/* * ramdisk.c - Multiple RAM disk driver - gzip-loading version - v. 0.8 beta. * * (C) Chad Page, Theodore Ts'o, et. al, 1995. * * This RAM disk is designed to have filesystems created on it and mounted * just like a regular floppy disk. * * It also does something suggested by Linus: use the buffer cache as the * RAM disk data. This makes it possible to dynamically allocate the RAM disk * buffer - with some consequences I have to deal with as I write this. * * This code is based on the original ramdisk.c, written mostly by * Theodore Ts'o (TYT) in 1991. The code was largely rewritten by * Chad Page to use the buffer cache to store the RAM disk data in * 1995; Theodore then took over the driver again, and cleaned it up * for inclusion in the mainline kernel. * * The original CRAMDISK code was written by Richard Lyons, and * adapted by Chad Page to use the new RAM disk interface. Theodore * Ts'o rewrote it so that both the compressed RAM disk loader and the * kernel decompressor uses the same inflate.c codebase. The RAM disk * loader now also loads into a dynamic (buffer cache based) RAM disk, * not the old static RAM disk. Support for the old static RAM disk has * been completely removed. * * Loadable module support added by Tom Dyas. * * Further cleanups by Chad Page (page0588@sundance.sjsu.edu): * Cosmetic changes in #ifdef MODULE, code movement, etc. * When the RAM disk module is removed, free the protected buffers * Default RAM disk size changed to 2.88 MB * * Added initrd: Werner Almesberger & Hans Lermen, Feb '96 * * 4/25/96 : Made RAM disk size a parameter (default is now 4 MB) * - Chad Page * * Add support for fs images split across >1 disk, Paul Gortmaker, Mar '98 * * Make block size and block size shift for RAM disks a global macro * and set blk_size for -ENOSPC, Werner Fink <werner@suse.de>, Apr '99 */ #include <linux/string.h> #include <linux/slab.h> #include <asm/atomic.h> #include <linux/bio.h> #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/init.h> #include <linux/pagemap.h> #include <linux/blkdev.h> #include <linux/genhd.h> #include <linux/buffer_head.h> /* for invalidate_bdev() */ #include <linux/backing-dev.h> #include <linux/blkpg.h> #include <linux/writeback.h> #include <asm/uaccess.h> /* Various static variables go here. Most are used only in the RAM disk code. */ static struct gendisk *rd_disks[CONFIG_BLK_DEV_RAM_COUNT]; static struct block_device *rd_bdev[CONFIG_BLK_DEV_RAM_COUNT];/* Protected device data */ static struct request_queue *rd_queue[CONFIG_BLK_DEV_RAM_COUNT]; /* * Parameters for the boot-loading of the RAM disk. These are set by * init/main.c (from arguments to the kernel command line) or from the * architecture-specific setup routine (from the stored boot sector * information). */ int rd_size = CONFIG_BLK_DEV_RAM_SIZE; /* Size of the RAM disks */ /* * It would be very desirable to have a soft-blocksize (that in the case * of the ramdisk driver is also the hardblocksize ;) of PAGE_SIZE because * doing that we'll achieve a far better MM footprint. Using a rd_blocksize of * BLOCK_SIZE in the worst case we'll make PAGE_SIZE/BLOCK_SIZE buffer-pages * unfreeable. With a rd_blocksize of PAGE_SIZE instead we are sure that only * 1 page will be protected. Depending on the size of the ramdisk you * may want to change the ramdisk blocksize to achieve a better or worse MM * behaviour. The default is still BLOCK_SIZE (needed by rd_load_image that * supposes the filesystem in the image uses a BLOCK_SIZE blocksize). */ static int rd_blocksize = CONFIG_BLK_DEV_RAM_BLOCKSIZE; /* * Copyright (C) 2000 Linus Torvalds. * 2000 Transmeta Corp. * aops copied from ramfs. */ /* * If a ramdisk page has buffers, some may be uptodate and some may be not. * To bring the page uptodate we zero out the non-uptodate buffers. The * page must be locked. */ static void make_page_uptodate(struct page *page) { if (page_has_buffers(page)) { struct buffer_head *bh = page_buffers(page); struct buffer_head *head = bh; do { if (!buffer_uptodate(bh)) { memset(bh->b_data, 0, bh->b_size); /* * akpm: I'm totally undecided about this. The * buffer has just been magically brought "up to * date", but nobody should want to be reading * it anyway, because it hasn't been used for * anything yet. It is still in a "not read * from disk yet" state. * * But non-uptodate buffers against an uptodate * page are against the rules. So do it anyway. */ set_buffer_uptodate(bh); } } while ((bh = bh->b_this_page) != head); } else { memset(page_address(page), 0, PAGE_CACHE_SIZE); } flush_dcache_page(page); SetPageUptodate(page); } static int ramdisk_readpage(struct file *file, struct page *page) { if (!PageUptodate(page)) make_page_uptodate(page); unlock_page(page); return 0; } static int ramdisk_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to) { if (!PageUptodate(page)) make_page_uptodate(page); return 0; } static int ramdisk_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to) { set_page_dirty(page); return 0; } /* * ->writepage to the blockdev's mapping has to redirty the page so that the * VM doesn't go and steal it. We return AOP_WRITEPAGE_ACTIVATE so that the VM * won't try to (pointlessly) write the page again for a while. * * Really, these pages should not be on the LRU at all. */ static int ramdisk_writepage(struct page *page, struct writeback_control *wbc) { if (!PageUptodate(page)) make_page_uptodate(page); SetPageDirty(page); if (wbc->for_reclaim) return AOP_WRITEPAGE_ACTIVATE; unlock_page(page); return 0; } /* * This is a little speedup thing: short-circuit attempts to write back the * ramdisk blockdev inode to its non-existent backing store. */ static int ramdisk_writepages(struct address_space *mapping, struct writeback_control *wbc) { return 0; } /* * ramdisk blockdev pages have their own ->set_page_dirty() because we don't * want them to contribute to dirty memory accounting. */ static int ramdisk_set_page_dirty(struct page *page) { if (!TestSetPageDirty(page)) return 1; return 0; } /* * releasepage is called by pagevec_strip/try_to_release_page if * buffers_heads_over_limit is true. Without a releasepage function * try_to_free_buffers is called instead. That can unset the dirty * bit of our ram disk pages, which will be eventually freed, even * if the page is still in use. */ static int ramdisk_releasepage(struct page *page, gfp_t dummy) { return 0; } static const struct address_space_operations ramdisk_aops = { .readpage = ramdisk_readpage, .prepare_write = ramdisk_prepare_write, .commit_write = ramdisk_commit_write, .writepage = ramdisk_writepage, .set_page_dirty = ramdisk_set_page_dirty, .writepages = ramdisk_writepages, .releasepage = ramdisk_releasepage, }; static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector, struct address_space *mapping) { pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9); unsigned int vec_offset = vec->bv_offset; int offset = (sector << 9) & ~PAGE_CACHE_MASK; int size = vec->bv_len; int err = 0; do { int count; struct page *page; char *src; char *dst; count = PAGE_CACHE_SIZE - offset; if (count > size) count = size; size -= count; page = grab_cache_page(mapping, index); if (!page) { err = -ENOMEM; goto out; } if (!PageUptodate(page)) make_page_uptodate(page); index++; if (rw == READ) { src = kmap_atomic(page, KM_USER0) + offset; dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset; } else { src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset; dst = kmap_atomic(page, KM_USER1) + offset; } offset = 0; vec_offset += count; memcpy(dst, src, count); kunmap_atomic(src, KM_USER0); kunmap_atomic(dst, KM_USER1); if (rw == READ) flush_dcache_page(vec->bv_page); else set_page_dirty(page); unlock_page(page); put_page(page); } while (size); out: return err; } /* * Basically, my strategy here is to set up a buffer-head which can't be * deleted, and make that my Ramdisk. If the request is outside of the * allocated size, we must get rid of it... * * 19-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Added devfs support * */ static int rd_make_request(struct request_queue *q, struct bio *bio) { struct block_device *bdev = bio->bi_bdev; struct address_space * mapping = bdev->bd_inode->i_mapping; sector_t sector = bio->bi_sector; unsigned long len = bio->bi_size >> 9; int rw = bio_data_dir(bio); struct bio_vec *bvec; int ret = 0, i; if (sector + len > get_capacity(bdev->bd_disk)) goto fail; if (rw==READA) rw=READ; bio_for_each_segment(bvec, bio, i) { ret |= rd_blkdev_pagecache_IO(rw, bvec, sector, mapping); sector += bvec->bv_len >> 9; } if (ret) goto fail; bio_endio(bio, 0); return 0; fail: bio_io_error(bio); return 0; } static int rd_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg) { int error; struct block_device *bdev = inode->i_bdev; if (cmd != BLKFLSBUF) return -ENOTTY; /* * special: we want to release the ramdisk memory, it's not like with * the other blockdevices where this ioctl only flushes away the buffer * cache */ error = -EBUSY; mutex_lock(&bdev->bd_mutex); if (bdev->bd_openers <= 2) { truncate_inode_pages(bdev->bd_inode->i_mapping, 0); error = 0; } mutex_unlock(&bdev->bd_mutex); return error; } /* * This is the backing_dev_info for the blockdev inode itself. It doesn't need * writeback and it does not contribute to dirty memory accounting. */ static struct backing_dev_info rd_backing_dev_info = { .ra_pages = 0, /* No readahead */ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_COPY, .unplug_io_fn = default_unplug_io_fn, }; /* * This is the backing_dev_info for the files which live atop the ramdisk * "device". These files do need writeback and they do contribute to dirty * memory accounting. */ static struct backing_dev_info rd_file_backing_dev_info = { .ra_pages = 0, /* No readahead */ .capabilities = BDI_CAP_MAP_COPY, /* Does contribute to dirty memory */ .unplug_io_fn = default_unplug_io_fn, }; static int rd_open(struct inode *inode, struct file *filp) { unsigned unit = iminor(inode); if (rd_bdev[unit] == NULL) { struct block_device *bdev = inode->i_bdev; struct address_space *mapping; unsigned bsize; gfp_t gfp_mask; inode = igrab(bdev->bd_inode); rd_bdev[unit] = bdev; bdev->bd_openers++; bsize = bdev_hardsect_size(bdev); bdev->bd_block_size = bsize; inode->i_blkbits = blksize_bits(bsize); inode->i_size = get_capacity(bdev->bd_disk)<<9; mapping = inode->i_mapping; mapping->a_ops = &ramdisk_aops; mapping->backing_dev_info = &rd_backing_dev_info; bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info; /* * Deep badness. rd_blkdev_pagecache_IO() needs to allocate * pagecache pages within a request_fn. We cannot recur back * into the filesystem which is mounted atop the ramdisk, because * that would deadlock on fs locks. And we really don't want * to reenter rd_blkdev_pagecache_IO when we're already within * that function. * * So we turn off __GFP_FS and __GFP_IO. * * And to give this thing a hope of working, turn on __GFP_HIGH. * Hopefully, there's enough regular memory allocation going on * for the page allocator emergency pools to keep the ramdisk * driver happy. */ gfp_mask = mapping_gfp_mask(mapping); gfp_mask &= ~(__GFP_FS|__GFP_IO); gfp_mask |= __GFP_HIGH; mapping_set_gfp_mask(mapping, gfp_mask); } return 0; } static struct block_device_operations rd_bd_op = { .owner = THIS_MODULE, .open = rd_open, .ioctl = rd_ioctl, }; /* * Before freeing the module, invalidate all of the protected buffers! */ static void __exit rd_cleanup(void) { int i; for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) { struct block_device *bdev = rd_bdev[i]; rd_bdev[i] = NULL; if (bdev) { invalidate_bdev(bdev); blkdev_put(bdev); } del_gendisk(rd_disks[i]); put_disk(rd_disks[i]); blk_cleanup_queue(rd_queue[i]); } unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); bdi_destroy(&rd_file_backing_dev_info); bdi_destroy(&rd_backing_dev_info); } /* * This is the registration and initialization section of the RAM disk driver */ static int __init rd_init(void) { int i; int err; err = bdi_init(&rd_backing_dev_info); if (err) goto out2; err = bdi_init(&rd_file_backing_dev_info); if (err) { bdi_destroy(&rd_backing_dev_info); goto out2; } err = -ENOMEM; if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 || (rd_blocksize & (rd_blocksize-1))) { printk("RAMDISK: wrong blocksize %d, reverting to defaults\n", rd_blocksize); rd_blocksize = BLOCK_SIZE; } for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) { rd_disks[i] = alloc_disk(1); if (!rd_disks[i]) goto out; rd_queue[i] = blk_alloc_queue(GFP_KERNEL); if (!rd_queue[i]) { put_disk(rd_disks[i]); goto out; } } if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) { err = -EIO; goto out; } for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) { struct gendisk *disk = rd_disks[i]; blk_queue_make_request(rd_queue[i], &rd_make_request); blk_queue_hardsect_size(rd_queue[i], rd_blocksize); /* rd_size is given in kB */ disk->major = RAMDISK_MAJOR; disk->first_minor = i; disk->fops = &rd_bd_op; disk->queue = rd_queue[i]; disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; sprintf(disk->disk_name, "ram%d", i); set_capacity(disk, rd_size * 2); add_disk(rd_disks[i]); } /* rd_size is given in kB */ printk("RAMDISK driver initialized: " "%d RAM disks of %dK size %d blocksize\n", CONFIG_BLK_DEV_RAM_COUNT, rd_size, rd_blocksize); return 0; out: while (i--) { put_disk(rd_disks[i]); blk_cleanup_queue(rd_queue[i]); } bdi_destroy(&rd_backing_dev_info); bdi_destroy(&rd_file_backing_dev_info); out2: return err; } module_init(rd_init); module_exit(rd_cleanup); /* options - nonmodular */ #ifndef MODULE static int __init ramdisk_size(char *str) { rd_size = simple_strtol(str,NULL,0); return 1; } static int __init ramdisk_blocksize(char *str) { rd_blocksize = simple_strtol(str,NULL,0); return 1; } __setup("ramdisk_size=", ramdisk_size); __setup("ramdisk_blocksize=", ramdisk_blocksize); #endif /* options - modular */ module_param(rd_size, int, 0); MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); module_param(rd_blocksize, int, 0); MODULE_PARM_DESC(rd_blocksize, "Blocksize of each RAM disk in bytes."); MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR); MODULE_LICENSE("GPL");