2 * ramdisk.c - Multiple RAM disk driver - gzip-loading version - v. 0.8 beta.
4 * (C) Chad Page, Theodore Ts'o, et. al, 1995.
6 * This RAM disk is designed to have filesystems created on it and mounted
7 * just like a regular floppy disk.
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.
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.
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.
27 * Loadable module support added by Tom Dyas.
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
34 * Added initrd: Werner Almesberger & Hans Lermen, Feb '96
36 * 4/25/96 : Made RAM disk size a parameter (default is now 4 MB)
39 * Add support for fs images split across >1 disk, Paul Gortmaker, Mar '98
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
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/init.h>
52 #include <linux/devfs_fs_kernel.h>
53 #include <linux/pagemap.h>
54 #include <linux/blkdev.h>
55 #include <linux/genhd.h>
56 #include <linux/buffer_head.h> /* for invalidate_bdev() */
57 #include <linux/backing-dev.h>
58 #include <linux/blkpg.h>
59 #include <linux/writeback.h>
61 #include <asm/uaccess.h>
63 /* The RAM disk size is now a parameter */
64 #define NUM_RAMDISKS 16 /* This cannot be overridden (yet) */
66 /* Various static variables go here. Most are used only in the RAM disk code.
69 static struct gendisk *rd_disks[NUM_RAMDISKS];
70 static struct block_device *rd_bdev[NUM_RAMDISKS];/* Protected device data */
71 static struct request_queue *rd_queue[NUM_RAMDISKS];
74 * Parameters for the boot-loading of the RAM disk. These are set by
75 * init/main.c (from arguments to the kernel command line) or from the
76 * architecture-specific setup routine (from the stored boot sector
79 int rd_size = CONFIG_BLK_DEV_RAM_SIZE; /* Size of the RAM disks */
81 * It would be very desirable to have a soft-blocksize (that in the case
82 * of the ramdisk driver is also the hardblocksize ;) of PAGE_SIZE because
83 * doing that we'll achieve a far better MM footprint. Using a rd_blocksize of
84 * BLOCK_SIZE in the worst case we'll make PAGE_SIZE/BLOCK_SIZE buffer-pages
85 * unfreeable. With a rd_blocksize of PAGE_SIZE instead we are sure that only
86 * 1 page will be protected. Depending on the size of the ramdisk you
87 * may want to change the ramdisk blocksize to achieve a better or worse MM
88 * behaviour. The default is still BLOCK_SIZE (needed by rd_load_image that
89 * supposes the filesystem in the image uses a BLOCK_SIZE blocksize).
91 int rd_blocksize = BLOCK_SIZE; /* blocksize of the RAM disks */
94 * Copyright (C) 2000 Linus Torvalds.
95 * 2000 Transmeta Corp.
96 * aops copied from ramfs.
100 * If a ramdisk page has buffers, some may be uptodate and some may be not.
101 * To bring the page uptodate we zero out the non-uptodate buffers. The
102 * page must be locked.
104 static void make_page_uptodate(struct page *page)
106 if (page_has_buffers(page)) {
107 struct buffer_head *bh = page_buffers(page);
108 struct buffer_head *head = bh;
111 if (!buffer_uptodate(bh)) {
112 memset(bh->b_data, 0, bh->b_size);
114 * akpm: I'm totally undecided about this. The
115 * buffer has just been magically brought "up to
116 * date", but nobody should want to be reading
117 * it anyway, because it hasn't been used for
118 * anything yet. It is still in a "not read
119 * from disk yet" state.
121 * But non-uptodate buffers against an uptodate
122 * page are against the rules. So do it anyway.
124 set_buffer_uptodate(bh);
126 } while ((bh = bh->b_this_page) != head);
128 memset(page_address(page), 0, PAGE_CACHE_SIZE);
130 flush_dcache_page(page);
131 SetPageUptodate(page);
134 static int ramdisk_readpage(struct file *file, struct page *page)
136 if (!PageUptodate(page))
137 make_page_uptodate(page);
142 static int ramdisk_prepare_write(struct file *file, struct page *page,
143 unsigned offset, unsigned to)
145 if (!PageUptodate(page))
146 make_page_uptodate(page);
150 static int ramdisk_commit_write(struct file *file, struct page *page,
151 unsigned offset, unsigned to)
153 set_page_dirty(page);
158 * ->writepage to the the blockdev's mapping has to redirty the page so that the
159 * VM doesn't go and steal it. We return WRITEPAGE_ACTIVATE so that the VM
160 * won't try to (pointlessly) write the page again for a while.
162 * Really, these pages should not be on the LRU at all.
164 static int ramdisk_writepage(struct page *page, struct writeback_control *wbc)
166 if (!PageUptodate(page))
167 make_page_uptodate(page);
169 if (wbc->for_reclaim)
170 return WRITEPAGE_ACTIVATE;
176 * This is a little speedup thing: short-circuit attempts to write back the
177 * ramdisk blockdev inode to its non-existent backing store.
179 static int ramdisk_writepages(struct address_space *mapping,
180 struct writeback_control *wbc)
186 * ramdisk blockdev pages have their own ->set_page_dirty() because we don't
187 * want them to contribute to dirty memory accounting.
189 static int ramdisk_set_page_dirty(struct page *page)
195 static struct address_space_operations ramdisk_aops = {
196 .readpage = ramdisk_readpage,
197 .prepare_write = ramdisk_prepare_write,
198 .commit_write = ramdisk_commit_write,
199 .writepage = ramdisk_writepage,
200 .set_page_dirty = ramdisk_set_page_dirty,
201 .writepages = ramdisk_writepages,
204 static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
205 struct address_space *mapping)
207 pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9);
208 unsigned int vec_offset = vec->bv_offset;
209 int offset = (sector << 9) & ~PAGE_CACHE_MASK;
210 int size = vec->bv_len;
219 count = PAGE_CACHE_SIZE - offset;
224 page = grab_cache_page(mapping, index);
230 if (!PageUptodate(page))
231 make_page_uptodate(page);
236 src = kmap_atomic(page, KM_USER0) + offset;
237 dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset;
239 src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset;
240 dst = kmap_atomic(page, KM_USER1) + offset;
245 memcpy(dst, src, count);
247 kunmap_atomic(src, KM_USER0);
248 kunmap_atomic(dst, KM_USER1);
251 flush_dcache_page(vec->bv_page);
253 set_page_dirty(page);
263 * Basically, my strategy here is to set up a buffer-head which can't be
264 * deleted, and make that my Ramdisk. If the request is outside of the
265 * allocated size, we must get rid of it...
267 * 19-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Added devfs support
270 static int rd_make_request(request_queue_t *q, struct bio *bio)
272 struct block_device *bdev = bio->bi_bdev;
273 struct address_space * mapping = bdev->bd_inode->i_mapping;
274 sector_t sector = bio->bi_sector;
275 unsigned long len = bio->bi_size >> 9;
276 int rw = bio_data_dir(bio);
277 struct bio_vec *bvec;
280 if (sector + len > get_capacity(bdev->bd_disk))
286 bio_for_each_segment(bvec, bio, i) {
287 ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping);
288 sector += bvec->bv_len >> 9;
293 bio_endio(bio, bio->bi_size, 0);
296 bio_io_error(bio, bio->bi_size);
300 static int rd_ioctl(struct inode *inode, struct file *file,
301 unsigned int cmd, unsigned long arg)
304 struct block_device *bdev = inode->i_bdev;
306 if (cmd != BLKFLSBUF)
310 * special: we want to release the ramdisk memory, it's not like with
311 * the other blockdevices where this ioctl only flushes away the buffer
316 if (bdev->bd_openers <= 2) {
317 truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
325 * This is the backing_dev_info for the blockdev inode itself. It doesn't need
326 * writeback and it does not contribute to dirty memory accounting.
328 static struct backing_dev_info rd_backing_dev_info = {
329 .ra_pages = 0, /* No readahead */
330 .memory_backed = 1, /* Does not contribute to dirty memory */
331 .unplug_io_fn = default_unplug_io_fn,
335 * This is the backing_dev_info for the files which live atop the ramdisk
336 * "device". These files do need writeback and they do contribute to dirty
339 static struct backing_dev_info rd_file_backing_dev_info = {
340 .ra_pages = 0, /* No readahead */
341 .memory_backed = 0, /* Does contribute to dirty memory */
342 .unplug_io_fn = default_unplug_io_fn,
345 static int rd_open(struct inode *inode, struct file *filp)
347 unsigned unit = iminor(inode);
349 if (rd_bdev[unit] == NULL) {
350 struct block_device *bdev = inode->i_bdev;
351 struct address_space *mapping;
354 inode = igrab(bdev->bd_inode);
355 rd_bdev[unit] = bdev;
357 bdev->bd_block_size = rd_blocksize;
358 inode->i_size = get_capacity(rd_disks[unit])<<9;
359 mapping = inode->i_mapping;
360 mapping->a_ops = &ramdisk_aops;
361 mapping->backing_dev_info = &rd_backing_dev_info;
362 bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info;
365 * Deep badness. rd_blkdev_pagecache_IO() needs to allocate
366 * pagecache pages within a request_fn. We cannot recur back
367 * into the filesytem which is mounted atop the ramdisk, because
368 * that would deadlock on fs locks. And we really don't want
369 * to reenter rd_blkdev_pagecache_IO when we're already within
372 * So we turn off __GFP_FS and __GFP_IO.
374 * And to give this thing a hope of working, turn on __GFP_HIGH.
375 * Hopefully, there's enough regular memory allocation going on
376 * for the page allocator emergency pools to keep the ramdisk
379 gfp_mask = mapping_gfp_mask(mapping);
380 gfp_mask &= ~(__GFP_FS|__GFP_IO);
381 gfp_mask |= __GFP_HIGH;
382 mapping_set_gfp_mask(mapping, gfp_mask);
388 static struct block_device_operations rd_bd_op = {
389 .owner = THIS_MODULE,
395 * Before freeing the module, invalidate all of the protected buffers!
397 static void __exit rd_cleanup(void)
401 for (i = 0; i < NUM_RAMDISKS; i++) {
402 struct block_device *bdev = rd_bdev[i];
405 invalidate_bdev(bdev, 1);
408 del_gendisk(rd_disks[i]);
409 put_disk(rd_disks[i]);
410 blk_cleanup_queue(rd_queue[i]);
413 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
417 * This is the registration and initialization section of the RAM disk driver
419 static int __init rd_init(void)
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",
428 rd_blocksize = BLOCK_SIZE;
431 for (i = 0; i < NUM_RAMDISKS; i++) {
432 rd_disks[i] = alloc_disk(1);
437 if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) {
444 for (i = 0; i < NUM_RAMDISKS; i++) {
445 struct gendisk *disk = rd_disks[i];
447 rd_queue[i] = blk_alloc_queue(GFP_KERNEL);
451 blk_queue_make_request(rd_queue[i], &rd_make_request);
453 /* rd_size is given in kB */
454 disk->major = RAMDISK_MAJOR;
455 disk->first_minor = i;
456 disk->fops = &rd_bd_op;
457 disk->queue = rd_queue[i];
458 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
459 sprintf(disk->disk_name, "ram%d", i);
460 sprintf(disk->devfs_name, "rd/%d", i);
461 set_capacity(disk, rd_size * 2);
462 add_disk(rd_disks[i]);
465 /* rd_size is given in kB */
466 printk("RAMDISK driver initialized: "
467 "%d RAM disks of %dK size %d blocksize\n",
468 NUM_RAMDISKS, rd_size, rd_blocksize);
472 unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
475 put_disk(rd_disks[i]);
476 blk_cleanup_queue(rd_queue[i]);
481 module_init(rd_init);
482 module_exit(rd_cleanup);
484 /* options - nonmodular */
486 static int __init ramdisk_size(char *str)
488 rd_size = simple_strtol(str,NULL,0);
491 static int __init ramdisk_size2(char *str) /* kludge */
493 return ramdisk_size(str);
495 static int __init ramdisk_blocksize(char *str)
497 rd_blocksize = simple_strtol(str,NULL,0);
500 __setup("ramdisk=", ramdisk_size);
501 __setup("ramdisk_size=", ramdisk_size2);
502 __setup("ramdisk_blocksize=", ramdisk_blocksize);
505 /* options - modular */
506 MODULE_PARM (rd_size, "1i");
507 MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
508 MODULE_PARM (rd_blocksize, "i");
509 MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes.");
511 MODULE_LICENSE("GPL");