This fix only affects UBI debugging.

If the the background thread is disabled for debugging purposes,
start it anyway, because otherwise we see tonns of kernel debugging
complaints like this:

INFO: task ubi_bgt0d:26857 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
ubi_bgt0d     D dd37bf94     0 26857      2
       dd37bfcc 00000086 f8e17cea dd37bf94 00000046 00000000 00000000 f5c62430
       f5c62430 f5c62590 c2a09c80 f6cbd498 dd8e9cbc 00000296 dd37bfb0 00000296
       dd8e9cb8 dd8e9cbc dd37bfcc c0119774 00000000 00000000 c0132e89 f6961560
Call Trace:
 [<f8e17cea>] ? ubi_thread+0x0/0x127 [ubi]
 [<c0119774>] ? complete+0x43/0x4b
 [<c0132e89>] ? kthread+0x0/0x5b
 [<f8e17cea>] ? ubi_thread+0x0/0x127 [ubi]
 [<c0132eae>] kthread+0x25/0x5b
 [<c0132e89>] ? kthread+0x0/0x5b
 [<c0104953>] kernel_thread_helper+0x7/0x14
 =======================

So start it, and go sleep inside it, instead of creating it and never
start.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

No functional changes, just tweak comments to make kernel-doc
work fine and stop complaining.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Just out or curiousity ran checkpatch.pl for whole UBI,
and discovered there are quite a few of stylistic issues.
Fix them.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Quite useful ioctl which allows to make atomic system upgrades.
The idea belongs to Richard Titmuss <richard_titmuss@logitech.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Hch asked not to use "unit" for sub-systems, let it be so.
Also some other commentaries modifications.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Normally UBI volumes are freed in the release function of
the struct device object. However, on error path they may
have to be freed before the struct device objects have been
initialized.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI forgets to free internal volumes when detaching MTD device.
Fix this.
Pointed-out-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

ubi_free_volume() function sets ubi->volumes[] to NULL, so
ubi_eba_close() is useless, it does not free what has to be freed.
So zap it and free vol->eba_tbl at the volume release function.
Pointed-out-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI already checks that @min io size is the power of 2 at io_init.
It is save to use bit operations then.
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI scan takes quite a time on some systems, so it is nice
to print a message that we started attaching an MTD device.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

Print information about logicale eraseblock size, sub-page
size and so on at early stage, befor an attempt to attach
the MTD device was made. This is more convenient to do so
because the attempt to attach may fail, and the information
is never printed then.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Use existing ubi_err() as the rest of the code does.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Make it print "UBI error: cannot attach mtd4"
instead of "UBI error: cannot attach 4"
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Data offset is VID header offset + VID header size aligned to
the min. I/O unit size up.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Since the data offset parameter was removed, the size of
the parameters array is now 2, not 3.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

The problem: NAND flashes have different amount of initial bad physical
eraseblocks (marked as bad by the manufacturer). For example, for 256MiB
Samsung OneNAND flash there might be from 0 to 40 bad initial eraseblocks,
which is about 2%. When UBI is used as the base system, one needs to know
the exact amount of good physical eraseblocks, because this number is
needed to create the UBI image which is put to the devices during
production. But this number is not know, which forces us to use the
minimum number of good physical eraseblocks. And UBI additionally
reserves some percentage of physical eraseblocks for bad block handling
(default is 1%), so we have 1-3% of PEBs reserved at the end, depending
on the amount of initial bad PEBs. But it is desired to always have
1% (or more, depending on the configuration).

Solution: this patch adds an "auto-resize" flag to the volume table.
The volume which has the "auto-resize" flag will automatically be re-sized
(enlarged) on the first UBI initialization. UBI clears the flag when
the volume is re-sized. Only one volume may have the "auto-resize" flag.

So, the production UBI image may have one volume with "auto-resize"
flag set, and its size is automatically adjusted on the first boot
of the device.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This slab cache is not really needed since the number of objects
is low and the constructor does not make much sense because we
allocate oblects when doint I/O, which is way slower then allocation.
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When creating a new volume, do not forget to increment the
vol_count variable.

Also, users are not interested in internal volumes, so do not show
them in the volumes_count sysfs file.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Be strict and accept only KiB, MiB and GiB, not Kib, not kib, etc.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Expose number or the underlying MTD device in sysfs.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI allows to specify MTD device name or number when the module is being
loaded. When parsing MTD device identity string, it first tries to treat
it as device NAME, and if that fails, it treats it as device number.

Make it vice-versa as this is more logical and makes less troubles when
you have an MTD device named "1" and try to load mtd1 which has different
name. This is especially easy to hit when gluebi is enabled.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Introduce a separate mutex which serializes volumes checking,
because we cammot really use volumes_mutex - it cases reverse
locking problems with mtd_tbl_mutex when gluebi is used -
thanks to lockdep.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Actually implement the MTD device attach/detach handlers.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

'data_offset' parameter does not really make sense and it is not
needed. Get rid of it.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Prepare the attach and detach functions to by used outside of
module initialization:

* detach function checks reference count before detaching
* it kills the background thread as well
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This is one more step on the way to "removable" UBI devices. It
adds reference counting for UBI devices. Every time a volume on
this device is opened - the device's refcount is increased. It
is also increased if someone is reading any sysfs file of this
UBI device or of one of its volumes.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch is a preparation to make UBI devices dynamic. It
adds an UBI control device which has dynamically allocated
major number and registers itself as "ubi_ctrl". It does not
do anything so far. The idea is that this device will allow
to attach/detach MTD devices from userspace.

This is symilar to what the Linux device mapper has.

The next things to do are:
* Fix UBI, because it now assumes UBI devices cannot go away
* Implement control device ioctls which will attach/detach MTD
  devices
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Add proper log level to printk's.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

If we fail halfway through sysfs file creation, we may just call
sysfs remove function and it will delete all the files we created.
For non-existing files it will also be OK - the remove functions
just return -ENOENT.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Transform vtbl_mutex to volumes_mutex - this just makes code
easier to understand.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Pass volume description object to the EBA function which makes
more sense, and EBA function do not have to find the volume
description object by volume ID.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

E.g., it oopsed in case of: modprobe ubi mtd = 0
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This global variablea is not really needed, remove it
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Similarly to ltree_entry_slab, it makes more sense to create
and destroy ubi_wl_entry slab on module initialization/exit.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Since the ltree_entry slab cache is a global entity, which is
used by all UBI devices, it is more logical to create it on
module initialization time and destro on module exit time.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Always print error code with error messages, sometimes it is
extremely helpful info.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Remove redundant ubi->major field - we have it in ubi->cdev.dev
already.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Similar reason as in case of the previous patch: it causes
deadlocks if a filesystem with writeback support works on top
of UBI. So pre-allocate needed buffers when attaching MTD device.
We also need mutexes to protect the buffers, but they do not
cause much contantion because they are used in recovery, torture,
and WL copy routines, which are called seldom.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Pointed to by viro.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>