Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [patch][rfc] rewrite ramdisk | Date | Tue, 16 Oct 2007 03:08:46 -0600 |
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Well on that same tune. But with a slightly different implementation. It compiles but I need to head to bed so I haven't had a chance to test it yet.
Nick it is very similar to yours with the big difference being that I embedded a struct address_space instead of rolled rerolled it by hand, which saves a lot of lines of code.
Eric
--- drivers/block/rd.c /* * 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>
#define RAMDISK_MINORS 250
struct ramdisk { struct address_space rd_mapping; struct gendisk *rd_disk; struct request_queue *rd_queue; struct list_head rd_list; };
/* Various static variables go here. Most are used only in the RAM disk code. */
static LIST_HEAD(ramdisks); static DEFINE_MUTEX(ramdisks_mutex);
/* * 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. */
static const struct address_space_operations ramdisk_aops = { .readpage = simple_readpage, .set_page_dirty = __set_page_dirty_no_writeback, };
static struct ramdisk *bdev_ramdisk(struct block_device *bdev) { return bdev->bd_disk->private_data; }
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)) { clear_highpage(page); SetPageUptodate(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 == WRITE) 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 ramdisk *rd = bdev_ramdisk(bdev); struct address_space * mapping = &rd->rd_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; struct ramdisk *rd = bdev_ramdisk(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 <= 1) { truncate_inode_pages(&rd->rd_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, .unplug_io_fn = default_unplug_io_fn, };
static struct block_device_operations rd_bd_op = { .owner = THIS_MODULE, .ioctl = rd_ioctl, };
static struct ramdisk *rd_alloc(int i) { struct ramdisk *rd; struct request_queue *queue; struct gendisk *disk; struct address_space *mapping;
rd = kzalloc(sizeof(*rd), GFP_KERNEL); if (!rd) goto out;
rd->rd_queue = queue = blk_alloc_queue(GFP_KERNEL); if (!rd->rd_queue) goto out_free_dev;
disk = rd->rd_disk = alloc_disk(1); if (!disk) goto out_free_queue;
mapping = &rd->rd_mapping; mapping->a_ops = &ramdisk_aops; mapping->backing_dev_info = &rd_backing_dev_info; mapping_set_gfp_mask(mapping, __GFP_WAIT | __GFP_HIGH | __GFP_HIGHMEM);
blk_queue_make_request(queue, &rd_make_request); blk_queue_hardsect_size(queue, rd_blocksize);
/* rd_size is given in kB */ disk->major = RAMDISK_MAJOR; disk->first_minor = i; disk->fops = &rd_bd_op; disk->queue = queue; disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; sprintf(disk->disk_name, "ram%d", i); set_capacity(disk, rd_size * 2); disk->private_data = rd; add_disk(rd->rd_disk); list_add_tail(&rd->rd_list, &ramdisks); return rd;
out_free_queue: blk_cleanup_queue(queue); out_free_dev: kfree(rd); out: return NULL; }
static void rd_free(struct ramdisk *rd) { del_gendisk(rd->rd_disk); put_disk(rd->rd_disk); blk_cleanup_queue(rd->rd_queue); truncate_inode_pages(&rd->rd_mapping, 0); list_del(&rd->rd_list); kfree(rd); }
static struct kobject *rd_probe(dev_t dev, int *part, void *data) { struct ramdisk *rd; struct kobject *kobj; unsigned int unit;
kobj = ERR_PTR(-ENOMEM); unit = MINOR(dev);
mutex_lock(&ramdisks_mutex); list_for_each_entry(rd, &ramdisks, rd_list) { if (rd->rd_disk->first_minor == unit) goto found; } rd = rd_alloc(MINOR(dev)); found: if (rd) kobj = get_disk(rd->rd_disk); mutex_unlock(&ramdisks_mutex);
*part = 0; return kobj; }
/* * Before freeing the module, invalidate all of the protected buffers! */ static void __exit rd_cleanup(void) { struct ramdisk *rd, *next;
list_for_each_entry_safe(rd, next, &ramdisks, rd_list) rd_free(rd);
blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), RAMDISK_MINORS); unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); }
/* * This is the registration and initialization section of the RAM disk driver */ static int __init rd_init(void) { 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; }
if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) return -EIO;
blk_register_region(MKDEV(RAMDISK_MAJOR, 0), RAMDISK_MINORS, THIS_MODULE, rd_probe, NULL, NULL);
/* 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; }
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);
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