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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * ramdisk.c - Multiple RAM disk driver - gzip-loading version - v. 0.8 beta.
3 *
4 * (C) Chad Page, Theodore Ts'o, et. al, 1995.
5 *
6 * This RAM disk is designed to have filesystems created on it and mounted
7 * just like a regular floppy disk.
8 *
9 * It also does something suggested by Linus: use the buffer cache as the
10 * RAM disk data. This makes it possible to dynamically allocate the RAM disk
11 * buffer - with some consequences I have to deal with as I write this.
12 *
13 * This code is based on the original ramdisk.c, written mostly by
14 * Theodore Ts'o (TYT) in 1991. The code was largely rewritten by
15 * Chad Page to use the buffer cache to store the RAM disk data in
16 * 1995; Theodore then took over the driver again, and cleaned it up
17 * for inclusion in the mainline kernel.
18 *
19 * The original CRAMDISK code was written by Richard Lyons, and
20 * adapted by Chad Page to use the new RAM disk interface. Theodore
21 * Ts'o rewrote it so that both the compressed RAM disk loader and the
22 * kernel decompressor uses the same inflate.c codebase. The RAM disk
23 * loader now also loads into a dynamic (buffer cache based) RAM disk,
24 * not the old static RAM disk. Support for the old static RAM disk has
25 * been completely removed.
26 *
27 * Loadable module support added by Tom Dyas.
28 *
29 * Further cleanups by Chad Page (page0588@sundance.sjsu.edu):
30 * Cosmetic changes in #ifdef MODULE, code movement, etc.
31 * When the RAM disk module is removed, free the protected buffers
32 * Default RAM disk size changed to 2.88 MB
33 *
34 * Added initrd: Werner Almesberger & Hans Lermen, Feb '96
35 *
36 * 4/25/96 : Made RAM disk size a parameter (default is now 4 MB)
37 * - Chad Page
38 *
39 * Add support for fs images split across >1 disk, Paul Gortmaker, Mar '98
40 *
41 * Make block size and block size shift for RAM disks a global macro
42 * and set blk_size for -ENOSPC, Werner Fink <werner@suse.de>, Apr '99
43 */
44
Linus Torvalds1da177e2005-04-16 15:20:36 -070045#include <linux/string.h>
46#include <linux/slab.h>
47#include <asm/atomic.h>
48#include <linux/bio.h>
49#include <linux/module.h>
50#include <linux/moduleparam.h>
51#include <linux/init.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070052#include <linux/pagemap.h>
53#include <linux/blkdev.h>
54#include <linux/genhd.h>
55#include <linux/buffer_head.h> /* for invalidate_bdev() */
56#include <linux/backing-dev.h>
57#include <linux/blkpg.h>
58#include <linux/writeback.h>
59
60#include <asm/uaccess.h>
61
62/* Various static variables go here. Most are used only in the RAM disk code.
63 */
64
65static struct gendisk *rd_disks[CONFIG_BLK_DEV_RAM_COUNT];
66static struct block_device *rd_bdev[CONFIG_BLK_DEV_RAM_COUNT];/* Protected device data */
67static struct request_queue *rd_queue[CONFIG_BLK_DEV_RAM_COUNT];
68
69/*
70 * Parameters for the boot-loading of the RAM disk. These are set by
71 * init/main.c (from arguments to the kernel command line) or from the
72 * architecture-specific setup routine (from the stored boot sector
73 * information).
74 */
Adrian Bunkcccf2502005-05-07 01:28:45 +020075int rd_size = CONFIG_BLK_DEV_RAM_SIZE; /* Size of the RAM disks */
Linus Torvalds1da177e2005-04-16 15:20:36 -070076/*
77 * It would be very desirable to have a soft-blocksize (that in the case
78 * of the ramdisk driver is also the hardblocksize ;) of PAGE_SIZE because
79 * doing that we'll achieve a far better MM footprint. Using a rd_blocksize of
80 * BLOCK_SIZE in the worst case we'll make PAGE_SIZE/BLOCK_SIZE buffer-pages
81 * unfreeable. With a rd_blocksize of PAGE_SIZE instead we are sure that only
82 * 1 page will be protected. Depending on the size of the ramdisk you
83 * may want to change the ramdisk blocksize to achieve a better or worse MM
84 * behaviour. The default is still BLOCK_SIZE (needed by rd_load_image that
85 * supposes the filesystem in the image uses a BLOCK_SIZE blocksize).
86 */
87static int rd_blocksize = BLOCK_SIZE; /* blocksize of the RAM disks */
88
89/*
90 * Copyright (C) 2000 Linus Torvalds.
91 * 2000 Transmeta Corp.
92 * aops copied from ramfs.
93 */
94
95/*
96 * If a ramdisk page has buffers, some may be uptodate and some may be not.
97 * To bring the page uptodate we zero out the non-uptodate buffers. The
98 * page must be locked.
99 */
100static void make_page_uptodate(struct page *page)
101{
102 if (page_has_buffers(page)) {
103 struct buffer_head *bh = page_buffers(page);
104 struct buffer_head *head = bh;
105
106 do {
107 if (!buffer_uptodate(bh)) {
108 memset(bh->b_data, 0, bh->b_size);
109 /*
110 * akpm: I'm totally undecided about this. The
111 * buffer has just been magically brought "up to
112 * date", but nobody should want to be reading
113 * it anyway, because it hasn't been used for
114 * anything yet. It is still in a "not read
115 * from disk yet" state.
116 *
117 * But non-uptodate buffers against an uptodate
118 * page are against the rules. So do it anyway.
119 */
120 set_buffer_uptodate(bh);
121 }
122 } while ((bh = bh->b_this_page) != head);
123 } else {
124 memset(page_address(page), 0, PAGE_CACHE_SIZE);
125 }
126 flush_dcache_page(page);
127 SetPageUptodate(page);
128}
129
130static int ramdisk_readpage(struct file *file, struct page *page)
131{
132 if (!PageUptodate(page))
133 make_page_uptodate(page);
134 unlock_page(page);
135 return 0;
136}
137
138static int ramdisk_prepare_write(struct file *file, struct page *page,
139 unsigned offset, unsigned to)
140{
141 if (!PageUptodate(page))
142 make_page_uptodate(page);
143 return 0;
144}
145
146static int ramdisk_commit_write(struct file *file, struct page *page,
147 unsigned offset, unsigned to)
148{
149 set_page_dirty(page);
150 return 0;
151}
152
153/*
154 * ->writepage to the the blockdev's mapping has to redirty the page so that the
Zach Brown994fc28c2005-12-15 14:28:17 -0800155 * VM doesn't go and steal it. We return AOP_WRITEPAGE_ACTIVATE so that the VM
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 * won't try to (pointlessly) write the page again for a while.
157 *
158 * Really, these pages should not be on the LRU at all.
159 */
160static int ramdisk_writepage(struct page *page, struct writeback_control *wbc)
161{
162 if (!PageUptodate(page))
163 make_page_uptodate(page);
164 SetPageDirty(page);
165 if (wbc->for_reclaim)
Zach Brown994fc28c2005-12-15 14:28:17 -0800166 return AOP_WRITEPAGE_ACTIVATE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167 unlock_page(page);
168 return 0;
169}
170
171/*
172 * This is a little speedup thing: short-circuit attempts to write back the
173 * ramdisk blockdev inode to its non-existent backing store.
174 */
175static int ramdisk_writepages(struct address_space *mapping,
176 struct writeback_control *wbc)
177{
178 return 0;
179}
180
181/*
182 * ramdisk blockdev pages have their own ->set_page_dirty() because we don't
183 * want them to contribute to dirty memory accounting.
184 */
185static int ramdisk_set_page_dirty(struct page *page)
186{
Andrew Morton4741c9f2006-03-24 03:18:11 -0800187 if (!TestSetPageDirty(page))
188 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 return 0;
190}
191
Christoph Hellwigf5e54d62006-06-28 04:26:44 -0700192static const struct address_space_operations ramdisk_aops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 .readpage = ramdisk_readpage,
194 .prepare_write = ramdisk_prepare_write,
195 .commit_write = ramdisk_commit_write,
196 .writepage = ramdisk_writepage,
197 .set_page_dirty = ramdisk_set_page_dirty,
198 .writepages = ramdisk_writepages,
199};
200
201static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
202 struct address_space *mapping)
203{
204 pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9);
205 unsigned int vec_offset = vec->bv_offset;
206 int offset = (sector << 9) & ~PAGE_CACHE_MASK;
207 int size = vec->bv_len;
208 int err = 0;
209
210 do {
211 int count;
212 struct page *page;
213 char *src;
214 char *dst;
215
216 count = PAGE_CACHE_SIZE - offset;
217 if (count > size)
218 count = size;
219 size -= count;
220
221 page = grab_cache_page(mapping, index);
222 if (!page) {
223 err = -ENOMEM;
224 goto out;
225 }
226
227 if (!PageUptodate(page))
228 make_page_uptodate(page);
229
230 index++;
231
232 if (rw == READ) {
233 src = kmap_atomic(page, KM_USER0) + offset;
234 dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset;
235 } else {
236 src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset;
237 dst = kmap_atomic(page, KM_USER1) + offset;
238 }
239 offset = 0;
240 vec_offset += count;
241
242 memcpy(dst, src, count);
243
244 kunmap_atomic(src, KM_USER0);
245 kunmap_atomic(dst, KM_USER1);
246
247 if (rw == READ)
248 flush_dcache_page(vec->bv_page);
249 else
250 set_page_dirty(page);
251 unlock_page(page);
252 put_page(page);
253 } while (size);
254
255 out:
256 return err;
257}
258
259/*
260 * Basically, my strategy here is to set up a buffer-head which can't be
261 * deleted, and make that my Ramdisk. If the request is outside of the
262 * allocated size, we must get rid of it...
263 *
264 * 19-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Added devfs support
265 *
266 */
267static int rd_make_request(request_queue_t *q, struct bio *bio)
268{
269 struct block_device *bdev = bio->bi_bdev;
270 struct address_space * mapping = bdev->bd_inode->i_mapping;
271 sector_t sector = bio->bi_sector;
272 unsigned long len = bio->bi_size >> 9;
273 int rw = bio_data_dir(bio);
274 struct bio_vec *bvec;
275 int ret = 0, i;
276
277 if (sector + len > get_capacity(bdev->bd_disk))
278 goto fail;
279
280 if (rw==READA)
281 rw=READ;
282
283 bio_for_each_segment(bvec, bio, i) {
284 ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping);
285 sector += bvec->bv_len >> 9;
286 }
287 if (ret)
288 goto fail;
289
290 bio_endio(bio, bio->bi_size, 0);
291 return 0;
292fail:
293 bio_io_error(bio, bio->bi_size);
294 return 0;
295}
296
297static int rd_ioctl(struct inode *inode, struct file *file,
298 unsigned int cmd, unsigned long arg)
299{
300 int error;
301 struct block_device *bdev = inode->i_bdev;
302
303 if (cmd != BLKFLSBUF)
304 return -ENOTTY;
305
306 /*
307 * special: we want to release the ramdisk memory, it's not like with
308 * the other blockdevices where this ioctl only flushes away the buffer
309 * cache
310 */
311 error = -EBUSY;
Arjan van de Venc039e312006-03-23 03:00:28 -0800312 mutex_lock(&bdev->bd_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 if (bdev->bd_openers <= 2) {
314 truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
315 error = 0;
316 }
Arjan van de Venc039e312006-03-23 03:00:28 -0800317 mutex_unlock(&bdev->bd_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318 return error;
319}
320
321/*
322 * This is the backing_dev_info for the blockdev inode itself. It doesn't need
323 * writeback and it does not contribute to dirty memory accounting.
324 */
325static struct backing_dev_info rd_backing_dev_info = {
326 .ra_pages = 0, /* No readahead */
327 .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_COPY,
328 .unplug_io_fn = default_unplug_io_fn,
329};
330
331/*
332 * This is the backing_dev_info for the files which live atop the ramdisk
333 * "device". These files do need writeback and they do contribute to dirty
334 * memory accounting.
335 */
336static struct backing_dev_info rd_file_backing_dev_info = {
337 .ra_pages = 0, /* No readahead */
338 .capabilities = BDI_CAP_MAP_COPY, /* Does contribute to dirty memory */
339 .unplug_io_fn = default_unplug_io_fn,
340};
341
342static int rd_open(struct inode *inode, struct file *filp)
343{
344 unsigned unit = iminor(inode);
345
346 if (rd_bdev[unit] == NULL) {
347 struct block_device *bdev = inode->i_bdev;
348 struct address_space *mapping;
349 unsigned bsize;
Al Virob4e3ca12005-10-21 03:22:34 -0400350 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351
352 inode = igrab(bdev->bd_inode);
353 rd_bdev[unit] = bdev;
354 bdev->bd_openers++;
355 bsize = bdev_hardsect_size(bdev);
356 bdev->bd_block_size = bsize;
357 inode->i_blkbits = blksize_bits(bsize);
358 inode->i_size = get_capacity(bdev->bd_disk)<<9;
359
360 mapping = inode->i_mapping;
361 mapping->a_ops = &ramdisk_aops;
362 mapping->backing_dev_info = &rd_backing_dev_info;
363 bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info;
364
365 /*
366 * Deep badness. rd_blkdev_pagecache_IO() needs to allocate
367 * pagecache pages within a request_fn. We cannot recur back
368 * into the filesytem which is mounted atop the ramdisk, because
369 * that would deadlock on fs locks. And we really don't want
370 * to reenter rd_blkdev_pagecache_IO when we're already within
371 * that function.
372 *
373 * So we turn off __GFP_FS and __GFP_IO.
374 *
375 * And to give this thing a hope of working, turn on __GFP_HIGH.
376 * Hopefully, there's enough regular memory allocation going on
377 * for the page allocator emergency pools to keep the ramdisk
378 * driver happy.
379 */
380 gfp_mask = mapping_gfp_mask(mapping);
381 gfp_mask &= ~(__GFP_FS|__GFP_IO);
382 gfp_mask |= __GFP_HIGH;
383 mapping_set_gfp_mask(mapping, gfp_mask);
384 }
385
386 return 0;
387}
388
389static struct block_device_operations rd_bd_op = {
390 .owner = THIS_MODULE,
391 .open = rd_open,
392 .ioctl = rd_ioctl,
393};
394
395/*
396 * Before freeing the module, invalidate all of the protected buffers!
397 */
398static void __exit rd_cleanup(void)
399{
400 int i;
401
402 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
403 struct block_device *bdev = rd_bdev[i];
404 rd_bdev[i] = NULL;
405 if (bdev) {
406 invalidate_bdev(bdev, 1);
407 blkdev_put(bdev);
408 }
409 del_gendisk(rd_disks[i]);
410 put_disk(rd_disks[i]);
411 blk_cleanup_queue(rd_queue[i]);
412 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
414}
415
416/*
417 * This is the registration and initialization section of the RAM disk driver
418 */
419static int __init rd_init(void)
420{
421 int i;
422 int err = -ENOMEM;
423
424 if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 ||
425 (rd_blocksize & (rd_blocksize-1))) {
426 printk("RAMDISK: wrong blocksize %d, reverting to defaults\n",
427 rd_blocksize);
428 rd_blocksize = BLOCK_SIZE;
429 }
430
431 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
432 rd_disks[i] = alloc_disk(1);
433 if (!rd_disks[i])
434 goto out;
435 }
436
437 if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) {
438 err = -EIO;
439 goto out;
440 }
441
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
443 struct gendisk *disk = rd_disks[i];
444
445 rd_queue[i] = blk_alloc_queue(GFP_KERNEL);
446 if (!rd_queue[i])
447 goto out_queue;
448
449 blk_queue_make_request(rd_queue[i], &rd_make_request);
450 blk_queue_hardsect_size(rd_queue[i], rd_blocksize);
451
452 /* rd_size is given in kB */
453 disk->major = RAMDISK_MAJOR;
454 disk->first_minor = i;
455 disk->fops = &rd_bd_op;
456 disk->queue = rd_queue[i];
457 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
458 sprintf(disk->disk_name, "ram%d", i);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459 set_capacity(disk, rd_size * 2);
460 add_disk(rd_disks[i]);
461 }
462
463 /* rd_size is given in kB */
464 printk("RAMDISK driver initialized: "
465 "%d RAM disks of %dK size %d blocksize\n",
466 CONFIG_BLK_DEV_RAM_COUNT, rd_size, rd_blocksize);
467
468 return 0;
469out_queue:
470 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
471out:
472 while (i--) {
473 put_disk(rd_disks[i]);
474 blk_cleanup_queue(rd_queue[i]);
475 }
476 return err;
477}
478
479module_init(rd_init);
480module_exit(rd_cleanup);
481
482/* options - nonmodular */
483#ifndef MODULE
484static int __init ramdisk_size(char *str)
485{
486 rd_size = simple_strtol(str,NULL,0);
487 return 1;
488}
489static int __init ramdisk_size2(char *str) /* kludge */
490{
491 return ramdisk_size(str);
492}
493static int __init ramdisk_blocksize(char *str)
494{
495 rd_blocksize = simple_strtol(str,NULL,0);
496 return 1;
497}
498__setup("ramdisk=", ramdisk_size);
499__setup("ramdisk_size=", ramdisk_size2);
500__setup("ramdisk_blocksize=", ramdisk_blocksize);
501#endif
502
503/* options - modular */
504module_param(rd_size, int, 0);
505MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
506module_param(rd_blocksize, int, 0);
507MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes.");
508MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
509
510MODULE_LICENSE("GPL");