[MTD] return error code from get_mtd_device()

get_mtd_device() returns NULL in case of any failure. Teach it to return an
error code instead. Fix all users as well.
Signed-off-by: Artem Bityutskiy <dedekind@infradead.org>

drivers/mtd/maps/nettel.c

@@ -20,6 +20,7 @@
 #include <linux/mtd/partitions.h>
 #include <linux/mtd/cfi.h>
 #include <linux/reboot.h>
+#include <linux/err.h>
 #include <linux/kdev_t.h>
 #include <linux/root_dev.h>
 #include <asm/io.h>
@@ -178,7 +179,7 @@ int nettel_eraseconfig(void)
 
 	init_waitqueue_head(&wait_q);
 	mtd = get_mtd_device(NULL, 2);
-	if (mtd) {
+	if (!IS_ERR(mtd)) {
 		nettel_erase.mtd = mtd;
 		nettel_erase.callback = nettel_erasecallback;
 		nettel_erase.callback = NULL;

drivers/mtd/mtdchar.c

@@ -7,6 +7,7 @@
 
 #include <linux/device.h>
 #include <linux/fs.h>
+#include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -100,8 +101,8 @@ static int mtd_open(struct inode *inode, struct file *file)
 
 	mtd = get_mtd_device(NULL, devnum);
 
-	if (!mtd)
-		return -ENODEV;
+	if (IS_ERR(mtd))
+		return PTR_ERR(mtd);
 
 	if (MTD_ABSENT == mtd->type) {
 		put_mtd_device(mtd);

drivers/mtd/mtdcore.c

@@ -193,14 +193,14 @@ int unregister_mtd_user (struct mtd_notifier *old)
  *	Given a number and NULL address, return the num'th entry in the device
  *	table, if any.	Given an address and num == -1, search the device table
  *	for a device with that address and return if it's still present. Given
- *	both, return the num'th driver only if its address matches. Return NULL
- *	if not.
+ *	both, return the num'th driver only if its address matches. Return
+ *	error code if not.
  */
 
 struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
 {
 	struct mtd_info *ret = NULL;
-	int i;
+	int i, err = -ENODEV;
 
 	mutex_lock(&mtd_table_mutex);
 
@@ -217,22 +217,24 @@ struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
 	if (!ret)
 		goto out_unlock;
 
-	if (!try_module_get(ret->owner)) {
-		ret = NULL;
+	if (!try_module_get(ret->owner))
 		goto out_unlock;
-	}
 
-	if (ret->get_device && ret->get_device(ret)) {
-		module_put(ret->owner);
-		ret = NULL;
-		goto out_unlock;
+	if (ret->get_device) {
+		err = ret->get_device(ret);
+		if (err)
+			goto out_put;
 	}
 
 	ret->usecount++;
+	mutex_unlock(&mtd_table_mutex);
+	return ret;
 
+out_put:
+	module_put(ret->owner);
 out_unlock:
 	mutex_unlock(&mtd_table_mutex);
-	return ret;
+	return ERR_PTR(err);
 }
 
 /**

fs/jffs/jffs_fm.c

@@ -17,6 +17,7 @@
  *
  */
 #include <linux/slab.h>
+#include <linux/err.h>
 #include <linux/blkdev.h>
 #include <linux/jffs.h>
 #include "jffs_fm.h"
@@ -104,7 +105,7 @@ jffs_build_begin(struct jffs_control *c, int unit)
 
 	mtd = get_mtd_device(NULL, unit);
 
-	if (!mtd) {
+	if (IS_ERR(mtd)) {
 		kfree(fmc);
 		DJM(no_jffs_fmcontrol--);
 		return NULL;

fs/jffs2/super.c

@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/fs.h>
+#include <linux/err.h>
 #include <linux/mount.h>
 #include <linux/jffs2.h>
 #include <linux/pagemap.h>
@@ -184,9 +185,9 @@ static int jffs2_get_sb_mtdnr(struct file_system_type *fs_type,
 	struct mtd_info *mtd;
 
 	mtd = get_mtd_device(NULL, mtdnr);
-	if (!mtd) {
+	if (IS_ERR(mtd)) {
 		D1(printk(KERN_DEBUG "jffs2: MTD device #%u doesn't appear to exist\n", mtdnr));
-		return -EINVAL;
+		return PTR_ERR(mtd);
 	}
 
 	return jffs2_get_sb_mtd(fs_type, flags, dev_name, data, mtd, mnt);
@@ -221,7 +222,7 @@ static int jffs2_get_sb(struct file_system_type *fs_type,
 			D1(printk(KERN_DEBUG "jffs2_get_sb(): mtd:%%s, name \"%s\"\n", dev_name+4));
 			for (mtdnr = 0; mtdnr < MAX_MTD_DEVICES; mtdnr++) {
 				mtd = get_mtd_device(NULL, mtdnr);
-				if (mtd) {
+				if (!IS_ERR(mtd)) {
 					if (!strcmp(mtd->name, dev_name+4))
 						return jffs2_get_sb_mtd(fs_type, flags, dev_name, data, mtd, mnt);
 					put_mtd_device(mtd);