diff options
Diffstat (limited to 'drivers/block/rd.c')
| -rw-r--r-- | drivers/block/rd.c | 515 |
1 files changed, 515 insertions, 0 deletions
diff --git a/drivers/block/rd.c b/drivers/block/rd.c new file mode 100644 index 000000000000..145c1fbffe01 --- /dev/null +++ b/drivers/block/rd.c @@ -0,0 +1,515 @@ +/* + * 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/config.h> +#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/devfs_fs_kernel.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 = BLOCK_SIZE; /* blocksize of the RAM disks */ + +/* + * 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 the blockdev's mapping has to redirty the page so that the + * VM doesn't go and steal it. We return 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 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) +{ + SetPageDirty(page); + return 0; +} + +static 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, +}; + +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(request_queue_t *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, bio->bi_size, 0); + return 0; +fail: + bio_io_error(bio, bio->bi_size); + 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; + down(&bdev->bd_sem); + if (bdev->bd_openers <= 2) { + truncate_inode_pages(bdev->bd_inode->i_mapping, 0); + error = 0; + } + up(&bdev->bd_sem); + 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; + int 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 filesytem 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, 1); + blkdev_put(bdev); + } + del_gendisk(rd_disks[i]); + put_disk(rd_disks[i]); + blk_cleanup_queue(rd_queue[i]); + } + devfs_remove("rd"); + unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); +} + +/* + * This is the registration and initialization section of the RAM disk driver + */ +static int __init rd_init(void) +{ + int i; + int 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; + } + + if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) { + err = -EIO; + goto out; + } + + devfs_mk_dir("rd"); + + for (i = 0; i < CONFIG_BLK_DEV_RAM_COUNT; i++) { + struct gendisk *disk = rd_disks[i]; + + rd_queue[i] = blk_alloc_queue(GFP_KERNEL); + if (!rd_queue[i]) + goto out_queue; + + 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); + sprintf(disk->devfs_name, "rd/%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_queue: + unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); +out: + while (i--) { + put_disk(rd_disks[i]); + blk_cleanup_queue(rd_queue[i]); + } + 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_size2(char *str) /* kludge */ +{ + return ramdisk_size(str); +} +static int __init ramdisk_blocksize(char *str) +{ + rd_blocksize = simple_strtol(str,NULL,0); + return 1; +} +__setup("ramdisk=", ramdisk_size); +__setup("ramdisk_size=", ramdisk_size2); +__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"); |