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-rw-r--r--drivers/block/brd.c471
1 files changed, 471 insertions, 0 deletions
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 0000000000..970bd6ff38
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,471 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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/initrd.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/mutex.h>
+#include <linux/pagemap.h>
+#include <linux/xarray.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#include <linux/debugfs.h>
+
+#include <linux/uaccess.h>
+
+/*
+ * Each block ramdisk device has a xarray 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;
+ struct gendisk *brd_disk;
+ struct list_head brd_list;
+
+ /*
+ * Backing store of pages. This is the contents of the block device.
+ */
+ struct xarray brd_pages;
+ u64 brd_nr_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;
+
+ idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
+ page = xa_load(&brd->brd_pages, idx);
+
+ BUG_ON(page && page->index != idx);
+
+ return page;
+}
+
+/*
+ * Insert a new page for a given sector, if one does not already exist.
+ */
+static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
+{
+ pgoff_t idx;
+ struct page *page, *cur;
+ int ret = 0;
+
+ page = brd_lookup_page(brd, sector);
+ if (page)
+ return 0;
+
+ page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM);
+ if (!page)
+ return -ENOMEM;
+
+ xa_lock(&brd->brd_pages);
+
+ idx = sector >> PAGE_SECTORS_SHIFT;
+ page->index = idx;
+
+ cur = __xa_cmpxchg(&brd->brd_pages, idx, NULL, page, gfp);
+
+ if (unlikely(cur)) {
+ __free_page(page);
+ ret = xa_err(cur);
+ if (!ret && (cur->index != idx))
+ ret = -EIO;
+ } else {
+ brd->brd_nr_pages++;
+ }
+
+ xa_unlock(&brd->brd_pages);
+
+ return ret;
+}
+
+/*
+ * Free all backing store pages and xarray. This must only be called when
+ * there are no other users of the device.
+ */
+static void brd_free_pages(struct brd_device *brd)
+{
+ struct page *page;
+ pgoff_t idx;
+
+ xa_for_each(&brd->brd_pages, idx, page) {
+ __free_page(page);
+ cond_resched();
+ }
+
+ xa_destroy(&brd->brd_pages);
+}
+
+/*
+ * 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,
+ gfp_t gfp)
+{
+ unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+ size_t copy;
+ int ret;
+
+ copy = min_t(size_t, n, PAGE_SIZE - offset);
+ ret = brd_insert_page(brd, sector, gfp);
+ if (ret)
+ return ret;
+ if (copy < n) {
+ sector += copy >> SECTOR_SHIFT;
+ ret = brd_insert_page(brd, sector, gfp);
+ }
+ return ret;
+}
+
+/*
+ * 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);
+ memcpy(dst + offset, src, copy);
+ kunmap_atomic(dst);
+
+ 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);
+ memcpy(dst, src, copy);
+ kunmap_atomic(dst);
+ }
+}
+
+/*
+ * 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);
+ memcpy(dst, src + offset, copy);
+ kunmap_atomic(src);
+ } 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);
+ memcpy(dst, src, copy);
+ kunmap_atomic(src);
+ } 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, blk_opf_t opf,
+ sector_t sector)
+{
+ void *mem;
+ int err = 0;
+
+ if (op_is_write(opf)) {
+ /*
+ * Must use NOIO because we don't want to recurse back into the
+ * block or filesystem layers from page reclaim.
+ */
+ gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO;
+
+ err = copy_to_brd_setup(brd, sector, len, gfp);
+ if (err)
+ goto out;
+ }
+
+ mem = kmap_atomic(page);
+ if (!op_is_write(opf)) {
+ copy_from_brd(mem + off, brd, sector, len);
+ flush_dcache_page(page);
+ } else {
+ flush_dcache_page(page);
+ copy_to_brd(brd, mem + off, sector, len);
+ }
+ kunmap_atomic(mem);
+
+out:
+ return err;
+}
+
+static void brd_submit_bio(struct bio *bio)
+{
+ struct brd_device *brd = bio->bi_bdev->bd_disk->private_data;
+ sector_t sector = bio->bi_iter.bi_sector;
+ struct bio_vec bvec;
+ struct bvec_iter iter;
+
+ bio_for_each_segment(bvec, bio, iter) {
+ unsigned int len = bvec.bv_len;
+ int err;
+
+ /* Don't support un-aligned buffer */
+ WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) ||
+ (len & (SECTOR_SIZE - 1)));
+
+ err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset,
+ bio->bi_opf, sector);
+ if (err) {
+ if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) {
+ bio_wouldblock_error(bio);
+ return;
+ }
+ bio_io_error(bio);
+ return;
+ }
+ sector += len >> SECTOR_SHIFT;
+ }
+
+ bio_endio(bio);
+}
+
+static const struct block_device_operations brd_fops = {
+ .owner = THIS_MODULE,
+ .submit_bio = brd_submit_bio,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
+module_param(rd_nr, int, 0444);
+MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
+
+unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_size, ulong, 0444);
+MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+
+static int max_part = 1;
+module_param(max_part, int, 0444);
+MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
+MODULE_ALIAS("rd");
+
+#ifndef MODULE
+/* Legacy boot options - nonmodular */
+static int __init ramdisk_size(char *str)
+{
+ rd_size = simple_strtol(str, NULL, 0);
+ return 1;
+}
+__setup("ramdisk_size=", ramdisk_size);
+#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 struct dentry *brd_debugfs_dir;
+
+static int brd_alloc(int i)
+{
+ struct brd_device *brd;
+ struct gendisk *disk;
+ char buf[DISK_NAME_LEN];
+ int err = -ENOMEM;
+
+ list_for_each_entry(brd, &brd_devices, brd_list)
+ if (brd->brd_number == i)
+ return -EEXIST;
+ brd = kzalloc(sizeof(*brd), GFP_KERNEL);
+ if (!brd)
+ return -ENOMEM;
+ brd->brd_number = i;
+ list_add_tail(&brd->brd_list, &brd_devices);
+
+ xa_init(&brd->brd_pages);
+
+ snprintf(buf, DISK_NAME_LEN, "ram%d", i);
+ if (!IS_ERR_OR_NULL(brd_debugfs_dir))
+ debugfs_create_u64(buf, 0444, brd_debugfs_dir,
+ &brd->brd_nr_pages);
+
+ disk = brd->brd_disk = blk_alloc_disk(NUMA_NO_NODE);
+ if (!disk)
+ goto out_free_dev;
+
+ disk->major = RAMDISK_MAJOR;
+ disk->first_minor = i * max_part;
+ disk->minors = max_part;
+ disk->fops = &brd_fops;
+ disk->private_data = brd;
+ strscpy(disk->disk_name, buf, DISK_NAME_LEN);
+ set_capacity(disk, rd_size * 2);
+
+ /*
+ * This is so fdisk will align partitions on 4k, because of
+ * direct_access API needing 4k alignment, returning a PFN
+ * (This is only a problem on very small devices <= 4M,
+ * otherwise fdisk will align on 1M. Regardless this call
+ * is harmless)
+ */
+ blk_queue_physical_block_size(disk->queue, PAGE_SIZE);
+
+ /* Tell the block layer that this is not a rotational device */
+ blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
+ blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, disk->queue);
+ blk_queue_flag_set(QUEUE_FLAG_NOWAIT, disk->queue);
+ err = add_disk(disk);
+ if (err)
+ goto out_cleanup_disk;
+
+ return 0;
+
+out_cleanup_disk:
+ put_disk(disk);
+out_free_dev:
+ list_del(&brd->brd_list);
+ kfree(brd);
+ return err;
+}
+
+static void brd_probe(dev_t dev)
+{
+ brd_alloc(MINOR(dev) / max_part);
+}
+
+static void brd_cleanup(void)
+{
+ struct brd_device *brd, *next;
+
+ debugfs_remove_recursive(brd_debugfs_dir);
+
+ list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+ del_gendisk(brd->brd_disk);
+ put_disk(brd->brd_disk);
+ brd_free_pages(brd);
+ list_del(&brd->brd_list);
+ kfree(brd);
+ }
+}
+
+static inline void brd_check_and_reset_par(void)
+{
+ if (unlikely(!max_part))
+ max_part = 1;
+
+ /*
+ * make sure 'max_part' can be divided exactly by (1U << MINORBITS),
+ * otherwise, it is possiable to get same dev_t when adding partitions.
+ */
+ if ((1U << MINORBITS) % max_part != 0)
+ max_part = 1UL << fls(max_part);
+
+ if (max_part > DISK_MAX_PARTS) {
+ pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n",
+ DISK_MAX_PARTS, DISK_MAX_PARTS);
+ max_part = DISK_MAX_PARTS;
+ }
+}
+
+static int __init brd_init(void)
+{
+ int err, i;
+
+ brd_check_and_reset_par();
+
+ brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
+
+ for (i = 0; i < rd_nr; i++) {
+ err = brd_alloc(i);
+ if (err)
+ goto out_free;
+ }
+
+ /*
+ * brd module now has a feature to instantiate underlying device
+ * structure on-demand, provided that there is an access dev node.
+ *
+ * (1) if rd_nr is specified, create that many upfront. else
+ * it defaults to CONFIG_BLK_DEV_RAM_COUNT
+ * (2) User can further extend brd devices by create dev node themselves
+ * and have kernel automatically instantiate actual device
+ * on-demand. Example:
+ * mknod /path/devnod_name b 1 X # 1 is the rd major
+ * fdisk -l /path/devnod_name
+ * If (X / max_part) was not already created it will be created
+ * dynamically.
+ */
+
+ if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {
+ err = -EIO;
+ goto out_free;
+ }
+
+ pr_info("brd: module loaded\n");
+ return 0;
+
+out_free:
+ brd_cleanup();
+
+ pr_info("brd: module NOT loaded !!!\n");
+ return err;
+}
+
+static void __exit brd_exit(void)
+{
+
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+ brd_cleanup();
+
+ pr_info("brd: module unloaded\n");
+}
+
+module_init(brd_init);
+module_exit(brd_exit);
+