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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /drivers/block/brd.c
Initial import
Diffstat (limited to 'drivers/block/brd.c')
-rw-r--r--drivers/block/brd.c651
1 files changed, 651 insertions, 0 deletions
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 000000000..64ab4951e
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,651 @@
+/*
+ * 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/mutex.h>
+#include <linux/radix-tree.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+
+#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;
+
+ 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 DEFINE_MUTEX(brd_mutex);
+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;
+ gfp_t gfp_flags;
+
+ 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.
+ *
+ * Cannot support DAX and highmem, because our ->direct_access
+ * routine for DAX must return memory that is always addressable.
+ * If DAX was reworked to use pfns and kmap throughout, this
+ * restriction might be able to be lifted.
+ */
+ gfp_flags = GFP_NOIO | __GFP_ZERO;
+#ifndef CONFIG_BLK_DEV_RAM_DAX
+ gfp_flags |= __GFP_HIGHMEM;
+#endif
+ page = alloc_page(gfp_flags);
+ 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;
+ page->index = idx;
+ 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);
+ }
+ spin_unlock(&brd->brd_lock);
+
+ radix_tree_preload_end();
+
+ return page;
+}
+
+static void brd_free_page(struct brd_device *brd, sector_t sector)
+{
+ struct page *page;
+ pgoff_t idx;
+
+ spin_lock(&brd->brd_lock);
+ idx = sector >> PAGE_SECTORS_SHIFT;
+ page = radix_tree_delete(&brd->brd_pages, idx);
+ spin_unlock(&brd->brd_lock);
+ if (page)
+ __free_page(page);
+}
+
+static void brd_zero_page(struct brd_device *brd, sector_t sector)
+{
+ struct page *page;
+
+ page = brd_lookup_page(brd, sector);
+ if (page)
+ clear_highpage(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 -ENOSPC;
+ if (copy < n) {
+ sector += copy >> SECTOR_SHIFT;
+ if (!brd_insert_page(brd, sector))
+ return -ENOSPC;
+ }
+ return 0;
+}
+
+static void discard_from_brd(struct brd_device *brd,
+ sector_t sector, size_t n)
+{
+ while (n >= PAGE_SIZE) {
+ /*
+ * Don't want to actually discard pages here because
+ * re-allocating the pages can result in writeback
+ * deadlocks under heavy load.
+ */
+ if (0)
+ brd_free_page(brd, sector);
+ else
+ brd_zero_page(brd, sector);
+ sector += PAGE_SIZE >> SECTOR_SHIFT;
+ n -= PAGE_SIZE;
+ }
+}
+
+/*
+ * 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, 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);
+ if (rw == READ) {
+ 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_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;
+ struct bvec_iter iter;
+ int err = -EIO;
+
+ sector = bio->bi_iter.bi_sector;
+ if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
+ goto out;
+
+ if (unlikely(bio->bi_rw & REQ_DISCARD)) {
+ err = 0;
+ discard_from_brd(brd, sector, bio->bi_iter.bi_size);
+ goto out;
+ }
+
+ rw = bio_rw(bio);
+ if (rw == READA)
+ rw = READ;
+
+ bio_for_each_segment(bvec, bio, iter) {
+ 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);
+}
+
+static int brd_rw_page(struct block_device *bdev, sector_t sector,
+ struct page *page, int rw)
+{
+ struct brd_device *brd = bdev->bd_disk->private_data;
+ int err = brd_do_bvec(brd, page, PAGE_CACHE_SIZE, 0, rw, sector);
+ page_endio(page, rw & WRITE, err);
+ return err;
+}
+
+#ifdef CONFIG_BLK_DEV_RAM_DAX
+static long brd_direct_access(struct block_device *bdev, sector_t sector,
+ void **kaddr, unsigned long *pfn, long size)
+{
+ struct brd_device *brd = bdev->bd_disk->private_data;
+ struct page *page;
+
+ if (!brd)
+ return -ENODEV;
+ page = brd_insert_page(brd, sector);
+ if (!page)
+ return -ENOSPC;
+ *kaddr = page_address(page);
+ *pfn = page_to_pfn(page);
+
+ /*
+ * TODO: If size > PAGE_SIZE, we could look to see if the next page in
+ * the file happens to be mapped to the next page of physical RAM.
+ */
+ return PAGE_SIZE;
+}
+#else
+#define brd_direct_access NULL
+#endif
+
+static int brd_ioctl(struct block_device *bdev, fmode_t mode,
+ unsigned int cmd, unsigned long arg)
+{
+ int error;
+ 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(&brd_mutex);
+ mutex_lock(&bdev->bd_mutex);
+ error = -EBUSY;
+ if (bdev->bd_openers <= 1) {
+ /*
+ * Kill 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.
+ */
+ kill_bdev(bdev);
+ brd_free_pages(brd);
+ error = 0;
+ }
+ mutex_unlock(&bdev->bd_mutex);
+ mutex_unlock(&brd_mutex);
+
+ return error;
+}
+
+static const struct block_device_operations brd_fops = {
+ .owner = THIS_MODULE,
+ .rw_page = brd_rw_page,
+ .ioctl = brd_ioctl,
+ .direct_access = brd_direct_access,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
+module_param(rd_nr, int, S_IRUGO);
+MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
+
+int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_size, int, S_IRUGO);
+MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+
+static int max_part = 1;
+module_param(max_part, int, S_IRUGO);
+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 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_hw_sectors(brd->brd_queue, 1024);
+ blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
+
+ /* 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(brd->brd_queue, PAGE_SIZE);
+
+ brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
+ brd->brd_queue->limits.max_discard_sectors = UINT_MAX;
+ brd->brd_queue->limits.discard_zeroes_data = 1;
+ queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
+
+ disk = brd->brd_disk = alloc_disk(max_part);
+ if (!disk)
+ goto out_free_queue;
+ disk->major = RAMDISK_MAJOR;
+ disk->first_minor = i * max_part;
+ disk->fops = &brd_fops;
+ disk->private_data = brd;
+ disk->queue = brd->brd_queue;
+ disk->flags = GENHD_FL_EXT_DEVT;
+ 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, bool *new)
+{
+ struct brd_device *brd;
+
+ *new = false;
+ 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);
+ }
+ *new = true;
+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;
+ bool new;
+
+ mutex_lock(&brd_devices_mutex);
+ brd = brd_init_one(MINOR(dev) / max_part, &new);
+ kobj = brd ? get_disk(brd->brd_disk) : NULL;
+ mutex_unlock(&brd_devices_mutex);
+
+ if (new)
+ *part = 0;
+
+ return kobj;
+}
+
+static int __init brd_init(void)
+{
+ struct brd_device *brd, *next;
+ int i;
+
+ /*
+ * 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"))
+ return -EIO;
+
+ if (unlikely(!max_part))
+ max_part = 1;
+
+ for (i = 0; i < rd_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), 1UL << MINORBITS,
+ THIS_MODULE, brd_probe, NULL, NULL);
+
+ pr_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, "ramdisk");
+
+ pr_info("brd: module NOT loaded !!!\n");
+ return -ENOMEM;
+}
+
+static void __exit brd_exit(void)
+{
+ struct brd_device *brd, *next;
+
+ list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
+ brd_del_one(brd);
+
+ blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS);
+ unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+
+ pr_info("brd: module unloaded\n");
+}
+
+module_init(brd_init);
+module_exit(brd_exit);
+