[PATCH] Add commandline partitions for block devices v2

[PATCH] Add commandline partitions for block devices v2

[Linus Walleij]

From: Ulf Hansson <ulf.hansson@stericsson.com>

This adds an option to pass in block device partitions from the kernel
cmdline.

The rationale is that in embedded systems we sometimes have no standard
partition table available: often due to the fact that raw binary data is
read out from the first sectors of the device by ROM code in ASICs. We
have for a long time supplied custom partition information to embedded
flash memories through the MTDparts interface which has similar
semantics, and with the advent of embedded MMC block devices this now
comes to standard block devices.

Reviewed-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Ulf Hansson <ulf.hansson@stericsson.com>
---
Changes v1->v2:
- Changed file permissions to 644 in blkdev_parts.[c|h]
- Changed a printk() to include a hint that this comes from
  blkdev_parts
- Ready for merging? Andries, you are listed as maintainer for
  the partitions, will you take this patch?
---
 fs/partitions/Kconfig        |   19 ++++++
 fs/partitions/Makefile       |    1 +
 fs/partitions/blkdev_parts.c |  127 ++++++++++++++++++++++++++++++++++++++++++
 fs/partitions/blkdev_parts.h |   14 +++++
 fs/partitions/check.c        |    4 +
 5 files changed, 165 insertions(+), 0 deletions(-)
 create mode 100644 fs/partitions/blkdev_parts.c
 create mode 100644 fs/partitions/blkdev_parts.h

diff --git a/fs/partitions/Kconfig b/fs/partitions/Kconfig
index cb5f0a3..097be19 100644
--- a/fs/partitions/Kconfig
+++ b/fs/partitions/Kconfig
@@ -68,6 +68,25 @@ config ACORN_PARTITION_RISCIX
 	  of machines called RISCiX.  If you say 'Y' here, Linux will be able
 	  to read disks partitioned under RISCiX.
 
+config BLKDEV_PARTITION
+	bool "Blockdev commandline partition support" if PARTITION_ADVANCED
+	default n
+	help
+	  Say Y if you like to setup partitions for block devices by reading
+	  from the kernel command line (kernel boot arguments).
+
+	  The format of the partitions on the command line:
+	  blkdevparts=<blkdev-def>[;<blkdev-def>]
+	  <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>]
+	  <partdef>    := <size>[@<offset>]
+
+	  <blkdev-id>  := unique id used to map driver to blockdev name
+	  <size>       := size in numbers of sectors
+	  <offset>     := offset in sectors for partition to start at
+
+	  Example:
+	  blkdevparts=mmc0:1024@0,524288@1024;mmc1:8192@0,8192@8192
+
 config OSF_PARTITION
 	bool "Alpha OSF partition support" if PARTITION_ADVANCED
 	default y if ALPHA
diff --git a/fs/partitions/Makefile b/fs/partitions/Makefile
index 03af8ea..48b216c 100644
--- a/fs/partitions/Makefile
+++ b/fs/partitions/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_BLOCK) := check.o
 obj-$(CONFIG_ACORN_PARTITION) += acorn.o
 obj-$(CONFIG_AMIGA_PARTITION) += amiga.o
 obj-$(CONFIG_ATARI_PARTITION) += atari.o
+obj-$(CONFIG_BLKDEV_PARTITION) += blkdev_parts.o
 obj-$(CONFIG_MAC_PARTITION) += mac.o
 obj-$(CONFIG_LDM_PARTITION) += ldm.o
 obj-$(CONFIG_MSDOS_PARTITION) += msdos.o
diff --git a/fs/partitions/blkdev_parts.c b/fs/partitions/blkdev_parts.c
new file mode 100644
index 0000000..b1c6297
--- /dev/null
+++ b/fs/partitions/blkdev_parts.c
@@ -0,0 +1,127 @@
+/*
+ *
+ * Copyright (C) ST-Ericsson SA 2010
+ *
+ * Author: Ulf Hansson <ulf.hansson@stericsson.com> for ST-Ericsson
+ * License terms: GNU General Public License (GPL) version 2
+ *
+ * Create partitions for block devices by reading from the kernel
+ * command line (kernel boot arguments).
+ *
+ */
+
+#include "check.h"
+#include "blkdev_parts.h"
+
+static char *cmdline;
+
+/*
+ * This is the handler for our kernel commandline parameter,
+ * called from main.c::checksetup().
+ * Note that we can not yet kmalloc() anything, so we only save
+ * the commandline for later processing.
+ */
+static int cmdline_setup(char *s)
+{
+	cmdline = s;
+	return 1;
+}
+__setup("blkdevparts=", cmdline_setup);
+
+/* Parse for a matching blkdev-id and return pointer to partdef */
+static char *parse_blkdev_id(char *blkdev_name)
+{
+	int blkdev_id_len;
+	char *p, *blkdev_id;
+
+	/* Start parsing for a matching blkdev-id */
+	p = blkdev_id = cmdline;
+	while (blkdev_id != NULL) {
+
+		/* Find the end of the blkdev-id string */
+		p = strchr(blkdev_id, ':');
+		if (p == NULL)
+			return NULL;
+
+		/* Check if we found a matching blkdev-id */
+		blkdev_id_len = p - blkdev_id;
+		if (strlen(blkdev_name)	== blkdev_id_len) {
+			if (strncmp(blkdev_name, blkdev_id, blkdev_id_len) == 0)
+				return p;
+		}
+
+		/* Move to next blkdev-id string if there is one */
+		blkdev_id = strchr(p, ';');
+		if (blkdev_id != NULL)
+			blkdev_id++;
+	}
+	return NULL;
+}
+
+static int parse_partdef(char **part, struct parsed_partitions *state, int part_nbr)
+{
+	sector_t size, offset;
+	char *p = *part;
+
+	/* Skip the beginning "," or ":" */
+	p++;
+
+	/* Fetch and verify size from partdef */
+	size = simple_strtoull(p, &p, 10);
+	if ((size == 0) || (*p != '@'))
+		return 0;
+
+	/* Skip the "@" */
+	p++;
+
+	/* Fetch offset from partdef and check if there are more parts */
+	offset = simple_strtoull(p, &p, 10);
+	if (*p == ',')
+		*part = p;
+	else
+		*part = NULL;
+
+	/* Add partition to state */
+	put_partition(state, part_nbr, offset, size);
+	printk(KERN_INFO "\nPartition: size=%llu, offset=%llu\n",
+		(unsigned long long) size,
+		(unsigned long long) offset);
+	return 1;
+}
+
+static int parse_blkdev_parts(char *blkdev_name, struct parsed_partitions *state)
+{
+	char *partdef;
+	int part_nbr = 0;
+
+	/* Find partdef */
+	partdef = parse_blkdev_id(blkdev_name);
+
+	/* Add parts */
+	while (partdef != NULL) {
+		/* Find next part and add it to state */
+		part_nbr++;
+		if (!parse_partdef(&partdef, state, part_nbr))
+			return 0;
+	}
+	return part_nbr;
+}
+
+int blkdev_partition(struct parsed_partitions *state, struct block_device *bdev)
+{
+	char blkdev_name[BDEVNAME_SIZE];
+
+	/* Check if there are any partitions to handle */
+	if (cmdline == NULL)
+		return 0;
+
+	/* Get the name of the blockdevice we are operating upon */
+	if (bdevname(bdev, blkdev_name) == NULL) {
+		printk(KERN_WARNING "blkdevparts: Could not get a blkdev name\n");
+		return 0;
+	}
+
+	/* Parse for partitions and add them to the state */
+	return parse_blkdev_parts(blkdev_name, state);
+}
+
diff --git a/fs/partitions/blkdev_parts.h b/fs/partitions/blkdev_parts.h
new file mode 100644
index 0000000..e6c5d40
--- /dev/null
+++ b/fs/partitions/blkdev_parts.h
@@ -0,0 +1,14 @@
+/*
+ *
+ * Copyright (C) ST-Ericsson SA 2010
+ *
+ * Author: Ulf Hansson <ulf.hansson@stericsson.com> for ST-Ericsson
+ * License terms: GNU General Public License (GPL) version 2
+ *
+ * Create partitions for block devices by reading from the kernel
+ * command line (kernel boot arguments).
+ *
+ */
+
+int blkdev_partition(struct parsed_partitions *state, struct block_device *bdev);
+
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index e238ab2..e669059 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -27,6 +27,7 @@
 #include "acorn.h"
 #include "amiga.h"
 #include "atari.h"
+#include "blkdev_parts.h"
 #include "ldm.h"
 #include "mac.h"
 #include "msdos.h"
@@ -50,6 +51,9 @@ static int (*check_part[])(struct parsed_partitions *, struct block_device *) =
 	 * Probe partition formats with tables at disk address 0
 	 * that also have an ADFS boot block at 0xdc0.
 	 */
+#ifdef CONFIG_BLKDEV_PARTITION
+	blkdev_partition,
+#endif
 #ifdef CONFIG_ACORN_PARTITION_ICS
 	adfspart_check_ICS,
 #endif
-- 
1.6.3.3

Re: [PATCH] Add commandline partitions for block devices v2

[Linus Walleij]

2010/6/8 Linus Walleij <linus.walleij@stericsson.com>:

> From: Ulf Hansson <ulf.hansson@stericsson.com>
>
> This adds an option to pass in block device partitions from the kernel
> cmdline.

I don't get any reply from this, Andrew could you please stack this
patch up in your tree unless the partition maintainer turns up?

Yours,
Linus Walleij

Re: [PATCH] Add commandline partitions for block devices v2

[Andrew Morton]

On Tue, 8 Jun 2010 13:39:01 +0200
Linus Walleij <linus.walleij@stericsson.com> wrote:

> From: Ulf Hansson <ulf.hansson@stericsson.com>
> 
> This adds an option to pass in block device partitions from the kernel
> cmdline.
> 
> The rationale is that in embedded systems we sometimes have no standard
> partition table available: often due to the fact that raw binary data is
> read out from the first sectors of the device by ROM code in ASICs. We
> have for a long time supplied custom partition information to embedded
> flash memories through the MTDparts interface which has similar
> semantics, and with the advent of embedded MMC block devices this now
> comes to standard block devices.
> 
> Reviewed-by: Linus Walleij <linus.walleij@stericsson.com>
> Signed-off-by: Ulf Hansson <ulf.hansson@stericsson.com>

This should include your Signed-off-by: as well, since you were on the
patch delivery path.

> Changes v1->v2:
> - Changed file permissions to 644 in blkdev_parts.[c|h]
> - Changed a printk() to include a hint that this comes from
>   blkdev_parts
> - Ready for merging? Andries, you are listed as maintainer for
>   the partitions, will you take this patch?
> ---
>  fs/partitions/Kconfig        |   19 ++++++
>  fs/partitions/Makefile       |    1 +
>  fs/partitions/blkdev_parts.c |  127 ++++++++++++++++++++++++++++++++++++++++++
>  fs/partitions/blkdev_parts.h |   14 +++++
>  fs/partitions/check.c        |    4 +
>  5 files changed, 165 insertions(+), 0 deletions(-)
>  create mode 100644 fs/partitions/blkdev_parts.c
>  create mode 100644 fs/partitions/blkdev_parts.h
> 
> diff --git a/fs/partitions/Kconfig b/fs/partitions/Kconfig
> index cb5f0a3..097be19 100644
> --- a/fs/partitions/Kconfig
> +++ b/fs/partitions/Kconfig
> @@ -68,6 +68,25 @@ config ACORN_PARTITION_RISCIX
>  	  of machines called RISCiX.  If you say 'Y' here, Linux will be able
>  	  to read disks partitioned under RISCiX.
>  
> +config BLKDEV_PARTITION
> +	bool "Blockdev commandline partition support" if PARTITION_ADVANCED
> +	default n
> +	help
> +	  Say Y if you like to setup partitions for block devices by reading
> +	  from the kernel command line (kernel boot arguments).
> +
> +	  The format of the partitions on the command line:
> +	  blkdevparts=<blkdev-def>[;<blkdev-def>]
> +	  <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>]
> +	  <partdef>    := <size>[@<offset>]
> +
> +	  <blkdev-id>  := unique id used to map driver to blockdev name
> +	  <size>       := size in numbers of sectors
> +	  <offset>     := offset in sectors for partition to start at
> +
> +	  Example:
> +	  blkdevparts=mmc0:1024@0,524288@1024;mmc1:8192@0,8192@8192

This is a bit terse, and perhaps the Kconfig file was not the best
place to document the feature.  I'd suggest a standalone file in
Documentation/block[dev]/.  Then add a pointer to that documentation
within the Kconfig help record and in
Documentation/kernel-parameters.txt.

Because it does need more explanation and perhaps more examples, IMO. 
I'm particularly scratching my head over the dynamic behaviour.  This
code will get reexecuted each time the kernel runs rescan_partitions(),
no?  For example ioctl(BLKRRPART).  What happens then and under which
circumstances is that a non-insane thing to do.


>  config OSF_PARTITION
>  	bool "Alpha OSF partition support" if PARTITION_ADVANCED
>  	default y if ALPHA
> diff --git a/fs/partitions/Makefile b/fs/partitions/Makefile
> index 03af8ea..48b216c 100644
> --- a/fs/partitions/Makefile
> +++ b/fs/partitions/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_BLOCK) := check.o
>  obj-$(CONFIG_ACORN_PARTITION) += acorn.o
>  obj-$(CONFIG_AMIGA_PARTITION) += amiga.o
>  obj-$(CONFIG_ATARI_PARTITION) += atari.o
> +obj-$(CONFIG_BLKDEV_PARTITION) += blkdev_parts.o
>  obj-$(CONFIG_MAC_PARTITION) += mac.o
>  obj-$(CONFIG_LDM_PARTITION) += ldm.o
>  obj-$(CONFIG_MSDOS_PARTITION) += msdos.o
> diff --git a/fs/partitions/blkdev_parts.c b/fs/partitions/blkdev_parts.c
> new file mode 100644
> index 0000000..b1c6297
> --- /dev/null
> +++ b/fs/partitions/blkdev_parts.c
> @@ -0,0 +1,127 @@
> +/*
> + *
> + * Copyright (C) ST-Ericsson SA 2010
> + *
> + * Author: Ulf Hansson <ulf.hansson@stericsson.com> for ST-Ericsson
> + * License terms: GNU General Public License (GPL) version 2
> + *
> + * Create partitions for block devices by reading from the kernel
> + * command line (kernel boot arguments).
> + *
> + */
> +
> +#include "check.h"
> +#include "blkdev_parts.h"
> +
> +static char *cmdline;
> +
> +/*
> + * This is the handler for our kernel commandline parameter,
> + * called from main.c::checksetup().
> + * Note that we can not yet kmalloc() anything, so we only save
> + * the commandline for later processing.
> + */
> +static int cmdline_setup(char *s)
> +{
> +	cmdline = s;
> +	return 1;
> +}
> +__setup("blkdevparts=", cmdline_setup);

Is the string at *s preserved for all time on all architectures?  It
seems that way.

This function should be __init.

> +/* Parse for a matching blkdev-id and return pointer to partdef */
> +static char *parse_blkdev_id(char *blkdev_name)
> +{
> +	int blkdev_id_len;
> +	char *p, *blkdev_id;
> +
> +	/* Start parsing for a matching blkdev-id */
> +	p = blkdev_id = cmdline;
> +	while (blkdev_id != NULL) {
> +
> +		/* Find the end of the blkdev-id string */
> +		p = strchr(blkdev_id, ':');
> +		if (p == NULL)
> +			return NULL;
> +
> +		/* Check if we found a matching blkdev-id */
> +		blkdev_id_len = p - blkdev_id;
> +		if (strlen(blkdev_name)	== blkdev_id_len) {
> +			if (strncmp(blkdev_name, blkdev_id, blkdev_id_len) == 0)
> +				return p;
> +		}
> +
> +		/* Move to next blkdev-id string if there is one */
> +		blkdev_id = strchr(p, ';');
> +		if (blkdev_id != NULL)
> +			blkdev_id++;
> +	}
> +	return NULL;
> +}

See, the documentation didn't tell me what a "blkkdev-id" is.  How does
the user determine the blkdev-id of his devide so he knows how to
configure his command line?

> +static int parse_partdef(char **part, struct parsed_partitions *state, int part_nbr)
> +{
> +	sector_t size, offset;
> +	char *p = *part;
> +
> +	/* Skip the beginning "," or ":" */
> +	p++;
> +
> +	/* Fetch and verify size from partdef */
> +	size = simple_strtoull(p, &p, 10);
> +	if ((size == 0) || (*p != '@'))
> +		return 0;
> +
> +	/* Skip the "@" */
> +	p++;
> +
> +	/* Fetch offset from partdef and check if there are more parts */
> +	offset = simple_strtoull(p, &p, 10);
> +	if (*p == ',')
> +		*part = p;
> +	else
> +		*part = NULL;
> +
> +	/* Add partition to state */
> +	put_partition(state, part_nbr, offset, size);
> +	printk(KERN_INFO "\nPartition: size=%llu, offset=%llu\n",
> +		(unsigned long long) size,
> +		(unsigned long long) offset);
> +	return 1;
> +}

Is all this code warning-free and tested on 32-bit CONFIG_LBDAF=n? 
>From the above typecasts I assume "yes, at some stage".

> +static int parse_blkdev_parts(char *blkdev_name, struct parsed_partitions *state)
> +{
> +	char *partdef;
> +	int part_nbr = 0;
> +
> +	/* Find partdef */
> +	partdef = parse_blkdev_id(blkdev_name);
> +
> +	/* Add parts */
> +	while (partdef != NULL) {
> +		/* Find next part and add it to state */
> +		part_nbr++;
> +		if (!parse_partdef(&partdef, state, part_nbr))
> +			return 0;
> +	}
> +	return part_nbr;
> +}
> +
> +int blkdev_partition(struct parsed_partitions *state, struct block_device *bdev)
> +{
> +	char blkdev_name[BDEVNAME_SIZE];
> +
> +	/* Check if there are any partitions to handle */
> +	if (cmdline == NULL)
> +		return 0;
> +
> +	/* Get the name of the blockdevice we are operating upon */
> +	if (bdevname(bdev, blkdev_name) == NULL) {
> +		printk(KERN_WARNING "blkdevparts: Could not get a blkdev name\n");
> +		return 0;
> +	}
> +
> +	/* Parse for partitions and add them to the state */
> +	return parse_blkdev_parts(blkdev_name, state);
> +}

It kinda sucks that all this new code cannot be __init.  If, as I
suspect, there is no valid post-boot use case for this code then
perhaps we can somehow arrange for it to get tossed away at
free_initmem() time.  That'll probably cause a build-time sections
warning however we do it :(

Re: [PATCH] Add commandline partitions for block devices v2

[Andries E. Brouwer]

On Tue, Jun 22, 2010 Andrew Morton wrote:
> On Tue, 8 Jun 2010 Linus Walleij wrote:
> 
> > From: Ulf Hansson <ulf.hansson@stericsson.com>
> > 
> > This adds an option to pass in block device partitions from the kernel
> > cmdline.
> > 
> > The rationale is that in embedded systems we sometimes have no standard
> > partition table available: often due to the fact that raw binary data is
> > read out from the first sectors of the device by ROM code in ASICs. We
> > have for a long time supplied custom partition information to embedded
> > flash memories through the MTDparts interface which has similar
> > semantics, and with the advent of embedded MMC block devices this now
> > comes to standard block devices.

There exist ioctls BLKPG_ADD_PARTITION and BLKPG_DEL_PARTITION that
allow one to add or remove partitions at run time, without having
a partition table, or without having a partition table in a format
understood by the kernel. Things can be done in user space.

In general there are many things one would like the kernel to do at
init time, and it is a bad idea to do all of this from the kernel
command line. So adding options like these should be done only
if it would be really awkward to do the same from an initial
ramdisk.

Andries

Re: [PATCH] Add commandline partitions for block devices v2

[Ulf Hansson]

Andries E. Brouwer wrote:
> On Tue, Jun 22, 2010 Andrew Morton wrote:
>   
>> On Tue, 8 Jun 2010 Linus Walleij wrote:
>>
>>     
>>> From: Ulf Hansson <ulf.hansson@stericsson.com>
>>>
>>> This adds an option to pass in block device partitions from the kernel
>>> cmdline.
>>>
>>> The rationale is that in embedded systems we sometimes have no standard
>>> partition table available: often due to the fact that raw binary data is
>>> read out from the first sectors of the device by ROM code in ASICs. We
>>> have for a long time supplied custom partition information to embedded
>>> flash memories through the MTDparts interface which has similar
>>> semantics, and with the advent of embedded MMC block devices this now
>>> comes to standard block devices.
>>>       
>
> There exist ioctls BLKPG_ADD_PARTITION and BLKPG_DEL_PARTITION that
> allow one to add or remove partitions at run time, without having
> a partition table, or without having a partition table in a format
> understood by the kernel. Things can be done in user space.
>
> In general there are many things one would like the kernel to do at
> init time, and it is a bad idea to do all of this from the kernel
> command line. So adding options like these should be done only
> if it would be really awkward to do the same from an initial
> ramdisk.
>
> Andries
>
>   
I see your point!

Although, in an embedded system it is not always convenient to use an 
initial ramdisk. Instead your init program will be found directy from 
your rootfs, which means the kernel must itself be able to setup the 
partitions.

Regards
Uffe