linux-toradex.git/drivers/md/dm-ioctl.c, branch v3.12-rc2

dm: add statistics support

2013-09-06T00:46:06+00:00

Support the collection of I/O statistics on user-defined regions of
a DM device.  If no regions are defined no statistics are collected so
there isn't any performance impact.  Only bio-based DM devices are
currently supported.

Each user-defined region specifies a starting sector, length and step.
Individual statistics will be collected for each step-sized area within
the range specified.

The I/O statistics counters for each step-sized area of a region are
in the same format as /sys/block/*/stat or /proc/diskstats but extra
counters (12 and 13) are provided: total time spent reading and
writing in milliseconds.  All these counters may be accessed by sending
the @stats_print message to the appropriate DM device via dmsetup.

The creation of DM statistics will allocate memory via kmalloc or
fallback to using vmalloc space.  At most, 1/4 of the overall system
memory may be allocated by DM statistics.  The admin can see how much
memory is used by reading
/sys/module/dm_mod/parameters/stats_current_allocated_bytes

See Documentation/device-mapper/statistics.txt for more details.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm ioctl: cleanup error handling in table_load

2013-09-06T00:46:06+00:00

Make use of common cleanup code.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm ioctl: increase granularity of type_lock when loading table

2013-09-06T00:46:06+00:00

Hold the mapped device's type_lock before calling populate_table() since
it is where the table's type is determined based on the specified
targets.  There is no need to allow concurrent table loads to race to
establish the table's targets or type.

This eliminates the need to grab the lock in dm_table_set_type().

Also verify that the type_lock is held in both dm_set_md_type() and
dm_get_md_type().

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm ioctl: prevent rename to empty name or uuid

2013-09-06T00:46:06+00:00

A device-mapper device must always have a name consisting of a non-empty
string.  If the device also has a uuid, this similarly must not be an
empty string.

The DM_DEV_CREATE ioctl enforces these rules when the device is created,
but this patch is needed to enforce them when DM_DEV_RENAME is used to
change the name or uuid.

Reported-by: Zdenek Kabelac 
Signed-off-by: Alasdair G Kergon 
Signed-off-by: Mike Snitzer 
Acked-by: Mikulas Patocka

dm: optimize use SRCU and RCU

2013-07-10T22:41:18+00:00

This patch removes "io_lock" and "map_lock" in struct mapped_device and
"holders" in struct dm_table and replaces these mechanisms with
sleepable-rcu.

Previously, the code would call "dm_get_live_table" and "dm_table_put" to
get and release table. Now, the code is changed to call "dm_get_live_table"
and "dm_put_live_table". dm_get_live_table locks sleepable-rcu and
dm_put_live_table unlocks it.

dm_get_live_table_fast/dm_put_live_table_fast can be used instead of
dm_get_live_table/dm_put_live_table. These *_fast functions use
non-sleepable RCU, so the caller must not block between them.

If the code changes active or inactive dm table, it must call
dm_sync_table before destroying the old table.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Jun'ichi Nomura 
Signed-off-by: Alasdair G Kergon

dm: use __GFP_HIGHMEM in __vmalloc

2013-07-10T22:41:16+00:00

Use __GFP_HIGHMEM in __vmalloc.

Pages allocated with __vmalloc can be allocated in high memory that is not
directly mapped to kernel space, so use __GFP_HIGHMEM just like vmalloc
does. This patch reduces memory pressure slightly because pages can be
allocated in the high zone.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm ioctl: set noio flag to avoid __vmalloc deadlock

2013-07-10T22:41:15+00:00

Set noio flag while calling __vmalloc() because it doesn't fully respect
gfp flags to avoid a possible deadlock (see commit
502624bdad3dba45dfaacaf36b7d83e39e74b2d2).

This should be backported to stable kernels 3.8 and newer. The kernel 3.8
doesn't have memalloc_noio_save(), so we should set and restore process
flag PF_MEMALLOC instead.

Signed-off-by: Mikulas Patocka 
Cc: stable@vger.kernel.org
Signed-off-by: Alasdair G Kergon

dm ioctl: allow message to return data

2013-03-01T22:45:49+00:00

This patch introduces enhanced message support that allows the
device-mapper core to recognise messages that are common to all devices,
and for messages to return data to userspace.

Core messages are processed by the function "message_for_md".  If the
device mapper doesn't support the message, it is passed to the target
driver.

If the message returns data, the kernel sets the flag
DM_MESSAGE_OUT_FLAG.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm ioctl: optimize functions without variable params

2013-03-01T22:45:49+00:00

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 
Signed-off-by: Alasdair G Kergon

dm ioctl: introduce ioctl_flags

2013-03-01T22:45:48+00:00

This patch introduces flags for each ioctl function.

So far, one flag is defined, IOCTL_FLAGS_NO_PARAMS.  It is set if the
function processing the ioctl doesn't take or produce any parameters in
the section of the data buffer that has a variable size.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon