Date:	Fri, 23 Mar 2007 18:44:07 +0200
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Frank Haverkamp <haver@...t.ibm.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	Artem Bityutskiy <dedekind@...radead.org>
Subject: [PATCH 14/20 take 4] UBI: character devices functionality

diff -auNrp tmp-from/drivers/mtd/ubi/cdev.c tmp-to/drivers/mtd/ubi/cdev.c
--- tmp-from/drivers/mtd/ubi/cdev.c	1970-01-01 02:00:00.000000000 +0200
+++ tmp-to/drivers/mtd/ubi/cdev.c	2007-03-23 18:20:02.000000000 +0200
@@ -0,0 +1,724 @@
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ *
+ * 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: Artem Bityutskiy (Битюцкий Артём)
+ */
+
+/*
+ * This file includes implementation of UBI character device operations.
+ *
+ * There are two kinds of character devices in UBI: UBI character devices and
+ * UBI volume character devices. UBI character devices allow users to
+ * manipulate whole volumes: create, remove, and re-size them. Volume character
+ * devices provide volume I/O capabilities.
+ *
+ * Major and minor numbers are assigned dynamically to both UBI and volume
+ * character devices.
+ */
+
+#include <linux/module.h>
+#include <linux/stat.h>
+#include <linux/ioctl.h>
+#include <linux/capability.h>
+#include <mtd/ubi-user.h>
+#include <asm/uaccess.h>
+#include <asm/div64.h>
+#include "ubi.h"
+
+/*
+ * Maximum sequence numbers of UBI and volume character device IOCTLs (direct
+ * logical eraseblock erase is a debug-only feature).
+ */
+#define UBI_CDEV_IOC_MAX_SEQ 2
+#ifndef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
+#define VOL_CDEV_IOC_MAX_SEQ 1
+#else
+#define VOL_CDEV_IOC_MAX_SEQ 2
+#endif
+
+/**
+ * major_to_device - get UBI device object by character device major number.
+ * @major: major number
+ *
+ * This function returns a pointer to the UBI device object.
+ */
+static struct ubi_device *major_to_device(int major)
+{
+	int i;
+
+	for (i = 0; i < ubi_devices_cnt; i++)
+		if (ubi_devices[i] && ubi_devices[i]->major == major)
+			return ubi_devices[i];
+	BUG();
+}
+
+/**
+ * get_exclusive - get exclusive access to an UBI volume.
+ * @desc: volume descriptor
+ *
+ * This function changes UBI volume open mode to "exclusive". Returns previous
+ * mode value (positive integer) in case of success and a negative error code
+ * in case of failure.
+ */
+static int get_exclusive(struct ubi_volume_desc *desc)
+{
+	int users, err;
+	struct ubi_volume *vol = desc->vol;
+
+	spin_lock(&vol->ubi->volumes_lock);
+	users = vol->readers + vol->writers + vol->exclusive;
+	ubi_assert(users > 0);
+	if (users > 1) {
+		dbg_err("%d users for volume %d", users, vol->vol_id);
+		err = -EBUSY;
+	} else {
+		vol->readers = vol->writers = 0;
+		vol->exclusive = 1;
+		err = desc->mode;
+		desc->mode = UBI_EXCLUSIVE;
+	}
+	spin_unlock(&vol->ubi->volumes_lock);
+
+	return err;
+}
+
+/**
+ * revoke_exclusive - revoke exclusive mode.
+ * @desc: volume descriptor
+ * @mode: new mode to switch to
+ */
+static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
+{
+	struct ubi_volume *vol = desc->vol;
+
+	spin_lock(&vol->ubi->volumes_lock);
+	ubi_assert(vol->readers == 0 && vol->writers == 0);
+	ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
+	vol->exclusive = 0;
+	if (mode == UBI_READONLY)
+		vol->readers = 1;
+	else if (mode == UBI_READWRITE)
+		vol->writers = 1;
+	else
+		vol->exclusive = 1;
+	spin_unlock(&vol->ubi->volumes_lock);
+
+	desc->mode = mode;
+}
+
+static int vol_cdev_open(struct inode *inode, struct file *file)
+{
+	struct ubi_volume_desc *desc;
+	const struct ubi_device *ubi = major_to_device(imajor(inode));
+	int vol_id = iminor(inode) - 1;
+	int mode;
+
+	if (file->f_mode & FMODE_WRITE)
+		mode = UBI_READWRITE;
+	else
+		mode = UBI_READONLY;
+
+	dbg_msg("open volume %d, mode %d", vol_id, mode);
+
+	desc = ubi_open_volume(ubi->ubi_num, vol_id, mode);
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	file->private_data = desc;
+	return 0;
+}
+
+static int vol_cdev_release(struct inode *inode, struct file *file)
+{
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+
+	dbg_msg("release volume %d, mode %d", vol->vol_id, desc->mode);
+
+	if (vol->updating) {
+		ubi_warn("update of volume %d not finished, volume is damaged",
+			 vol->vol_id);
+		vol->updating = 0;
+		kfree(vol->upd_buf);
+	}
+
+	ubi_close_volume(desc);
+	return 0;
+}
+
+static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
+{
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+	loff_t new_offset;
+
+	if (vol->updating) {
+		 /* Update is in progress, seeking is prohibited */
+		dbg_err("updating");
+		return -EBUSY;
+	}
+
+	switch (origin) {
+	case 0: /* SEEK_SET */
+		new_offset = offset;
+		break;
+	case 1: /* SEEK_CUR */
+		new_offset = file->f_pos + offset;
+		break;
+	case 2: /* SEEK_END */
+		new_offset = vol->used_bytes + offset;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (new_offset < 0 || new_offset > vol->used_bytes) {
+		dbg_err("bad seek %lld", new_offset);
+		return -EINVAL;
+	}
+
+	dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
+		vol->vol_id, offset, origin, new_offset);
+
+	file->f_pos = new_offset;
+	return new_offset;
+}
+
+static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
+			     loff_t *offp)
+{
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int err, lnum, off, len,  vol_id = desc->vol->vol_id, tbuf_size;
+	size_t count_save = count;
+	void *tbuf;
+	uint64_t tmp;
+
+	dbg_msg("read %zd bytes from offset %lld of volume %d",
+		count, *offp, vol_id);
+
+	if (vol->updating) {
+		dbg_err("updating");
+		return -EBUSY;
+	}
+	if (vol->upd_marker) {
+		dbg_err("damaged volume, update marker is set");
+		return -EBADF;
+	}
+	if (*offp == vol->used_bytes || count == 0)
+		return 0;
+
+	if (vol->corrupted)
+		dbg_msg("read from corrupted volume %d", vol_id);
+
+	if (*offp + count > vol->used_bytes)
+		count_save = count = vol->used_bytes - *offp;
+
+	tbuf_size = vol->usable_leb_size;
+	if (count < tbuf_size)
+		tbuf_size = ubi_align_up(count, ubi->min_io_size);
+	tbuf = kmalloc(tbuf_size, GFP_KERNEL);
+	if (!tbuf)
+		return -ENOMEM;
+
+	len = count > tbuf_size ? tbuf_size : count;
+
+	tmp = *offp;
+	off = do_div(tmp, vol->usable_leb_size);
+	lnum = tmp;
+
+	do {
+		cond_resched();
+
+		if (off + len >= vol->usable_leb_size)
+			len = vol->usable_leb_size - off;
+
+		err = ubi_eba_read_leb(ubi, vol_id, lnum, tbuf, off, len, 0);
+		if (unlikely(err))
+			break;
+
+		off += len;
+		if (off == vol->usable_leb_size) {
+			lnum += 1;
+			off -= vol->usable_leb_size;
+		}
+
+		count -= len;
+		*offp += len;
+
+		err = copy_to_user(buf, tbuf, len);
+		if (unlikely(err)) {
+			err = -EFAULT;
+			break;
+		}
+
+		buf += len;
+		len = count > tbuf_size ? tbuf_size : count;
+	} while (count);
+
+	kfree(tbuf);
+	return err ? err : count_save - count;
+}
+
+#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
+
+/*
+ * This function allows to directly write to dynamic UBI volumes, without
+ * issuing the volume update operation. Available only as a debugging feature.
+ * Very useful for testing UBI.
+ */
+static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
+				     size_t count, loff_t *offp)
+{
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int lnum, off, len, tbuf_size, vol_id = vol->vol_id, err = 0;
+	size_t count_save = count;
+	char *tbuf;
+	uint64_t tmp;
+
+	dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
+		count, *offp, desc->vol->vol_id);
+
+	if (vol->vol_type == UBI_STATIC_VOLUME)
+		return -EROFS;
+
+	tmp = *offp;
+	off = do_div(tmp, vol->usable_leb_size);
+	lnum = tmp;
+
+	if (off % ubi->min_io_size) {
+		dbg_err("unaligned position");
+		return -EINVAL;
+	}
+
+	if (*offp + count > vol->used_bytes)
+		count_save = count = vol->used_bytes - *offp;
+
+	/* We can write only in fractions of the minimum I/O unit */
+	if (count % ubi->min_io_size) {
+		dbg_err("unaligned write length");
+		return -EINVAL;
+	}
+
+	tbuf_size = vol->usable_leb_size;
+	if (count < tbuf_size)
+		tbuf_size = ubi_align_up(count, ubi->min_io_size);
+	tbuf = kmalloc(tbuf_size, GFP_KERNEL);
+	if (!tbuf)
+		return -ENOMEM;
+
+	len = count > tbuf_size ? tbuf_size : count;
+
+	while (count) {
+		cond_resched();
+
+		if (off + len >= vol->usable_leb_size)
+			len = vol->usable_leb_size - off;
+
+		err = copy_from_user(tbuf, buf, len);
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		err = ubi_eba_write_leb(ubi, vol_id, lnum, tbuf, off, len,
+					UBI_DATA_UNKNOWN);
+		if (unlikely(err))
+			break;
+
+		off += len;
+		if (off == vol->usable_leb_size) {
+			lnum += 1;
+			off -= vol->usable_leb_size;
+		}
+
+		count -= len;
+		*offp += len;
+		buf += len;
+		len = count > tbuf_size ? tbuf_size : count;
+	}
+
+	kfree(tbuf);
+	return err ? err : count_save - count;
+}
+
+#else
+#define vol_cdev_direct_write(file, buf, count, offp) -EPERM
+#endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */
+
+static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
+			      size_t count, loff_t *offp)
+{
+	int err = 0;
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+
+	if (!vol->updating)
+		return vol_cdev_direct_write(file, buf, count, offp);
+
+	err = ubi_more_update_data(ubi, vol->vol_id, buf, count);
+	if (err < 0) {
+		ubi_err("cannot write %zd bytes of update data", count);
+		return err;
+	}
+
+	if (err) {
+		/*
+		 * Update is finished, @err contains number of actually written
+		 * bytes now.
+		 */
+		count = err;
+
+		err = ubi_check_volume(ubi, vol->vol_id);
+		if (err < 0)
+			return err;
+
+		if (err) {
+			ubi_warn("volume %d on UBI device %d is corrupted",
+				 vol->vol_id, ubi->ubi_num);
+			vol->corrupted = 1;
+		}
+		vol->checked = 1;
+		revoke_exclusive(desc, UBI_READWRITE);
+	}
+
+	*offp += count;
+	return count;
+}
+
+static int vol_cdev_ioctl(struct inode *inode, struct file *file,
+			  unsigned int cmd, unsigned long arg)
+{
+	int err = 0;
+	struct ubi_volume_desc *desc = file->private_data;
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	void __user *argp = (void __user *)arg;
+
+	if (_IOC_NR(cmd) > VOL_CDEV_IOC_MAX_SEQ ||
+	    _IOC_TYPE(cmd) != UBI_VOL_IOC_MAGIC)
+		return -ENOTTY;
+
+	if (_IOC_DIR(cmd) && _IOC_READ)
+		err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
+	else if (_IOC_DIR(cmd) && _IOC_WRITE)
+		err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
+	if (err)
+		return -EFAULT;
+
+	switch (cmd) {
+
+	/* Volume update command */
+	case UBI_IOCVOLUP:
+	{
+		int64_t bytes, rsvd_bytes;
+
+		if (!capable(CAP_SYS_RESOURCE)) {
+			err = -EPERM;
+			break;
+		}
+
+		err = copy_from_user(&bytes, argp, sizeof(int64_t));
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		if (desc->mode == UBI_READONLY) {
+			err = -EROFS;
+			break;
+		}
+
+		rsvd_bytes = vol->reserved_pebs * (ubi->leb_size-vol->data_pad);
+		if (bytes < 0 || bytes > rsvd_bytes) {
+			err = -EINVAL;
+			break;
+		}
+
+		err = get_exclusive(desc);
+		if (err < 0)
+			break;
+
+		err = ubi_start_update(ubi, vol->vol_id, bytes);
+		if (bytes == 0)
+			revoke_exclusive(desc, UBI_READWRITE);
+
+		file->f_pos = 0;
+		break;
+	}
+
+#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
+	/* Logical eraseblock erasure command */
+	case UBI_IOCEBER:
+	{
+		int32_t lnum;
+
+		err = __get_user(lnum, (__user int32_t *)argp);
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		if (desc->mode == UBI_READONLY) {
+			err = -EROFS;
+			break;
+		}
+
+		if (lnum < 0 || lnum >= vol->reserved_pebs) {
+			err = -EINVAL;
+			break;
+		}
+
+		if (vol->vol_type != UBI_DYNAMIC_VOLUME) {
+			err = -EROFS;
+			break;
+		}
+
+		dbg_msg("erase LEB %d:%d", vol->vol_id, lnum);
+		err = ubi_eba_unmap_leb(ubi, vol->vol_id, lnum);
+		if (err)
+			break;
+
+		err = ubi_wl_flush(ubi);
+		break;
+	}
+#endif
+
+	default:
+		err = -ENOTTY;
+		break;
+	}
+
+	return err;
+}
+
+/**
+ * verify_mkvol_req - verify volume creation request.
+ * @ubi: UBI device description object
+ * @req: the request to check
+ *
+ * This function zero if the request is correct, and %-EINVAL if not.
+ */
+static int verify_mkvol_req(const struct ubi_device *ubi,
+			    const struct ubi_mkvol_req *req)
+{
+	int n;
+
+	if (req->bytes < 0 || req->alignment < 0 || req->vol_type < 0 ||
+	    req->name_len < 0)
+		goto bad;
+
+	if ((req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots) &&
+	    req->vol_id != UBI_VOL_NUM_AUTO)
+		goto bad;
+
+	if (req->alignment == 0)
+		goto bad;
+
+	if (req->bytes == 0)
+		goto bad;
+
+	if (req->vol_type != UBI_DYNAMIC_VOLUME &&
+	    req->vol_type != UBI_STATIC_VOLUME)
+		goto bad;
+
+	if (req->alignment > ubi->leb_size)
+		goto bad;
+
+	n = req->alignment % ubi->min_io_size;
+	if (req->alignment != 1 && n)
+		goto bad;
+
+	if (req->name_len > UBI_VOL_NAME_MAX)
+		goto bad;
+
+	return 0;
+
+bad:
+	dbg_err("bad volume creation request");
+	ubi_dbg_dump_mkvol_req(req);
+	return -EINVAL;
+}
+
+/**
+ * verify_rsvol_req - verify volume re-size request.
+ * @ubi: UBI device description object
+ * @req: the request to check
+ *
+ * This function returns zero if the request is correct, and %-EINVAL if not.
+ */
+static int verify_rsvol_req(const struct ubi_device *ubi,
+			    const struct ubi_rsvol_req *req)
+{
+	if (req->bytes <= 0)
+		return -EINVAL;
+
+	if (req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
+			  unsigned int cmd, unsigned long arg)
+{
+	int err = 0;
+	struct ubi_device *ubi;
+	struct ubi_volume_desc *desc;
+	void __user *argp = (void __user *)arg;
+
+	if (_IOC_NR(cmd) > UBI_CDEV_IOC_MAX_SEQ ||
+	    _IOC_TYPE(cmd) != UBI_IOC_MAGIC)
+		return -ENOTTY;
+
+	if (_IOC_DIR(cmd) && _IOC_READ)
+		err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
+	else if (_IOC_DIR(cmd) && _IOC_WRITE)
+		err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
+	if (err)
+		return -EFAULT;
+
+	if (!capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+
+	ubi = major_to_device(imajor(inode));
+	if (IS_ERR(ubi))
+		return PTR_ERR(ubi);
+
+	switch (cmd) {
+	/* Create volume command */
+	case UBI_IOCMKVOL:
+	{
+		struct ubi_mkvol_req req;
+
+		dbg_msg("create volume");
+		err = __copy_from_user(&req, argp,
+				       sizeof(struct ubi_mkvol_req));
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		err = verify_mkvol_req(ubi, &req);
+		if (err)
+			break;
+
+		req.name[req.name_len] = '\0';
+
+		err = ubi_create_volume(ubi, &req);
+		if (err)
+			break;
+
+		err = __put_user(req.vol_id, (__user int32_t *)argp);
+		if (err)
+			err = -EFAULT;
+
+		break;
+	}
+
+	/* Remove volume command */
+	case UBI_IOCRMVOL:
+	{
+		int vol_id;
+
+		dbg_msg("remove volume");
+		err = __get_user(vol_id, (__user int32_t *)argp);
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_EXCLUSIVE);
+		if (IS_ERR(desc)) {
+			err = PTR_ERR(desc);
+			break;
+		}
+
+		err = ubi_remove_volume(desc);
+		if (err)
+			ubi_close_volume(desc);
+
+		break;
+	}
+
+	/* Re-size volume command */
+	case UBI_IOCRSVOL:
+	{
+		int pebs;
+		uint64_t tmp;
+		struct ubi_rsvol_req req;
+
+		dbg_msg("re-size volume");
+		err = __copy_from_user(&req, argp,
+				       sizeof(struct ubi_rsvol_req));
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+
+		err = verify_rsvol_req(ubi, &req);
+		if (err)
+			break;
+
+		desc = ubi_open_volume(ubi->ubi_num, req.vol_id, UBI_EXCLUSIVE);
+		if (IS_ERR(desc)) {
+			err = PTR_ERR(desc);
+			break;
+		}
+
+		tmp = req.bytes;
+		pebs = !!do_div(tmp, desc->vol->usable_leb_size);
+		pebs += tmp;
+
+dbg_msg("desc %p", desc);
+dbg_msg("desc->vol %p", desc->vol);
+dbg_msg("desc->vol->vol_id %d", desc->vol->vol_id);
+dbg_msg("desc->vol->ubi %d", desc->vol->ubi);
+		err = ubi_resize_volume(desc, pebs);
+		ubi_close_volume(desc);
+		break;
+	}
+
+	default:
+		err = -ENOTTY;
+		break;
+	}
+
+	return err;
+}
+
+/* UBI character device operations */
+struct file_operations ubi_cdev_operations = {
+	.owner = THIS_MODULE,
+	.ioctl = ubi_cdev_ioctl,
+	.llseek = no_llseek
+};
+
+/* UBI volume character device operations */
+struct file_operations ubi_vol_cdev_operations = {
+	.owner   = THIS_MODULE,
+	.open    = vol_cdev_open,
+	.release = vol_cdev_release,
+	.llseek  = vol_cdev_llseek,
+	.read    = vol_cdev_read,
+	.write   = vol_cdev_write,
+	.ioctl   = vol_cdev_ioctl
+};
-
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