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