2 * Ram backed block device driver.
4 * Copyright (C) 2007 Nick Piggin
5 * Copyright (C) 2007 Novell Inc.
7 * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
8 * of their respective owners.
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>
18 #include <linux/gfp.h>
19 #include <linux/radix-tree.h>
20 #include <linux/buffer_head.h> /* invalidate_bh_lrus() */
22 #include <asm/uaccess.h>
24 #define SECTOR_SHIFT 9
25 #define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
26 #define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
29 * Each block ramdisk device has a radix_tree brd_pages of pages that stores
30 * the pages containing the block device's contents. A brd page's ->index is
31 * its offset in PAGE_SIZE units. This is similar to, but in no way connected
32 * with, the kernel's pagecache or buffer cache (which sit above our block
40 unsigned brd_blocksize
;
42 struct request_queue
*brd_queue
;
43 struct gendisk
*brd_disk
;
44 struct list_head brd_list
;
47 * Backing store of pages and lock to protect it. This is the contents
48 * of the block device.
51 struct radix_tree_root brd_pages
;
55 * Look up and return a brd's page for a given sector.
57 static struct page
*brd_lookup_page(struct brd_device
*brd
, sector_t sector
)
63 * The page lifetime is protected by the fact that we have opened the
64 * device node -- brd pages will never be deleted under us, so we
65 * don't need any further locking or refcounting.
67 * This is strictly true for the radix-tree nodes as well (ie. we
68 * don't actually need the rcu_read_lock()), however that is not a
69 * documented feature of the radix-tree API so it is better to be
70 * safe here (we don't have total exclusion from radix tree updates
71 * here, only deletes).
74 idx
= sector
>> PAGE_SECTORS_SHIFT
; /* sector to page index */
75 page
= radix_tree_lookup(&brd
->brd_pages
, idx
);
78 BUG_ON(page
&& page
->index
!= idx
);
84 * Look up and return a brd's page for a given sector.
85 * If one does not exist, allocate an empty page, and insert that. Then
88 static struct page
*brd_insert_page(struct brd_device
*brd
, sector_t sector
)
93 page
= brd_lookup_page(brd
, sector
);
98 * Must use NOIO because we don't want to recurse back into the
99 * block or filesystem layers from page reclaim.
101 page
= alloc_page(GFP_NOIO
| __GFP_HIGHMEM
| __GFP_ZERO
);
105 if (radix_tree_preload(GFP_NOIO
)) {
110 spin_lock(&brd
->brd_lock
);
111 idx
= sector
>> PAGE_SECTORS_SHIFT
;
112 if (radix_tree_insert(&brd
->brd_pages
, idx
, page
)) {
114 page
= radix_tree_lookup(&brd
->brd_pages
, idx
);
116 BUG_ON(page
->index
!= idx
);
119 spin_unlock(&brd
->brd_lock
);
121 radix_tree_preload_end();
127 * Free all backing store pages and radix tree. This must only be called when
128 * there are no other users of the device.
130 #define FREE_BATCH 16
131 static void brd_free_pages(struct brd_device
*brd
)
133 unsigned long pos
= 0;
134 struct page
*pages
[FREE_BATCH
];
140 nr_pages
= radix_tree_gang_lookup(&brd
->brd_pages
,
141 (void **)pages
, pos
, FREE_BATCH
);
143 for (i
= 0; i
< nr_pages
; i
++) {
146 BUG_ON(pages
[i
]->index
< pos
);
147 pos
= pages
[i
]->index
;
148 ret
= radix_tree_delete(&brd
->brd_pages
, pos
);
149 BUG_ON(!ret
|| ret
!= pages
[i
]);
150 __free_page(pages
[i
]);
156 * This assumes radix_tree_gang_lookup always returns as
157 * many pages as possible. If the radix-tree code changes,
158 * so will this have to.
160 } while (nr_pages
== FREE_BATCH
);
164 * copy_to_brd_setup must be called before copy_to_brd. It may sleep.
166 static int copy_to_brd_setup(struct brd_device
*brd
, sector_t sector
, size_t n
)
168 unsigned int offset
= (sector
& (PAGE_SECTORS
-1)) << SECTOR_SHIFT
;
171 copy
= min_t(size_t, n
, PAGE_SIZE
- offset
);
172 if (!brd_insert_page(brd
, sector
))
175 sector
+= copy
>> SECTOR_SHIFT
;
176 if (!brd_insert_page(brd
, sector
))
183 * Copy n bytes from src to the brd starting at sector. Does not sleep.
185 static void copy_to_brd(struct brd_device
*brd
, const void *src
,
186 sector_t sector
, size_t n
)
190 unsigned int offset
= (sector
& (PAGE_SECTORS
-1)) << SECTOR_SHIFT
;
193 copy
= min_t(size_t, n
, PAGE_SIZE
- offset
);
194 page
= brd_lookup_page(brd
, sector
);
197 dst
= kmap_atomic(page
, KM_USER1
);
198 memcpy(dst
+ offset
, src
, copy
);
199 kunmap_atomic(dst
, KM_USER1
);
203 sector
+= copy
>> SECTOR_SHIFT
;
205 page
= brd_lookup_page(brd
, sector
);
208 dst
= kmap_atomic(page
, KM_USER1
);
209 memcpy(dst
, src
, copy
);
210 kunmap_atomic(dst
, KM_USER1
);
215 * Copy n bytes to dst from the brd starting at sector. Does not sleep.
217 static void copy_from_brd(void *dst
, struct brd_device
*brd
,
218 sector_t sector
, size_t n
)
222 unsigned int offset
= (sector
& (PAGE_SECTORS
-1)) << SECTOR_SHIFT
;
225 copy
= min_t(size_t, n
, PAGE_SIZE
- offset
);
226 page
= brd_lookup_page(brd
, sector
);
228 src
= kmap_atomic(page
, KM_USER1
);
229 memcpy(dst
, src
+ offset
, copy
);
230 kunmap_atomic(src
, KM_USER1
);
232 memset(dst
, 0, copy
);
236 sector
+= copy
>> SECTOR_SHIFT
;
238 page
= brd_lookup_page(brd
, sector
);
240 src
= kmap_atomic(page
, KM_USER1
);
241 memcpy(dst
, src
, copy
);
242 kunmap_atomic(src
, KM_USER1
);
244 memset(dst
, 0, copy
);
249 * Process a single bvec of a bio.
251 static int brd_do_bvec(struct brd_device
*brd
, struct page
*page
,
252 unsigned int len
, unsigned int off
, int rw
,
259 err
= copy_to_brd_setup(brd
, sector
, len
);
264 mem
= kmap_atomic(page
, KM_USER0
);
266 copy_from_brd(mem
+ off
, brd
, sector
, len
);
267 flush_dcache_page(page
);
269 copy_to_brd(brd
, mem
+ off
, sector
, len
);
270 kunmap_atomic(mem
, KM_USER0
);
276 static int brd_make_request(struct request_queue
*q
, struct bio
*bio
)
278 struct block_device
*bdev
= bio
->bi_bdev
;
279 struct brd_device
*brd
= bdev
->bd_disk
->private_data
;
281 struct bio_vec
*bvec
;
286 sector
= bio
->bi_sector
;
287 if (sector
+ (bio
->bi_size
>> SECTOR_SHIFT
) >
288 get_capacity(bdev
->bd_disk
))
295 bio_for_each_segment(bvec
, bio
, i
) {
296 unsigned int len
= bvec
->bv_len
;
297 err
= brd_do_bvec(brd
, bvec
->bv_page
, len
,
298 bvec
->bv_offset
, rw
, sector
);
301 sector
+= len
>> SECTOR_SHIFT
;
310 static int brd_ioctl(struct inode
*inode
, struct file
*file
,
311 unsigned int cmd
, unsigned long arg
)
314 struct block_device
*bdev
= inode
->i_bdev
;
315 struct brd_device
*brd
= bdev
->bd_disk
->private_data
;
317 if (cmd
!= BLKFLSBUF
)
321 * ram device BLKFLSBUF has special semantics, we want to actually
322 * release and destroy the ramdisk data.
324 mutex_lock(&bdev
->bd_mutex
);
326 if (bdev
->bd_openers
<= 1) {
328 * Invalidate the cache first, so it isn't written
329 * back to the device.
331 * Another thread might instantiate more buffercache here,
332 * but there is not much we can do to close that race.
334 invalidate_bh_lrus();
335 truncate_inode_pages(bdev
->bd_inode
->i_mapping
, 0);
339 mutex_unlock(&bdev
->bd_mutex
);
344 static struct block_device_operations brd_fops
= {
345 .owner
= THIS_MODULE
,
350 * And now the modules code and kernel interface.
353 int rd_size
= CONFIG_BLK_DEV_RAM_SIZE
;
354 module_param(rd_nr
, int, 0);
355 MODULE_PARM_DESC(rd_nr
, "Maximum number of brd devices");
356 module_param(rd_size
, int, 0);
357 MODULE_PARM_DESC(rd_size
, "Size of each RAM disk in kbytes.");
358 MODULE_LICENSE("GPL");
359 MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR
);
362 /* Legacy boot options - nonmodular */
363 static int __init
ramdisk_size(char *str
)
365 rd_size
= simple_strtol(str
, NULL
, 0);
368 static int __init
ramdisk_size2(char *str
)
370 return ramdisk_size(str
);
372 __setup("ramdisk=", ramdisk_size
);
373 __setup("ramdisk_size=", ramdisk_size2
);
377 * The device scheme is derived from loop.c. Keep them in synch where possible
378 * (should share code eventually).
380 static LIST_HEAD(brd_devices
);
381 static DEFINE_MUTEX(brd_devices_mutex
);
383 static struct brd_device
*brd_alloc(int i
)
385 struct brd_device
*brd
;
386 struct gendisk
*disk
;
388 brd
= kzalloc(sizeof(*brd
), GFP_KERNEL
);
392 spin_lock_init(&brd
->brd_lock
);
393 INIT_RADIX_TREE(&brd
->brd_pages
, GFP_ATOMIC
);
395 brd
->brd_queue
= blk_alloc_queue(GFP_KERNEL
);
398 blk_queue_make_request(brd
->brd_queue
, brd_make_request
);
399 blk_queue_max_sectors(brd
->brd_queue
, 1024);
400 blk_queue_bounce_limit(brd
->brd_queue
, BLK_BOUNCE_ANY
);
402 disk
= brd
->brd_disk
= alloc_disk(1);
405 disk
->major
= RAMDISK_MAJOR
;
406 disk
->first_minor
= i
;
407 disk
->fops
= &brd_fops
;
408 disk
->private_data
= brd
;
409 disk
->queue
= brd
->brd_queue
;
410 sprintf(disk
->disk_name
, "ram%d", i
);
411 set_capacity(disk
, rd_size
* 2);
416 blk_cleanup_queue(brd
->brd_queue
);
423 static void brd_free(struct brd_device
*brd
)
425 put_disk(brd
->brd_disk
);
426 blk_cleanup_queue(brd
->brd_queue
);
431 static struct brd_device
*brd_init_one(int i
)
433 struct brd_device
*brd
;
435 list_for_each_entry(brd
, &brd_devices
, brd_list
) {
436 if (brd
->brd_number
== i
)
442 add_disk(brd
->brd_disk
);
443 list_add_tail(&brd
->brd_list
, &brd_devices
);
449 static void brd_del_one(struct brd_device
*brd
)
451 list_del(&brd
->brd_list
);
452 del_gendisk(brd
->brd_disk
);
456 static struct kobject
*brd_probe(dev_t dev
, int *part
, void *data
)
458 struct brd_device
*brd
;
459 struct kobject
*kobj
;
461 mutex_lock(&brd_devices_mutex
);
462 brd
= brd_init_one(dev
& MINORMASK
);
463 kobj
= brd
? get_disk(brd
->brd_disk
) : ERR_PTR(-ENOMEM
);
464 mutex_unlock(&brd_devices_mutex
);
470 static int __init
brd_init(void)
474 struct brd_device
*brd
, *next
;
477 * brd module now has a feature to instantiate underlying device
478 * structure on-demand, provided that there is an access dev node.
479 * However, this will not work well with user space tool that doesn't
480 * know about such "feature". In order to not break any existing
481 * tool, we do the following:
483 * (1) if rd_nr is specified, create that many upfront, and this
484 * also becomes a hard limit.
485 * (2) if rd_nr is not specified, create 1 rd device on module
486 * load, user can further extend brd device by create dev node
487 * themselves and have kernel automatically instantiate actual
490 if (rd_nr
> 1UL << MINORBITS
)
497 nr
= CONFIG_BLK_DEV_RAM_COUNT
;
498 range
= 1UL << MINORBITS
;
501 if (register_blkdev(RAMDISK_MAJOR
, "ramdisk"))
504 for (i
= 0; i
< nr
; i
++) {
508 list_add_tail(&brd
->brd_list
, &brd_devices
);
511 /* point of no return */
513 list_for_each_entry(brd
, &brd_devices
, brd_list
)
514 add_disk(brd
->brd_disk
);
516 blk_register_region(MKDEV(RAMDISK_MAJOR
, 0), range
,
517 THIS_MODULE
, brd_probe
, NULL
, NULL
);
519 printk(KERN_INFO
"brd: module loaded\n");
523 list_for_each_entry_safe(brd
, next
, &brd_devices
, brd_list
) {
524 list_del(&brd
->brd_list
);
528 unregister_blkdev(RAMDISK_MAJOR
, "brd");
532 static void __exit
brd_exit(void)
535 struct brd_device
*brd
, *next
;
537 range
= rd_nr
? rd_nr
: 1UL << MINORBITS
;
539 list_for_each_entry_safe(brd
, next
, &brd_devices
, brd_list
)
542 blk_unregister_region(MKDEV(RAMDISK_MAJOR
, 0), range
);
543 unregister_blkdev(RAMDISK_MAJOR
, "ramdisk");
546 module_init(brd_init
);
547 module_exit(brd_exit
);