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linux-next/include/linux/blkpg.h
Vivek Goyal c83f6bf98d block: add partition resize function to blkpg ioctl
Add a new operation code (BLKPG_RESIZE_PARTITION) to the BLKPG ioctl that
allows altering the size of an existing partition, even if it is currently
in use.

This patch converts hd_struct->nr_sects into sequence counter because
One might extend a partition while IO is happening to it and update of
nr_sects can be non-atomic on 32bit machines with 64bit sector_t. This
can lead to issues like reading inconsistent size of a partition. Sequence
counter have been used so that readers don't have to take bdev mutex lock
as we call sector_in_part() very frequently.

Now all the access to hd_struct->nr_sects should happen using sequence
counter read/update helper functions part_nr_sects_read/part_nr_sects_write.
There is one exception though, set_capacity()/get_capacity(). I think
theoritically race should exist there too but this patch does not
modify set_capacity()/get_capacity() due to sheer number of call sites
and I am afraid that change might break something. I have left that as a
TODO item. We can handle it later if need be. This patch does not introduce
any new races as such w.r.t set_capacity()/get_capacity().

v2: Add CONFIG_LBDAF test to UP preempt case as suggested by Phillip.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Phillip Susi <psusi@ubuntu.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-01 12:24:18 +02:00

60 lines
1.6 KiB
C

#ifndef _LINUX_BLKPG_H
#define _LINUX_BLKPG_H
/*
* Partition table and disk geometry handling
*
* A single ioctl with lots of subfunctions:
*
* Device number stuff:
* get_whole_disk() (given the device number of a partition,
* find the device number of the encompassing disk)
* get_all_partitions() (given the device number of a disk, return the
* device numbers of all its known partitions)
*
* Partition stuff:
* add_partition()
* delete_partition()
* test_partition_in_use() (also for test_disk_in_use)
*
* Geometry stuff:
* get_geometry()
* set_geometry()
* get_bios_drivedata()
*
* For today, only the partition stuff - aeb, 990515
*/
#include <linux/compiler.h>
#include <linux/ioctl.h>
#define BLKPG _IO(0x12,105)
/* The argument structure */
struct blkpg_ioctl_arg {
int op;
int flags;
int datalen;
void __user *data;
};
/* The subfunctions (for the op field) */
#define BLKPG_ADD_PARTITION 1
#define BLKPG_DEL_PARTITION 2
#define BLKPG_RESIZE_PARTITION 3
/* Sizes of name fields. Unused at present. */
#define BLKPG_DEVNAMELTH 64
#define BLKPG_VOLNAMELTH 64
/* The data structure for ADD_PARTITION and DEL_PARTITION */
struct blkpg_partition {
long long start; /* starting offset in bytes */
long long length; /* length in bytes */
int pno; /* partition number */
char devname[BLKPG_DEVNAMELTH]; /* partition name, like sda5 or c0d1p2,
to be used in kernel messages */
char volname[BLKPG_VOLNAMELTH]; /* volume label */
};
#endif /* _LINUX_BLKPG_H */