Commit | Line | Data |
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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> | |
1647b9b9 | 24 | #include <linux/dax.h> |
5d61e43b | 25 | #include <linux/uio.h> |
34c0fd54 | 26 | #endif |
9db5579b | 27 | |
7c0f6ba6 | 28 | #include <linux/uaccess.h> |
9db5579b NP |
29 | |
30 | #define SECTOR_SHIFT 9 | |
31 | #define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) | |
32 | #define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT) | |
33 | ||
34 | /* | |
35 | * Each block ramdisk device has a radix_tree brd_pages of pages that stores | |
36 | * the pages containing the block device's contents. A brd page's ->index is | |
37 | * its offset in PAGE_SIZE units. This is similar to, but in no way connected | |
38 | * with, the kernel's pagecache or buffer cache (which sit above our block | |
39 | * device). | |
40 | */ | |
41 | struct brd_device { | |
42 | int brd_number; | |
9db5579b NP |
43 | |
44 | struct request_queue *brd_queue; | |
45 | struct gendisk *brd_disk; | |
1647b9b9 DW |
46 | #ifdef CONFIG_BLK_DEV_RAM_DAX |
47 | struct dax_device *dax_dev; | |
48 | #endif | |
9db5579b NP |
49 | struct list_head brd_list; |
50 | ||
51 | /* | |
52 | * Backing store of pages and lock to protect it. This is the contents | |
53 | * of the block device. | |
54 | */ | |
55 | spinlock_t brd_lock; | |
56 | struct radix_tree_root brd_pages; | |
57 | }; | |
58 | ||
59 | /* | |
60 | * Look up and return a brd's page for a given sector. | |
61 | */ | |
2a48fc0a | 62 | static DEFINE_MUTEX(brd_mutex); |
9db5579b NP |
63 | static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) |
64 | { | |
65 | pgoff_t idx; | |
66 | struct page *page; | |
67 | ||
68 | /* | |
69 | * The page lifetime is protected by the fact that we have opened the | |
70 | * device node -- brd pages will never be deleted under us, so we | |
71 | * don't need any further locking or refcounting. | |
72 | * | |
73 | * This is strictly true for the radix-tree nodes as well (ie. we | |
74 | * don't actually need the rcu_read_lock()), however that is not a | |
75 | * documented feature of the radix-tree API so it is better to be | |
76 | * safe here (we don't have total exclusion from radix tree updates | |
77 | * here, only deletes). | |
78 | */ | |
79 | rcu_read_lock(); | |
80 | idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */ | |
81 | page = radix_tree_lookup(&brd->brd_pages, idx); | |
82 | rcu_read_unlock(); | |
83 | ||
84 | BUG_ON(page && page->index != idx); | |
85 | ||
86 | return page; | |
87 | } | |
88 | ||
89 | /* | |
90 | * Look up and return a brd's page for a given sector. | |
91 | * If one does not exist, allocate an empty page, and insert that. Then | |
92 | * return it. | |
93 | */ | |
94 | static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) | |
95 | { | |
96 | pgoff_t idx; | |
97 | struct page *page; | |
75acb9cd | 98 | gfp_t gfp_flags; |
9db5579b NP |
99 | |
100 | page = brd_lookup_page(brd, sector); | |
101 | if (page) | |
102 | return page; | |
103 | ||
104 | /* | |
105 | * Must use NOIO because we don't want to recurse back into the | |
106 | * block or filesystem layers from page reclaim. | |
75acb9cd | 107 | * |
a7a97fc9 MW |
108 | * Cannot support DAX and highmem, because our ->direct_access |
109 | * routine for DAX must return memory that is always addressable. | |
110 | * If DAX was reworked to use pfns and kmap throughout, this | |
75acb9cd | 111 | * restriction might be able to be lifted. |
9db5579b | 112 | */ |
75acb9cd | 113 | gfp_flags = GFP_NOIO | __GFP_ZERO; |
a7a97fc9 | 114 | #ifndef CONFIG_BLK_DEV_RAM_DAX |
75acb9cd NP |
115 | gfp_flags |= __GFP_HIGHMEM; |
116 | #endif | |
26defe34 | 117 | page = alloc_page(gfp_flags); |
9db5579b NP |
118 | if (!page) |
119 | return NULL; | |
120 | ||
121 | if (radix_tree_preload(GFP_NOIO)) { | |
122 | __free_page(page); | |
123 | return NULL; | |
124 | } | |
125 | ||
126 | spin_lock(&brd->brd_lock); | |
127 | idx = sector >> PAGE_SECTORS_SHIFT; | |
dfd20b2b | 128 | page->index = idx; |
9db5579b NP |
129 | if (radix_tree_insert(&brd->brd_pages, idx, page)) { |
130 | __free_page(page); | |
131 | page = radix_tree_lookup(&brd->brd_pages, idx); | |
132 | BUG_ON(!page); | |
133 | BUG_ON(page->index != idx); | |
dfd20b2b | 134 | } |
9db5579b NP |
135 | spin_unlock(&brd->brd_lock); |
136 | ||
137 | radix_tree_preload_end(); | |
138 | ||
139 | return page; | |
140 | } | |
141 | ||
142 | /* | |
143 | * Free all backing store pages and radix tree. This must only be called when | |
144 | * there are no other users of the device. | |
145 | */ | |
146 | #define FREE_BATCH 16 | |
147 | static void brd_free_pages(struct brd_device *brd) | |
148 | { | |
149 | unsigned long pos = 0; | |
150 | struct page *pages[FREE_BATCH]; | |
151 | int nr_pages; | |
152 | ||
153 | do { | |
154 | int i; | |
155 | ||
156 | nr_pages = radix_tree_gang_lookup(&brd->brd_pages, | |
157 | (void **)pages, pos, FREE_BATCH); | |
158 | ||
159 | for (i = 0; i < nr_pages; i++) { | |
160 | void *ret; | |
161 | ||
162 | BUG_ON(pages[i]->index < pos); | |
163 | pos = pages[i]->index; | |
164 | ret = radix_tree_delete(&brd->brd_pages, pos); | |
165 | BUG_ON(!ret || ret != pages[i]); | |
166 | __free_page(pages[i]); | |
167 | } | |
168 | ||
169 | pos++; | |
170 | ||
171 | /* | |
172 | * This assumes radix_tree_gang_lookup always returns as | |
173 | * many pages as possible. If the radix-tree code changes, | |
174 | * so will this have to. | |
175 | */ | |
176 | } while (nr_pages == FREE_BATCH); | |
177 | } | |
178 | ||
179 | /* | |
180 | * copy_to_brd_setup must be called before copy_to_brd. It may sleep. | |
181 | */ | |
182 | static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n) | |
183 | { | |
184 | unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; | |
185 | size_t copy; | |
186 | ||
187 | copy = min_t(size_t, n, PAGE_SIZE - offset); | |
188 | if (!brd_insert_page(brd, sector)) | |
96f8d8e0 | 189 | return -ENOSPC; |
9db5579b NP |
190 | if (copy < n) { |
191 | sector += copy >> SECTOR_SHIFT; | |
192 | if (!brd_insert_page(brd, sector)) | |
96f8d8e0 | 193 | return -ENOSPC; |
9db5579b NP |
194 | } |
195 | return 0; | |
196 | } | |
197 | ||
198 | /* | |
199 | * Copy n bytes from src to the brd starting at sector. Does not sleep. | |
200 | */ | |
201 | static void copy_to_brd(struct brd_device *brd, const void *src, | |
202 | sector_t sector, size_t n) | |
203 | { | |
204 | struct page *page; | |
205 | void *dst; | |
206 | unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; | |
207 | size_t copy; | |
208 | ||
209 | copy = min_t(size_t, n, PAGE_SIZE - offset); | |
210 | page = brd_lookup_page(brd, sector); | |
211 | BUG_ON(!page); | |
212 | ||
cfd8005c | 213 | dst = kmap_atomic(page); |
9db5579b | 214 | memcpy(dst + offset, src, copy); |
cfd8005c | 215 | kunmap_atomic(dst); |
9db5579b NP |
216 | |
217 | if (copy < n) { | |
218 | src += copy; | |
219 | sector += copy >> SECTOR_SHIFT; | |
220 | copy = n - copy; | |
221 | page = brd_lookup_page(brd, sector); | |
222 | BUG_ON(!page); | |
223 | ||
cfd8005c | 224 | dst = kmap_atomic(page); |
9db5579b | 225 | memcpy(dst, src, copy); |
cfd8005c | 226 | kunmap_atomic(dst); |
9db5579b NP |
227 | } |
228 | } | |
229 | ||
230 | /* | |
231 | * Copy n bytes to dst from the brd starting at sector. Does not sleep. | |
232 | */ | |
233 | static void copy_from_brd(void *dst, struct brd_device *brd, | |
234 | sector_t sector, size_t n) | |
235 | { | |
236 | struct page *page; | |
237 | void *src; | |
238 | unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; | |
239 | size_t copy; | |
240 | ||
241 | copy = min_t(size_t, n, PAGE_SIZE - offset); | |
242 | page = brd_lookup_page(brd, sector); | |
243 | if (page) { | |
cfd8005c | 244 | src = kmap_atomic(page); |
9db5579b | 245 | memcpy(dst, src + offset, copy); |
cfd8005c | 246 | kunmap_atomic(src); |
9db5579b NP |
247 | } else |
248 | memset(dst, 0, copy); | |
249 | ||
250 | if (copy < n) { | |
251 | dst += copy; | |
252 | sector += copy >> SECTOR_SHIFT; | |
253 | copy = n - copy; | |
254 | page = brd_lookup_page(brd, sector); | |
255 | if (page) { | |
cfd8005c | 256 | src = kmap_atomic(page); |
9db5579b | 257 | memcpy(dst, src, copy); |
cfd8005c | 258 | kunmap_atomic(src); |
9db5579b NP |
259 | } else |
260 | memset(dst, 0, copy); | |
261 | } | |
262 | } | |
263 | ||
264 | /* | |
265 | * Process a single bvec of a bio. | |
266 | */ | |
267 | static int brd_do_bvec(struct brd_device *brd, struct page *page, | |
c11f0c0b | 268 | unsigned int len, unsigned int off, bool is_write, |
9db5579b NP |
269 | sector_t sector) |
270 | { | |
271 | void *mem; | |
272 | int err = 0; | |
273 | ||
c11f0c0b | 274 | if (is_write) { |
9db5579b NP |
275 | err = copy_to_brd_setup(brd, sector, len); |
276 | if (err) | |
277 | goto out; | |
278 | } | |
279 | ||
cfd8005c | 280 | mem = kmap_atomic(page); |
c11f0c0b | 281 | if (!is_write) { |
9db5579b NP |
282 | copy_from_brd(mem + off, brd, sector, len); |
283 | flush_dcache_page(page); | |
c2572f2b NP |
284 | } else { |
285 | flush_dcache_page(page); | |
9db5579b | 286 | copy_to_brd(brd, mem + off, sector, len); |
c2572f2b | 287 | } |
cfd8005c | 288 | kunmap_atomic(mem); |
9db5579b NP |
289 | |
290 | out: | |
291 | return err; | |
292 | } | |
293 | ||
dece1635 | 294 | static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio) |
9db5579b NP |
295 | { |
296 | struct block_device *bdev = bio->bi_bdev; | |
297 | struct brd_device *brd = bdev->bd_disk->private_data; | |
7988613b | 298 | struct bio_vec bvec; |
9db5579b | 299 | sector_t sector; |
7988613b | 300 | struct bvec_iter iter; |
9db5579b | 301 | |
4f024f37 | 302 | sector = bio->bi_iter.bi_sector; |
f73a1c7d | 303 | if (bio_end_sector(bio) > get_capacity(bdev->bd_disk)) |
4246a0b6 | 304 | goto io_error; |
9db5579b | 305 | |
7988613b KO |
306 | bio_for_each_segment(bvec, bio, iter) { |
307 | unsigned int len = bvec.bv_len; | |
4246a0b6 CH |
308 | int err; |
309 | ||
c11f0c0b JA |
310 | err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, |
311 | op_is_write(bio_op(bio)), sector); | |
9db5579b | 312 | if (err) |
4246a0b6 | 313 | goto io_error; |
9db5579b NP |
314 | sector += len >> SECTOR_SHIFT; |
315 | } | |
316 | ||
4246a0b6 | 317 | bio_endio(bio); |
dece1635 | 318 | return BLK_QC_T_NONE; |
4246a0b6 CH |
319 | io_error: |
320 | bio_io_error(bio); | |
dece1635 | 321 | return BLK_QC_T_NONE; |
9db5579b NP |
322 | } |
323 | ||
a72132c3 | 324 | static int brd_rw_page(struct block_device *bdev, sector_t sector, |
c11f0c0b | 325 | struct page *page, bool is_write) |
a72132c3 MW |
326 | { |
327 | struct brd_device *brd = bdev->bd_disk->private_data; | |
c11f0c0b JA |
328 | int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, is_write, sector); |
329 | page_endio(page, is_write, err); | |
a72132c3 MW |
330 | return err; |
331 | } | |
332 | ||
a7a97fc9 | 333 | #ifdef CONFIG_BLK_DEV_RAM_DAX |
1647b9b9 DW |
334 | static long __brd_direct_access(struct brd_device *brd, pgoff_t pgoff, |
335 | long nr_pages, void **kaddr, pfn_t *pfn) | |
75acb9cd | 336 | { |
75acb9cd NP |
337 | struct page *page; |
338 | ||
339 | if (!brd) | |
340 | return -ENODEV; | |
1647b9b9 | 341 | page = brd_insert_page(brd, PFN_PHYS(pgoff) / 512); |
75acb9cd | 342 | if (!page) |
96f8d8e0 | 343 | return -ENOSPC; |
7a9eb206 | 344 | *kaddr = page_address(page); |
34c0fd54 | 345 | *pfn = page_to_pfn_t(page); |
75acb9cd | 346 | |
1647b9b9 | 347 | return 1; |
75acb9cd | 348 | } |
1647b9b9 | 349 | |
1647b9b9 DW |
350 | static long brd_dax_direct_access(struct dax_device *dax_dev, |
351 | pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn) | |
352 | { | |
353 | struct brd_device *brd = dax_get_private(dax_dev); | |
354 | ||
355 | return __brd_direct_access(brd, pgoff, nr_pages, kaddr, pfn); | |
75acb9cd | 356 | } |
1647b9b9 | 357 | |
5d61e43b DW |
358 | static size_t brd_dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, |
359 | void *addr, size_t bytes, struct iov_iter *i) | |
360 | { | |
361 | return copy_from_iter(addr, bytes, i); | |
362 | } | |
363 | ||
1647b9b9 DW |
364 | static const struct dax_operations brd_dax_ops = { |
365 | .direct_access = brd_dax_direct_access, | |
5d61e43b | 366 | .copy_from_iter = brd_dax_copy_from_iter, |
1647b9b9 | 367 | }; |
75acb9cd NP |
368 | #endif |
369 | ||
83d5cde4 | 370 | static const struct block_device_operations brd_fops = { |
75acb9cd | 371 | .owner = THIS_MODULE, |
a72132c3 | 372 | .rw_page = brd_rw_page, |
9db5579b NP |
373 | }; |
374 | ||
375 | /* | |
376 | * And now the modules code and kernel interface. | |
377 | */ | |
937af5ec | 378 | static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT; |
8892cbaf | 379 | module_param(rd_nr, int, S_IRUGO); |
9db5579b | 380 | MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); |
937af5ec | 381 | |
366f4aea JK |
382 | unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE; |
383 | module_param(rd_size, ulong, S_IRUGO); | |
9db5579b | 384 | MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); |
937af5ec BH |
385 | |
386 | static int max_part = 1; | |
8892cbaf | 387 | module_param(max_part, int, S_IRUGO); |
937af5ec BH |
388 | MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); |
389 | ||
9db5579b NP |
390 | MODULE_LICENSE("GPL"); |
391 | MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR); | |
efedf51c | 392 | MODULE_ALIAS("rd"); |
9db5579b NP |
393 | |
394 | #ifndef MODULE | |
395 | /* Legacy boot options - nonmodular */ | |
396 | static int __init ramdisk_size(char *str) | |
397 | { | |
398 | rd_size = simple_strtol(str, NULL, 0); | |
399 | return 1; | |
400 | } | |
1adbee50 | 401 | __setup("ramdisk_size=", ramdisk_size); |
9db5579b NP |
402 | #endif |
403 | ||
404 | /* | |
405 | * The device scheme is derived from loop.c. Keep them in synch where possible | |
406 | * (should share code eventually). | |
407 | */ | |
408 | static LIST_HEAD(brd_devices); | |
409 | static DEFINE_MUTEX(brd_devices_mutex); | |
410 | ||
411 | static struct brd_device *brd_alloc(int i) | |
412 | { | |
413 | struct brd_device *brd; | |
414 | struct gendisk *disk; | |
415 | ||
416 | brd = kzalloc(sizeof(*brd), GFP_KERNEL); | |
417 | if (!brd) | |
418 | goto out; | |
419 | brd->brd_number = i; | |
420 | spin_lock_init(&brd->brd_lock); | |
421 | INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC); | |
422 | ||
423 | brd->brd_queue = blk_alloc_queue(GFP_KERNEL); | |
424 | if (!brd->brd_queue) | |
425 | goto out_free_dev; | |
c8fa3173 | 426 | |
9db5579b | 427 | blk_queue_make_request(brd->brd_queue, brd_make_request); |
086fa5ff | 428 | blk_queue_max_hw_sectors(brd->brd_queue, 1024); |
9db5579b | 429 | |
c8fa3173 BH |
430 | /* This is so fdisk will align partitions on 4k, because of |
431 | * direct_access API needing 4k alignment, returning a PFN | |
432 | * (This is only a problem on very small devices <= 4M, | |
433 | * otherwise fdisk will align on 1M. Regardless this call | |
434 | * is harmless) | |
435 | */ | |
436 | blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE); | |
937af5ec | 437 | disk = brd->brd_disk = alloc_disk(max_part); |
9db5579b NP |
438 | if (!disk) |
439 | goto out_free_queue; | |
440 | disk->major = RAMDISK_MAJOR; | |
937af5ec | 441 | disk->first_minor = i * max_part; |
9db5579b NP |
442 | disk->fops = &brd_fops; |
443 | disk->private_data = brd; | |
444 | disk->queue = brd->brd_queue; | |
937af5ec | 445 | disk->flags = GENHD_FL_EXT_DEVT; |
9db5579b NP |
446 | sprintf(disk->disk_name, "ram%d", i); |
447 | set_capacity(disk, rd_size * 2); | |
448 | ||
1647b9b9 DW |
449 | #ifdef CONFIG_BLK_DEV_RAM_DAX |
450 | queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue); | |
1ef97fe4 GS |
451 | brd->dax_dev = alloc_dax(brd, disk->disk_name, &brd_dax_ops); |
452 | if (!brd->dax_dev) | |
1647b9b9 DW |
453 | goto out_free_inode; |
454 | #endif | |
455 | ||
456 | ||
9db5579b NP |
457 | return brd; |
458 | ||
1647b9b9 DW |
459 | #ifdef CONFIG_BLK_DEV_RAM_DAX |
460 | out_free_inode: | |
1ef97fe4 GS |
461 | kill_dax(brd->dax_dev); |
462 | put_dax(brd->dax_dev); | |
1647b9b9 | 463 | #endif |
9db5579b NP |
464 | out_free_queue: |
465 | blk_cleanup_queue(brd->brd_queue); | |
466 | out_free_dev: | |
467 | kfree(brd); | |
468 | out: | |
469 | return NULL; | |
470 | } | |
471 | ||
472 | static void brd_free(struct brd_device *brd) | |
473 | { | |
474 | put_disk(brd->brd_disk); | |
475 | blk_cleanup_queue(brd->brd_queue); | |
476 | brd_free_pages(brd); | |
477 | kfree(brd); | |
478 | } | |
479 | ||
937af5ec | 480 | static struct brd_device *brd_init_one(int i, bool *new) |
9db5579b NP |
481 | { |
482 | struct brd_device *brd; | |
483 | ||
937af5ec | 484 | *new = false; |
9db5579b NP |
485 | list_for_each_entry(brd, &brd_devices, brd_list) { |
486 | if (brd->brd_number == i) | |
487 | goto out; | |
488 | } | |
489 | ||
490 | brd = brd_alloc(i); | |
491 | if (brd) { | |
492 | add_disk(brd->brd_disk); | |
493 | list_add_tail(&brd->brd_list, &brd_devices); | |
494 | } | |
937af5ec | 495 | *new = true; |
9db5579b NP |
496 | out: |
497 | return brd; | |
498 | } | |
499 | ||
500 | static void brd_del_one(struct brd_device *brd) | |
501 | { | |
502 | list_del(&brd->brd_list); | |
1647b9b9 DW |
503 | #ifdef CONFIG_BLK_DEV_RAM_DAX |
504 | kill_dax(brd->dax_dev); | |
505 | put_dax(brd->dax_dev); | |
506 | #endif | |
9db5579b NP |
507 | del_gendisk(brd->brd_disk); |
508 | brd_free(brd); | |
509 | } | |
510 | ||
511 | static struct kobject *brd_probe(dev_t dev, int *part, void *data) | |
512 | { | |
513 | struct brd_device *brd; | |
514 | struct kobject *kobj; | |
937af5ec | 515 | bool new; |
9db5579b NP |
516 | |
517 | mutex_lock(&brd_devices_mutex); | |
937af5ec | 518 | brd = brd_init_one(MINOR(dev) / max_part, &new); |
a207f593 | 519 | kobj = brd ? get_disk(brd->brd_disk) : NULL; |
9db5579b NP |
520 | mutex_unlock(&brd_devices_mutex); |
521 | ||
937af5ec BH |
522 | if (new) |
523 | *part = 0; | |
524 | ||
9db5579b NP |
525 | return kobj; |
526 | } | |
527 | ||
528 | static int __init brd_init(void) | |
529 | { | |
9db5579b | 530 | struct brd_device *brd, *next; |
937af5ec | 531 | int i; |
9db5579b NP |
532 | |
533 | /* | |
534 | * brd module now has a feature to instantiate underlying device | |
535 | * structure on-demand, provided that there is an access dev node. | |
9db5579b | 536 | * |
937af5ec BH |
537 | * (1) if rd_nr is specified, create that many upfront. else |
538 | * it defaults to CONFIG_BLK_DEV_RAM_COUNT | |
539 | * (2) User can further extend brd devices by create dev node themselves | |
540 | * and have kernel automatically instantiate actual device | |
541 | * on-demand. Example: | |
542 | * mknod /path/devnod_name b 1 X # 1 is the rd major | |
543 | * fdisk -l /path/devnod_name | |
544 | * If (X / max_part) was not already created it will be created | |
545 | * dynamically. | |
9db5579b | 546 | */ |
d7853d1f | 547 | |
9db5579b NP |
548 | if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) |
549 | return -EIO; | |
550 | ||
937af5ec BH |
551 | if (unlikely(!max_part)) |
552 | max_part = 1; | |
553 | ||
554 | for (i = 0; i < rd_nr; i++) { | |
9db5579b NP |
555 | brd = brd_alloc(i); |
556 | if (!brd) | |
557 | goto out_free; | |
558 | list_add_tail(&brd->brd_list, &brd_devices); | |
559 | } | |
560 | ||
561 | /* point of no return */ | |
562 | ||
563 | list_for_each_entry(brd, &brd_devices, brd_list) | |
564 | add_disk(brd->brd_disk); | |
565 | ||
937af5ec | 566 | blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS, |
9db5579b NP |
567 | THIS_MODULE, brd_probe, NULL, NULL); |
568 | ||
937af5ec | 569 | pr_info("brd: module loaded\n"); |
9db5579b NP |
570 | return 0; |
571 | ||
572 | out_free: | |
573 | list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { | |
574 | list_del(&brd->brd_list); | |
575 | brd_free(brd); | |
576 | } | |
c82f2966 | 577 | unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
9db5579b | 578 | |
937af5ec | 579 | pr_info("brd: module NOT loaded !!!\n"); |
9db5579b NP |
580 | return -ENOMEM; |
581 | } | |
582 | ||
583 | static void __exit brd_exit(void) | |
584 | { | |
9db5579b NP |
585 | struct brd_device *brd, *next; |
586 | ||
9db5579b NP |
587 | list_for_each_entry_safe(brd, next, &brd_devices, brd_list) |
588 | brd_del_one(brd); | |
589 | ||
937af5ec | 590 | blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS); |
9db5579b | 591 | unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
937af5ec BH |
592 | |
593 | pr_info("brd: module unloaded\n"); | |
9db5579b NP |
594 | } |
595 | ||
596 | module_init(brd_init); | |
597 | module_exit(brd_exit); | |
598 |