diff options
Diffstat (limited to 'drivers/block/brd.c')
| -rw-r--r-- | drivers/block/brd.c | 583 |
1 files changed, 583 insertions, 0 deletions
diff --git a/drivers/block/brd.c b/drivers/block/brd.c new file mode 100644 index 00000000000..85364804364 --- /dev/null +++ b/drivers/block/brd.c @@ -0,0 +1,583 @@ +/* + * 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; + 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 XIP and highmem, because our ->direct_access + * routine for XIP must return memory that is always addressable. + * If XIP 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_XIP + gfp_flags |= __GFP_HIGHMEM; +#endif + 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; +} + +#ifdef CONFIG_BLK_DEV_XIP +static int brd_direct_access (struct block_device *bdev, sector_t sector, + unsigned long *data) +{ + struct brd_device *brd = bdev->bd_disk->private_data; + struct page *page; + + if (!brd) + return -ENODEV; + if (sector & (PAGE_SECTORS-1)) + return -EINVAL; + if (sector + PAGE_SECTORS > get_capacity(bdev->bd_disk)) + return -ERANGE; + page = brd_insert_page(brd, sector); + if (!page) + return -ENOMEM; + *data = (unsigned long)page_address(page); + + return 0; +} +#endif + +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, +#ifdef CONFIG_BLK_DEV_XIP + .direct_access = brd_direct_access, +#endif +}; + +/* + * 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); + |