1 files changed, 548 insertions, 0 deletions

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 000000000000..50b659bedc8f
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,548 @@
+/*
+ * Ram backed block device driver.
+ *
+ * Copyright (C) 2007 Nick Piggin
+ * Copyright (C) 2007 Novell Inc.
+ *
+ * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
+ * of their respective owners.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/major.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/highmem.h>
+#include <linux/gfp.h>
+#include <linux/radix-tree.h>
+#include <linux/buffer_head.h> /* invalidate_bh_lrus() */
+
+#include <asm/uaccess.h>
+
+#define SECTOR_SHIFT            9
+#define PAGE_SECTORS_SHIFT      (PAGE_SHIFT - SECTOR_SHIFT)
+#define PAGE_SECTORS            (1 << PAGE_SECTORS_SHIFT)
+
+/*
+ * Each block ramdisk device has a radix_tree brd_pages of pages that stores
+ * the pages containing the block device's contents. A brd page's ->index is
+ * its offset in PAGE_SIZE units. This is similar to, but in no way connected
+ * with, the kernel's pagecache or buffer cache (which sit above our block
+ * device).
+ */
+struct brd_device {
+        int             brd_number;
+        int             brd_refcnt;
+        loff_t          brd_offset;
+        loff_t          brd_sizelimit;
+        unsigned        brd_blocksize;
+
+        struct request_queue    *brd_queue;
+        struct gendisk          *brd_disk;
+        struct list_head        brd_list;
+
+        /*
+         * Backing store of pages and lock to protect it. This is the contents
+         * of the block device.
+         */
+        spinlock_t              brd_lock;
+        struct radix_tree_root  brd_pages;
+};
+
+/*
+ * Look up and return a brd's page for a given sector.
+ */
+static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
+{
+        pgoff_t idx;
+        struct page *page;
+
+        /*
+         * The page lifetime is protected by the fact that we have opened the
+         * device node -- brd pages will never be deleted under us, so we
+         * don't need any further locking or refcounting.
+         *
+         * This is strictly true for the radix-tree nodes as well (ie. we
+         * don't actually need the rcu_read_lock()), however that is not a
+         * documented feature of the radix-tree API so it is better to be
+         * safe here (we don't have total exclusion from radix tree updates
+         * here, only deletes).
+         */
+        rcu_read_lock();
+        idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
+        page = radix_tree_lookup(&brd->brd_pages, idx);
+        rcu_read_unlock();
+
+        BUG_ON(page && page->index != idx);
+
+        return page;
+}
+
+/*
+ * Look up and return a brd's page for a given sector.
+ * If one does not exist, allocate an empty page, and insert that. Then
+ * return it.
+ */
+static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
+{
+        pgoff_t idx;
+        struct page *page;
+
+        page = brd_lookup_page(brd, sector);
+        if (page)
+                return page;
+
+        /*
+         * Must use NOIO because we don't want to recurse back into the
+         * block or filesystem layers from page reclaim.
+         */
+        page = alloc_page(GFP_NOIO | __GFP_HIGHMEM | __GFP_ZERO);
+        if (!page)
+                return NULL;
+
+        if (radix_tree_preload(GFP_NOIO)) {
+                __free_page(page);
+                return NULL;
+        }
+
+        spin_lock(&brd->brd_lock);
+        idx = sector >> PAGE_SECTORS_SHIFT;
+        if (radix_tree_insert(&brd->brd_pages, idx, page)) {
+                __free_page(page);
+                page = radix_tree_lookup(&brd->brd_pages, idx);
+                BUG_ON(!page);
+                BUG_ON(page->index != idx);
+        } else
+                page->index = idx;
+        spin_unlock(&brd->brd_lock);
+
+        radix_tree_preload_end();
+
+        return page;
+}
+
+/*
+ * Free all backing store pages and radix tree. This must only be called when
+ * there are no other users of the device.
+ */
+#define FREE_BATCH 16
+static void brd_free_pages(struct brd_device *brd)
+{
+        unsigned long pos = 0;
+        struct page *pages[FREE_BATCH];
+        int nr_pages;
+
+        do {
+                int i;
+
+                nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
+                                (void **)pages, pos, FREE_BATCH);
+
+                for (i = 0; i < nr_pages; i++) {
+                        void *ret;
+
+                        BUG_ON(pages[i]->index < pos);
+                        pos = pages[i]->index;
+                        ret = radix_tree_delete(&brd->brd_pages, pos);
+                        BUG_ON(!ret || ret != pages[i]);
+                        __free_page(pages[i]);
+                }
+
+                pos++;
+
+                /*
+                 * This assumes radix_tree_gang_lookup always returns as
+                 * many pages as possible. If the radix-tree code changes,
+                 * so will this have to.
+                 */
+        } while (nr_pages == FREE_BATCH);
+}
+
+/*
+ * copy_to_brd_setup must be called before copy_to_brd. It may sleep.
+ */
+static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
+{
+        unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+        size_t copy;
+
+        copy = min_t(size_t, n, PAGE_SIZE - offset);
+        if (!brd_insert_page(brd, sector))
+                return -ENOMEM;
+        if (copy < n) {
+                sector += copy >> SECTOR_SHIFT;
+                if (!brd_insert_page(brd, sector))
+                        return -ENOMEM;
+        }
+        return 0;
+}
+
+/*
+ * Copy n bytes from src to the brd starting at sector. Does not sleep.
+ */
+static void copy_to_brd(struct brd_device *brd, const void *src,
+                        sector_t sector, size_t n)
+{
+        struct page *page;
+        void *dst;
+        unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+        size_t copy;
+
+        copy = min_t(size_t, n, PAGE_SIZE - offset);
+        page = brd_lookup_page(brd, sector);
+        BUG_ON(!page);
+
+        dst = kmap_atomic(page, KM_USER1);
+        memcpy(dst + offset, src, copy);
+        kunmap_atomic(dst, KM_USER1);
+
+        if (copy < n) {
+                src += copy;
+                sector += copy >> SECTOR_SHIFT;
+                copy = n - copy;
+                page = brd_lookup_page(brd, sector);
+                BUG_ON(!page);
+
+                dst = kmap_atomic(page, KM_USER1);
+                memcpy(dst, src, copy);
+                kunmap_atomic(dst, KM_USER1);
+        }
+}
+
+/*
+ * Copy n bytes to dst from the brd starting at sector. Does not sleep.
+ */
+static void copy_from_brd(void *dst, struct brd_device *brd,
+                        sector_t sector, size_t n)
+{
+        struct page *page;
+        void *src;
+        unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+        size_t copy;
+
+        copy = min_t(size_t, n, PAGE_SIZE - offset);
+        page = brd_lookup_page(brd, sector);
+        if (page) {
+                src = kmap_atomic(page, KM_USER1);
+                memcpy(dst, src + offset, copy);
+                kunmap_atomic(src, KM_USER1);
+        } else
+                memset(dst, 0, copy);
+
+        if (copy < n) {
+                dst += copy;
+                sector += copy >> SECTOR_SHIFT;
+                copy = n - copy;
+                page = brd_lookup_page(brd, sector);
+                if (page) {
+                        src = kmap_atomic(page, KM_USER1);
+                        memcpy(dst, src, copy);
+                        kunmap_atomic(src, KM_USER1);
+                } else
+                        memset(dst, 0, copy);
+        }
+}
+
+/*
+ * Process a single bvec of a bio.
+ */
+static int brd_do_bvec(struct brd_device *brd, struct page *page,
+                        unsigned int len, unsigned int off, int rw,
+                        sector_t sector)
+{
+        void *mem;
+        int err = 0;
+
+        if (rw != READ) {
+                err = copy_to_brd_setup(brd, sector, len);
+                if (err)
+                        goto out;
+        }
+
+        mem = kmap_atomic(page, KM_USER0);
+        if (rw == READ) {
+                copy_from_brd(mem + off, brd, sector, len);
+                flush_dcache_page(page);
+        } else
+                copy_to_brd(brd, mem + off, sector, len);
+        kunmap_atomic(mem, KM_USER0);
+
+out:
+        return err;
+}
+
+static int brd_make_request(struct request_queue *q, struct bio *bio)
+{
+        struct block_device *bdev = bio->bi_bdev;
+        struct brd_device *brd = bdev->bd_disk->private_data;
+        int rw;
+        struct bio_vec *bvec;
+        sector_t sector;
+        int i;
+        int err = -EIO;
+
+        sector = bio->bi_sector;
+        if (sector + (bio->bi_size >> SECTOR_SHIFT) >
+                                                get_capacity(bdev->bd_disk))
+                goto out;
+
+        rw = bio_rw(bio);
+        if (rw == READA)
+                rw = READ;
+
+        bio_for_each_segment(bvec, bio, i) {
+                unsigned int len = bvec->bv_len;
+                err = brd_do_bvec(brd, bvec->bv_page, len,
+                                        bvec->bv_offset, rw, sector);
+                if (err)
+                        break;
+                sector += len >> SECTOR_SHIFT;
+        }
+
+out:
+        bio_endio(bio, err);
+
+        return 0;
+}
+
+static int brd_ioctl(struct inode *inode, struct file *file,
+                        unsigned int cmd, unsigned long arg)
+{
+        int error;
+        struct block_device *bdev = inode->i_bdev;
+        struct brd_device *brd = bdev->bd_disk->private_data;
+
+        if (cmd != BLKFLSBUF)
+                return -ENOTTY;
+
+        /*
+         * ram device BLKFLSBUF has special semantics, we want to actually
+         * release and destroy the ramdisk data.
+         */
+        mutex_lock(&bdev->bd_mutex);
+        error = -EBUSY;
+        if (bdev->bd_openers <= 1) {
+                /*
+                 * Invalidate the cache first, so it isn't written
+                 * back to the device.
+                 *
+                 * Another thread might instantiate more buffercache here,
+                 * but there is not much we can do to close that race.
+                 */
+                invalidate_bh_lrus();
+                truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
+                brd_free_pages(brd);
+                error = 0;
+        }
+        mutex_unlock(&bdev->bd_mutex);
+
+        return error;
+}
+
+static struct block_device_operations brd_fops = {
+        .owner =        THIS_MODULE,
+        .ioctl =        brd_ioctl,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int rd_nr;
+int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_nr, int, 0);
+MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
+module_param(rd_size, int, 0);
+MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
+
+#ifndef MODULE
+/* Legacy boot options - nonmodular */
+static int __init ramdisk_size(char *str)
+{
+        rd_size = simple_strtol(str, NULL, 0);
+        return 1;
+}
+static int __init ramdisk_size2(char *str)
+{
+        return ramdisk_size(str);
+}
+__setup("ramdisk=", ramdisk_size);
+__setup("ramdisk_size=", ramdisk_size2);
+#endif
+
+/*
+ * The device scheme is derived from loop.c. Keep them in synch where possible
+ * (should share code eventually).
+ */
+static LIST_HEAD(brd_devices);
+static DEFINE_MUTEX(brd_devices_mutex);
+
+static struct brd_device *brd_alloc(int i)
+{
+        struct brd_device *brd;
+        struct gendisk *disk;
+
+        brd = kzalloc(sizeof(*brd), GFP_KERNEL);
+        if (!brd)
+                goto out;
+        brd->brd_number         = i;
+        spin_lock_init(&brd->brd_lock);
+        INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
+
+        brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
+        if (!brd->brd_queue)
+                goto out_free_dev;
+        blk_queue_make_request(brd->brd_queue, brd_make_request);
+        blk_queue_max_sectors(brd->brd_queue, 1024);
+        blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
+
+        disk = brd->brd_disk = alloc_disk(1);
+        if (!disk)
+                goto out_free_queue;
+        disk->major             = RAMDISK_MAJOR;
+        disk->first_minor       = i;
+        disk->fops              = &brd_fops;
+        disk->private_data      = brd;
+        disk->queue             = brd->brd_queue;
+        sprintf(disk->disk_name, "ram%d", i);
+        set_capacity(disk, rd_size * 2);
+
+        return brd;
+
+out_free_queue:
+        blk_cleanup_queue(brd->brd_queue);
+out_free_dev:
+        kfree(brd);
+out:
+        return NULL;
+}
+
+static void brd_free(struct brd_device *brd)
+{
+        put_disk(brd->brd_disk);
+        blk_cleanup_queue(brd->brd_queue);
+        brd_free_pages(brd);
+        kfree(brd);
+}
+
+static struct brd_device *brd_init_one(int i)
+{
+        struct brd_device *brd;
+
+        list_for_each_entry(brd, &brd_devices, brd_list) {
+                if (brd->brd_number == i)
+                        goto out;
+        }
+
+        brd = brd_alloc(i);
+        if (brd) {
+                add_disk(brd->brd_disk);
+                list_add_tail(&brd->brd_list, &brd_devices);
+        }
+out:
+        return brd;
+}
+
+static void brd_del_one(struct brd_device *brd)
+{
+        list_del(&brd->brd_list);
+        del_gendisk(brd->brd_disk);
+        brd_free(brd);
+}
+
+static struct kobject *brd_probe(dev_t dev, int *part, void *data)
+{
+        struct brd_device *brd;
+        struct kobject *kobj;
+
+        mutex_lock(&brd_devices_mutex);
+        brd = brd_init_one(dev & MINORMASK);
+        kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);
+        mutex_unlock(&brd_devices_mutex);
+
+        *part = 0;
+        return kobj;
+}
+
+static int __init brd_init(void)
+{
+        int i, nr;
+        unsigned long range;
+        struct brd_device *brd, *next;
+
+        /*
+         * brd module now has a feature to instantiate underlying device
+         * structure on-demand, provided that there is an access dev node.
+         * However, this will not work well with user space tool that doesn't
+         * know about such "feature".  In order to not break any existing
+         * tool, we do the following:
+         *
+         * (1) if rd_nr is specified, create that many upfront, and this
+         *     also becomes a hard limit.
+         * (2) if rd_nr is not specified, create 1 rd device on module
+         *     load, user can further extend brd device by create dev node
+         *     themselves and have kernel automatically instantiate actual
+         *     device on-demand.
+         */
+        if (rd_nr > 1UL << MINORBITS)
+                return -EINVAL;
+
+        if (rd_nr) {
+                nr = rd_nr;
+                range = rd_nr;
+        } else {
+                nr = CONFIG_BLK_DEV_RAM_COUNT;
+                range = 1UL << MINORBITS;
+        }
+
+        if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
+                return -EIO;
+
+        for (i = 0; i < nr; i++) {
+                brd = brd_alloc(i);
+                if (!brd)
+                        goto out_free;
+                list_add_tail(&brd->brd_list, &brd_devices);
+        }
+
+        /* point of no return */
+
+        list_for_each_entry(brd, &brd_devices, brd_list)
+                add_disk(brd->brd_disk);
+
+        blk_register_region(MKDEV(RAMDISK_MAJOR, 0), range,
+                                  THIS_MODULE, brd_probe, NULL, NULL);
+
+        printk(KERN_INFO "brd: module loaded\n");
+        return 0;
+
+out_free:
+        list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+                list_del(&brd->brd_list);
+                brd_free(brd);
+        }
+
+        unregister_blkdev(RAMDISK_MAJOR, "brd");
+        return -ENOMEM;
+}
+
+static void __exit brd_exit(void)
+{
+        unsigned long range;
+        struct brd_device *brd, *next;
+
+        range = rd_nr ? rd_nr :  1UL << MINORBITS;
+
+        list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
+                brd_del_one(brd);
+
+        blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);
+        unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+}
+
+module_init(brd_init);
+module_exit(brd_exit);
+