	41
	42	struct request_queue *brd_queue;
	43	struct gendisk *brd_disk;
	44	struct list_head brd_list;
	45
	46	/*
	47	* Backing store of pages and lock to protect it. This is the contents
	48	* of the block device.
	49	*/
	50	spinlock_t brd_lock;
	51	struct radix_tree_root brd_pages;
	52	};
	53
	54	/*
	55	* Look up and return a brd's page for a given sector.
	56	*/
2a48fc0a	57	static DEFINE_MUTEX(brd_mutex);
9db5579b NP	58	static struct page brd_lookup_page(struct brd_device brd, sector_t sector)
	59	{
	60	pgoff_t idx;
	61	struct page *page;
	62
	63	/*
	64	* The page lifetime is protected by the fact that we have opened the
	65	* device node -- brd pages will never be deleted under us, so we
	66	* don't need any further locking or refcounting.
	67	*
	68	* This is strictly true for the radix-tree nodes as well (ie. we
	69	* don't actually need the rcu_read_lock()), however that is not a
	70	* documented feature of the radix-tree API so it is better to be
	71	* safe here (we don't have total exclusion from radix tree updates
	72	* here, only deletes).
	73	*/
	74	rcu_read_lock();
	75	idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
	76	page = radix_tree_lookup(&brd->brd_pages, idx);
	77	rcu_read_unlock();
	78
	79	BUG_ON(page && page->index != idx);
	80
	81	return page;
	82	}
	83
	84	/*
	85	* Look up and return a brd's page for a given sector.
	86	* If one does not exist, allocate an empty page, and insert that. Then
	87	* return it.
	88	*/
	89	static struct page brd_insert_page(struct brd_device brd, sector_t sector)
	90	{
	91	pgoff_t idx;
	92	struct page *page;
75acb9cd	93	gfp_t gfp_flags;
9db5579b NP	94
	95	page = brd_lookup_page(brd, sector);
	96	if (page)
	97	return page;
	98
	99	/*
	100	* Must use NOIO because we don't want to recurse back into the
	101	* block or filesystem layers from page reclaim.
75acb9cd	102	*
a7a97fc9 MW	103	* Cannot support DAX and highmem, because our ->direct_access
	104	* routine for DAX must return memory that is always addressable.
	105	* If DAX was reworked to use pfns and kmap throughout, this
75acb9cd	106	* restriction might be able to be lifted.
9db5579b	107	*/
75acb9cd	108	gfp_flags = GFP_NOIO \| __GFP_ZERO;
a7a97fc9	109	#ifndef CONFIG_BLK_DEV_RAM_DAX
75acb9cd NP	110	gfp_flags \|= __GFP_HIGHMEM;
75acb9cd NP	111	#endif
26defe34	112	page = alloc_page(gfp_flags);
9db5579b NP	113	if (!page)
	114	return NULL;
	115
	116	if (radix_tree_preload(GFP_NOIO)) {
	117	__free_page(page);
	118	return NULL;
	119	}
	120
	121	spin_lock(&brd->brd_lock);
	122	idx = sector >> PAGE_SECTORS_SHIFT;
dfd20b2b	123	page->index = idx;
9db5579b NP	124	if (radix_tree_insert(&brd->brd_pages, idx, page)) {
	125	__free_page(page);
	126	page = radix_tree_lookup(&brd->brd_pages, idx);
	127	BUG_ON(!page);
	128	BUG_ON(page->index != idx);
dfd20b2b	129	}
9db5579b NP	130	spin_unlock(&brd->brd_lock);
	131
	132	radix_tree_preload_end();
	133
	134	return page;
	135	}
	136
b7c33571 NP	137	static void brd_free_page(struct brd_device *brd, sector_t sector)
	138	{
	139	struct page *page;
	140	pgoff_t idx;
	141
	142	spin_lock(&brd->brd_lock);
	143	idx = sector >> PAGE_SECTORS_SHIFT;
	144	page = radix_tree_delete(&brd->brd_pages, idx);
	145	spin_unlock(&brd->brd_lock);
	146	if (page)
	147	__free_page(page);
	148	}
	149
	150	static void brd_zero_page(struct brd_device *brd, sector_t sector)
	151	{
	152	struct page *page;
	153
	154	page = brd_lookup_page(brd, sector);
	155	if (page)
	156	clear_highpage(page);
	157	}
	158
9db5579b NP	159	/*
	160	* Free all backing store pages and radix tree. This must only be called when
	161	* there are no other users of the device.
	162	*/
	163	#define FREE_BATCH 16
	164	static void brd_free_pages(struct brd_device *brd)
	165	{
	166	unsigned long pos = 0;
	167	struct page *pages[FREE_BATCH];
	168	int nr_pages;
	169
	170	do {
	171	int i;
	172
	173	nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
	174	(void **)pages, pos, FREE_BATCH);
	175
	176	for (i = 0; i < nr_pages; i++) {
	177	void *ret;
	178
	179	BUG_ON(pages[i]->index < pos);
	180	pos = pages[i]->index;
	181	ret = radix_tree_delete(&brd->brd_pages, pos);
	182	BUG_ON(!ret \|\| ret != pages[i]);
	183	__free_page(pages[i]);
	184	}
	185
	186	pos++;
	187
	188	/*
	189	* This assumes radix_tree_gang_lookup always returns as
	190	* many pages as possible. If the radix-tree code changes,
	191	* so will this have to.
	192	*/
	193	} while (nr_pages == FREE_BATCH);
	194	}
	195
	196	/*
	197	* copy_to_brd_setup must be called before copy_to_brd. It may sleep.
	198	*/
	199	static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
	200	{
	201	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
	202	size_t copy;
	203
	204	copy = min_t(size_t, n, PAGE_SIZE - offset);
	205	if (!brd_insert_page(brd, sector))
96f8d8e0	206	return -ENOSPC;
9db5579b NP	207	if (copy < n) {
	208	sector += copy >> SECTOR_SHIFT;
	209	if (!brd_insert_page(brd, sector))
96f8d8e0	210	return -ENOSPC;
9db5579b NP	211	}
	212	return 0;
	213	}
	214
b7c33571 NP	215	static void discard_from_brd(struct brd_device *brd,
	216	sector_t sector, size_t n)
	217	{
	218	while (n >= PAGE_SIZE) {
	219	/*
	220	* Don't want to actually discard pages here because
	221	* re-allocating the pages can result in writeback
	222	* deadlocks under heavy load.
	223	*/
	224	if (0)
	225	brd_free_page(brd, sector);
	226	else
	227	brd_zero_page(brd, sector);
	228	sector += PAGE_SIZE >> SECTOR_SHIFT;
	229	n -= PAGE_SIZE;
	230	}
	231	}
	232
9db5579b NP	233	/*
	234	* Copy n bytes from src to the brd starting at sector. Does not sleep.
	235	*/
	236	static void copy_to_brd(struct brd_device brd, const void src,
	237	sector_t sector, size_t n)
	238	{
	239	struct page *page;
	240	void *dst;
	241	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
	242	size_t copy;
	243
	244	copy = min_t(size_t, n, PAGE_SIZE - offset);
	245	page = brd_lookup_page(brd, sector);
	246	BUG_ON(!page);
	247
cfd8005c	248	dst = kmap_atomic(page);
9db5579b	249	memcpy(dst + offset, src, copy);
cfd8005c	250	kunmap_atomic(dst);
9db5579b NP	251
	252	if (copy < n) {
	253	src += copy;
	254	sector += copy >> SECTOR_SHIFT;
	255	copy = n - copy;
	256	page = brd_lookup_page(brd, sector);
	257	BUG_ON(!page);
	258
cfd8005c	259	dst = kmap_atomic(page);
9db5579b	260	memcpy(dst, src, copy);
cfd8005c	261	kunmap_atomic(dst);
9db5579b NP	262	}
	263	}
	264
	265	/*
	266	* Copy n bytes to dst from the brd starting at sector. Does not sleep.
	267	*/
	268	static void copy_from_brd(void dst, struct brd_device brd,
	269	sector_t sector, size_t n)
	270	{
	271	struct page *page;
	272	void *src;
	273	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
	274	size_t copy;
	275
	276	copy = min_t(size_t, n, PAGE_SIZE - offset);
	277	page = brd_lookup_page(brd, sector);
	278	if (page) {
cfd8005c	279	src = kmap_atomic(page);
9db5579b	280	memcpy(dst, src + offset, copy);
cfd8005c	281	kunmap_atomic(src);
9db5579b NP	282	} else
	283	memset(dst, 0, copy);
	284
	285	if (copy < n) {
	286	dst += copy;
	287	sector += copy >> SECTOR_SHIFT;
	288	copy = n - copy;
	289	page = brd_lookup_page(brd, sector);
	290	if (page) {
cfd8005c	291	src = kmap_atomic(page);
9db5579b	292	memcpy(dst, src, copy);
cfd8005c	293	kunmap_atomic(src);
9db5579b NP	294	} else
	295	memset(dst, 0, copy);
	296	}
	297	}
	298
	299	/*
	300	* Process a single bvec of a bio.
	301	*/
	302	static int brd_do_bvec(struct brd_device brd, struct page page,
	303	unsigned int len, unsigned int off, int rw,
	304	sector_t sector)
	305	{
	306	void *mem;
	307	int err = 0;
	308
	309	if (rw != READ) {
	310	err = copy_to_brd_setup(brd, sector, len);
	311	if (err)
	312	goto out;
	313	}
	314
cfd8005c	315	mem = kmap_atomic(page);
9db5579b NP	316	if (rw == READ) {
	317	copy_from_brd(mem + off, brd, sector, len);
	318	flush_dcache_page(page);
c2572f2b NP	319	} else {
c2572f2b NP	320	flush_dcache_page(page);
9db5579b	321	copy_to_brd(brd, mem + off, sector, len);
c2572f2b	322	}
cfd8005c	323	kunmap_atomic(mem);
9db5579b NP	324
	325	out:
	326	return err;
	327	}
	328
dece1635	329	static blk_qc_t brd_make_request(struct request_queue q, struct bio bio)
9db5579b NP	330	{
	331	struct block_device *bdev = bio->bi_bdev;
	332	struct brd_device *brd = bdev->bd_disk->private_data;
	333	int rw;
7988613b	334	struct bio_vec bvec;
9db5579b	335	sector_t sector;
7988613b	336	struct bvec_iter iter;
9db5579b	337
4f024f37	338	sector = bio->bi_iter.bi_sector;
f73a1c7d	339	if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
4246a0b6	340	goto io_error;
9db5579b	341
7b6d91da	342	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
2dbe5495	343	if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) \|\|
5e4298be	344	bio->bi_iter.bi_size & ~PAGE_MASK)
2dbe5495	345	goto io_error;
4f024f37	346	discard_from_brd(brd, sector, bio->bi_iter.bi_size);
b7c33571 NP	347	goto out;
	348	}
	349
9db5579b NP	350	rw = bio_rw(bio);
	351	if (rw == READA)
	352	rw = READ;
	353
7988613b KO	354	bio_for_each_segment(bvec, bio, iter) {
7988613b KO	355	unsigned int len = bvec.bv_len;
4246a0b6 CH	356	int err;
4246a0b6 CH	357
7988613b KO	358	err = brd_do_bvec(brd, bvec.bv_page, len,
7988613b KO	359	bvec.bv_offset, rw, sector);
9db5579b	360	if (err)
4246a0b6	361	goto io_error;
9db5579b NP	362	sector += len >> SECTOR_SHIFT;
	363	}
	364
	365	out:
4246a0b6	366	bio_endio(bio);
dece1635	367	return BLK_QC_T_NONE;
4246a0b6 CH	368	io_error:
4246a0b6 CH	369	bio_io_error(bio);
dece1635	370	return BLK_QC_T_NONE;
9db5579b NP	371	}
9db5579b NP	372
a72132c3 MW	373	static int brd_rw_page(struct block_device *bdev, sector_t sector,
	374	struct page *page, int rw)
	375	{
	376	struct brd_device *brd = bdev->bd_disk->private_data;
09cbfeaf	377	int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, rw, sector);
a72132c3 MW	378	page_endio(page, rw & WRITE, err);
	379	return err;
	380	}
	381
a7a97fc9	382	#ifdef CONFIG_BLK_DEV_RAM_DAX
dd22f551	383	static long brd_direct_access(struct block_device *bdev, sector_t sector,
34c0fd54	384	void __pmem *kaddr, pfn_t pfn)
75acb9cd NP	385	{
	386	struct brd_device *brd = bdev->bd_disk->private_data;
	387	struct page *page;
	388
	389	if (!brd)
	390	return -ENODEV;
75acb9cd NP	391	page = brd_insert_page(brd, sector);
75acb9cd NP	392	if (!page)
96f8d8e0	393	return -ENOSPC;
e2e05394	394	kaddr = (void __pmem )page_address(page);
34c0fd54	395	*pfn = page_to_pfn_t(page);
75acb9cd	396
dd22f551	397	return PAGE_SIZE;
75acb9cd	398	}
a7a97fc9 MW	399	#else
a7a97fc9 MW	400	#define brd_direct_access NULL
75acb9cd NP	401	#endif
75acb9cd NP	402
2b9ecd03	403	static int brd_ioctl(struct block_device *bdev, fmode_t mode,
9db5579b NP	404	unsigned int cmd, unsigned long arg)
	405	{
	406	int error;
9db5579b NP	407	struct brd_device *brd = bdev->bd_disk->private_data;
	408
	409	if (cmd != BLKFLSBUF)
	410	return -ENOTTY;
	411
	412	/*
	413	* ram device BLKFLSBUF has special semantics, we want to actually
	414	* release and destroy the ramdisk data.
	415	*/
2a48fc0a	416	mutex_lock(&brd_mutex);
9db5579b NP	417	mutex_lock(&bdev->bd_mutex);
	418	error = -EBUSY;
	419	if (bdev->bd_openers <= 1) {
	420	/*
ff01bb48 AV	421	* Kill the cache first, so it isn't written back to the
ff01bb48 AV	422	* device.
9db5579b NP	423	*
	424	* Another thread might instantiate more buffercache here,
	425	* but there is not much we can do to close that race.
	426	*/
ff01bb48	427	kill_bdev(bdev);
9db5579b NP	428	brd_free_pages(brd);
	429	error = 0;
	430	}
	431	mutex_unlock(&bdev->bd_mutex);
2a48fc0a	432	mutex_unlock(&brd_mutex);
9db5579b NP	433
	434	return error;
	435	}
	436
83d5cde4	437	static const struct block_device_operations brd_fops = {
75acb9cd	438	.owner = THIS_MODULE,
a72132c3	439	.rw_page = brd_rw_page,
8a6cfeb6	440	.ioctl = brd_ioctl,
75acb9cd	441	.direct_access = brd_direct_access,
9db5579b NP	442	};
	443
	444	/*
	445	* And now the modules code and kernel interface.
	446	*/
937af5ec	447	static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
8892cbaf	448	module_param(rd_nr, int, S_IRUGO);
9db5579b	449	MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
937af5ec BH	450
937af5ec BH	451	int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
8892cbaf	452	module_param(rd_size, int, S_IRUGO);
9db5579b	453	MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
937af5ec BH	454
937af5ec BH	455	static int max_part = 1;
8892cbaf	456	module_param(max_part, int, S_IRUGO);
937af5ec BH	457	MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
937af5ec BH	458
9db5579b NP	459	MODULE_LICENSE("GPL");
9db5579b NP	460	MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
efedf51c	461	MODULE_ALIAS("rd");
9db5579b NP	462
	463	#ifndef MODULE
	464	/* Legacy boot options - nonmodular */
	465	static int __init ramdisk_size(char *str)
	466	{
	467	rd_size = simple_strtol(str, NULL, 0);
	468	return 1;
	469	}
1adbee50	470	__setup("ramdisk_size=", ramdisk_size);
9db5579b NP	471	#endif
	472
	473	/*
	474	* The device scheme is derived from loop.c. Keep them in synch where possible
	475	* (should share code eventually).
	476	*/
	477	static LIST_HEAD(brd_devices);
	478	static DEFINE_MUTEX(brd_devices_mutex);
	479
	480	static struct brd_device *brd_alloc(int i)
	481	{
	482	struct brd_device *brd;
	483	struct gendisk *disk;
	484
	485	brd = kzalloc(sizeof(*brd), GFP_KERNEL);
	486	if (!brd)
	487	goto out;
	488	brd->brd_number = i;
	489	spin_lock_init(&brd->brd_lock);
	490	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
	491
	492	brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
	493	if (!brd->brd_queue)
	494	goto out_free_dev;
c8fa3173	495
9db5579b	496	blk_queue_make_request(brd->brd_queue, brd_make_request);
086fa5ff	497	blk_queue_max_hw_sectors(brd->brd_queue, 1024);
9db5579b NP	498	blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
9db5579b NP	499
c8fa3173 BH	500	/* This is so fdisk will align partitions on 4k, because of
	501	* direct_access API needing 4k alignment, returning a PFN
	502	* (This is only a problem on very small devices <= 4M,
	503	* otherwise fdisk will align on 1M. Regardless this call
	504	* is harmless)
	505	*/
	506	blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
	507
b7c33571	508	brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
2bb4cd5c	509	blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
b7c33571 NP	510	brd->brd_queue->limits.discard_zeroes_data = 1;
	511	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
	512
937af5ec	513	disk = brd->brd_disk = alloc_disk(max_part);
9db5579b NP	514	if (!disk)
	515	goto out_free_queue;
	516	disk->major = RAMDISK_MAJOR;
937af5ec	517	disk->first_minor = i * max_part;
9db5579b NP	518	disk->fops = &brd_fops;
	519	disk->private_data = brd;
	520	disk->queue = brd->brd_queue;
937af5ec	521	disk->flags = GENHD_FL_EXT_DEVT;
9db5579b NP	522	sprintf(disk->disk_name, "ram%d", i);
	523	set_capacity(disk, rd_size * 2);
	524
	525	return brd;
	526
	527	out_free_queue:
	528	blk_cleanup_queue(brd->brd_queue);
	529	out_free_dev:
	530	kfree(brd);
	531	out:
	532	return NULL;
	533	}
	534
	535	static void brd_free(struct brd_device *brd)
	536	{
	537	put_disk(brd->brd_disk);
	538	blk_cleanup_queue(brd->brd_queue);
	539	brd_free_pages(brd);
	540	kfree(brd);
	541	}
	542
937af5ec	543	static struct brd_device brd_init_one(int i, bool new)
9db5579b NP	544	{
	545	struct brd_device *brd;
	546
937af5ec	547	*new = false;
9db5579b NP	548	list_for_each_entry(brd, &brd_devices, brd_list) {
	549	if (brd->brd_number == i)
	550	goto out;
	551	}
	552
	553	brd = brd_alloc(i);
	554	if (brd) {
	555	add_disk(brd->brd_disk);
	556	list_add_tail(&brd->brd_list, &brd_devices);
	557	}
937af5ec	558	*new = true;
9db5579b NP	559	out:
	560	return brd;
	561	}
	562
	563	static void brd_del_one(struct brd_device *brd)
	564	{
	565	list_del(&brd->brd_list);
	566	del_gendisk(brd->brd_disk);
	567	brd_free(brd);
	568	}
	569
	570	static struct kobject brd_probe(dev_t dev, int part, void *data)
	571	{
	572	struct brd_device *brd;
	573	struct kobject *kobj;
937af5ec	574	bool new;
9db5579b NP	575
9db5579b NP	576	mutex_lock(&brd_devices_mutex);
937af5ec	577	brd = brd_init_one(MINOR(dev) / max_part, &new);
a207f593	578	kobj = brd ? get_disk(brd->brd_disk) : NULL;
9db5579b NP	579	mutex_unlock(&brd_devices_mutex);
9db5579b NP	580
937af5ec BH	581	if (new)
	582	*part = 0;
	583
9db5579b NP	584	return kobj;
	585	}
	586
	587	static int __init brd_init(void)
	588	{
9db5579b	589	struct brd_device brd, next;
937af5ec	590	int i;
9db5579b NP	591
	592	/*
	593	* brd module now has a feature to instantiate underlying device
	594	* structure on-demand, provided that there is an access dev node.
9db5579b	595	*
937af5ec BH	596	* (1) if rd_nr is specified, create that many upfront. else
	597	* it defaults to CONFIG_BLK_DEV_RAM_COUNT
	598	* (2) User can further extend brd devices by create dev node themselves
	599	* and have kernel automatically instantiate actual device
	600	* on-demand. Example:
	601	* mknod /path/devnod_name b 1 X # 1 is the rd major
	602	* fdisk -l /path/devnod_name
	603	* If (X / max_part) was not already created it will be created
	604	* dynamically.
9db5579b	605	*/
d7853d1f	606
9db5579b NP	607	if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
	608	return -EIO;
	609
937af5ec BH	610	if (unlikely(!max_part))
	611	max_part = 1;
	612
	613	for (i = 0; i < rd_nr; i++) {
9db5579b NP	614	brd = brd_alloc(i);
	615	if (!brd)
	616	goto out_free;
	617	list_add_tail(&brd->brd_list, &brd_devices);
	618	}
	619
	620	/* point of no return */
	621
	622	list_for_each_entry(brd, &brd_devices, brd_list)
	623	add_disk(brd->brd_disk);
	624
937af5ec	625	blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS,
9db5579b NP	626	THIS_MODULE, brd_probe, NULL, NULL);
9db5579b NP	627
937af5ec	628	pr_info("brd: module loaded\n");
9db5579b NP	629	return 0;
	630
	631	out_free:
	632	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
	633	list_del(&brd->brd_list);
	634	brd_free(brd);
	635	}
c82f2966	636	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
9db5579b	637
937af5ec	638	pr_info("brd: module NOT loaded !!!\n");
9db5579b NP	639	return -ENOMEM;
	640	}
	641
	642	static void __exit brd_exit(void)
	643	{
9db5579b NP	644	struct brd_device brd, next;
9db5579b NP	645
9db5579b NP	646	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
	647	brd_del_one(brd);
	648
937af5ec	649	blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS);
9db5579b	650	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
937af5ec BH	651
937af5ec BH	652	pr_info("brd: module unloaded\n");
9db5579b NP	653	}
	654
	655	module_init(brd_init);
	656	module_exit(brd_exit);
	657