Message-Id: <1308922482-14967-2-git-send-email-david.wagner@free-electrons.com>
Date:	Fri, 24 Jun 2011 15:34:42 +0200
From:	david.wagner@...e-electrons.com
To:	linux-mtd@...ts.infradead.org
Cc:	dedekind1@...il.com, dwmw2@...radead.org,
	linux-kernel@...r.kernel.org,
	David Wagner <david.wagner@...e-electrons.com>
Subject: [PATCH] UBI: new module ubiblk: block layer on top of UBI

From: David Wagner <david.wagner@...e-electrons.com>

ubiblk is a read-only block layer on top of UBI.  It presents UBI volumes as
read-only block devices.

It is used by putting a block filesystem image on a UBI volume and then mounting
the corresponding device.

It uses the UBI API to register to UBI notifications (to dynamically create and
delete devices as volumes are added or removed) and to read from the volumes.

Known issues:
 * UBI_VOLUME_RESIZED notification hook isn't implemented yet ;

 * only squashfs is known to work. With ext2/3 and vfat, errors appear randomly
   in the middle of some files.  The reason for that is still unknown ;

 * the modules keeps a table of the devices which length is the maximum number
   of UBI volumes.  It should make use of a linked list.

A lot of code is taken from mtd_blkdevs and gluebi

Signed-off-by: David Wagner <david.wagner@...e-electrons.com>
---
 drivers/mtd/ubi/Kconfig  |    9 +
 drivers/mtd/ubi/Makefile |    1 +
 drivers/mtd/ubi/ubiblk.c |  462 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 472 insertions(+), 0 deletions(-)
 create mode 100644 drivers/mtd/ubi/ubiblk.c

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 4dcc752..389a996 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -60,4 +60,13 @@ config MTD_UBI_DEBUG
 	help
 	  This option enables UBI debugging.
 
+config MTD_UBI_UBIBLK
+	tristate "Read-only block transition layer on top of UBI"
+	help
+	   Read-only block interface on top of UBI.
+
+	   Creates block devices that can be used to mount read-only block
+	   filesystems. Caches reads on a raw UBI volume. Filesystems images
+	   can be flashed using ubiupdatevol or put in a UBI image with
+	   ubinize
 endif # MTD_UBI
diff --git a/drivers/mtd/ubi/Makefile b/drivers/mtd/ubi/Makefile
index c9302a5..354b2df 100644
--- a/drivers/mtd/ubi/Makefile
+++ b/drivers/mtd/ubi/Makefile
@@ -5,3 +5,4 @@ ubi-y += misc.o
 
 ubi-$(CONFIG_MTD_UBI_DEBUG) += debug.o
 obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
+obj-$(CONFIG_MTD_UBI_UBIBLK) += ubiblk.o
diff --git a/drivers/mtd/ubi/ubiblk.c b/drivers/mtd/ubi/ubiblk.c
new file mode 100644
index 0000000..aab940a
--- /dev/null
+++ b/drivers/mtd/ubi/ubiblk.c
@@ -0,0 +1,462 @@
+/*
+ * Copyright (c) Free Electrons, 2011
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Author: David Wagner
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/vmalloc.h>
+#include <linux/mtd/ubi.h>
+#include <linux/blkdev.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include "ubi.h"
+
+#define BLK_SIZE 512
+
+#define UBIBLK_MAX_DEVS (UBI_MAX_DEVICES * UBI_MAX_VOLUMES)
+
+/*
+ * Structure representing a ubiblk device, proxying a UBI volume
+ */
+struct ubiblk_dev {
+	struct ubi_volume_desc *vol_desc;
+	struct ubi_volume_info *vol_info;
+	int ubi_num;
+	int vol_id;
+
+	/* Block stuff */
+	struct gendisk *gd;
+	struct request_queue *rq;
+	struct task_struct *thread;
+
+	/* Protects the access to the UBI volume */
+	struct mutex lock;
+
+	/* Avoids concurrent accesses to the request queue */
+	spinlock_t queue_lock;
+};
+
+/*
+ * Contains the pointers to all ubiblk_dev instances
+ * TODO: use a linked list
+ */
+static struct ubiblk_dev *ubiblk_devs[UBIBLK_MAX_DEVS];
+static struct mutex devtable_lock;
+
+int major;
+static const struct block_device_operations ubiblk_ops;
+
+/*
+ * Read a LEB and fill the request buffer with the requested sector
+ */
+static int do_ubiblk_request(struct request *req, struct ubiblk_dev *dev)
+{
+	unsigned long start, len;
+	int offset;
+	int leb;
+	int ret;
+
+	start = blk_rq_pos(req) << 9;
+	len = blk_rq_cur_bytes(req);
+
+	/* We are always reading. No need to handle writing for now */
+
+	leb = start / dev->vol_info->usable_leb_size;
+	offset = start % dev->vol_info->usable_leb_size;
+
+	if (offset + len > dev->vol_info->usable_leb_size)
+		len = dev->vol_info->usable_leb_size - offset;
+
+	pr_debug("%s(%s) of sector %llu (LEB %d). start=%lu, len=%lu\n",
+		 __func__, rq_data_dir(req) ? "Write" : "Read",
+		 blk_rq_pos(req), leb, start, len);
+
+	ret = ubi_read(dev->vol_desc, leb, req->buffer, offset, len);
+
+	if (ret) {
+		pr_err("ubi_read error\n");
+		return ret;
+	}
+
+	pr_debug("ubi_read done.\n");
+
+	return 0;
+}
+
+static void ubi_ubiblk_request(struct request_queue *rq)
+{
+	struct ubiblk_dev *dev;
+	struct request *req = NULL;
+
+	dev = rq->queuedata;
+
+	if (!dev)
+		while ((req = blk_fetch_request(rq)) != NULL)
+			__blk_end_request_all(req, -ENODEV);
+	else
+		wake_up_process(dev->thread);
+}
+
+/*
+ * Open a UBI volume (get the volume descriptor)
+ */
+static int ubiblk_open(struct block_device *bdev, fmode_t mode)
+{
+	struct ubiblk_dev *dev = bdev->bd_disk->private_data;
+	pr_debug("%s() disk_name=%s, mode=%d\n", __func__,
+		 bdev->bd_disk->disk_name, mode);
+
+	dev->vol_desc = ubi_open_volume(dev->ubi_num, dev->vol_id,
+					UBI_READONLY);
+	if (!dev->vol_desc) {
+		pr_err("open_volume failed");
+		return -EINVAL;
+	}
+
+	dev->vol_info = kzalloc(sizeof(struct ubi_volume_info), GFP_KERNEL);
+	if (!dev->vol_info) {
+		ubi_close_volume(dev->vol_desc);
+		dev->vol_desc = NULL;
+		return -ENOMEM;
+	}
+	ubi_get_volume_info(dev->vol_desc, dev->vol_info);
+
+	return 0;
+}
+
+/*
+ * Close a UBI volume (close the volume descriptor)
+ */
+static int ubiblk_release(struct gendisk *gd, fmode_t mode)
+{
+	struct ubiblk_dev *dev = gd->private_data;
+	pr_debug("%s() disk_name=%s, mode=%d\n", __func__, gd->disk_name,
+		 mode);
+
+	kfree(dev->vol_info);
+	dev->vol_info = NULL;
+	if (dev->vol_desc) {
+		ubi_close_volume(dev->vol_desc);
+		dev->vol_desc = NULL;
+	}
+
+	return 0;
+}
+
+/*
+ * Loop on the block request queue and wait for new requests ; run them with
+ * do_ubiblk_request()
+ *
+ * Mostly stolen from mtd_blkdevs.c
+ */
+static int ubi_ubiblk_thread(void *arg)
+{
+	struct ubiblk_dev *dev = arg;
+	struct request_queue *rq = dev->rq;
+	struct request *req = NULL;
+
+	spin_lock_irq(rq->queue_lock);
+
+	while (!kthread_should_stop()) {
+		int res;
+
+		if (!req && !(req = blk_fetch_request(rq))) {
+			set_current_state(TASK_INTERRUPTIBLE);
+
+			if (kthread_should_stop())
+				set_current_state(TASK_RUNNING);
+
+			spin_unlock_irq(rq->queue_lock);
+			schedule();
+			spin_lock_irq(rq->queue_lock);
+			continue;
+		}
+
+		spin_unlock_irq(rq->queue_lock);
+
+		mutex_lock(&dev->lock);
+		res = do_ubiblk_request(req, dev);
+		pr_debug("return from request: %d\n", res);
+		mutex_unlock(&dev->lock);
+
+		spin_lock_irq(rq->queue_lock);
+
+		if (!__blk_end_request_cur(req, res))
+			req = NULL;
+	}
+
+	if (req)
+		__blk_end_request_all(req, -EIO);
+
+	spin_unlock_irq(rq->queue_lock);
+
+	return 0;
+}
+
+static int ubiblk_create(struct ubi_device_info *dev_info,
+			 struct ubi_volume_info *vol_info)
+{
+	struct ubiblk_dev *dev;
+	struct gendisk *gd;
+	int i;
+	int ret = 0;
+
+	mutex_lock(&devtable_lock);
+	for (i = 0; i < UBIBLK_MAX_DEVS; i++)
+		if (!ubiblk_devs[i])
+			break;
+
+	if (i == UBIBLK_MAX_DEVS) {
+		/* Shouldn't happen: UBI can't make more volumes than that */
+		pr_err("no slot left for a new ubiblk device.\n");
+		mutex_unlock(&devtable_lock);
+		return -ENOMEM;
+	}
+
+	dev = kzalloc(sizeof(struct ubiblk_dev), GFP_KERNEL);
+	if (!dev) {
+		pr_err("UBIBLK: ENOMEM when trying to create a new"
+		       "ubiblk dev\n");
+		mutex_unlock(&devtable_lock);
+		return -ENOMEM;
+	}
+	ubiblk_devs[i] = dev;
+	mutex_unlock(&devtable_lock);
+
+	mutex_init(&dev->lock);
+	mutex_lock(&dev->lock);
+
+	dev->ubi_num = vol_info->ubi_num;
+	dev->vol_id = vol_info->vol_id;
+
+	dev->vol_desc = ubi_open_volume(dev->ubi_num, dev->vol_id,
+					UBI_READONLY);
+	if (IS_ERR(dev->vol_desc)) {
+		pr_err("open_volume failed\n");
+		ret = PTR_ERR(dev->vol_desc);
+		goto out_vol;
+	}
+
+	dev->vol_info = kzalloc(sizeof(struct ubi_volume_info), GFP_KERNEL);
+	if (!dev->vol_info) {
+		ret = -ENOMEM;
+		goto out_info;
+	}
+	ubi_get_volume_info(dev->vol_desc, dev->vol_info);
+
+	pr_info("Got volume %s: device %d/volume %d of size %d\n",
+		dev->vol_info->name, dev->ubi_num, dev->vol_id,
+		dev->vol_info->size);
+
+	/* Initialize the gendisk of this ubiblk device */
+	gd = alloc_disk(1);
+	if (!gd) {
+		pr_err("alloc_disk failed\n");
+		ret = -ENODEV;
+		goto out_disk;
+	}
+
+	gd->fops = &ubiblk_ops;
+	gd->major = major;
+	gd->first_minor = dev->ubi_num * UBI_MAX_VOLUMES + dev->vol_id;
+	gd->private_data = dev;
+	sprintf(gd->disk_name, "ubiblk%d_%d", dev->ubi_num, dev->vol_id);
+	pr_debug("creating a gd '%s'\n", gd->disk_name);
+	set_capacity(gd,
+		     (dev->vol_info->size *
+		      dev->vol_info->usable_leb_size) >> 9);
+	set_disk_ro(gd, 1);
+	dev->gd = gd;
+
+	spin_lock_init(&dev->queue_lock);
+	dev->rq = blk_init_queue(ubi_ubiblk_request, &dev->queue_lock);
+	if (!dev->rq) {
+		pr_err("init_queue failed\n");
+		ret = -ENODEV;
+		goto out_queue;
+	}
+	dev->rq->queuedata = dev;
+	blk_queue_logical_block_size(dev->rq, BLK_SIZE);
+	dev->gd->queue = dev->rq;
+
+	/* Stolen from mtd_blkdevs.c */
+	/* Create processing thread */
+	dev->thread = kthread_run(ubi_ubiblk_thread, dev, "%s%d_%d",
+				  "kubiblkd", dev->ubi_num, dev->vol_id);
+	if (IS_ERR(dev->thread)) {
+		ret = PTR_ERR(dev->thread);
+		goto out_thread;
+	}
+
+	add_disk(dev->gd);
+	kfree(dev->vol_info);
+	dev->vol_info = NULL;
+	ubi_close_volume(dev->vol_desc);
+	dev->vol_desc = NULL;
+	mutex_unlock(&dev->lock);
+
+	return 0;
+
+out_thread:
+	blk_cleanup_queue(dev->rq);
+out_queue:
+	put_disk(dev->gd);
+out_disk:
+	kfree(dev->vol_info);
+	dev->vol_info = NULL;
+out_info:
+	ubi_close_volume(dev->vol_desc);
+	dev->vol_desc = NULL;
+out_vol:
+	mutex_unlock(&dev->lock);
+
+	return ret;
+}
+
+static int ubiblk_remove(struct ubi_volume_info *vol_info)
+{
+	int i;
+	struct ubiblk_dev *dev;
+
+	for (i = 0; i < UBIBLK_MAX_DEVS; i++) {
+		dev = ubiblk_devs[i];
+		if (dev && dev->ubi_num == vol_info->ubi_num &&
+		    dev->vol_id == vol_info->vol_id)
+			break;
+	}
+	if (i == UBIBLK_MAX_DEVS) {
+		pr_warn("Trying to remove %s, which is unknown from ubiblk\n",
+			vol_info->name);
+		return -ENODEV;
+	}
+
+	pr_info("Removing %s\n", vol_info->name);
+
+	if (dev->vol_desc)
+		ubi_close_volume(dev->vol_desc);
+
+	del_gendisk(dev->gd);
+	blk_cleanup_queue(dev->rq);
+	kthread_stop(dev->thread);
+	put_disk(dev->gd);
+
+	kfree(dev->vol_info);
+
+	kfree(ubiblk_devs[i]);
+	ubiblk_devs[i] = NULL;
+
+	return 0;
+}
+
+static int ubiblk_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:
+		ubiblk_create(&nt->di, &nt->vi);
+		break;
+	case UBI_VOLUME_REMOVED:
+		/* TODO */
+		ubiblk_remove(&nt->vi);
+		break;
+	case UBI_VOLUME_RESIZED:
+		/* TODO. needed ? */
+		/* gluebi_resized(&nt->vi); */
+		break;
+	case UBI_VOLUME_UPDATED:
+		break;
+	case UBI_VOLUME_RENAMED:
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static const struct block_device_operations ubiblk_ops = {
+	.owner = THIS_MODULE,
+	.open = ubiblk_open,
+	.release = ubiblk_release,
+};
+
+static struct notifier_block ubiblk_notifier = {
+	.notifier_call = ubiblk_notify,
+};
+
+/*
+ * Initialize the module
+ */
+static int __init ubi_ubiblk_init(void)
+{
+	int ret;
+
+	pr_info("UBIBLK starting\n");
+
+	ret = register_blkdev(0, "ubiblk");
+	if (ret <= 0) {
+		pr_err("UBIBLK: could not register_blkdev\n");
+		return -ENODEV;
+	}
+	major = ret;
+	pr_info("UBIBLK: device's major: %d\n", major);
+
+	mutex_init(&devtable_lock);
+	ret = ubi_register_volume_notifier(&ubiblk_notifier, 0);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static void __exit ubi_ubiblk_exit(void)
+{
+	int i;
+
+	pr_info("UBIBLK: going to exit\n");
+
+	ubi_unregister_volume_notifier(&ubiblk_notifier);
+
+	for (i = 0; i < UBIBLK_MAX_DEVS; i++) {
+		struct ubiblk_dev *dev = ubiblk_devs[i];
+		if (!dev)
+			continue;
+
+		if (dev->vol_desc)
+			ubi_close_volume(dev->vol_desc);
+
+		del_gendisk(dev->gd);
+		blk_cleanup_queue(dev->rq);
+		kthread_stop(dev->thread);
+		put_disk(dev->gd);
+
+		kfree(dev->vol_info);
+		kfree(dev);
+	}
+
+	unregister_blkdev(major, "ubiblk");
+	pr_info("UBIBLK: The End\n");
+}
+
+module_init(ubi_ubiblk_init);
+module_exit(ubi_ubiblk_exit);
+MODULE_DESCRIPTION("Read-only block transition layer on top of UBI");
+MODULE_AUTHOR("David Wagner");
+MODULE_LICENSE("GPL");
-- 
1.7.0.4

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