[PATCH/RFC] partitions: let partitions inherit policy from disk

[PATCH/RFC] partitions: let partitions inherit policy from disk

[Peter Oberparleiter]

I'd like to suggest to change the partition code in
fs/partitions/check.c to initialize a newly detected partition's policy
field with that of the containing block device (see patch below).

My reasoning is that function set_disk_ro() in block/genhd.c
modifies the policy field (read-only indicator) of a disk and all
contained partitions. When a partition is detected after the call to
set_disk_ro(), the policy field of this partition will currently not
inherit the disk's policy field. This behavior poses a problem in cases
where a block device can be 'logically de- and reactivated' like e.g.
the s390 DASD driver because partition detection may run after the
policy field has been modified.

From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>

Initialize the policy field of partitions with that of the containing
block device.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
---
diff -Naurp linux-2.6.17/fs/partitions/check.c linux-2.6.17b/fs/partitions/check.c
--- linux-2.6.17/fs/partitions/check.c	2006-06-18 03:49:35.000000000 +0200
+++ linux-2.6.17b/fs/partitions/check.c	2006-07-03 12:49:13.000000000 +0200
@@ -348,6 +348,7 @@ void add_partition(struct gendisk *disk,
 	p->start_sect = start;-
 	p->nr_sects = len;
 	p->partno = part;
+	p->policy = disk->policy;

 	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor + part),
 			S_IFBLK|S_IRUSR|S_IWUSR,

Re: [PATCH/RFC] partitions: let partitions inherit policy from disk

[Jens Axboe]

On Mon, Jul 03 2006, Peter Oberparleiter wrote:
> I'd like to suggest to change the partition code in
> fs/partitions/check.c to initialize a newly detected partition's policy
> field with that of the containing block device (see patch below).
> 
> My reasoning is that function set_disk_ro() in block/genhd.c
> modifies the policy field (read-only indicator) of a disk and all
> contained partitions. When a partition is detected after the call to
> set_disk_ro(), the policy field of this partition will currently not
> inherit the disk's policy field. This behavior poses a problem in cases
> where a block device can be 'logically de- and reactivated' like e.g.
> the s390 DASD driver because partition detection may run after the
> policy field has been modified.
> 
> From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> 
> Initialize the policy field of partitions with that of the containing
> block device.
> 
> Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> ---
> diff -Naurp linux-2.6.17/fs/partitions/check.c linux-2.6.17b/fs/partitions/check.c
> --- linux-2.6.17/fs/partitions/check.c	2006-06-18 03:49:35.000000000 +0200
> +++ linux-2.6.17b/fs/partitions/check.c	2006-07-03 12:49:13.000000000 +0200
> @@ -348,6 +348,7 @@ void add_partition(struct gendisk *disk,
>  	p->start_sect = start;-
>  	p->nr_sects = len;
>  	p->partno = part;
> +	p->policy = disk->policy;
> 
>  	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor + part),
>  			S_IFBLK|S_IRUSR|S_IWUSR,

Makes sense to me, however I'll let Al ack this for inclusion. Al?

-- 
Jens Axboe

Re: [PATCH/RFC] partitions: let partitions inherit policy from disk

[Al Viro]

> Makes sense to me, however I'll let Al ack this for inclusion. Al?

ACK, looks sane.