UBI: prepare attach and detach functions

Prepare the attach and detach functions to by used outside of
module initialization:

* detach function checks reference count before detaching
* it kills the background thread as well

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/build.c

@@ -40,6 +40,7 @@
 #include <linux/stat.h>
 #include <linux/miscdevice.h>
 #include <linux/log2.h>
+#include <linux/kthread.h>
 #include "ubi.h"
 
 /* Maximum length of the 'mtd=' parameter */
@@ -83,6 +84,9 @@ static struct miscdevice ubi_ctrl_cdev = {
 /* All UBI devices in system */
 static struct ubi_device *ubi_devices[UBI_MAX_DEVICES];
 
+/* Serializes UBI devices creations and removals */
+DEFINE_MUTEX(ubi_devices_mutex);
+
 /* Protects @ubi_devices and @ubi->ref_count */
 static DEFINE_SPINLOCK(ubi_devices_lock);
 
@@ -192,7 +196,7 @@ struct ubi_device *ubi_get_by_major(int major)
  * @major: major number
  *
  * This function searches UBI device number object by its major number. If UBI
- * device was not found, this function returns -ENODEV, othewise the UBI device
+ * device was not found, this function returns -ENODEV, otherwise the UBI device
  * number is returned.
  */
 int ubi_major2num(int major)
@@ -485,9 +489,9 @@ out_si:
  * assumed:
  *   o EC header is always at offset zero - this cannot be changed;
  *   o VID header starts just after the EC header at the closest address
- *   aligned to @io->@hdrs_min_io_size;
+ *     aligned to @io->hdrs_min_io_size;
  *   o data starts just after the VID header at the closest address aligned to
- *     @io->@min_io_size
+ *     @io->min_io_size
  *
  * This function returns zero in case of success and a negative error code in
  * case of failure.
@@ -508,6 +512,9 @@ static int io_init(struct ubi_device *ubi)
 		return -EINVAL;
 	}
 
+	if (ubi->vid_hdr_offset < 0 || ubi->leb_start < ubi->vid_hdr_offset)
+		return -EINVAL;
+
 	/*
 	 * Note, in this implementation we support MTD devices with 0x7FFFFFFF
 	 * physical eraseblocks maximum.
@@ -616,84 +623,62 @@ static int io_init(struct ubi_device *ubi)
 }
 
 /**
- * attach_mtd_dev - attach an MTD device.
- * @mtd_dev: MTD device name or number string
+ * ubi_attach_mtd_dev - attach an MTD device.
+ * @mtd_dev: MTD device description object
  * @vid_hdr_offset: VID header offset
  * @data_offset: data offset
  *
  * This function attaches an MTD device to UBI. It first treats @mtd_dev as the
  * MTD device name, and tries to open it by this name. If it is unable to open,
  * it tries to convert @mtd_dev to an integer and open the MTD device by its
- * number. Returns zero in case of success and a negative error code in case of
- * failure.
+ * number. Returns new UBI device's number in case of success and a negative
+ * error code in case of failure.
+ *
+ * Note, the invocations of this function has to be serialized by the
+ * @ubi_devices_mutex.
  */
-static int attach_mtd_dev(const char *mtd_dev, int vid_hdr_offset,
-			  int data_offset)
+int ubi_attach_mtd_dev(struct mtd_info *mtd, int vid_hdr_offset,
+		       int data_offset)
 {
 	struct ubi_device *ubi;
-	struct mtd_info *mtd;
 	int i, err;
 
-	mtd = get_mtd_device_nm(mtd_dev);
-	if (IS_ERR(mtd)) {
-		int mtd_num;
-		char *endp;
-
-		if (PTR_ERR(mtd) != -ENODEV)
-			return PTR_ERR(mtd);
-
-		/*
-		 * Probably this is not MTD device name but MTD device number -
-		 * check this out.
-		 */
-		mtd_num = simple_strtoul(mtd_dev, &endp, 0);
-		if (*endp != '\0' || mtd_dev == endp) {
-			ubi_err("incorrect MTD device: \"%s\"", mtd_dev);
-			return -ENODEV;
-		}
-
-		mtd = get_mtd_device(NULL, mtd_num);
-		if (IS_ERR(mtd))
-			return PTR_ERR(mtd);
-	}
-
-	/* Check if we already have the same MTD device attached */
+	/*
+	 * Check if we already have the same MTD device attached.
+	 *
+	 * Note, this function assumes that UBI devices creations and deletions
+	 * are serialized, so it does not take the &ubi_devices_lock.
+	 */
 	for (i = 0; i < UBI_MAX_DEVICES; i++)
 		ubi = ubi_devices[i];
-		if (ubi && ubi->mtd->index == mtd->index) {
+		if (ubi && mtd->index == ubi->mtd->index) {
 			ubi_err("mtd%d is already attached to ubi%d",
 				mtd->index, i);
-			err = -EINVAL;
-			goto out_mtd;
+			return -EINVAL;
 		}
 
-	ubi = kzalloc(sizeof(struct ubi_device), GFP_KERNEL);
-	if (!ubi) {
-		err = -ENOMEM;
-		goto out_mtd;
-	}
-
-	ubi->mtd = mtd;
-
 	/* Search for an empty slot in the @ubi_devices array */
-	ubi->ubi_num = -1;
 	for (i = 0; i < UBI_MAX_DEVICES; i++)
-		if (!ubi_devices[i]) {
-			ubi->ubi_num = i;
+		if (!ubi_devices[i])
 			break;
-		}
 
-	if (ubi->ubi_num == -1) {
+	if (i == UBI_MAX_DEVICES) {
 		ubi_err("only %d UBI devices may be created", UBI_MAX_DEVICES);
-		err = -ENFILE;
-		goto out_free;
+		return -ENFILE;
 	}
 
-	dbg_msg("attaching mtd%d to ubi%d: VID header offset %d data offset %d",
-		ubi->mtd->index, ubi->ubi_num, vid_hdr_offset, data_offset);
+	ubi = kzalloc(sizeof(struct ubi_device), GFP_KERNEL);
+	if (!ubi)
+		return -ENOMEM;
 
+	ubi->mtd = mtd;
+	ubi->ubi_num = i;
 	ubi->vid_hdr_offset = vid_hdr_offset;
 	ubi->leb_start = data_offset;
+
+	dbg_msg("attaching mtd%d to ubi%d: VID header offset %d data offset %d",
+		mtd->index, ubi->ubi_num, vid_hdr_offset, data_offset);
+
 	err = io_init(ubi);
 	if (err)
 		goto out_free;
@@ -724,8 +709,16 @@ static int attach_mtd_dev(const char *mtd_dev, int vid_hdr_offset,
 	if (err)
 		goto out_detach;
 
-	ubi_msg("attached mtd%d to ubi%d", ubi->mtd->index, ubi->ubi_num);
-	ubi_msg("MTD device name:            \"%s\"", ubi->mtd->name);
+	ubi->bgt_thread = kthread_create(ubi_thread, ubi, ubi->bgt_name);
+	if (IS_ERR(ubi->bgt_thread)) {
+		err = PTR_ERR(ubi->bgt_thread);
+		ubi_err("cannot spawn \"%s\", error %d", ubi->bgt_name,
+			err);
+		goto out_uif;
+	}
+
+	ubi_msg("attached mtd%d to ubi%d", mtd->index, ubi->ubi_num);
+	ubi_msg("MTD device name:            \"%s\"", mtd->name);
 	ubi_msg("MTD device size:            %llu MiB", ubi->flash_size >> 20);
 	ubi_msg("physical eraseblock size:   %d bytes (%d KiB)",
 		ubi->peb_size, ubi->peb_size >> 10);
@@ -754,8 +747,10 @@ static int attach_mtd_dev(const char *mtd_dev, int vid_hdr_offset,
 	}
 
 	ubi_devices[ubi->ubi_num] = ubi;
-	return 0;
+	return ubi->ubi_num;
 
+out_uif:
+	uif_close(ubi);
 out_detach:
 	ubi_eba_close(ubi);
 	ubi_wl_close(ubi);
@@ -767,21 +762,57 @@ out_free:
 	vfree(ubi->dbg_peb_buf);
 #endif
 	kfree(ubi);
-out_mtd:
-	put_mtd_device(mtd);
 	return err;
 }
 
 /**
- * detach_mtd_dev - detach an MTD device.
- * @ubi: UBI device description object
+ * ubi_detach_mtd_dev - detach an MTD device.
+ * @ubi_num: UBI device number to detach from
+ * @anyway: detach MTD even if device reference count is not zero
+ *
+ * This function destroys an UBI device number @ubi_num and detaches the
+ * underlying MTD device. Returns zero in case of success and %-EBUSY if the
+ * UBI device is busy and cannot be destroyed, and %-EINVAL if it does not
+ * exist.
+ *
+ * Note, the invocations of this function has to be serialized by the
+ * @ubi_devices_mutex.
  */
-static void detach_mtd_dev(struct ubi_device *ubi)
+int ubi_detach_mtd_dev(int ubi_num, int anyway)
 {
-	int ubi_num = ubi->ubi_num, mtd_num = ubi->mtd->index;
+	struct ubi_device *ubi;
+
+	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
+		return -EINVAL;
+
+	spin_lock(&ubi_devices_lock);
+	ubi = ubi_devices[ubi_num];
+	if (!ubi) {
+		spin_lock(&ubi_devices_lock);
+		return -EINVAL;
+	}
+
+	if (ubi->ref_count) {
+		if (!anyway) {
+			spin_lock(&ubi_devices_lock);
+			return -EBUSY;
+		}
+		/* This may only happen if there is a bug */
+		ubi_err("%s reference count %d, destroy anyway",
+			ubi->ubi_name, ubi->ref_count);
+	}
+	ubi_devices[ubi->ubi_num] = NULL;
+	spin_unlock(&ubi_devices_lock);
+
+	dbg_msg("detaching mtd%d from ubi%d", ubi->mtd->index, ubi->ubi_num);
+
+	/*
+	 * Before freeing anything, we have to stop the background thread to
+	 * prevent it from doing anything on this device while we are freeing.
+	 */
+	if (ubi->bgt_thread)
+		kthread_stop(ubi->bgt_thread);
 
-	dbg_msg("detaching mtd%d from ubi%d", ubi->mtd->index, ubi_num);
-	ubi_assert(ubi->ref_count == 0);
 	uif_close(ubi);
 	ubi_eba_close(ubi);
 	ubi_wl_close(ubi);
@@ -792,9 +823,9 @@ static void detach_mtd_dev(struct ubi_device *ubi)
 #ifdef CONFIG_MTD_UBI_DEBUG
 	vfree(ubi->dbg_peb_buf);
 #endif
-	kfree(ubi_devices[ubi_num]);
-	ubi_devices[ubi_num] = NULL;
-	ubi_msg("mtd%d is detached from ubi%d", mtd_num, ubi_num);
+	ubi_msg("mtd%d is detached from ubi%d", ubi->mtd->index, ubi->ubi_num);
+	kfree(ubi);
+	return 0;
 }
 
 /**
@@ -811,6 +842,46 @@ static void ltree_entry_ctor(struct kmem_cache *cache, void *obj)
 	init_rwsem(&le->mutex);
 }
 
+/**
+ * find_mtd_device - open an MTD device by its name or number.
+ * @mtd_dev: name or number of the device
+ *
+ * This function tries to open and MTD device with name @mtd_dev, and if it
+ * fails, then it tries to interpret the @mtd_dev string as an ASCII-coded
+ * integer and open an MTD device with this number. Returns MTD device
+ * description object in case of success and a negative error code in case of
+ * failure.
+ */
+static struct mtd_info * __init open_mtd_device(const char *mtd_dev)
+{
+	struct mtd_info *mtd;
+
+	mtd = get_mtd_device_nm(mtd_dev);
+	if (IS_ERR(mtd)) {
+		int mtd_num;
+		char *endp;
+
+		if (PTR_ERR(mtd) != -ENODEV)
+			return mtd;
+
+		/*
+		 * Probably this is not MTD device name but MTD device number -
+		 * check this out.
+		 */
+		mtd_num = simple_strtoul(mtd_dev, &endp, 0);
+		if (*endp != '\0' || mtd_dev == endp) {
+			ubi_err("incorrect MTD device: \"%s\"", mtd_dev);
+			return ERR_PTR(-ENODEV);
+		}
+
+		mtd = get_mtd_device(NULL, mtd_num);
+		if (IS_ERR(mtd))
+			return mtd;
+	}
+
+	return mtd;
+}
+
 static int __init ubi_init(void)
 {
 	int err, i, k;
@@ -860,10 +931,21 @@ static int __init ubi_init(void)
 	/* Attach MTD devices */
 	for (i = 0; i < mtd_devs; i++) {
 		struct mtd_dev_param *p = &mtd_dev_param[i];
+		struct mtd_info *mtd;
 
 		cond_resched();
-		err = attach_mtd_dev(p->name, p->vid_hdr_offs, p->data_offs);
-		if (err) {
+
+		mtd = open_mtd_device(p->name);
+		if (IS_ERR(mtd)) {
+			err = PTR_ERR(mtd);
+			goto out_detach;
+		}
+
+		mutex_lock(&ubi_devices_mutex);
+		err = ubi_attach_mtd_dev(mtd, p->vid_hdr_offs, p->data_offs);
+		mutex_unlock(&ubi_devices_mutex);
+		if (err < 0) {
+			put_mtd_device(mtd);
 			printk(KERN_ERR "UBI error: cannot attach %s\n",
 			       p->name);
 			goto out_detach;
@@ -874,7 +956,11 @@ static int __init ubi_init(void)
 
 out_detach:
 	for (k = 0; k < i; k++)
-		detach_mtd_dev(ubi_devices[k]);
+		if (ubi_devices[k]) {
+			mutex_lock(&ubi_devices_mutex);
+			ubi_detach_mtd_dev(ubi_devices[k]->ubi_num, 1);
+			mutex_unlock(&ubi_devices_mutex);
+		}
 	kmem_cache_destroy(ubi_wl_entry_slab);
 out_ltree:
 	kmem_cache_destroy(ubi_ltree_slab);
@@ -895,8 +981,11 @@ static void __exit ubi_exit(void)
 	int i;
 
 	for (i = 0; i < UBI_MAX_DEVICES; i++)
-		if (ubi_devices[i])
-			detach_mtd_dev(ubi_devices[i]);
+		if (ubi_devices[i]) {
+			mutex_lock(&ubi_devices_mutex);
+			ubi_detach_mtd_dev(ubi_devices[i]->ubi_num, 1);
+			mutex_unlock(&ubi_devices_mutex);
+		}
 	kmem_cache_destroy(ubi_wl_entry_slab);
 	kmem_cache_destroy(ubi_ltree_slab);
 	misc_deregister(&ubi_ctrl_cdev);

drivers/mtd/ubi/ubi.h

@@ -404,6 +404,7 @@ extern struct file_operations ubi_ctrl_cdev_operations;
 extern struct file_operations ubi_cdev_operations;
 extern struct file_operations ubi_vol_cdev_operations;
 extern struct class *ubi_class;
+extern struct mutex ubi_devices_mutex;
 
 /* vtbl.c */
 int ubi_change_vtbl_record(struct ubi_device *ubi, int idx,
@@ -462,6 +463,7 @@ int ubi_wl_flush(struct ubi_device *ubi);
 int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum);
 int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si);
 void ubi_wl_close(struct ubi_device *ubi);
+int ubi_thread(void *u);
 
 /* io.c */
 int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
@@ -481,6 +483,9 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 			 struct ubi_vid_hdr *vid_hdr);
 
 /* build.c */
+int ubi_attach_mtd_dev(struct mtd_info *mtd, int vid_hdr_offset,
+		       int data_offset);
+int ubi_detach_mtd_dev(int ubi_num, int anyway);
 struct ubi_device *ubi_get_device(int ubi_num);
 void ubi_put_device(struct ubi_device *ubi);
 struct ubi_device *ubi_get_by_major(int major);

drivers/mtd/ubi/wl.c

@@ -1356,7 +1356,7 @@ static void tree_destroy(struct rb_root *root)
  * ubi_thread - UBI background thread.
  * @u: the UBI device description object pointer
  */
-static int ubi_thread(void *u)
+int ubi_thread(void *u)
 {
 	int failures = 0;
 	struct ubi_device *ubi = u;
@@ -1454,18 +1454,10 @@ int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
 
 	sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);
 
-	ubi->bgt_thread = kthread_create(ubi_thread, ubi, ubi->bgt_name);
-	if (IS_ERR(ubi->bgt_thread)) {
-		err = PTR_ERR(ubi->bgt_thread);
-		ubi_err("cannot spawn \"%s\", error %d", ubi->bgt_name,
-			err);
-		return err;
-	}
-
 	err = -ENOMEM;
 	ubi->lookuptbl = kzalloc(ubi->peb_count * sizeof(void *), GFP_KERNEL);
 	if (!ubi->lookuptbl)
-		goto out_free;
+		return err;
 
 	list_for_each_entry_safe(seb, tmp, &si->erase, u.list) {
 		cond_resched();
@@ -1598,10 +1590,6 @@ static void protection_trees_destroy(struct ubi_device *ubi)
  */
 void ubi_wl_close(struct ubi_device *ubi)
 {
-	dbg_wl("disable \"%s\"", ubi->bgt_name);
-	if (ubi->bgt_thread)
-		kthread_stop(ubi->bgt_thread);
-
 	dbg_wl("close the UBI wear-leveling unit");
 
 	cancel_pending(ubi);