blob: 68c60a5bcdabaf4f172854bbd1df959ecbe80689 [file] [log] [blame]
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
45#include <linux/config.h>
46#include <linux/string.h>
47#include <linux/slab.h>
48#include <asm/atomic.h>
49#include <linux/bio.h>
50#include <linux/module.h>
51#include <linux/moduleparam.h>
52#include <linux/init.h>
53#include <linux/devfs_fs_kernel.h>
54#include <linux/pagemap.h>
55#include <linux/blkdev.h>
56#include <linux/genhd.h>
57#include <linux/buffer_head.h> /* for invalidate_bdev() */
58#include <linux/backing-dev.h>
59#include <linux/blkpg.h>
60#include <linux/writeback.h>
61
62#include <asm/uaccess.h>
63
64/* Various static variables go here. Most are used only in the RAM disk code.
65 */
66
67static struct gendisk *rd_disks[CONFIG_BLK_DEV_RAM_COUNT];
68static struct block_device *rd_bdev[CONFIG_BLK_DEV_RAM_COUNT];/* Protected device data */
69static struct request_queue *rd_queue[CONFIG_BLK_DEV_RAM_COUNT];
70
71/*
72 * Parameters for the boot-loading of the RAM disk. These are set by
73 * init/main.c (from arguments to the kernel command line) or from the
74 * architecture-specific setup routine (from the stored boot sector
75 * information).
76 */
Adrian Bunkcccf2502005-05-07 01:28:45 +020077int rd_size = CONFIG_BLK_DEV_RAM_SIZE; /* Size of the RAM disks */
Linus Torvalds1da177e2005-04-16 15:20:36 -070078/*
79 * It would be very desirable to have a soft-blocksize (that in the case
80 * of the ramdisk driver is also the hardblocksize ;) of PAGE_SIZE because
81 * doing that we'll achieve a far better MM footprint. Using a rd_blocksize of
82 * BLOCK_SIZE in the worst case we'll make PAGE_SIZE/BLOCK_SIZE buffer-pages
83 * unfreeable. With a rd_blocksize of PAGE_SIZE instead we are sure that only
84 * 1 page will be protected. Depending on the size of the ramdisk you
85 * may want to change the ramdisk blocksize to achieve a better or worse MM
86 * behaviour. The default is still BLOCK_SIZE (needed by rd_load_image that
87 * supposes the filesystem in the image uses a BLOCK_SIZE blocksize).
88 */
89static int rd_blocksize = BLOCK_SIZE; /* blocksize of the RAM disks */
90
91/*
92 * Copyright (C) 2000 Linus Torvalds.
93 * 2000 Transmeta Corp.
94 * aops copied from ramfs.
95 */
96
97/*
98 * If a ramdisk page has buffers, some may be uptodate and some may be not.
99 * To bring the page uptodate we zero out the non-uptodate buffers. The
100 * page must be locked.
101 */
102static void make_page_uptodate(struct page *page)
103{
104 if (page_has_buffers(page)) {
105 struct buffer_head *bh = page_buffers(page);
106 struct buffer_head *head = bh;
107
108 do {
109 if (!buffer_uptodate(bh)) {
110 memset(bh->b_data, 0, bh->b_size);
111 /*
112 * akpm: I'm totally undecided about this. The
113 * buffer has just been magically brought "up to
114 * date", but nobody should want to be reading
115 * it anyway, because it hasn't been used for
116 * anything yet. It is still in a "not read
117 * from disk yet" state.
118 *
119 * But non-uptodate buffers against an uptodate
120 * page are against the rules. So do it anyway.
121 */
122 set_buffer_uptodate(bh);
123 }
124 } while ((bh = bh->b_this_page) != head);
125 } else {
126 memset(page_address(page), 0, PAGE_CACHE_SIZE);
127 }
128 flush_dcache_page(page);
129 SetPageUptodate(page);
130}
131
132static int ramdisk_readpage(struct file *file, struct page *page)
133{
134 if (!PageUptodate(page))
135 make_page_uptodate(page);
136 unlock_page(page);
137 return 0;
138}
139
140static int ramdisk_prepare_write(struct file *file, struct page *page,
141 unsigned offset, unsigned to)
142{
143 if (!PageUptodate(page))
144 make_page_uptodate(page);
145 return 0;
146}
147
148static int ramdisk_commit_write(struct file *file, struct page *page,
149 unsigned offset, unsigned to)
150{
151 set_page_dirty(page);
152 return 0;
153}
154
155/*
156 * ->writepage to the the blockdev's mapping has to redirty the page so that the
157 * VM doesn't go and steal it. We return WRITEPAGE_ACTIVATE so that the VM
158 * won't try to (pointlessly) write the page again for a while.
159 *
160 * Really, these pages should not be on the LRU at all.
161 */
162static int ramdisk_writepage(struct page *page, struct writeback_control *wbc)
163{
164 if (!PageUptodate(page))
165 make_page_uptodate(page);
166 SetPageDirty(page);
167 if (wbc->for_reclaim)
168 return WRITEPAGE_ACTIVATE;
169 unlock_page(page);
170 return 0;
171}
172
173/*
174 * This is a little speedup thing: short-circuit attempts to write back the
175 * ramdisk blockdev inode to its non-existent backing store.
176 */
177static int ramdisk_writepages(struct address_space *mapping,
178 struct writeback_control *wbc)
179{
180 return 0;
181}
182
183/*
184 * ramdisk blockdev pages have their own ->set_page_dirty() because we don't
185 * want them to contribute to dirty memory accounting.
186 */
187static int ramdisk_set_page_dirty(struct page *page)
188{
189 SetPageDirty(page);
190 return 0;
191}
192
193static struct address_space_operations ramdisk_aops = {
194 .readpage = ramdisk_readpage,
195 .prepare_write = ramdisk_prepare_write,
196 .commit_write = ramdisk_commit_write,
197 .writepage = ramdisk_writepage,
198 .set_page_dirty = ramdisk_set_page_dirty,
199 .writepages = ramdisk_writepages,
200};
201
202static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
203 struct address_space *mapping)
204{
205 pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9);
206 unsigned int vec_offset = vec->bv_offset;
207 int offset = (sector << 9) & ~PAGE_CACHE_MASK;
208 int size = vec->bv_len;
209 int err = 0;
210
211 do {
212 int count;
213 struct page *page;
214 char *src;
215 char *dst;
216
217 count = PAGE_CACHE_SIZE - offset;
218 if (count > size)
219 count = size;
220 size -= count;
221
222 page = grab_cache_page(mapping, index);
223 if (!page) {
224 err = -ENOMEM;
225 goto out;
226 }
227
228 if (!PageUptodate(page))
229 make_page_uptodate(page);
230
231 index++;
232
233 if (rw == READ) {
234 src = kmap_atomic(page, KM_USER0) + offset;
235 dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset;
236 } else {
237 src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset;
238 dst = kmap_atomic(page, KM_USER1) + offset;
239 }
240 offset = 0;
241 vec_offset += count;
242
243 memcpy(dst, src, count);
244
245 kunmap_atomic(src, KM_USER0);
246 kunmap_atomic(dst, KM_USER1);
247
248 if (rw == READ)
249 flush_dcache_page(vec->bv_page);
250 else
251 set_page_dirty(page);
252 unlock_page(page);
253 put_page(page);
254 } while (size);
255
256 out:
257 return err;
258}
259
260/*
261 * Basically, my strategy here is to set up a buffer-head which can't be
262 * deleted, and make that my Ramdisk. If the request is outside of the
263 * allocated size, we must get rid of it...
264 *
265 * 19-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Added devfs support
266 *
267 */
268static int rd_make_request(request_queue_t *q, struct bio *bio)
269{
270 struct block_device *bdev = bio->bi_bdev;
271 struct address_space * mapping = bdev->bd_inode->i_mapping;
272 sector_t sector = bio->bi_sector;
273 unsigned long len = bio->bi_size >> 9;
274 int rw = bio_data_dir(bio);
275 struct bio_vec *bvec;
276 int ret = 0, i;
277
278 if (sector + len > get_capacity(bdev->bd_disk))
279 goto fail;
280
281 if (rw==READA)
282 rw=READ;
283
284 bio_for_each_segment(bvec, bio, i) {
285 ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping);
286 sector += bvec->bv_len >> 9;
287 }
288 if (ret)
289 goto fail;
290
291 bio_endio(bio, bio->bi_size, 0);
292 return 0;
293fail:
294 bio_io_error(bio, bio->bi_size);
295 return 0;
296}
297
298static int rd_ioctl(struct inode *inode, struct file *file,
299 unsigned int cmd, unsigned long arg)
300{
301 int error;
302 struct block_device *bdev = inode->i_bdev;
303
304 if (cmd != BLKFLSBUF)
305 return -ENOTTY;
306
307 /*
308 * special: we want to release the ramdisk memory, it's not like with
309 * the other blockdevices where this ioctl only flushes away the buffer
310 * cache
311 */
312 error = -EBUSY;
313 down(&bdev->bd_sem);
314 if (bdev->bd_openers <= 2) {
315 truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
316 error = 0;
317 }
318 up(&bdev->bd_sem);
319 return error;
320}
321
322/*
323 * This is the backing_dev_info for the blockdev inode itself. It doesn't need
324 * writeback and it does not contribute to dirty memory accounting.
325 */
326static struct backing_dev_info rd_backing_dev_info = {
327 .ra_pages = 0, /* No readahead */
328 .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_COPY,
329 .unplug_io_fn = default_unplug_io_fn,
330};
331
332/*
333 * This is the backing_dev_info for the files which live atop the ramdisk
334 * "device". These files do need writeback and they do contribute to dirty
335 * memory accounting.
336 */
337static struct backing_dev_info rd_file_backing_dev_info = {
338 .ra_pages = 0, /* No readahead */
339 .capabilities = BDI_CAP_MAP_COPY, /* Does contribute to dirty memory */
340 .unplug_io_fn = default_unplug_io_fn,
341};
342
343static int rd_open(struct inode *inode, struct file *filp)
344{
345 unsigned unit = iminor(inode);
346
347 if (rd_bdev[unit] == NULL) {
348 struct block_device *bdev = inode->i_bdev;
349 struct address_space *mapping;
350 unsigned bsize;
Al Virob4e3ca12005-10-21 03:22:34 -0400351 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352
353 inode = igrab(bdev->bd_inode);
354 rd_bdev[unit] = bdev;
355 bdev->bd_openers++;
356 bsize = bdev_hardsect_size(bdev);
357 bdev->bd_block_size = bsize;
358 inode->i_blkbits = blksize_bits(bsize);
359 inode->i_size = get_capacity(bdev->bd_disk)<<9;
360
361 mapping = inode->i_mapping;
362 mapping->a_ops = &ramdisk_aops;
363 mapping->backing_dev_info = &rd_backing_dev_info;
364 bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info;
365
366 /*
367 * Deep badness. rd_blkdev_pagecache_IO() needs to allocate
368 * pagecache pages within a request_fn. We cannot recur back
369 * into the filesytem which is mounted atop the ramdisk, because
370 * that would deadlock on fs locks. And we really don't want
371 * to reenter rd_blkdev_pagecache_IO when we're already within
372 * that function.
373 *
374 * So we turn off __GFP_FS and __GFP_IO.
375 *
376 * And to give this thing a hope of working, turn on __GFP_HIGH.
377 * Hopefully, there's enough regular memory allocation going on
378 * for the page allocator emergency pools to keep the ramdisk
379 * driver happy.
380 */
381 gfp_mask = mapping_gfp_mask(mapping);
382 gfp_mask &= ~(__GFP_FS|__GFP_IO);
383 gfp_mask |= __GFP_HIGH;
384 mapping_set_gfp_mask(mapping, gfp_mask);
385 }
386
387 return 0;
388}
389
390static struct block_device_operations rd_bd_op = {
391 .owner = THIS_MODULE,
392 .open = rd_open,
393 .ioctl = rd_ioctl,
394};
395
396/*
397 * Before freeing the module, invalidate all of the protected buffers!
398 */
399static void __exit rd_cleanup(void)
400{
401 int i;
402
403 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
404 struct block_device *bdev = rd_bdev[i];
405 rd_bdev[i] = NULL;
406 if (bdev) {
407 invalidate_bdev(bdev, 1);
408 blkdev_put(bdev);
409 }
410 del_gendisk(rd_disks[i]);
411 put_disk(rd_disks[i]);
412 blk_cleanup_queue(rd_queue[i]);
413 }
414 devfs_remove("rd");
415 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
416}
417
418/*
419 * This is the registration and initialization section of the RAM disk driver
420 */
421static int __init rd_init(void)
422{
423 int i;
424 int err = -ENOMEM;
425
426 if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 ||
427 (rd_blocksize & (rd_blocksize-1))) {
428 printk("RAMDISK: wrong blocksize %d, reverting to defaults\n",
429 rd_blocksize);
430 rd_blocksize = BLOCK_SIZE;
431 }
432
433 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
434 rd_disks[i] = alloc_disk(1);
435 if (!rd_disks[i])
436 goto out;
437 }
438
439 if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) {
440 err = -EIO;
441 goto out;
442 }
443
444 devfs_mk_dir("rd");
445
446 for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
447 struct gendisk *disk = rd_disks[i];
448
449 rd_queue[i] = blk_alloc_queue(GFP_KERNEL);
450 if (!rd_queue[i])
451 goto out_queue;
452
453 blk_queue_make_request(rd_queue[i], &rd_make_request);
454 blk_queue_hardsect_size(rd_queue[i], rd_blocksize);
455
456 /* rd_size is given in kB */
457 disk->major = RAMDISK_MAJOR;
458 disk->first_minor = i;
459 disk->fops = &rd_bd_op;
460 disk->queue = rd_queue[i];
461 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
462 sprintf(disk->disk_name, "ram%d", i);
463 sprintf(disk->devfs_name, "rd/%d", i);
464 set_capacity(disk, rd_size * 2);
465 add_disk(rd_disks[i]);
466 }
467
468 /* rd_size is given in kB */
469 printk("RAMDISK driver initialized: "
470 "%d RAM disks of %dK size %d blocksize\n",
471 CONFIG_BLK_DEV_RAM_COUNT, rd_size, rd_blocksize);
472
473 return 0;
474out_queue:
475 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
476out:
477 while (i--) {
478 put_disk(rd_disks[i]);
479 blk_cleanup_queue(rd_queue[i]);
480 }
481 return err;
482}
483
484module_init(rd_init);
485module_exit(rd_cleanup);
486
487/* options - nonmodular */
488#ifndef MODULE
489static int __init ramdisk_size(char *str)
490{
491 rd_size = simple_strtol(str,NULL,0);
492 return 1;
493}
494static int __init ramdisk_size2(char *str) /* kludge */
495{
496 return ramdisk_size(str);
497}
498static int __init ramdisk_blocksize(char *str)
499{
500 rd_blocksize = simple_strtol(str,NULL,0);
501 return 1;
502}
503__setup("ramdisk=", ramdisk_size);
504__setup("ramdisk_size=", ramdisk_size2);
505__setup("ramdisk_blocksize=", ramdisk_blocksize);
506#endif
507
508/* options - modular */
509module_param(rd_size, int, 0);
510MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
511module_param(rd_blocksize, int, 0);
512MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes.");
513MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
514
515MODULE_LICENSE("GPL");