1 files changed, 548 insertions, 0 deletions
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 00000000000..50b659bedc8
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,548 @@
+/*
+ * 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);
+