Block device emulation on top of ubi volumes with read/write support.
Block devices get automatically created for each ubi volume present.
Each ubiblock is fairly cheap since it's based on workqueues
and not on threads.
Read/write access is expected to work fairly well because the
request queue at block elevator orders block transfers to be space-effective.
In other words, it's expected that reads and writes gets ordered
to point to the same LEB.
To help this and reduce access to the UBI volume, a 1-LEB size
write-back cache has been implemented.
Every read and every write, goes through this cache and the write is
only done when a request arrives to read or write to a different LEB
or when the device is released, when the last file handle is closed.
This cache is 1-LEB bytes, vmalloced at open() and freed at release().
Cc: Artem Bityutskiy <dedeki...@gmail.com>
Signed-off-by: Ezequiel Garcia <elezegar...@gmail.com>
---
drivers/mtd/ubi/Kconfig | 12 +
drivers/mtd/ubi/Makefile | 1 +
drivers/mtd/ubi/ubiblock.c | 673 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 686 insertions(+), 0 deletions(-)
create mode 100644 drivers/mtd/ubi/ubiblock.c
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 36663af..aa6c592 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -87,4 +87,16 @@ config MTD_UBI_GLUEBI
work on top of UBI. Do not enable this unless you use legacy
software.
+config MTD_UBI_BLOCK
+ tristate "Caching block device access to UBI volumes"
+ help
+ Since UBI already takes care of eraseblock wear leveling
+ and bad block handling, it's possible to implement a block
+ device on top of it and therefore mount regular filesystems
+ (i.e. not flash-oriented, as ext4).
+
+ In other words, this is a software flash translation layer.
+
+ If in doubt, say "N".
+
endif # MTD_UBI
diff --git a/drivers/mtd/ubi/Makefile b/drivers/mtd/ubi/Makefile
index b46b0c97..1578733 100644
--- a/drivers/mtd/ubi/Makefile
+++ b/drivers/mtd/ubi/Makefile
@@ -5,3 +5,4 @@ ubi-y += misc.o debug.o
ubi-$(CONFIG_MTD_UBI_FASTMAP) += fastmap.o
obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
+obj-$(CONFIG_MTD_UBI_BLOCK) += ubiblock.o
diff --git a/drivers/mtd/ubi/ubiblock.c b/drivers/mtd/ubi/ubiblock.c
new file mode 100644
index 0000000..97655c1
--- /dev/null
+++ b/drivers/mtd/ubi/ubiblock.c
@@ -0,0 +1,673 @@
+/*
+ * Copyright (c) 2012 Ezequiel Garcia
+ * Copyright (c) 2011 Free Electrons
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ * the GNU General Public License for more details.
+ *
+ */
+
+/*#define DEBUG*/
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/mtd/ubi.h>
+#include <linux/workqueue.h>
+#include <linux/blkdev.h>
+
+#include "ubi-media.h"
+
+struct ubiblock {
+ struct ubi_volume_desc *desc;
+ struct ubi_volume_info *vi;
+ int ubi_num;
+ int vol_id;
+ int refcnt;
+
+ struct gendisk *gd;
+ struct request_queue *rq;
+
+ struct workqueue_struct *wq;
+ struct work_struct work;
+
+ struct mutex vol_mutex;
+ spinlock_t queue_lock;
+ struct list_head list;
+
+ enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
+ void *cache;
+ int cache_leb_num;
+ int leb_size;
+
+#ifdef DEBUG
+ /*
+ * TODO: Output this information through a debugfs file.
+ * We can re-use ubi debugfs directories.
+ */
+ unsigned cache_read_hit, cache_read_miss;
+ unsigned cache_write_hit, cache_write_miss;
+#endif
+};
+
+/* Linked list of all ubiblock instances */
+static LIST_HEAD(ubiblock_devices);
+static DEFINE_MUTEX(devices_mutex);
+static int ubiblock_major;
+
+static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
+{
+ struct ubiblock *dev;
+
+ list_for_each_entry(dev, &ubiblock_devices, list)
+ if (dev->ubi_num == ubi_num && dev->vol_id == vol_id)
+ return dev;
+ return NULL;
+}
+
+static bool leb_on_cache(struct ubiblock *dev, int leb_num)
+{
+ return dev->cache_leb_num == leb_num;
+}
+
+static int ubiblock_fill_cache(struct ubiblock *dev, int leb_num)
+{
+ int ret;
+
+ /* Warn if we fill cache while being dirty */
+ WARN_ON(dev->cache_state == STATE_DIRTY);
+
+ dev->cache_leb_num = leb_num;
+ dev->cache_state = STATE_CLEAN;
+
+ ret = ubi_read(dev->desc, leb_num, dev->cache, 0, dev->leb_size);
+ if (ret) {
+ dev_err(disk_to_dev(dev->gd), "ubi_read error %d\n", ret);
+ return ret;
+ }
+ return 0;
+}
+
+static int ubiblock_flush(struct ubiblock *dev, bool sync)
+{
+ int ret = 0;
+
+ if (dev->cache_state != STATE_DIRTY)
+ return 0;
+
+ /*
+ * TODO: mtdblock sets STATE_EMPTY, arguing that it prevents the
+ * underlying media to get changed without notice.
+ * I'm not fully convinced, so I just put STATE_CLEAN.
+ */
+ dev->cache_state = STATE_CLEAN;
+
+ /* Atomically change leb with buffer contents */
+ ret = ubi_leb_change(dev->desc, dev->cache_leb_num,
+ dev->cache, dev->leb_size);
+ if (ret) {
+ dev_err(disk_to_dev(dev->gd), "ubi_leb_change error %d\n", ret);
+ return ret;
+ }
+
+ /* Sync ubi device when device is released and on block flush ioctl */
+ if (sync)
+ ret = ubi_sync(dev->ubi_num);
+
+ return ret;
+}
+
+static int ubiblock_read(struct ubiblock *dev, char *buffer,
+ int pos, int len)
+{
+ int leb, offset, ret;
+ int bytes_left = len;
+ int to_read = len;
+ bool cached;
+
+ /* Get leb:offset address to read from */
+ leb = pos / dev->leb_size;
+ offset = pos % dev->leb_size;
+
+ while (bytes_left) {
+
+ /*
+ * We can only read one leb at a time.
+ * Therefore if the read length is larger than
+ * one leb size, we split the operation.
+ */
+ if (offset + to_read > dev->leb_size)
+ to_read = dev->leb_size - offset;
+
+ /*
+ * If leb is not cached, we flush current cached leb to disk
+ * and read new leb to cache. Then we read from cache to buffer.
+ * This means we share the cache between reads and writes.
+ *
+ * Might this be suboptimal, it's possible to:
+ * 1. Split caches, though this looks overly complicated.
+ * 2. Don't read always from cache, but rather from cache only
+ * if the leb is cached, and from disk otherwise.
+ */
+ cached = leb_on_cache(dev, leb);
+ if (!cached) {
+ ret = ubiblock_flush(dev, false);
+ if (ret)
+ return ret;
+
+ ret = ubiblock_fill_cache(dev, leb);
+ if (ret)
+ return ret;
+ }
+ memcpy(buffer, dev->cache + offset, to_read);
+
+ buffer += to_read;
+ bytes_left -= to_read;
+ to_read = bytes_left;
+ leb++;
+ offset = 0;
+#ifdef DEBUG
+ if (cached)
+ dev->cache_read_hit++;
+ else
+ dev->cache_read_miss++;
+#endif
+ }
+ return 0;
+}
+
+static int ubiblock_write(struct ubiblock *dev, const char *buffer,
+ int pos, int len)
+{
+ int leb, offset, ret;
+ int bytes_left = len;
+ int to_write = len;
+ bool cached;
+
+ /* Get (leb:offset) address to write */
+ leb = pos / dev->leb_size;
+ offset = pos % dev->leb_size;
+
+ while (bytes_left) {
+ /*
+ * We can only write one leb at a time.
+ * Therefore if the write length is larger than
+ * one leb size, we split the operation.
+ */
+ if (offset + to_write > dev->leb_size)
+ to_write = dev->leb_size - offset;
+
+ /*
+ * If leb is not cached, we flush current cached leb to disk
+ * and read new leb to cache. Then we write to cached buffer.
+ */
+ cached = leb_on_cache(dev, leb);
+ if (!cached) {
+ ret = ubiblock_flush(dev, false);
+ if (ret)
+ return ret;
+
+ ret = ubiblock_fill_cache(dev, leb);
+ if (ret)
+ return ret;
+ }
+
+ /* Write to local cache */
+ memcpy(dev->cache + offset, buffer, to_write);
+
+ /* This is the only place where we dirt the cache */
+ dev->cache_state = STATE_DIRTY;
+
+ buffer += to_write;
+ bytes_left -= to_write;
+ to_write = bytes_left;
+ offset = 0;
+ leb++;
+#ifdef DEBUG
+ if (cached)
+ dev->cache_write_hit++;
+ else
+ dev->cache_write_miss++;
+#endif
+ }
+ return 0;
+}
+
+static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
+{
+ int pos, len;
+
+ if (req->cmd_type != REQ_TYPE_FS)
+ return -EIO;
+
+ if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
+ get_capacity(req->rq_disk))
+ return -EIO;
+
+ pos = blk_rq_pos(req) << 9;
+ len = blk_rq_cur_bytes(req);
+
+ switch (rq_data_dir(req)) {
+ case READ:
+ return ubiblock_read(dev, req->buffer, pos, len);
+ case WRITE:
+ return ubiblock_write(dev, req->buffer, pos, len);
+ default:
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static void ubiblock_do_work(struct work_struct *work)
+{
+ struct ubiblock *dev =
+ container_of(work, struct ubiblock, work);
+ struct request_queue *rq = dev->rq;
+ struct request *req;
+ int res;
+
+ spin_lock_irq(rq->queue_lock);
+
+ req = blk_fetch_request(rq);
+ while (req) {
+
+ spin_unlock_irq(rq->queue_lock);
+
+ mutex_lock(&dev->vol_mutex);
+ res = do_ubiblock_request(dev, req);
+ mutex_unlock(&dev->vol_mutex);
+
+ spin_lock_irq(rq->queue_lock);
+
+ /*
+ * If we're done with this request,
+ * we need to fetch a new one
+ */
+ if (!__blk_end_request_cur(req, res))
+ req = blk_fetch_request(rq);
+ }
+
+ spin_unlock_irq(rq->queue_lock);
+}
+
+static void ubiblock_request(struct request_queue *rq)
+{
+ struct ubiblock *dev;
+ struct request *req;
+
+ dev = rq->queuedata;
+
+ if (!dev)
+ while ((req = blk_fetch_request(rq)) != NULL)
+ __blk_end_request_all(req, -ENODEV);
+ else
+ queue_work(dev->wq, &dev->work);
+}
+
+static int ubiblock_open(struct block_device *bdev, fmode_t mode)
+{
+ struct ubiblock *dev = bdev->bd_disk->private_data;
+ int ubi_mode = UBI_READONLY;
+ int ret;
+
+ mutex_lock(&dev->vol_mutex);
+ if (dev->refcnt > 0) {
+ /*
+ * The volume is already opened,
+ * just increase the reference counter
+ */
+ dev->refcnt++;
+ mutex_unlock(&dev->vol_mutex);
+ return 0;
+ }
+
+ if (mode & FMODE_WRITE)
+ ubi_mode = UBI_READWRITE;
+
+ dev->desc = ubi_open_volume(dev->ubi_num, dev->vol_id, ubi_mode);
+ if (IS_ERR(dev->desc)) {
+ dev_err(disk_to_dev(dev->gd),
+ "failed to open ubi volume %d_%d\n",
+ dev->ubi_num, dev->vol_id);
+
+ ret = PTR_ERR(dev->desc);
+ dev->desc = NULL;
+ goto out_unlock;
+ }
+
+ dev->vi = kzalloc(sizeof(struct ubi_volume_info), GFP_KERNEL);
+ if (!dev->vi) {
+ ret = -ENOMEM;
+ goto out_close;
+ }
+ ubi_get_volume_info(dev->desc, dev->vi);
+
+ /* Allocate cache buffer, mtdblock uses vmalloc and we do too */
+ dev->leb_size = dev->vi->usable_leb_size;
+ dev->cache_leb_num = -1;
+ dev->cache = vmalloc(dev->leb_size);
+ if (!dev->cache) {
+ ret = -ENOMEM;
+ goto out_free;
+ }
+
+ dev->refcnt++;
+ mutex_unlock(&dev->vol_mutex);
+ return 0;
+
+out_free:
+ kfree(dev->vi);
+out_close:
+ ubi_close_volume(dev->desc);
+ dev->desc = NULL;
+out_unlock:
+ mutex_unlock(&dev->vol_mutex);
+ return ret;
+}
+
+static int ubiblock_release(struct gendisk *gd, fmode_t mode)
+{
+ struct ubiblock *dev = gd->private_data;
+
+ mutex_lock(&dev->vol_mutex);
+
+ dev->refcnt--;
+ if (dev->refcnt == 0) {
+ ubiblock_flush(dev, true);
+
+ vfree(dev->cache);
+ dev->cache_leb_num = -1;
+ dev->cache_state = STATE_EMPTY;
+
+ kfree(dev->vi);
+ ubi_close_volume(dev->desc);
+
+ dev->vi = NULL;
+ dev->desc = NULL;
+ }
+
+ mutex_unlock(&dev->vol_mutex);
+ return 0;
+}
+
+static int ubiblock_ioctl(struct block_device *bdev, fmode_t mode,
+ unsigned int cmd, unsigned long arg)
+{
+ struct ubiblock *dev = bdev->bd_disk->private_data;
+ int ret = -ENXIO;
+
+ if (!dev)
+ return ret;
+
+ mutex_lock(&dev->vol_mutex);
+
+ /* I can't get this to get called. What's going on? */
+ switch (cmd) {
+ case BLKFLSBUF:
+ ret = ubiblock_flush(dev, true);
+ break;
+ default:
+ ret = -ENOTTY;
+ }
+
+ mutex_unlock(&dev->vol_mutex);
+ return ret;
+}
+
+static const struct block_device_operations ubiblock_ops = {
+ .owner = THIS_MODULE,
+ .open = ubiblock_open,
+ .release = ubiblock_release,
+ .ioctl = ubiblock_ioctl,
+};
+
+static int ubiblock_add(struct ubi_volume_info *vi)
+{
+ struct ubiblock *dev;
+ struct gendisk *gd;
+ int disk_capacity;
+ int ret;
+
+ /* Check that the volume isn't already handled */
+ mutex_lock(&devices_mutex);
+ if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {
+ mutex_unlock(&devices_mutex);
+ return -EEXIST;
+ }
+ mutex_unlock(&devices_mutex);
+
+ dev = kzalloc(sizeof(struct ubiblock), GFP_KERNEL);
+ if (!dev)
+ return -ENOMEM;
+
+ mutex_init(&dev->vol_mutex);
+
+ dev->ubi_num = vi->ubi_num;
+ dev->vol_id = vi->vol_id;
+
+ /* Initialize the gendisk of this ubiblock device */
+ gd = alloc_disk(1);
+ if (!gd) {
+ pr_err("alloc_disk failed\n");
+ ret = -ENODEV;
+ goto out_free_dev;
+ }
+
+ gd->fops = &ubiblock_ops;
+ gd->major = ubiblock_major;
+ gd->first_minor = dev->ubi_num * UBI_MAX_VOLUMES + dev->vol_id;
+ gd->private_data = dev;
+ sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);
+ disk_capacity = (vi->size * vi->usable_leb_size) >> 9;
+ set_capacity(gd, disk_capacity);
+ dev->gd = gd;
+
+ spin_lock_init(&dev->queue_lock);
+ dev->rq = blk_init_queue(ubiblock_request, &dev->queue_lock);
+ if (!dev->rq) {
+ pr_err("blk_init_queue failed\n");
+ ret = -ENODEV;
+ goto out_put_disk;
+ }
+
+ dev->rq->queuedata = dev;
+ dev->gd->queue = dev->rq;
+
+ /* TODO: Is performance better or worse with this flag? */
+ /* queue_flag_set_unlocked(QUEUE_FLAG_NONROT, dev->rq);*/
+
+ /*
+ * Create one workqueue per volume (per registered block device).
+ * Rembember workqueues are cheap, they're not threads.
+ */
+ dev->wq = alloc_workqueue(gd->disk_name, 0, 0);
+ if (!dev->wq)
+ goto out_free_queue;
+ INIT_WORK(&dev->work, ubiblock_do_work);
+
+ mutex_lock(&devices_mutex);
+ list_add_tail(&dev->list, &ubiblock_devices);
+ mutex_unlock(&devices_mutex);
+
+ /* Must be the last step: anyone can call file ops from now on */
+ add_disk(dev->gd);
+
+ dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)\n",
+ dev->ubi_num, dev->vol_id, vi->name);
+
+ return 0;
+
+out_free_queue:
+ blk_cleanup_queue(dev->rq);
+out_put_disk:
+ put_disk(dev->gd);
+out_free_dev:
+ kfree(dev);
+
+ return ret;
+}
+
+static void ubiblock_cleanup(struct ubiblock *dev)
+{
+#ifdef DEBUG
+ pr_debug("%s: read hit/miss %d/%d, write hit/miss %d/%d\n",
+ dev->gd->disk_name,
+ dev->cache_read_hit, dev->cache_read_miss,
+ dev->cache_write_hit, dev->cache_write_miss);
+#endif
+ del_gendisk(dev->gd);
+ blk_cleanup_queue(dev->rq);
+ put_disk(dev->gd);
+}
+
+static int ubiblock_del(struct ubi_volume_info *vi)
+{
+ struct ubiblock *dev;
+
+ mutex_lock(&devices_mutex);
+ dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
+ if (!dev) {
+ mutex_unlock(&devices_mutex);
+ pr_warn("trying to remove %s, but it isn't handled\n",
+ vi->name);
+ return -ENODEV;
+ }
+ /* Remove from device list */
+ list_del(&dev->list);
+ mutex_unlock(&devices_mutex);
+
+ /* Flush pending work and stop this workqueue */
+ destroy_workqueue(dev->wq);
+
+ mutex_lock(&dev->vol_mutex);
+
+ /*
+ * This means that ubiblock device is opened and in usage.
+ * However, this shouldn't happen, since we have
+ * called ubi_open_volume() at open() time, thus preventing
+ * volume removal.
+ */
+ WARN_ON(dev->desc);
+ ubiblock_cleanup(dev);
+
+ mutex_unlock(&dev->vol_mutex);
+
+ kfree(dev);
+
+ return 0;
+}
+
+static int ubiblock_resize(struct ubi_volume_info *vi)
+{
+ struct ubiblock *dev;
+ int disk_capacity;
+
+ /*
+ * We don't touch the list, but we better lock it: it could be that the
+ * device gets removed between the time the device has been found and
+ * the time we access dev->gd
+ */
+ mutex_lock(&devices_mutex);
+ dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
+ if (!dev) {
+ mutex_unlock(&devices_mutex);
+ pr_warn("trying to resize %s, which isn't handled\n",
+ vi->name);
+ return -ENODEV;
+ }
+ mutex_unlock(&devices_mutex);
+
+ mutex_lock(&dev->vol_mutex);
+ disk_capacity = (vi->size * vi->usable_leb_size) >> 9;
+ set_capacity(dev->gd, disk_capacity);
+ dev_dbg(disk_to_dev(dev->gd), "resized to %d LEBs\n", vi->size);
+ mutex_unlock(&dev->vol_mutex);
+
+ return 0;
+}
+
+static int ubiblock_notify(struct notifier_block *nb,
+ unsigned long notification_type, void *ns_ptr)
+{
+ struct ubi_notification *nt = ns_ptr;
+
+ switch (notification_type) {
+ case UBI_VOLUME_ADDED:
+ ubiblock_add(&nt->vi);
+ break;
+ case UBI_VOLUME_REMOVED:
+ ubiblock_del(&nt->vi);
+ break;
+ case UBI_VOLUME_RESIZED:
+ ubiblock_resize(&nt->vi);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block ubiblock_notifier = {
+ .notifier_call = ubiblock_notify,
+};
+
+static int __init ubiblock_init(void)
+{
+ ubiblock_major = register_blkdev(0, "ubiblock");
+ if (ubiblock_major < 0)
+ return ubiblock_major;
+
+ /*
+ * Blocks will get registered dynamically.
+ * Each ubi volume will get a corresponding block device.
+ */
+ return ubi_register_volume_notifier(&ubiblock_notifier, 0);
+}
+
+static void __exit ubiblock_exit(void)
+{
+ struct ubiblock *next;
+ struct ubiblock *dev;
+
+ ubi_unregister_volume_notifier(&ubiblock_notifier);
+
+ list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
+
+ /* Flush pending work and stop workqueue */
+ destroy_workqueue(dev->wq);
+
+ /* The module is being forcefully removed */
+ WARN_ON(dev->desc);
+
+ /* Remove from device list */
+ list_del(&dev->list);
+
+ ubiblock_cleanup(dev);
+
+ kfree(dev);
+ }
+
+ unregister_blkdev(ubiblock_major, "ubiblock");
+}
+
+module_init(ubiblock_init);
+module_exit(ubiblock_exit);
+
+MODULE_DESCRIPTION("Block device emulation access to UBI volumes");
+MODULE_AUTHOR("David Wagner");
+MODULE_AUTHOR("Ezequiel Garcia <elezegar...@gmail.com>");
+MODULE_LICENSE("GPL");
--
1.7.8.6
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
