// SPDX-License-Identifier: GPL-2.0-only/* * 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/initrd.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/pagemap.h>#include <linux/xarray.h>#include <linux/fs.h>#include <linux/slab.h>#include <linux/backing-dev.h>#include <linux/debugfs.h> #include <linux/uaccess.h> /* * Each block ramdisk device has a xarray brd_pages of pages that stores * the pages containing the block device's contents. */struct brd_device { int brd_number; struct gendisk *brd_disk; struct list_head brd_list; /* * Backing store of pages. This is the contents of the block device. */ struct xarray brd_pages; u64 brd_nr_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){ return xa_load(&brd->brd_pages, sector >> PAGE_SECTORS_SHIFT);} /* * Insert a new page for a given sector, if one does not already exist. */static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp){ pgoff_t idx = sector >> PAGE_SECTORS_SHIFT; struct page *page; int ret = 0; page = brd_lookup_page(brd, sector); if (page) return 0; page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM); if (!page) return -ENOMEM; xa_lock(&brd->brd_pages); ret = __xa_insert(&brd->brd_pages, idx, page, gfp); if (!ret) brd->brd_nr_pages++; xa_unlock(&brd->brd_pages); if (ret < 0) { __free_page(page); if (ret == -EBUSY) ret = 0; } return ret;} /* * Free all backing store pages and xarray. This must only be called when * there are no other users of the device. */static void brd_free_pages(struct brd_device *brd){ struct page *page; pgoff_t idx; xa_for_each(&brd->brd_pages, idx, page) { __free_page(page); cond_resched(); } xa_destroy(&brd->brd_pages);} /* * 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, gfp_t gfp){ unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; int ret; copy = min_t(size_t, n, PAGE_SIZE - offset); ret = brd_insert_page(brd, sector, gfp); if (ret) return ret; if (copy < n) { sector += copy >> SECTOR_SHIFT; ret = brd_insert_page(brd, sector, gfp); } return ret;} /* * 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, blk_opf_t opf, sector_t sector){ void *mem; int err = 0; if (op_is_write(opf)) { /* * Must use NOIO because we don't want to recurse back into the * block or filesystem layers from page reclaim. */ gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO; err = copy_to_brd_setup(brd, sector, len, gfp); if (err) goto out; } mem = kmap_atomic(page); if (!op_is_write(opf)) { 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 void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size){ sector_t aligned_sector = (sector + PAGE_SECTORS) & ~PAGE_SECTORS; struct page *page; size -= (aligned_sector - sector) * SECTOR_SIZE; xa_lock(&brd->brd_pages); while (size >= PAGE_SIZE && aligned_sector < rd_size * 2) { page = __xa_erase(&brd->brd_pages, aligned_sector >> PAGE_SECTORS_SHIFT); if (page) { __free_page(page); brd->brd_nr_pages--; } aligned_sector += PAGE_SECTORS; size -= PAGE_SIZE; } xa_unlock(&brd->brd_pages);} static void brd_submit_bio(struct bio *bio){ struct brd_device *brd = bio->bi_bdev->bd_disk->private_data; sector_t sector = bio->bi_iter.bi_sector; struct bio_vec bvec; struct bvec_iter iter; if (unlikely(op_is_discard(bio->bi_opf))) { brd_do_discard(brd, sector, bio->bi_iter.bi_size); bio_endio(bio); return; } bio_for_each_segment(bvec, bio, iter) { unsigned int len = bvec.bv_len; int err; /* Don't support un-aligned buffer */ WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) || (len & (SECTOR_SIZE - 1))); err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, bio->bi_opf, sector); if (err) { if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) { bio_wouldblock_error(bio); return; } bio_io_error(bio); return; } sector += len >> SECTOR_SHIFT; } bio_endio(bio);} static const struct block_device_operations brd_fops = { .owner = THIS_MODULE, .submit_bio = brd_submit_bio,}; /* * And now the modules code and kernel interface. */static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;module_param(rd_nr, int, 0444);MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;module_param(rd_size, ulong, 0444);MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); static int max_part = 1;module_param(max_part, int, 0444);MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); MODULE_DESCRIPTION("Ram backed block device driver");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 dentry *brd_debugfs_dir; static struct brd_device *brd_find_or_alloc_device(int i){ struct brd_device *brd; mutex_lock(&brd_devices_mutex); list_for_each_entry(brd, &brd_devices, brd_list) { if (brd->brd_number == i) { mutex_unlock(&brd_devices_mutex); return ERR_PTR(-EEXIST); } } brd = kzalloc(sizeof(*brd), GFP_KERNEL); if (!brd) { mutex_unlock(&brd_devices_mutex); return ERR_PTR(-ENOMEM); } brd->brd_number = i; list_add_tail(&brd->brd_list, &brd_devices); mutex_unlock(&brd_devices_mutex); return brd;} static void brd_free_device(struct brd_device *brd){ mutex_lock(&brd_devices_mutex); list_del(&brd->brd_list); mutex_unlock(&brd_devices_mutex); kfree(brd);} static int brd_alloc(int i){ struct brd_device *brd; struct gendisk *disk; char buf[DISK_NAME_LEN]; int err = -ENOMEM; struct queue_limits lim = { /* * 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) */ .physical_block_size = PAGE_SIZE, .max_hw_discard_sectors = UINT_MAX, .max_discard_segments = 1, .discard_granularity = PAGE_SIZE, .features = BLK_FEAT_SYNCHRONOUS | BLK_FEAT_NOWAIT, }; brd = brd_find_or_alloc_device(i); if (IS_ERR(brd)) return PTR_ERR(brd); xa_init(&brd->brd_pages); snprintf(buf, DISK_NAME_LEN, "ram%d", i); if (!IS_ERR_OR_NULL(brd_debugfs_dir)) debugfs_create_u64(buf, 0444, brd_debugfs_dir, &brd->brd_nr_pages); disk = brd->brd_disk = blk_alloc_disk(&lim, NUMA_NO_NODE); if (IS_ERR(disk)) { err = PTR_ERR(disk); goto out_free_dev; } disk->major = RAMDISK_MAJOR; disk->first_minor = i * max_part; disk->minors = max_part; disk->fops = &brd_fops; disk->private_data = brd; strscpy(disk->disk_name, buf, DISK_NAME_LEN); set_capacity(disk, rd_size * 2); err = add_disk(disk); if (err) goto out_cleanup_disk; return 0; out_cleanup_disk: put_disk(disk);out_free_dev: brd_free_device(brd); return err;} static void brd_probe(dev_t dev){ brd_alloc(MINOR(dev) / max_part);} static void brd_cleanup(void){ struct brd_device *brd, *next; debugfs_remove_recursive(brd_debugfs_dir); list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { del_gendisk(brd->brd_disk); put_disk(brd->brd_disk); brd_free_pages(brd); brd_free_device(brd); }} static inline void brd_check_and_reset_par(void){ if (unlikely(!max_part)) max_part = 1; /* * make sure 'max_part' can be divided exactly by (1U << MINORBITS), * otherwise, it is possiable to get same dev_t when adding partitions. */ if ((1U << MINORBITS) % max_part != 0) max_part = 1UL << fls(max_part); if (max_part > DISK_MAX_PARTS) { pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n", DISK_MAX_PARTS, DISK_MAX_PARTS); max_part = DISK_MAX_PARTS; }} static int __init brd_init(void){ int err, 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. */ brd_check_and_reset_par(); brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL); if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) { err = -EIO; goto out_free; } for (i = 0; i < rd_nr; i++) brd_alloc(i); pr_info("brd: module loaded\n"); return 0; out_free: brd_cleanup(); pr_info("brd: module NOT loaded !!!\n"); return err;} static void __exit brd_exit(void){ unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); brd_cleanup(); pr_info("brd: module unloaded\n");}Lines 1–500 of 504. Load more
// SPDX-License-Identifier: GPL-2.0-only /* * 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/initrd.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/pagemap.h> #include <linux/xarray.h> #include <linux/fs.h> #include <linux/slab.h> #include <linux/backing-dev.h> #include <linux/debugfs.h> #include <linux/uaccess.h> /* * Each block ramdisk device has a xarray brd_pages of pages that stores * the pages containing the block device's contents. */ struct brd_device { int brd_number; struct gendisk *brd_disk; struct list_head brd_list; /* * Backing store of pages. This is the contents of the block device. */ struct xarray brd_pages; u64 brd_nr_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) { return xa_load(&brd->brd_pages, sector >> PAGE_SECTORS_SHIFT); } /* * Insert a new page for a given sector, if one does not already exist. */ static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp) { pgoff_t idx = sector >> PAGE_SECTORS_SHIFT; struct page *page; int ret = 0; page = brd_lookup_page(brd, sector); if (page) return 0; page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM); if (!page) return -ENOMEM; xa_lock(&brd->brd_pages); ret = __xa_insert(&brd->brd_pages, idx, page, gfp); if (!ret) brd->brd_nr_pages++; xa_unlock(&brd->brd_pages); if (ret < 0) { __free_page(page); if (ret == -EBUSY) ret = 0; } return ret; } /* * Free all backing store pages and xarray. This must only be called when * there are no other users of the device. */ static void brd_free_pages(struct brd_device *brd) { struct page *page; pgoff_t idx; xa_for_each(&brd->brd_pages, idx, page) { __free_page(page); cond_resched(); } xa_destroy(&brd->brd_pages); } /* * 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, gfp_t gfp) { unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; int ret; copy = min_t(size_t, n, PAGE_SIZE - offset); ret = brd_insert_page(brd, sector, gfp); if (ret) return ret; if (copy < n) { sector += copy >> SECTOR_SHIFT; ret = brd_insert_page(brd, sector, gfp); } return ret; } /* * 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, blk_opf_t opf, sector_t sector) { void *mem; int err = 0; if (op_is_write(opf)) { /* * Must use NOIO because we don't want to recurse back into the * block or filesystem layers from page reclaim. */ gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO; err = copy_to_brd_setup(brd, sector, len, gfp); if (err) goto out; } mem = kmap_atomic(page); if (!op_is_write(opf)) { 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 void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size) { sector_t aligned_sector = (sector + PAGE_SECTORS) & ~PAGE_SECTORS; struct page *page; size -= (aligned_sector - sector) * SECTOR_SIZE; xa_lock(&brd->brd_pages); while (size >= PAGE_SIZE && aligned_sector < rd_size * 2) { page = __xa_erase(&brd->brd_pages, aligned_sector >> PAGE_SECTORS_SHIFT); if (page) { __free_page(page); brd->brd_nr_pages--; } aligned_sector += PAGE_SECTORS; size -= PAGE_SIZE; } xa_unlock(&brd->brd_pages); } static void brd_submit_bio(struct bio *bio) { struct brd_device *brd = bio->bi_bdev->bd_disk->private_data; sector_t sector = bio->bi_iter.bi_sector; struct bio_vec bvec; struct bvec_iter iter; if (unlikely(op_is_discard(bio->bi_opf))) { brd_do_discard(brd, sector, bio->bi_iter.bi_size); bio_endio(bio); return; } bio_for_each_segment(bvec, bio, iter) { unsigned int len = bvec.bv_len; int err; /* Don't support un-aligned buffer */ WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) || (len & (SECTOR_SIZE - 1))); err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, bio->bi_opf, sector); if (err) { if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) { bio_wouldblock_error(bio); return; } bio_io_error(bio); return; } sector += len >> SECTOR_SHIFT; } bio_endio(bio); } static const struct block_device_operations brd_fops = { .owner = THIS_MODULE, .submit_bio = brd_submit_bio, }; /* * And now the modules code and kernel interface. */ static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT; module_param(rd_nr, int, 0444); MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE; module_param(rd_size, ulong, 0444); MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); static int max_part = 1; module_param(max_part, int, 0444); MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); MODULE_DESCRIPTION("Ram backed block device driver"); 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 dentry *brd_debugfs_dir; static struct brd_device *brd_find_or_alloc_device(int i) { struct brd_device *brd; mutex_lock(&brd_devices_mutex); list_for_each_entry(brd, &brd_devices, brd_list) { if (brd->brd_number == i) { mutex_unlock(&brd_devices_mutex); return ERR_PTR(-EEXIST); } } brd = kzalloc(sizeof(*brd), GFP_KERNEL); if (!brd) { mutex_unlock(&brd_devices_mutex); return ERR_PTR(-ENOMEM); } brd->brd_number = i; list_add_tail(&brd->brd_list, &brd_devices); mutex_unlock(&brd_devices_mutex); return brd; } static void brd_free_device(struct brd_device *brd) { mutex_lock(&brd_devices_mutex); list_del(&brd->brd_list); mutex_unlock(&brd_devices_mutex); kfree(brd); } static int brd_alloc(int i) { struct brd_device *brd; struct gendisk *disk; char buf[DISK_NAME_LEN]; int err = -ENOMEM; struct queue_limits lim = { /* * 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) */ .physical_block_size = PAGE_SIZE, .max_hw_discard_sectors = UINT_MAX, .max_discard_segments = 1, .discard_granularity = PAGE_SIZE, .features = BLK_FEAT_SYNCHRONOUS | BLK_FEAT_NOWAIT, }; brd = brd_find_or_alloc_device(i); if (IS_ERR(brd)) return PTR_ERR(brd); xa_init(&brd->brd_pages); snprintf(buf, DISK_NAME_LEN, "ram%d", i); if (!IS_ERR_OR_NULL(brd_debugfs_dir)) debugfs_create_u64(buf, 0444, brd_debugfs_dir, &brd->brd_nr_pages); disk = brd->brd_disk = blk_alloc_disk(&lim, NUMA_NO_NODE); if (IS_ERR(disk)) { err = PTR_ERR(disk); goto out_free_dev; } disk->major = RAMDISK_MAJOR; disk->first_minor = i * max_part; disk->minors = max_part; disk->fops = &brd_fops; disk->private_data = brd; strscpy(disk->disk_name, buf, DISK_NAME_LEN); set_capacity(disk, rd_size * 2); err = add_disk(disk); if (err) goto out_cleanup_disk; return 0; out_cleanup_disk: put_disk(disk); out_free_dev: brd_free_device(brd); return err; } static void brd_probe(dev_t dev) { brd_alloc(MINOR(dev) / max_part); } static void brd_cleanup(void) { struct brd_device *brd, *next; debugfs_remove_recursive(brd_debugfs_dir); list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { del_gendisk(brd->brd_disk); put_disk(brd->brd_disk); brd_free_pages(brd); brd_free_device(brd); } } static inline void brd_check_and_reset_par(void) { if (unlikely(!max_part)) max_part = 1; /* * make sure 'max_part' can be divided exactly by (1U << MINORBITS), * otherwise, it is possiable to get same dev_t when adding partitions. */ if ((1U << MINORBITS) % max_part != 0) max_part = 1UL << fls(max_part); if (max_part > DISK_MAX_PARTS) { pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n", DISK_MAX_PARTS, DISK_MAX_PARTS); max_part = DISK_MAX_PARTS; } } static int __init brd_init(void) { int err, 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. */ brd_check_and_reset_par(); brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL); if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) { err = -EIO; goto out_free; } for (i = 0; i < rd_nr; i++) brd_alloc(i); pr_info("brd: module loaded\n"); return 0; out_free: brd_cleanup(); pr_info("brd: module NOT loaded !!!\n"); return err; } static void __exit brd_exit(void) { unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); brd_cleanup(); pr_info("brd: module unloaded\n"); }