Date:	Fri, 23 Mar 2007 18:43:52 +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 11/20 take 4] UBI: kernel API functions

diff -auNrp tmp-from/drivers/mtd/ubi/kapi.c tmp-to/drivers/mtd/ubi/kapi.c
--- tmp-from/drivers/mtd/ubi/kapi.c	1970-01-01 02:00:00.000000000 +0200
+++ tmp-to/drivers/mtd/ubi/kapi.c	2007-03-23 18:20:02.000000000 +0200
@@ -0,0 +1,545 @@
+/*
+ * 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 mostly implements UBI kernel API functions */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <asm/div64.h>
+#include "ubi.h"
+
+/**
+ * ubi_get_device_info - get information about UBI device.
+ * @ubi_num: UBI device number
+ * @di: the information is stored here
+ *
+ * This function returns %0 in case of success and a %-ENODEV if there is no
+ * such UBI device.
+ */
+int ubi_get_device_info(int ubi_num, struct ubi_device_info *di)
+{
+	const struct ubi_device *ubi;
+
+	if (!try_module_get(THIS_MODULE))
+		return -ENODEV;
+
+	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES ||
+	    !ubi_devices[ubi_num]) {
+		module_put(THIS_MODULE);
+		return -ENODEV;
+	}
+
+	ubi = ubi_devices[ubi_num];
+	di->ubi_num = ubi->ubi_num;
+	di->leb_size = ubi->leb_size;
+	di->min_io_size = ubi->min_io_size;
+	di->ro_mode = ubi->ro_mode;
+	di->cdev = MKDEV(ubi->major, 0);
+	module_put(THIS_MODULE);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ubi_get_device_info);
+
+/**
+ * ubi_get_volume_info - get information about UBI volume.
+ * @desc: volume descriptor
+ * @vi: the information is stored here
+ */
+void ubi_get_volume_info(struct ubi_volume_desc *desc,
+			 struct ubi_volume_info *vi)
+{
+	const struct ubi_volume *vol = desc->vol;
+	const struct ubi_device *ubi = vol->ubi;
+
+	vi->vol_id = vol->vol_id;
+	vi->ubi_num = ubi->ubi_num;
+	vi->size = vol->reserved_pebs;
+	vi->used_bytes = vol->used_bytes;
+	vi->vol_type = vol->vol_type;
+	vi->corrupted = vol->corrupted;
+	vi->upd_marker = vol->upd_marker;
+	vi->alignment = vol->alignment;
+	vi->usable_leb_size = vol->usable_leb_size;
+	vi->name_len = vol->name_len;
+	vi->name = vol->name;
+	vi->cdev = MKDEV(ubi->major, vi->vol_id + 1);
+}
+EXPORT_SYMBOL_GPL(ubi_get_volume_info);
+
+/**
+ * ubi_open_volume - open UBI volume.
+ * @ubi_num: UBI device number
+ * @vol_id: volume ID
+ * @mode: open mode
+ *
+ * The @mode parameter specifies if the volume should be opened in read-only
+ * mode, read-write mode, or exclusive mode. The exclusive mode guarantees that
+ * nobody else will be able to open this volume. UBI allows to have many volume
+ * readers and one writer at a time.
+ *
+ * If a static volume is being opened for the first time since boot, it will be
+ * checked by this function, which means it will be fully read and the CRC
+ * checksum of each logical eraseblock will be checked.
+ *
+ * This function returns volume descriptor in case of success and a negative
+ * error code in case of failure.
+ */
+struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
+{
+	int err;
+	struct ubi_volume_desc *desc;
+	struct ubi_device *ubi = ubi_devices[ubi_num];
+	struct ubi_volume *vol;
+
+	dbg_msg("open device %d volume %d, mode %d", ubi_num, vol_id, mode);
+
+	err = -ENODEV;
+	if (!try_module_get(THIS_MODULE))
+		return ERR_PTR(err);
+
+	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES || !ubi)
+		goto out_put;
+
+	err = -EINVAL;
+	if (vol_id < 0 || vol_id >= ubi->vtbl_slots)
+		goto out_put;
+	if (mode != UBI_READONLY && mode != UBI_READWRITE &&
+	    mode != UBI_EXCLUSIVE)
+		goto out_put;
+
+	desc = kmalloc(sizeof(struct ubi_volume_desc), GFP_KERNEL);
+	if (!desc) {
+		err = -ENOMEM;
+		goto out_put;
+	}
+
+	spin_lock(&ubi->volumes_lock);
+	vol = ubi->volumes[vol_id];
+	if (!vol) {
+		err = -ENODEV;
+		goto out_unlock;
+	}
+
+	err = -EBUSY;
+	switch (mode) {
+	case UBI_READONLY:
+		if (vol->exclusive)
+			goto out_unlock;
+		vol->readers += 1;
+		break;
+
+	case UBI_READWRITE:
+		if (vol->exclusive || vol->writers > 0)
+			goto out_unlock;
+		vol->writers += 1;
+		break;
+
+	case UBI_EXCLUSIVE:
+		if (vol->exclusive || vol->writers || vol->readers)
+			goto out_unlock;
+		vol->exclusive = 1;
+		break;
+	}
+	spin_unlock(&ubi->volumes_lock);
+
+	desc->vol = vol;
+	desc->mode = mode;
+
+	/*
+	 * To prevent simultaneous checks of the same volume we use @vtbl_mutex,
+	 * although it is not the purpose it was introduced for.
+	 */
+	mutex_lock(&ubi->vtbl_mutex);
+	if (!vol->checked) {
+		/*
+		 * This is the first open - check the volume. If it is
+		 * corrupted, still return success, but mark it as corrupted,
+		 * so %-EUCLEAN will be returned on any further read.
+		 */
+		err = ubi_check_volume(ubi, vol_id);
+		if (err < 0) {
+			mutex_unlock(&ubi->vtbl_mutex);
+			ubi_close_volume(desc);
+			return ERR_PTR(err);
+		}
+		if (err == 1) {
+			ubi_warn("volume %d on UBI device %d is corrupted",
+				 vol_id, ubi->ubi_num);
+			vol->corrupted = 1;
+		}
+		vol->checked = 1;
+	}
+	mutex_unlock(&ubi->vtbl_mutex);
+	return desc;
+
+out_unlock:
+	spin_unlock(&ubi->volumes_lock);
+	kfree(desc);
+out_put:
+	module_put(THIS_MODULE);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(ubi_open_volume);
+
+/**
+ * ubi_open_volume_nm - open UBI volume by name.
+ * @ubi_num: UBI device number
+ * @name: volume name
+ * @mode: open mode
+ *
+ * This function is similar to 'ubi_open_volume()', but opens a volume by name.
+ */
+struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
+					   int mode)
+{
+	int i, vol_id = -1, len;
+	struct ubi_volume_desc *ret;
+	struct ubi_device *ubi;
+
+	dbg_msg("open volume %s, mode %d", name, mode);
+
+	if (!name)
+		return ERR_PTR(-EINVAL);
+
+	len = strnlen(name, UBI_VOL_NAME_MAX + 1);
+	if (len > UBI_VOL_NAME_MAX)
+		return ERR_PTR(-EINVAL);
+
+	ret = ERR_PTR(-ENODEV);
+	if (!try_module_get(THIS_MODULE))
+		return ret;
+
+	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES || !ubi_devices[ubi_num])
+		goto out_put;
+
+	ubi = ubi_devices[ubi_num];
+
+	spin_lock(&ubi->volumes_lock);
+	/* Walk all volumes of this UBI device */
+	for (i = 0; i < ubi->vtbl_slots; i++) {
+		struct ubi_volume *vol = ubi->volumes[i];
+
+		if (vol && len == vol->name_len && !strcmp(name, vol->name)) {
+			vol_id = i;
+			break;
+		}
+	}
+	spin_unlock(&ubi->volumes_lock);
+
+	if (vol_id < 0)
+		goto out_put;
+
+	ret = ubi_open_volume(ubi_num, vol_id, mode);
+
+out_put:
+	module_put(THIS_MODULE);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ubi_open_volume_nm);
+
+/**
+ * ubi_close_volume - close UBI volume.
+ * @desc: volume descriptor
+ */
+void ubi_close_volume(struct ubi_volume_desc *desc)
+{
+	struct ubi_volume *vol = desc->vol;
+
+	dbg_msg("close volume %d, mode %d", vol->vol_id, desc->mode);
+
+	spin_lock(&vol->ubi->volumes_lock);
+	switch (desc->mode) {
+	case UBI_READONLY:
+		vol->readers -= 1;
+		break;
+	case UBI_READWRITE:
+		vol->writers -= 1;
+		break;
+	case UBI_EXCLUSIVE:
+		vol->exclusive = 0;
+	}
+	spin_unlock(&vol->ubi->volumes_lock);
+
+	kfree(desc);
+	module_put(THIS_MODULE);
+}
+EXPORT_SYMBOL_GPL(ubi_close_volume);
+
+/**
+ * ubi_eraseblock_read - read data.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to read from
+ * @buf: buffer where to store the read data
+ * @offset: offset within the logical eraseblock to read from
+ * @len: how many bytes to read
+ * @check: whether UBI has to check the read data's CRC or not.
+ *
+ * This function reads data from offset @offset of logical eraseblock @lnum and
+ * stores the data at @buf. When reading from static volumes, @check specifies
+ * whether the data has to be checked or not. If yes, the whole logical
+ * eraseblock will be read and its CRC checksum will be checked (i.e., the CRC
+ * checksum is per-eraseblock). So checking may substantially slow down the
+ * read speed. The @check argument is ignored for dynamic volumes.
+ *
+ * In case of success, this function returns zero. In case of failure, this
+ * function returns a negative error code.
+ *
+ * %-EBADMSG error code is returned:
+ * o for both static and dynamic volumes if MTD driver has detected a data
+ *   integrity problem (unrecoverable ECC checksum mismatch in case of NAND);
+ * o for static volumes in case of data CRC mismatch.
+ *
+ * If a corrupted UBI volume is read, this function never returns zero, but
+ * %-EUCLEAN is returned instead, even though the data was read without errors
+ * because the corruption did not affect this particular piece of data
+ * *otherwise %-EBADMSG would have been returned). Thus, %-EUCLEAN just means
+ * that the read static volume is corrupted, but the read data is actually OK.
+ * %-EUCLEAN is not returned for dynamic volumes, because UBI does not protect
+ * their contents.
+ *
+ * If the volume is damaged because of an interrupted update this function just
+ * returns immediately with %-EBADF error code.
+ */
+int ubi_eraseblock_read(struct ubi_volume_desc *desc, int lnum, char *buf,
+			int offset, int len, int check)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int err, vol_id = vol->vol_id;
+
+	dbg_msg("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
+
+	if (unlikely(vol_id < 0 || vol_id >= ubi->vtbl_slots ||
+		     lnum < 0 || lnum >= vol->used_ebs || offset < 0 ||
+		     len < 0 || offset + len > vol->usable_leb_size))
+		return -EINVAL;
+
+	if (unlikely(vol->vol_type == UBI_STATIC_VOLUME &&
+		     lnum == vol->used_ebs - 1 &&
+		     offset + len > vol->last_eb_bytes))
+		return -EINVAL;
+
+	if (unlikely(vol->upd_marker))
+		return -EBADF;
+	if (unlikely(len == 0))
+		return 0;
+
+	err = ubi_eba_read_leb(ubi, vol_id, lnum, buf, offset, len, check);
+	if (unlikely(err && err == -EBADMSG
+		     && vol->vol_type == UBI_STATIC_VOLUME)) {
+		ubi_warn("mark volume %d as corrupted", vol_id);
+		vol->corrupted = 1;
+		err = -EUCLEAN;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(ubi_eraseblock_read);
+
+/**
+ * ubi_eraseblock_write - write data.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to write to
+ * @buf: data to write
+ * @offset: offset within the logical eraseblock where to write
+ * @len: how many bytes to write
+ * @dtype: expected data type
+ *
+ * This function writes @len bytes of data from @buf to offset @offset of
+ * logical eraseblock @lnum. The @dtype argument describes expected lifetime of
+ * the data.
+ *
+ * This function takes care of physical eraseblock write failures. If write to
+ * the physical eraseblock write operation fails, the logical eraseblock is
+ * re-mapped to another physical eraseblock, the data is recovered, and the
+ * write finishes. UBI has a pool of reserved physical eraseblocks for this.
+ *
+ * If all the data were successfully written, zero is returned. If an error
+ * occurred and UBI has not been able to recover from it, this function returns
+ * a negative error code. Note, in case of an error, it is possible that
+ * something was still written to the flash media, but that may be some
+ * garbage.
+ *
+ * If the volume is damaged because of an interrupted update this function just
+ * returns immediately with %-EBADF code.
+ */
+int ubi_eraseblock_write(struct ubi_volume_desc *desc, int lnum,
+			 const void *buf, int offset, int len, int dtype)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int vol_id = vol->vol_id;
+
+	dbg_msg("write %d bytes to LEB %d:%d:%d", len, vol_id, lnum, offset);
+
+	if (unlikely(vol_id < 0 || vol_id >= ubi->vtbl_slots))
+		return -EINVAL;
+
+	if (unlikely(desc->mode == UBI_READONLY ||
+		     vol->vol_type == UBI_STATIC_VOLUME))
+		return -EROFS;
+
+	if (unlikely(lnum < 0 || lnum >= vol->reserved_pebs || offset < 0 ||
+		     len < 0 || offset + len > vol->usable_leb_size ||
+		     offset % ubi->min_io_size || len % ubi->min_io_size))
+		return -EINVAL;
+
+	if (unlikely(dtype != UBI_DATA_LONGTERM &&
+		     dtype != UBI_DATA_SHORTTERM &&
+		     dtype != UBI_DATA_UNKNOWN))
+		return -EINVAL;
+
+	if (unlikely(vol->upd_marker))
+		return -EBADF;
+
+	if (unlikely(len == 0))
+		return 0;
+
+	return ubi_eba_write_leb(ubi, vol_id, lnum, buf, offset, len, dtype);
+}
+EXPORT_SYMBOL_GPL(ubi_eraseblock_write);
+
+/**
+ * ubi_eraseblock_erase - erase logical eraseblock.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number
+ *
+ * This function un-maps logical eraseblock @lnum and synchronously erases the
+ * correspondent physical eraseblock. Returns zero in case of success and a
+ * negative error code in case of failure.
+ *
+ * If the volume is damaged because of an interrupted update this function just
+ * returns immediately with %-EBADF code.
+ */
+int ubi_eraseblock_erase(struct ubi_volume_desc *desc, int lnum)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int err, vol_id = vol->vol_id;
+
+	dbg_msg("erase LEB %d:%d", vol_id, lnum);
+
+	if (unlikely(desc->mode == UBI_READONLY ||
+	             vol->vol_type == UBI_STATIC_VOLUME))
+		return -EROFS;
+
+	if (unlikely(lnum < 0 || lnum >= vol->reserved_pebs))
+		return -EINVAL;
+
+	if (unlikely(vol->upd_marker))
+		return -EBADF;
+
+	err = ubi_eba_unmap_leb(ubi, vol_id, lnum);
+	if (unlikely(err))
+		return err;
+
+	return ubi_wl_flush(ubi);
+}
+EXPORT_SYMBOL_GPL(ubi_eraseblock_erase);
+
+/**
+ * ubi_eraseblock_unmap - un-map logical eraseblock.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number
+ *
+ * This function un-maps logical eraseblock @lnum and schedules the
+ * corresponding physical eraseblock for erasure, so that it will eventually be
+ * physically erased in background. This operation is much faster then the
+ * erase operation.
+ *
+ * Unlike erase, the un-map operation does not guarantee that the logical
+ * eraseblock will contain all 0xFF bytes when UBI is initialized again. For
+ * example, if several logical eraseblocks are un-mapped, and an unclean reboot
+ * happens after this, the logical eraseblocks will not necessarily be
+ * un-mapped again when this MTD device is attached. They may actually be
+ * mapped to the same physical eraseblocks again. So, this function has to be
+ * used with care.
+ *
+ * In other words, when un-mapping a logical eraseblock, UBI does not store
+ * any information about this on the flash media, it just marks the logical
+ * eraseblock as "un-mapped" in RAM. If UBI is detached before the physical
+ * eraseblock is physically erased, it will be mapped again to the same logical
+ * eraseblock when the MTD device is attached again.
+ *
+ * The main and obvious use-case of this function is when the contents of a
+ * logical eraseblock has to be re-written. Then it is much more efficient to
+ * first un-map it, then write new data, rather then first erase it, then write
+ * new data. Note, once new data has been written to the logical eraseblock,
+ * UBI guarantees that the old contents has gone forever. In other words, if an
+ * unclean reboot happens after the logical eraseblock has been un-mapped and
+ * then written to, it will contain the last written data.
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure. If the volume is damaged because of an interrupted update
+ * this function just returns immediately with %-EBADF code.
+ */
+int ubi_eraseblock_unmap(struct ubi_volume_desc *desc, int lnum)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int vol_id = vol->vol_id;
+
+	dbg_msg("unmap LEB %d:%d", vol_id, lnum);
+
+	if (unlikely(desc->mode == UBI_READONLY ||
+	             vol->vol_type == UBI_STATIC_VOLUME))
+		return -EROFS;
+
+	if (unlikely(lnum < 0 || lnum >= vol->reserved_pebs))
+		return -EINVAL;
+
+	if (unlikely(vol->upd_marker))
+		return -EBADF;
+
+	return ubi_eba_unmap_leb(ubi, vol_id, lnum);
+}
+EXPORT_SYMBOL_GPL(ubi_eraseblock_unmap);
+
+/**
+ * ubi_eraseblock_is_mapped - check if logical eraseblock is mapped.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number
+ *
+ * This function checks if logical eraseblock @lnum is mapped to a physical
+ * eraseblock. If a logical eraseblock is un-mapped, this does not necessarily
+ * mean it will still be un-mapped after the UBI device is re-attached. The
+ * logical eraseblock may become mapped to the physical eraseblock it was last
+ * mapped to.
+ *
+ * This function returns %1 if the LEB is mapped, %0 if not, and a negative
+ * error code in case of failure. If the volume is damaged because of an
+ * interrupted update this function just returns immediately with %-EBADF error
+ * code.
+ */
+int ubi_eraseblock_is_mapped(struct ubi_volume_desc *desc, int lnum)
+{
+	struct ubi_volume *vol = desc->vol;
+
+	dbg_msg("test LEB %d:%d", vol->vol_id, lnum);
+
+	if (unlikely(lnum < 0 || lnum >= vol->reserved_pebs))
+		return -EINVAL;
+
+	if (unlikely(vol->upd_marker))
+		return -EBADF;
+
+	return !!vol->eba_tbl[lnum];
+}
+EXPORT_SYMBOL_GPL(ubi_eraseblock_is_mapped);
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