drivers/block/rd.c

   1 /*
   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/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>
  52 #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
  65 static struct gendisk *rd_disks[CONFIG_BLK_DEV_RAM_COUNT];
  66 static struct block_device *rd_bdev[CONFIG_BLK_DEV_RAM_COUNT];/* Protected device data */
  67 static 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  */
  75 int rd_size = CONFIG_BLK_DEV_RAM_SIZE;          /* Size of the RAM disks */
  76 /*
  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  */
  87 static int rd_blocksize = CONFIG_BLK_DEV_RAM_BLOCKSIZE;
  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  */
 100 static 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
 130 static 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
 138 static 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
 146 static 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 blockdev's mapping has to redirty the page so that the
 155  * VM doesn't go and steal it.  We return AOP_WRITEPAGE_ACTIVATE so that the VM
 156  * 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  */
 160 static 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)
 166                 return AOP_WRITEPAGE_ACTIVATE;
 167         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  */
 175 static 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  */
 185 static int ramdisk_set_page_dirty(struct page *page)
 186 {
 187         if (!TestSetPageDirty(page))
 188                 return 1;
 189         return 0;
 190 }
 191
 192 /*
 193  * releasepage is called by pagevec_strip/try_to_release_page if
 194  * buffers_heads_over_limit is true. Without a releasepage function
 195  * try_to_free_buffers is called instead. That can unset the dirty
 196  * bit of our ram disk pages, which will be eventually freed, even
 197  * if the page is still in use.
 198  */
 199 static int ramdisk_releasepage(struct page *page, gfp_t dummy)
 200 {
 201         return 0;
 202 }
 203
 204 static const struct address_space_operations ramdisk_aops = {
 205         .readpage       = ramdisk_readpage,
 206         .prepare_write  = ramdisk_prepare_write,
 207         .commit_write   = ramdisk_commit_write,
 208         .writepage      = ramdisk_writepage,
 209         .set_page_dirty = ramdisk_set_page_dirty,
 210         .writepages     = ramdisk_writepages,
 211         .releasepage    = ramdisk_releasepage,
 212 };
 213
 214 static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
 215                                 struct address_space *mapping)
 216 {
 217         pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9);
 218         unsigned int vec_offset = vec->bv_offset;
 219         int offset = (sector << 9) & ~PAGE_CACHE_MASK;
 220         int size = vec->bv_len;
 221         int err = 0;
 222
 223         do {
 224                 int count;
 225                 struct page *page;
 226                 char *src;
 227                 char *dst;
 228
 229                 count = PAGE_CACHE_SIZE - offset;
 230                 if (count > size)
 231                         count = size;
 232                 size -= count;
 233
 234                 page = grab_cache_page(mapping, index);
 235                 if (!page) {
 236                         err = -ENOMEM;
 237                         goto out;
 238                 }
 239
 240                 if (!PageUptodate(page))
 241                         make_page_uptodate(page);
 242
 243                 index++;
 244
 245                 if (rw == READ) {
 246                         src = kmap_atomic(page, KM_USER0) + offset;
 247                         dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset;
 248                 } else {
 249                         src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset;
 250                         dst = kmap_atomic(page, KM_USER1) + offset;
 251                 }
 252                 offset = 0;
 253                 vec_offset += count;
 254
 255                 memcpy(dst, src, count);
 256
 257                 kunmap_atomic(src, KM_USER0);
 258                 kunmap_atomic(dst, KM_USER1);
 259
 260                 if (rw == READ)
 261                         flush_dcache_page(vec->bv_page);
 262                 else
 263                         set_page_dirty(page);
 264                 unlock_page(page);
 265                 put_page(page);
 266         } while (size);
 267
 268  out:
 269         return err;
 270 }
 271
 272 /*
 273  *  Basically, my strategy here is to set up a buffer-head which can't be
 274  *  deleted, and make that my Ramdisk.  If the request is outside of the
 275  *  allocated size, we must get rid of it...
 276  *
 277  * 19-JAN-1998  Richard Gooch <rgooch@atnf.csiro.au>  Added devfs support
 278  *
 279  */
 280 static int rd_make_request(struct request_queue *q, struct bio *bio)
 281 {
 282         struct block_device *bdev = bio->bi_bdev;
 283         struct address_space * mapping = bdev->bd_inode->i_mapping;
 284         sector_t sector = bio->bi_sector;
 285         unsigned long len = bio->bi_size >> 9;
 286         int rw = bio_data_dir(bio);
 287         struct bio_vec *bvec;
 288         int ret = 0, i;
 289
 290         if (sector + len > get_capacity(bdev->bd_disk))
 291                 goto fail;
 292
 293         if (rw==READA)
 294                 rw=READ;
 295
 296         bio_for_each_segment(bvec, bio, i) {
 297                 ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping);
 298                 sector += bvec->bv_len >> 9;
 299         }
 300         if (ret)
 301                 goto fail;
 302
 303         bio_endio(bio, 0);
 304         return 0;
 305 fail:
 306         bio_io_error(bio);
 307         return 0;
 308 }
 309
 310 static int rd_ioctl(struct inode *inode, struct file *file,
 311                         unsigned int cmd, unsigned long arg)
 312 {
 313         int error;
 314         struct block_device *bdev = inode->i_bdev;
 315
 316         if (cmd != BLKFLSBUF)
 317                 return -ENOTTY;
 318
 319         /*
 320          * special: we want to release the ramdisk memory, it's not like with
 321          * the other blockdevices where this ioctl only flushes away the buffer
 322          * cache
 323          */
 324         error = -EBUSY;
 325         mutex_lock(&bdev->bd_mutex);
 326         if (bdev->bd_openers <= 2) {
 327                 truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
 328                 error = 0;
 329         }
 330         mutex_unlock(&bdev->bd_mutex);
 331         return error;
 332 }
 333
 334 /*
 335  * This is the backing_dev_info for the blockdev inode itself.  It doesn't need
 336  * writeback and it does not contribute to dirty memory accounting.
 337  */
 338 static struct backing_dev_info rd_backing_dev_info = {
 339         .ra_pages       = 0,    /* No readahead */
 340         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_COPY,
 341         .unplug_io_fn   = default_unplug_io_fn,
 342 };
 343
 344 /*
 345  * This is the backing_dev_info for the files which live atop the ramdisk
 346  * "device".  These files do need writeback and they do contribute to dirty
 347  * memory accounting.
 348  */
 349 static struct backing_dev_info rd_file_backing_dev_info = {
 350         .ra_pages       = 0,    /* No readahead */
 351         .capabilities   = BDI_CAP_MAP_COPY,     /* Does contribute to dirty memory */
 352         .unplug_io_fn   = default_unplug_io_fn,
 353 };
 354
 355 static int rd_open(struct inode *inode, struct file *filp)
 356 {
 357         unsigned unit = iminor(inode);
 358
 359         if (rd_bdev[unit] == NULL) {
 360                 struct block_device *bdev = inode->i_bdev;
 361                 struct address_space *mapping;
 362                 unsigned bsize;
 363                 gfp_t gfp_mask;
 364
 365                 inode = igrab(bdev->bd_inode);
 366                 rd_bdev[unit] = bdev;
 367                 bdev->bd_openers++;
 368                 bsize = bdev_hardsect_size(bdev);
 369                 bdev->bd_block_size = bsize;
 370                 inode->i_blkbits = blksize_bits(bsize);
 371                 inode->i_size = get_capacity(bdev->bd_disk)<<9;
 372
 373                 mapping = inode->i_mapping;
 374                 mapping->a_ops = &ramdisk_aops;
 375                 mapping->backing_dev_info = &rd_backing_dev_info;
 376                 bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info;
 377
 378                 /*
 379                  * Deep badness.  rd_blkdev_pagecache_IO() needs to allocate
 380                  * pagecache pages within a request_fn.  We cannot recur back
 381                  * into the filesystem which is mounted atop the ramdisk, because
 382                  * that would deadlock on fs locks.  And we really don't want
 383                  * to reenter rd_blkdev_pagecache_IO when we're already within
 384                  * that function.
 385                  *
 386                  * So we turn off __GFP_FS and __GFP_IO.
 387                  *
 388                  * And to give this thing a hope of working, turn on __GFP_HIGH.
 389                  * Hopefully, there's enough regular memory allocation going on
 390                  * for the page allocator emergency pools to keep the ramdisk
 391                  * driver happy.
 392                  */
 393                 gfp_mask = mapping_gfp_mask(mapping);
 394                 gfp_mask &= ~(__GFP_FS|__GFP_IO);
 395                 gfp_mask |= __GFP_HIGH;
 396                 mapping_set_gfp_mask(mapping, gfp_mask);
 397         }
 398
 399         return 0;
 400 }
 401
 402 static struct block_device_operations rd_bd_op = {
 403         .owner =        THIS_MODULE,
 404         .open =         rd_open,
 405         .ioctl =        rd_ioctl,
 406 };
 407
 408 /*
 409  * Before freeing the module, invalidate all of the protected buffers!
 410  */
 411 static void __exit rd_cleanup(void)
 412 {
 413         int i;
 414
 415         for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
 416                 struct block_device *bdev = rd_bdev[i];
 417                 rd_bdev[i] = NULL;
 418                 if (bdev) {
 419                         invalidate_bdev(bdev);
 420                         blkdev_put(bdev);
 421                 }
 422                 del_gendisk(rd_disks[i]);
 423                 put_disk(rd_disks[i]);
 424                 blk_cleanup_queue(rd_queue[i]);
 425         }
 426         unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
 427
 428         bdi_destroy(&rd_file_backing_dev_info);
 429         bdi_destroy(&rd_backing_dev_info);
 430 }
 431
 432 /*
 433  * This is the registration and initialization section of the RAM disk driver
 434  */
 435 static int __init rd_init(void)
 436 {
 437         int i;
 438         int err;
 439
 440         err = bdi_init(&rd_backing_dev_info);
 441         if (err)
 442                 goto out2;
 443
 444         err = bdi_init(&rd_file_backing_dev_info);
 445         if (err) {
 446                 bdi_destroy(&rd_backing_dev_info);
 447                 goto out2;
 448         }
 449
 450         err = -ENOMEM;
 451
 452         if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 ||
 453                         (rd_blocksize & (rd_blocksize-1))) {
 454                 printk("RAMDISK: wrong blocksize %d, reverting to defaults\n",
 455                        rd_blocksize);
 456                 rd_blocksize = BLOCK_SIZE;
 457         }
 458
 459         for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
 460                 rd_disks[i] = alloc_disk(1);
 461                 if (!rd_disks[i])
 462                         goto out;
 463
 464                 rd_queue[i] = blk_alloc_queue(GFP_KERNEL);
 465                 if (!rd_queue[i]) {
 466                         put_disk(rd_disks[i]);
 467                         goto out;
 468                 }
 469         }
 470
 471         if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) {
 472                 err = -EIO;
 473                 goto out;
 474         }
 475
 476         for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) {
 477                 struct gendisk *disk = rd_disks[i];
 478
 479                 blk_queue_make_request(rd_queue[i], &rd_make_request);
 480                 blk_queue_hardsect_size(rd_queue[i], rd_blocksize);
 481
 482                 /* rd_size is given in kB */
 483                 disk->major = RAMDISK_MAJOR;
 484                 disk->first_minor = i;
 485                 disk->fops = &rd_bd_op;
 486                 disk->queue = rd_queue[i];
 487                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
 488                 sprintf(disk->disk_name, "ram%d", i);
 489                 set_capacity(disk, rd_size * 2);
 490                 add_disk(rd_disks[i]);
 491         }
 492
 493         /* rd_size is given in kB */
 494         printk("RAMDISK driver initialized: "
 495                 "%d RAM disks of %dK size %d blocksize\n",
 496                 CONFIG_BLK_DEV_RAM_COUNT, rd_size, rd_blocksize);
 497
 498         return 0;
 499 out:
 500         while (i--) {
 501                 put_disk(rd_disks[i]);
 502                 blk_cleanup_queue(rd_queue[i]);
 503         }
 504         bdi_destroy(&rd_backing_dev_info);
 505         bdi_destroy(&rd_file_backing_dev_info);
 506 out2:
 507         return err;
 508 }
 509
 510 module_init(rd_init);
 511 module_exit(rd_cleanup);
 512
 513 /* options - nonmodular */
 514 #ifndef MODULE
 515 static int __init ramdisk_size(char *str)
 516 {
 517         rd_size = simple_strtol(str,NULL,0);
 518         return 1;
 519 }
 520 static int __init ramdisk_blocksize(char *str)
 521 {
 522         rd_blocksize = simple_strtol(str,NULL,0);
 523         return 1;
 524 }
 525 __setup("ramdisk_size=", ramdisk_size);
 526 __setup("ramdisk_blocksize=", ramdisk_blocksize);
 527 #endif
 528
 529 /* options - modular */
 530 module_param(rd_size, int, 0);
 531 MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
 532 module_param(rd_blocksize, int, 0);
 533 MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes.");
 534 MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
 535
 536 MODULE_LICENSE("GPL");