block2mtd: mtd: Present block2mtd timely on boot time

From: Felix Fietkau <[email protected]>

block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2708 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.
This patchset also adds a MTD device name and a timeout option to the driver.

Original patchset:
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/440-block2mtd_init.patch?rev=40444
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/441-block2mtd_probe.patch?rev=40444

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

drivers/mtd/devices/block2mtd.c +34 -10

@@ -9,7 +9,15 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+/*
+* When the first attempt at device initialization fails, we may need to
+* wait a little bit and retry. This timeout, by default 3 seconds, gives
+* device time to start up. Required on BCM2708 and a few other chipsets.
+*/
+#define MTD_DEFAULT_TIMEOUT	3
+
 #include <linux/module.h>
+#include <linux/delay.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>

@@ -17,6 +25,7 @@
 #include <linux/list.h>
 #include <linux/init.h>
 #include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
 #include <linux/mutex.h>
 #include <linux/mount.h>
 #include <linux/slab.h>

@@ -209,12 +218,14 @@ static void block2mtd_free_device(struct
 }
 
 
-static struct block2mtd_dev *add_device(char *devname, int erase_size)
+static struct block2mtd_dev *add_device(char *devname, int erase_size, const char *mtdname, int timeout)
 {
 	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
-	struct block_device *bdev;
+	struct block_device *bdev = ERR_PTR(-ENODEV);
 	struct block2mtd_dev *dev;
+	struct mtd_partition *part;
 	char *name;
+	int i;
 
 	if (!devname)
 		return NULL;

@@ -225,15 +236,28 @@ static struct block2mtd_dev *add_device(
 
 	/* Get a handle on the device */
 	bdev = blkdev_get_by_path(devname, mode, dev);
-#ifndef MODULE
-	if (IS_ERR(bdev)) {
 
-		/* We might not have rootfs mounted at this point. Try
-		   to resolve the device name by other means. */
-
-		dev_t devt = name_to_dev_t(devname);
-		if (devt)
-			bdev = blkdev_get_by_dev(devt, mode, dev);
+#ifndef MODULE
+/*
+* We might not have the root device mounted at this point.
+* Try to resolve the device name by other means.
+*/
+	for (i = 0; IS_ERR(bdev) && i <= timeout; i++) {
+		dev_t devt;
+
+		if (i)
+			/*
+			 * Calling wait_for_device_probe in the first loop 
+			 * was not enough, sleep for a bit in subsequent
+			 * go-arounds.
+			*/
+			msleep(1000);
+		wait_for_device_probe();
+
+		devt = name_to_dev_t(devname);
+		if (!devt)
+			continue;
+		bdev = blkdev_get_by_dev(devt, mode, dev);
 	}
 #endif
 

@@ -257,13 +281,15 @@ static struct block2mtd_dev *add_device(
 

drivers/mtd/devices/block2mtd.c +11 -6

 	dev->mtd.erasesize = erase_size;
 	dev->mtd.writesize = 1;
 	dev->mtd.writebufsize = PAGE_SIZE;

@@ -276,15 +302,19 @@ static struct block2mtd_dev *add_device(
 	dev->mtd.priv = dev;
 	dev->mtd.owner = THIS_MODULE;
 
-	if (mtd_device_register(&dev->mtd, NULL, 0)) {
+	part = kzalloc(sizeof(struct mtd_partition), GFP_KERNEL);
+	part->name = name;
+	part->offset = 0;
+	part->size = dev->mtd.size;
+	if (mtd_device_register(&dev->mtd, part, 1)) {
 		/* Device didn't get added, so free the entry */
 		goto err_destroy_mutex;
 	}
+
 	list_add(&dev->list, &blkmtd_device_list);
 	pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 		dev->mtd.index,
-		dev->mtd.name + strlen("block2mtd: "),
-		dev->mtd.erasesize >> 10, dev->mtd.erasesize);
+		mtdname, dev->mtd.erasesize >> 10, dev->mtd.erasesize);
 	return dev;
 
 err_destroy_mutex:

@@ -353,11 +383,12 @@ static char block2mtd_paramline[80 + 12]
 
 static int block2mtd_setup2(const char *val)
 {
-	char buf[80 + 12]; /* 80 for device, 12 for erase size */
+	char buf[80 + 12 + 80 + 8]; /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
 	char *str = buf;
-	char *token[2];
+	char *token[4];
 	char *name;
 	size_t erase_size = PAGE_SIZE;
+	unsigned long timeout = MTD_DEFAULT_TIMEOUT;
 	int i, ret;
 
 	if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {

@@ -368,7 +399,7 @@ static int block2mtd_setup2(const char *
 	strcpy(str, val);
 	kill_final_newline(str);
 
-	for (i = 0; i < 2; i++)
+	for (i = 0; i < 4; i++)
 		token[i] = strsep(&str, ",");
 
 	if (str) {

drivers/mtd/devices/block2mtd.c +5 -1

+
+	if (token[3] && kstrtoul(token[3], 0, &timeout))
+		pr_err("invalid timeout");
+	add_device(name, erase_size, token[2], timeout);
 
 	return 0;
 }

@@ -429,7 +466,7 @@ static int block2mtd_setup(const char *v
 
 
 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
-MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
+MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]\"");
 
 static int __init block2mtd_init(void)
 {

Quoted 12 lines

drivers/mtd/devices/block2mtd.c +3 -1

@@ -257,13 +281,15 @@ static struct block2mtd_dev *add_device( 
 
 /* Setup the MTD structure */ 
 /* make the name contain the block device in */ 
- name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname); 
+ if (!mtdname) 
+ mtdname = devname; 
+ name = kmalloc(strlen(mtdname) + 1, GFP_KERNEL); 
 if (!name) 
 goto err_destroy_mutex; 
 

drivers/mtd/devices/block2mtd.c static struct block2mtd_dev *add_device( · line 290

Quoted 1 line

drivers/mtd/devices/block2mtd.c +1 -0

+ strcpy(name, mtdname); 

kstrdup.
And see below for the ABI change.

drivers/mtd/devices/block2mtd.c static struct block2mtd_dev *add_device( · line 292

Quoted 4 lines

drivers/mtd/devices/block2mtd.c +1 -2

 	dev->mtd.name = name;
-
-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK & ~(erase_size - 1);

PAGE_MASK is no longer needed with the new term. Or does anyone seriously want to support erase_size < PAGE_SIZE?

Timeout has a default value, but name defaults to NULL. Add three devices without specifying the name and you get funny results. If we handled the NULL case by doing what the driver used to do before this patch, I think this would be fine.

mtd: block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time.

Using block2mtd sounds a bit unusual. I see that you are trying to get a more robust fs.... have you tried using f2fs instead of jffs2?

Quoted 3 lines

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time.

It worries me a bit to add such a long delay to the boot. If for some reason the SD is not working, then the kernel will wait (by default) 3 seconds now?

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented timely on boot time

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue is seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 over block2mtd devices as the root filesystem.
This patchset also adds a MTD device name and a timeout option to the driver. Original patchset:
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/440-block2mtd_init.patch?rev=40444
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/441-block2mtd_probe.patch?rev=40444

Quoted 4 lines · Rodrigo Freire

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented timely on boot time

Quoted 9 lines

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue is seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 over block2mtd devices as the root filesystem.
This patchset also adds a MTD device name and a timeout option to the driver. Original patchset:
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/440-block2mtd_init.patch?rev=40444
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/441-block2mtd_probe.patch?rev=40444

I think you can mount jffs2 using /dev/mtdX, you do not need the block driver.

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.
This patchset also adds a MTD device name and a timeout option to the driver. Original patchset:
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/440-block2mtd_init.patch?rev=40444
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/441-block2mtd_probe.patch?rev=40444

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V2: Uses kstrdup, removed PAGE_MASK.

drivers/mtd/devices/block2mtd.c 2014-09-17 17:43:21.424944394 -0300 renamed from drivers/mtd/devices/block2mtd.c 2014-09-16 21:38:12.543952627 -0300 +45 -16

@@ -9,7 +9,15 @@ 
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 
 
+/* 
+* When the first attempt at device initialization fails, we may need to 
+* wait a little bit and retry. This timeout, by default 3 seconds, gives 
+* device time to start up. Required on BCM2708 and a few other chipsets. 
+*/ 
+#define MTD_DEFAULT_TIMEOUT 3 
+ 
 #include <linux/module.h> 
+#include <linux/delay.h> 
 #include <linux/fs.h> 
 #include <linux/blkdev.h> 
 #include <linux/bio.h> 

@@ -17,6 +25,7 @@ 
 #include <linux/list.h> 
 #include <linux/init.h> 
 #include <linux/mtd/mtd.h> 
+#include <linux/mtd/partitions.h> 
 #include <linux/mutex.h> 
 #include <linux/mount.h> 
 #include <linux/slab.h> 

@@ -209,12 +218,14 @@ static void block2mtd_free_device(struct 
 } 
 
 
-static struct block2mtd_dev *add_device(char *devname, int erase_size) 
+static struct block2mtd_dev *add_device(char *devname, int erase_size, const char *mtdname, int timeout) 
 { 
 const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL; 
- struct block_device *bdev; 
+ struct block_device *bdev = ERR_PTR(-ENODEV); 
 struct block2mtd_dev *dev; 
+ struct mtd_partition *part; 
 char *name; 
+ int i; 
 
 if (!devname) 
 return NULL; 

@@ -225,15 +236,28 @@ static struct block2mtd_dev *add_device( 
 
 /* Get a handle on the device */ 
 bdev = blkdev_get_by_path(devname, mode, dev); 
-#ifndef MODULE 
- if (IS_ERR(bdev)) { 
 
- /* We might not have rootfs mounted at this point. Try 
- to resolve the device name by other means. */ 
- 
- dev_t devt = name_to_dev_t(devname); 
- if (devt) 
- bdev = blkdev_get_by_dev(devt, mode, dev); 
+#ifndef MODULE 
+/* 
+* We might not have the root device mounted at this point. 
+* Try to resolve the device name by other means. 
+*/ 
+ for (i = 0; IS_ERR(bdev) && i <= timeout; i++) { 
+ dev_t devt; 
+ 
+ if (i) 
+ /* 
+ * Calling wait_for_device_probe in the first loop 
+ * was not enough, sleep for a bit in subsequent 
+ * go-arounds. 
+ */ 
+ msleep(1000); 
+ wait_for_device_probe(); 
+ 
+ devt = name_to_dev_t(devname); 
+ if (!devt) 
+ continue; 
+ bdev = blkdev_get_by_dev(devt, mode, dev); 
 } 
 #endif 
 

@@ -257,13 +281,14 @@ static struct block2mtd_dev *add_device( 
 
 /* Setup the MTD structure */ 
 /* make the name contain the block device in */ 
- name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname); 
+ if (!mtdname) 
+ mtdname = devname; 
+ name = kstrdup (mtdname, GFP_KERNEL); 
 if (!name) 
 goto err_destroy_mutex; 
 
 dev->mtd.name = name; 
- 
- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK; 
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1); 
 dev->mtd.erasesize = erase_size; 
 dev->mtd.writesize = 1; 
 dev->mtd.writebufsize = PAGE_SIZE; 

@@ -276,15 +301,19 @@ static struct block2mtd_dev *add_device( 
 dev->mtd.priv = dev; 
 dev->mtd.owner = THIS_MODULE; 
 
- if (mtd_device_register(&dev->mtd, NULL, 0)) { 
+ part = kzalloc(sizeof(struct mtd_partition), GFP_KERNEL); 
+ part->name = name; 
+ part->offset = 0; 
+ part->size = dev->mtd.size; 
+ if (mtd_device_register(&dev->mtd, part, 1)) { 
 /* Device didn't get added, so free the entry */ 
 goto err_destroy_mutex; 
 } 
+ 
 list_add(&dev->list, &blkmtd_device_list); 
 pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n", 
 dev->mtd.index, 
- dev->mtd.name + strlen("block2mtd: "), 
- dev->mtd.erasesize >> 10, dev->mtd.erasesize); 
+ mtdname, dev->mtd.erasesize >> 10, dev->mtd.erasesize); 
 return dev; 
 

err_destroy_mutex:

drivers/mtd/devices/block2mtd.c 2014-09-17 17:43:21.424944394 -0300 renamed from drivers/mtd/devices/block2mtd.c 2014-09-16 21:38:12.543952627 -0300 +13 -8

@@ -353,11 +382,12 @@ static char block2mtd_paramline[80 + 12] 
 
 static int block2mtd_setup2(const char *val) 
 { 
- char buf[80 + 12]; /* 80 for device, 12 for erase size */ 
+ char buf[80 + 12 + 80 + 8]; /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */ 
 char *str = buf; 
- char *token[2]; 
+ char *token[4]; 
 char *name; 
 size_t erase_size = PAGE_SIZE; 
+ unsigned long timeout = MTD_DEFAULT_TIMEOUT; 
 int i, ret; 
 
 if (strnlen(val, sizeof(buf)) >= sizeof(buf)) { 

@@ -368,7 +398,7 @@ static int block2mtd_setup2(const char * 
 strcpy(str, val); 
 kill_final_newline(str); 
 
- for (i = 0; i < 2; i++) 
+ for (i = 0; i < 4; i++) 
 token[i] = strsep(&str, ","); 
 
 if (str) { 

@@ -395,7 +425,13 @@ static int block2mtd_setup2(const char * 
 } 
 } 
 
- add_device(name, erase_size); 
+ if (token[2] && (strlen(token[2]) + 1 > 80)) 
+ pr_err("mtd device name too long"); 
+ 
+ 
+ if (token[3] && kstrtoul(token[3], 0, &timeout)) 
+ pr_err("invalid timeout"); 
+ add_device(name, erase_size, token[2], timeout); 
 
 return 0; 
 } 

@@ -429,7 +465,7 @@ static int block2mtd_setup(const char *v 
 
 
 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200); 
-MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\""); 
+MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]\""); 
 
 static int __init block2mtd_init(void) 
 { 

@@ -463,8 +499,7 @@ static void block2mtd_exit(void) 
 } 
 } 
 
- 
-module_init(block2mtd_init); 
+late_initcall(block2mtd_init); 
 module_exit(block2mtd_exit); 
 
 MODULE_LICENSE("GPL"); 
--- 

1.7.1

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.

This patchset also adds a MTD device name and a timeout option to the driver. Original patchset:
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/440-block2mtd_init.patch?rev=40444
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.12/441-block2mtd_probe.patch?rev=40444

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V2: Uses kstrdup, removed PAGE_MASK.

drivers/mtd/devices/block2mtd.c +9 -0

@@ -9,7 +9,15 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+/*
+* When the first attempt at device initialization fails, we may need to
+* wait a little bit and retry. This timeout, by default 3 seconds, gives
+* device time to start up. Required on BCM2708 and a few other chipsets.
+*/
+#define MTD_DEFAULT_TIMEOUT	3
+
 #include <linux/module.h>
+#include <linux/delay.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>

@@ -17,6 +25,7 @@
 #include <linux/list.h>
 #include <linux/init.h>
 #include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
 #include <linux/mutex.h>
 #include <linux/mount.h>
 #include <linux/slab.h>

drivers/mtd/devices/block2mtd.c +0 -3

 	if (!devname)
 		return NULL;

@@ -225,15 +236,28 @@ static struct block2mtd_dev *add_device(
 
 	/* Get a handle on the device */
 	bdev = blkdev_get_by_path(devname, mode, dev);
-#ifndef MODULE
-	if (IS_ERR(bdev)) {
 
-		/* We might not have rootfs mounted at this point. Try

drivers/mtd/devices/block2mtd.c +16 -1

+	for (i = 0; IS_ERR(bdev) && i <= timeout; i++) {
+		dev_t devt;
+
+		if (i)
+			/*
+			 * Calling wait_for_device_probe in the first loop 
+			 * was not enough, sleep for a bit in subsequent
+			 * go-arounds.
+			*/
+			msleep(1000);
+		wait_for_device_probe();
+
+		devt = name_to_dev_t(devname);
+		if (!devt)
+			continue;
+		bdev = blkdev_get_by_dev(devt, mode, dev);
 	}
 #endif
 

@@ -257,13 +281,14 @@ static struct block2mtd_dev *add_device(
 
 	/* Setup the MTD structure */
 	/* make the name contain the block device in */
-	name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);

drivers/mtd/devices/block2mtd.c +15 -7

+	if (mtd_device_register(&dev->mtd, part, 1)) {
 		/* Device didn't get added, so free the entry */
 		goto err_destroy_mutex;
 	}
+
 	list_add(&dev->list, &blkmtd_device_list);
 	pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 		dev->mtd.index,
-		dev->mtd.name + strlen("block2mtd: "),
-		dev->mtd.erasesize >> 10, dev->mtd.erasesize);
+		mtdname, dev->mtd.erasesize >> 10, dev->mtd.erasesize);
 	return dev;
 
 err_destroy_mutex:

@@ -353,11 +382,12 @@ static char block2mtd_paramline[80 + 12]
 
 static int block2mtd_setup2(const char *val)
 {
-	char buf[80 + 12]; /* 80 for device, 12 for erase size */
+	char buf[80 + 12 + 80 + 8]; /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
 	char *str = buf;
-	char *token[2];
+	char *token[4];
 	char *name;
 	size_t erase_size = PAGE_SIZE;
+	unsigned long timeout = MTD_DEFAULT_TIMEOUT;
 	int i, ret;
 
 	if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {

@@ -368,7 +398,7 @@ static int block2mtd_setup2(const char *
 	strcpy(str, val);
 	kill_final_newline(str);
 
-	for (i = 0; i < 2; i++)
+	for (i = 0; i < 4; i++)
 		token[i] = strsep(&str, ",");
 
 	if (str) {

@@ -395,7 +425,13 @@ static int block2mtd_setup2(const char *
 		}
 	}
 
-	add_device(name, erase_size);
+	if (token[2] && (strlen(token[2]) + 1 > 80))
+		pr_err("mtd device name too long");
+
+
+	if (token[3] && kstrtoul(token[3], 0, &timeout))
+		pr_err("invalid timeout");
+	add_device(name, erase_size, token[2], timeout);
 
 	return 0;
 }

@@ -429,7 +465,7 @@ static int block2mtd_setup(const char *v
 
 
 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
-MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
+MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]\"");
 
 static int __init block2mtd_init(void)
 {

Quoted 9 lines · Rodrigo Freire

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:

http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

Quoted 11 lines · Brian Norris

Quoted 9 lines · Rodrigo Freire

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is presented in a timely fashion

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.

Quoted 4 lines

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:

http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

At old days it was impossible to mount character devices, only block devices. So people ware using mtdblock to mount jffs2. This is just a work-around.

I did not look at this code for long time, and may have forgotten something, but I believe you do not need mtdblock anymore for this. You just mount the mtd device.

This driver should not be used for this.

The only usage of this driver is emulating a block device on top of NOR flash, and in most cases, only for debugging / research purposes. This is because (a) this driver does not handle bad blocks (and hence, NAND-incompatible) and (b) it does read-erase-write when you modify a block, so it is extremely slow and does not handle power cuts at all.

Quoted 5 lines

The only usage of this driver is emulating a block device on top of NOR flash, and in most cases, only for debugging / research purposes. This is because (a) this driver does not handle bad blocks (and hence, NAND-incompatible) and (b) it does read-erase-write when you modify a block, so it is extremely slow and does not handle power cuts at all.

I think you got things mixed up a bit. This is not about emulating a block device on top of NOR flash. This is about emulating NOR flash on top of a regular block device - e.g. USB sticks, SD cards.

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 5, 2014 6:23:03 PM

Quoted 5 lines · Rodrigo Freire

Currently, a block MTD device is not presented to the system on time, in order to start mounting the filesystems. This patch ensures that block2mtd is presented at the right time, so filesystems can be mounted on boot time. This issue was seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems.

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:
http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

You're stating right up front that this patch is doing several different things. Please split these up into separate commits which get their own description.

You have several checkpatch warnings. Please fix them.

The addition of this name parameter should definitely be its own patch.

This variable produces a warning when built as a module:

drivers/mtd/devices/block2mtd.c: In function ‘add_device’:
drivers/mtd/devices/block2mtd.c:228:6: warning: unused variable ‘i’ [-Wunused-variable]
int i;
^

drivers/mtd/devices/block2mtd.c static struct block2mtd_dev *add_device( · line 244

Quoted 5 lines

drivers/mtd/devices/block2mtd.c +5 -0

+#ifndef MODULE
+/*
+* We might not have the root device mounted at this point.
+* Try to resolve the device name by other means.
+*/

These lines should start with a space, so the asterisks line up.

Quoted 2 lines

- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

This deserves its own patch, or at least some explanation of why you're doing this. I guess you're seeing cases where the provided erasesize is not aligned with the size of the block device?

Quoted 7 lines

dev->mtd.erasesize = erase_size;
dev->mtd.writesize = 1;
dev->mtd.writebufsize = PAGE_SIZE;

drivers/mtd/devices/block2mtd.c +0 -0

@@ -276,15 +301,19 @@ static struct block2mtd_dev *add_device(
 dev->mtd.priv = dev;
 dev->mtd.owner = THIS_MODULE;
 

drivers/mtd/devices/block2mtd.c static struct block2mtd_dev *add_device( · line 307

Quoted 5 lines

drivers/mtd/devices/block2mtd.c +4 -1

- if (mtd_device_register(&dev->mtd, NULL, 0)) {
+ part = kzalloc(sizeof(struct mtd_partition), GFP_KERNEL);
+ part->name = name;
+ part->offset = 0;
+ part->size = dev->mtd.size;

Why are you doing this? This also does not fit the description of this patch. And what's wrong with using the default partitioning options? Won't we (if not specified in some other way) default to an unpartitioned MTD, which covers the entire device?

Quoted 6 lines

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 5, 2014 6:23:03 PM

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:
http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

As Felix stated on a previous message to the thread, I am using JFFS2 over block2mtd where regular filesystems failed to do so well. There are several
[1] threads pointing this issue, and JFFS2 over block2mtd works like a charm on more harsh scenarios.

[1] - http://bit.ly/1smGvwa

Quoted 12 lines

Quoted 6 lines

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 5, 2014 6:23:03 PM

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:
http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

As Felix stated on a previous message to the thread, I am using JFFS2 over block2mtd where regular filesystems failed to do so well. There are several
[1] threads pointing this issue, and JFFS2 over block2mtd works like a charm
on more harsh scenarios.

[...]

Quoted 1 line

[1] - http://bit.ly/1smGvwa

OK, so there are definitely problems with cheap SD card power cut tolerance. That's not news. But that doesn't mean block2mtd + JFFS2 is a good solution. In fact, when I add 'jffs2' to your Google search query of 'raspberry pi corrupt sd card', the only mentions I see are those who agree that this is not the right choice.

But anyway, we can look at supporting block2mtd (since you provided the patches), even if we don't agree how it should be used. And in fact, I might argue there are no good (production) uses for block2mtd, so I suppose I don't have much stake in it :)

Quoted 12 lines

Quoted 6 lines

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 5, 2014 6:23:03 PM

This still seems like a bad idea (using a block device + block2mtd + JFFS2). Why are you doing this? See comments here:
http://www.linux-mtd.infradead.org/faq/jffs2.html#L_hdd_jffs2

As Felix stated on a previous message to the thread, I am using JFFS2 over block2mtd where regular filesystems failed to do so well. There are several
[1] threads pointing this issue, and JFFS2 over block2mtd works like a charm
on more harsh scenarios.

[...]

Quoted 1 line

[1] - http://bit.ly/1smGvwa

OK, so there are definitely problems with cheap SD card power cut tolerance. That's not news. But that doesn't mean block2mtd + JFFS2 is a good solution. In fact, when I add 'jffs2' to your Google search query of 'raspberry pi corrupt sd card', the only mentions I see are those who agree that this is not the right choice.

But anyway, we can look at supporting block2mtd (since you provided the patches), even if we don't agree how it should be used. And in fact, I might argue there are no good (production) uses for block2mtd, so I suppose I don't have much stake in it :)

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Ensure that block2mtd is triggered after block devices are presented.

Ensures that block2mtd is triggered after the block devices are enumerated at boot time.
This issue is seen on BCM2835 (Raspberry Pi) systems when mounting JFFS2 block2mtd filesystems, probably because of the delay on enumerating a USB MMC card reader.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch, fixes a compiling warning, cosmethic changes
V2: Uses kstrdup, removed PAGE_MASK.

drivers/mtd/devices/block2mtd.c +0 -0

drivers/mtd/devices/block2mtd.c +0 -0

@@ -225,15 +237,28 @@ static struct block2mtd_dev *add_device(
 
 	/* Get a handle on the device */
 	bdev = blkdev_get_by_path(devname, mode, dev);

drivers/mtd/devices/block2mtd.c +22 -6

+	for (i = 0; IS_ERR(bdev) && i <= timeout; i++) {
+		dev_t devt;
 
-		dev_t devt = name_to_dev_t(devname);
-		if (devt)
-			bdev = blkdev_get_by_dev(devt, mode, dev);
+		if (i)
+			/*
+			 * Calling wait_for_device_probe in the first loop
+			 * was not enough, sleep for a bit in subsequent
+			 * go-arounds.
+			 */
+			msleep(1000);
+		wait_for_device_probe();
+
+		devt = name_to_dev_t(devname);
+		if (!devt)
+			continue;
+		bdev = blkdev_get_by_dev(devt, mode, dev);
 	}
 #endif
 

@@ -280,6 +305,7 @@ static struct block2mtd_dev *add_device(
 		/* Device didn't get added, so free the entry */
 		goto err_destroy_mutex;
 	}
+
 	list_add(&dev->list, &blkmtd_device_list);
 	pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 		dev->mtd.index,

@@ -348,16 +374,19 @@ static inline void kill_final_newline(ch
 
 #ifndef MODULE
 static int block2mtd_init_called = 0;
-static char block2mtd_paramline[80 + 12]; /* 80 for device, 12 for erase size */
+/* 80 for device, 12 for erase size */
+static char block2mtd_paramline[80 + 12];
 #endif
 
 static int block2mtd_setup2(const char *val)
 {
-	char buf[80 + 12]; /* 80 for device, 12 for erase size */
+	/* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
+	char buf[80 + 12 + 80 + 8];
 	char *str = buf;
 	char *token[2];
 	char *name;
 	size_t erase_size = PAGE_SIZE;
+	unsigned long timeout = MTD_DEFAULT_TIMEOUT;
 	int i, ret;
 
 	if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {

@@ -395,7 +424,7 @@ static int block2mtd_setup2(const char *
 		}
 	}
 
-	add_device(name, erase_size);
+	add_device(name, erase_size, timeout);
 
 	return 0;
 }

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Adds a mtd name and a block device timeout option

This patch adds support to a block2mtd MTD name and allows to specify a block device timeout when adding a block2mtd MTD drive.
Usage: block2mtd=<dev>[,<erasesize>[,<name>[,<timeout>]]]

The devices will be identified the following way:
[root@server01 ~]# cat /proc/mtd
dev: size erasesize name
mtd0: a0000000 00010000 "rootfs"
mtd1: 265080000 00010000 "anothername"
mtd2: acd00000 00010000 "/dev/mmcblk0p2"
Notice that the device mtd2 was added without specifying a name.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch

drivers/mtd/devices/block2mtd.c +6 -2

@@ -25,6 +25,7 @@
 #include <linux/list.h>
 #include <linux/init.h>
 #include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
 #include <linux/mutex.h>
 #include <linux/mount.h>
 #include <linux/slab.h>

@@ -218,7 +219,7 @@ static void block2mtd_free_device(struct
 
 
 static struct block2mtd_dev *add_device(char *devname, int erase_size,
-		int timeout)
+		const char *mtdname, int timeout)
 {
 #ifndef MODULE
 	int i;

@@ -226,6 +227,7 @@ static struct block2mtd_dev *add_device(
 	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
 	struct block_device *bdev = ERR_PTR(-ENODEV);
 	struct block2mtd_dev *dev;
+	struct mtd_partition *part;
 	char *name;
 
 	if (!devname)

@@ -282,7 +284,9 @@ static struct block2mtd_dev *add_device(
 
 	/* Setup the MTD structure */
 	/* make the name contain the block device in */
-	name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
+	if (!mtdname)
+		mtdname = devname;
+	name = kstrdup(mtdname, GFP_KERNEL);
 	if (!name)
 		goto err_destroy_mutex;
 

drivers/mtd/devices/block2mtd.c +6 -3

+	part->name = name;
+	part->offset = 0;
+	part->size = dev->mtd.size;
+	if (mtd_device_register(&dev->mtd, part, 1)) {
 		/* Device didn't get added, so free the entry */
 		goto err_destroy_mutex;
 	}

@@ -309,8 +317,7 @@ static struct block2mtd_dev *add_device(
 	list_add(&dev->list, &blkmtd_device_list);
 	pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 		dev->mtd.index,
-		dev->mtd.name + strlen("block2mtd: "),
-		dev->mtd.erasesize >> 10, dev->mtd.erasesize);
+		mtdname, dev->mtd.erasesize >> 10, dev->mtd.erasesize);
 	return dev;
 
 err_destroy_mutex:

@@ -383,7 +390,7 @@ static int block2mtd_setup2(const char *
 	/* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
 	char buf[80 + 12 + 80 + 8];
 	char *str = buf;
-	char *token[2];
+	char *token[4];
 	char *name;
 	size_t erase_size = PAGE_SIZE;
 	unsigned long timeout = MTD_DEFAULT_TIMEOUT;

From: Felix Fietkau <[email protected]>

mtd: block2mtd: Removes PAGE_MASK as a index to partition size

PAGE_MASK is no longer needed with the new term.

This patch keeps the device size aligned with the erase_size.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch

Quoted 1 line

PAGE_MASK is no longer needed with the new term.

This isn't too descriptive. What you probably mean is that we assume the erase size is always larger than PAGE_SIZE.

Quoted 10 lines

This patch keeps the device size aligned with the erase_size.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 static struct block2mtd_dev *add_device( · line 294

Quoted 6 lines

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 renamed from drivers/mtd/devices/block2mtd.c 2014-11-07 17:40:58.688747820 -0200 +1 -2

@@ -291,8 +291,7 @@ static struct block2mtd_dev *add_device(
 goto err_destroy_mutex;
 
 dev->mtd.name = name;
-
- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

You never guaranteed that erase_size is a power of two, so this doesn't necessarily mask the way you'd like...

But also, why is this even necessary? I see that we should already have errored out if this was actually significant, since we have above:

if ((long)dev->blkdev->bd_inode->i_size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd;
}

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 26, 2014 5:21:47 AM
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to partition size

Quoted 26 lines · Rodrigo Freire

Quoted 1 line

PAGE_MASK is no longer needed with the new term.

This isn't too descriptive. What you probably mean is that we assume the erase size is always larger than PAGE_SIZE.

Quoted 10 lines

This patch keeps the device size aligned with the erase_size.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 static struct block2mtd_dev *add_device( · line 294

Quoted 6 lines

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 renamed from drivers/mtd/devices/block2mtd.c 2014-11-07 17:40:58.688747820 -0200 +1 -2

@@ -291,8 +291,7 @@ static struct block2mtd_dev *add_device(
 goto err_destroy_mutex;
 
 dev->mtd.name = name;
-
- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

You never guaranteed that erase_size is a power of two, so this doesn't necessarily mask the way you'd like...

Quoted 7 lines

But also, why is this even necessary? I see that we should already have errored out if this was actually significant, since we have above:

if ((long)dev->blkdev->bd_inode->i_size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd;
}

Hello Brian, and thanks for the review.

Honestly, I'd leave that untouched, but Jörn pointed that it could be a issue at https://lkml.org/lkml/2014/9/9/680

I'd happily let it go without this patch 3, unless Jörg wants to state otherwise.

Quoted 39 lines · Rodrigo Freire

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 26, 2014 5:21:47 AM
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to partition size

Quoted 26 lines · Rodrigo Freire

Quoted 1 line

PAGE_MASK is no longer needed with the new term.

This isn't too descriptive. What you probably mean is that we assume the erase size is always larger than PAGE_SIZE.

Quoted 10 lines

This patch keeps the device size aligned with the erase_size.

Signed-off-by Felix Fietkau <[email protected]>

Signed-off-by Rodrigo Freire <[email protected]>

Signed-off-by Herton Krzesinski <[email protected]>

---
V3: Separated on a single patch

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 static struct block2mtd_dev *add_device( · line 294

Quoted 6 lines

drivers/mtd/devices/block2mtd.c 2014-11-07 17:41:28.054750893 -0200 renamed from drivers/mtd/devices/block2mtd.c 2014-11-07 17:40:58.688747820 -0200 +1 -2

@@ -291,8 +291,7 @@ static struct block2mtd_dev *add_device(
 goto err_destroy_mutex;
 
 dev->mtd.name = name;
-
- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

You never guaranteed that erase_size is a power of two, so this doesn't necessarily mask the way you'd like...

Quoted 7 lines

But also, why is this even necessary? I see that we should already have errored out if this was actually significant, since we have above:

if ((long)dev->blkdev->bd_inode->i_size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd;
}

Quoted 5 lines

Hello Brian, and thanks for the review.

Honestly, I'd leave that untouched, but Jörn pointed that it could be a issue at https://lkml.org/lkml/2014/9/9/680

I'd happily let it go without this patch 3, unless Jörg wants to state otherwise.

OK let's drop this patch from the series. At best, we could just do something like this instead:

(quoted diff) +1 -1

-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size;

But that's really just an unnecessary change.

Quoted 30 lines · Brian Norris

Quoted 20 lines · Rodrigo Freire

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 26, 2014 5:21:47 AM
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to partition size

Quoted 7 lines · Rodrigo Freire

Quoted 2 lines

- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

You never guaranteed that erase_size is a power of two, so this doesn't necessarily mask the way you'd like...

Quoted 7 lines

But also, why is this even necessary? I see that we should already have errored out if this was actually significant, since we have above:

if ((long)dev->blkdev->bd_inode->i_size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd;
}

Quoted 5 lines

Hello Brian, and thanks for the review.

Honestly, I'd leave that untouched, but Jörn pointed that it could be a issue at https://lkml.org/lkml/2014/9/9/680

I'd happily let it go without this patch 3, unless Jörg wants to state otherwise.

OK let's drop this patch from the series. At best, we could just do something like this instead:

Quoted 4 lines

(quoted diff) +1 -1

-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size;

But that's really just an unnecessary change.

If I remember correctly, it was problematic to have a dev->mtd.size value which is not a multiple of the erase size. I think that was the reason for patch 3.

Quoted 31 lines · Felix Fietkau

Quoted 30 lines · Brian Norris

Quoted 20 lines · Rodrigo Freire

From: "Brian Norris" <[email protected]>
Sent: Wednesday, November 26, 2014 5:21:47 AM
Subject: Re: [PATCH v3 3/3] mtd: block2mtd: Removes PAGE_MASK as a index to partition size

Quoted 7 lines · Rodrigo Freire

Quoted 2 lines

- dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+ dev->mtd.size = dev->blkdev->bd_inode->i_size & ~(erase_size - 1);

You never guaranteed that erase_size is a power of two, so this doesn't necessarily mask the way you'd like...

Quoted 7 lines

But also, why is this even necessary? I see that we should already have errored out if this was actually significant, since we have above:

if ((long)dev->blkdev->bd_inode->i_size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd;
}

Quoted 5 lines

Hello Brian, and thanks for the review.

Honestly, I'd leave that untouched, but Jörn pointed that it could be a issue at https://lkml.org/lkml/2014/9/9/680

I'd happily let it go without this patch 3, unless Jörg wants to state otherwise.

OK let's drop this patch from the series. At best, we could just do something like this instead:

Quoted 7 lines

Quoted 4 lines

(quoted diff) +1 -1

-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size;

But that's really just an unnecessary change.

If I remember correctly, it was problematic to have a dev->mtd.size value which is not a multiple of the erase size. I think that was the reason for patch 3.

The what's this for?

	if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
		pr_err("erasesize must be a divisor of device size\n");
		goto err_free_block2mtd;
	}

Quoted 13 lines · Brian Norris

Quoted 11 lines · Felix Fietkau

Quoted 7 lines · Brian Norris

OK let's drop this patch from the series. At best, we could just do something like this instead:

(quoted diff) +1 -1

-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size;

But that's really just an unnecessary change.

If I remember correctly, it was problematic to have a dev->mtd.size value which is not a multiple of the erase size. I think that was the reason for patch 3.

Quoted 6 lines

The what's this for?

	if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
		pr_err("erasesize must be a divisor of device size\n");
		goto err_free_block2mtd;
	}

I think we should just trim the mtd size to a multiple of erase size and remove this check. It is a bit impractical for many cases.