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dm ioctl: optimize functions without variable params

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Device-mapper ioctls receive and send data in a buffer supplied
by userspace.  The buffer has two parts.  The first part contains
a 'struct dm_ioctl' and has a fixed size.  The second part depends
on the ioctl and has a variable size.

This patch recognises the specific ioctls that do not use the variable
part of the buffer and skips allocating memory for it.

In particular, when a device is suspended and a resume ioctl is sent,
this now avoid memory allocation completely.

The variable "struct dm_ioctl tmp" is moved from the function
copy_params to its caller ctl_ioctl and renamed to param_kernel.
It is used directly when the ioctl function doesn't need any arguments.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka
2013-03-01 22:45:49 +00:00
committed by Alasdair G Kergon
parent e2914cc26b
commit 02cde50b7e
2 changed files with 39 additions and 23 deletions
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6
include/uapi/linux/dm-ioctl.h
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@@ -267,9 +267,9 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
#define DM_VERSION_MINOR 23
#define DM_VERSION_PATCHLEVEL 1
#define DM_VERSION_EXTRA "-ioctl (2012-12-18)"
#define DM_VERSION_MINOR 24
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2013-01-15)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */