Incorporate MTD write buffer size into UBI device information
because UBIFS needs this field. UBI does not use it ATM, just
provides to upper layers in 'struct ubi_device_info'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
During scanning UBI allocates one struct ubi_scan_leb object for each PEB,
so it can end up allocating thousands of them. Use slab cache to reduce
memory consumption for these 48-byte objects, because currently used
'kmalloc()' ends up allocating 64 bytes per object, instead of 48.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Wrong macro was used in calculating the data offset: UBI_EC_HDR_SIZE instead of
UBI_VID_HDR_SIZE. The data offset should be VID header offset + VID header size
(aligned to the minimum I/O unit).
This was not a bug only because currently UBI_EC_HDR_SIZE and UBI_VID_HDR_SIZE
have the same value of 64 bytes.
Commit message was amended by Artem.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Currently UBI erases all corrupted eraseblocks, irrespectively of the nature
of corruption: corruption due to power cuts and non-power cut corruption.
The former case is OK, but the latter is not, because UBI may destroy
potentially important data.
With this patch, during scanning, when UBI hits a PEB with corrupted VID
header, it checks whether this PEB contains only 0xFF data. If yes, it is
safe to erase this PEB and it is put to the 'erase' list. If not, this may
be important data and it is better to avoid erasing this PEB. Instead,
UBI puts it to the corr list and moves out of the pool of available PEB.
IOW, UBI preserves this PEB.
Such corrupted PEB lessen the amount of available PEBs. So the more of them
we accumulate, the less PEBs are available. The maximum amount of non-power
cut corrupted PEBs is 8.
This patch is a response to UBIFS problem where reporter
(Matthew L. Creech <mlcreech@gmail.com>) observes that UBIFS index points
to an unmapped LEB. The theory is that corresponding PEB somehow got
corrupted and UBI wiped it. This patch (actually a series of patches)
tries to make sure such PEBs are preserved - this would make it is easier
to analyze the corruption.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Currently, when UBI attaches an MTD device and cannot reserve all 1% (by
default) of PEBs for bad eraseblocks handling, it prints a warning. However,
Matthew L. Creech <mlcreech@gmail.com> is not very happy to see this warning,
because he did reserve enough of PEB at the beginning, but with time some
PEBs became bad. The warning is not necessary in this case.
This patch makes UBI print the warning
o if this is a new image
o of this is used image and the amount of reserved PEBs is only 10% (or less)
of the size of the reserved PEB pool.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI can be built into the kernel or be compiled as a kernel module.
Further on the command line one can specify MTD devices to be attach to
UBI while loading. In the current implementation the UBI driver refuses
to load if one of the MTD devices cannot be attached.
Consider:
1) UBI compiled into the kernel and
2) a MTD device specified on the command line and
3) this MTD device contains bogus data (for whatever reason).
During init UBI tries to attach the MTD device is this fails the whole
UBI subsystem isn't initialized. Later the userspace cannot attach any
MTD to UBI because UBI isn't loaded.
This patch keeps the current behaviour: if UBI is compiled as a module
and a MTD device cannot be attached the UBI module cannot be loaded,
but changes it for the UBI-is-built-into-the-kernel usecase.
If UBI is builtin, a not attachable MTD device doen't stop UBI from
initializing. This slightly modifies the behaviour if multiple MTD
devices are specified on the command line. Now every MTD device is
probed and, if possible, attached, i.e. a faulty MTD device doesn't
stop the others from being attached.
Artem: tweaked the patch
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The UBI reboot notifier causes problems with hibernation. Move this
functionality into the low-level MTD driver instead.
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Passing the attribute to the low level IO functions allows all kinds
of cleanups, by sharing low level IO code without requiring
an own function for every piece of data.
Also drivers can extend the attributes with own data fields
and use that in the low level function.
This makes the class attributes the same as sysdev_class attributes
and plain attributes.
This will allow further cleanups in drivers.
Full tree sweep converting all users.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
In the error path of 'ubi_attach_mtd_dev()' we have a tricky situation:
we have to release things differently depending on at which point
the failure happening. Namely, if @ubi->dev is not initialized, we have
to free everything ourselves. But if it was, we should not free the @ubi
object, because it will be freed in the 'dev_release()' function. And
we did not get this situation right.
This patch introduces additional argument to the 'uif_init()' function.
On exit, this argument indicates whether the final 'free(ubi)' will
happen in 'dev_release()' or not. So the caller always knows how to
properly release the resources.
Impact: all memory is now correctly released when UBI fails to attach
an MTD device.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch adds a capability to attach MTD devices by their character
device paths. For example, one can do:
$ modprobe ubi mtd=/dev/mtd0
to attach /dev/mtd0.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The @mtd_devs and @mtd_dev_param variables are used only during the
initialization, and all functions that use the variables have
the __init prefix. This means we can safely mark the variables
as __initdata, which is a tiny optimization.
Impact: tiny RAM consumption optimization when UBI is used as a kernel
module.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
result is unsigned, the wrong check was used.
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit fixes NOR flash recovery issues observed with Spansion
S29GL512N NOR.
When NOR erases, it first fills PEBs with zeroes, then sets all bytes
to 0xFF. Filling with zeroes starts from the end of the PEB. And when
power is cut, this results in PEBs containing correct EC and VID headers
but corrupted with zeros at the end. This confuses UBI and it mistakinly
accepts these PEBs and associate them with LEBs.
Fis this issue by zeroing EC and VID magics before erasing PEBs, to
make UBI later refuse zem.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
An image sequence number is added to the UBI erase-counter header
to be able determine if the root file system contains a mixture
of old and new images (because the flashing failed to complete).
A change to nolo is also needed for this to take effect.
Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Terminate the UBI background thread prior to restarting the system.
[Artem: amended comments a little]
Signed-off-by: Kevin Cernekee <kpc.mtd@gmail.com>
Tested-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI volume notifications are intended to create the API to get clients
notified about volume creation/deletion, renaming and re-sizing. A
client can subscribe to these notifications using 'ubi_volume_register()'
and cancel the subscription using 'ubi_volume_unregister()'. When UBI
volumes change, a blocking notifier is called. Clients also can request
"added" events on all volumes that existed before client subscribed
to the notifications.
If we use notifications instead of calling functions like 'ubi_gluebi_xxx()',
we can make the MTD emulation layer to be more flexible: build it as a
separate module and load/unload it on demand.
[Artem: many cleanups, rework locking, add "updated" event, provide
device/volume info in notifiers]
Signed-off-by: Dmitry Pervushin <dpervushin@embeddedalley.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch improves UBI errors handling. ATM UBI switches to
R/O mode when the WL worker fails to read the source PEB.
This means that the upper layers (e.g., UBIFS) has no
chances to unmap the erroneous PEB and fix the error.
This patch changes this behaviour and makes UBI put PEBs
like this into a separate RB-tree, thus preventing the
WL worker from hitting the same read errors again and
again.
But there is a 10% limit on a maximum amount of PEBs like this.
If there are too much of them, UBI switches to R/O mode.
Additionally, this patch teaches UBI not to panic and
switch to R/O mode if after a PEB has been copied, the
target LEB cannot be read back. Instead, now UBI cancels
the operation and schedules the target PEB for torturing.
The error paths has been tested by ingecting errors
into 'ubi_eba_copy_leb()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch fixes a minor problem where we may fail to wake
upe the UBI background thread. This is not fatal at all,
it may just result at sligtly worse performace for a short
period of time, just because the thread will be woken up
when real I/O on the UBI starts.
Anywey, the issue is the race condition between
'ubi_attach_mtd_dev()' and 'ubi_thread()'. If we do not
serialize them, the 'wake_up_process()' call may be done
before 'ubi_thread()' went seep, but after it checked
'ubi->thread_enabled'.
This issue was spotted by Shin Hong <hongshin@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The @ubi->dbg_peb_buf is needed only when paranoid checks are
enabled, not when debugging in general is enabled.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The mutex essencially protects the entire UBI device, so the
old @volumes_mutex name is a little misleading.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The @mult_mutex does not serve any purpose. We already have
@volumes_mutex and it is enough. The @volume mutex is pushed
down to the 'ubi_rename_volumes()', because we want first
to open all volumes in the exclusive mode, and then lock the
mutex, just like all other ioctl's (remove, re-size, etc) do.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
GregKH asked to fix UBI which has fake device release method. Indeed,
we have to free UBI device description object from the release method,
because otherwise we'll oops is someone opens a UBI device sysfs file,
then the device is removed, and he reads the file. With this fix, he
will get -ENODEV instead of an oops.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
MTD internal API presently uses 32-bit values to represent
device size. This patch updates them to 64-bits but leaves
the external API unchanged. Extending the external API
is a separate issue for several reasons. First, no one
needs it at the moment. Secondly, whether the implementation
is done with IOCTLs, sysfs or both is still debated. Thirdly
external API changes require the internal API to be accepted
first.
Note that although the MTD API will be able to support 64-bit
device sizes, existing drivers do not and are not required
to do so, although NAND base has been updated.
In general, changing from 32-bit to 64-bit values cause little
or no changes to the majority of the code with the following
exceptions:
- printk message formats
- division and modulus of 64-bit values
- NAND base support
- 32-bit local variables used by mtdpart and mtdconcat
- naughtily assuming one structure maps to another
in MEMERASE ioctl
Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Return with correct error code (-ENOMEM) from ubi_attach_mtd_dev() upon
failing vmalloc().
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
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: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
No functional changes, just tweak comments to make kernel-doc
work fine and stop complaining.
Signed-off-by: Artem 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: Artem 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: Artem 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: Artem 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: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI forgets to free internal volumes when detaching MTD device.
Fix this.
Pointed-out-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem 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: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem 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: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Artem 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: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David 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: Artem 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: Artem 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: Artem 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: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem 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: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Increase UBI devices couter after the message, not before.
Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Replacing (n & (n-1)) in the context of power of 2 checks
with is_power_of_2
Signed-off-by: Vignesh Babu <vignesh.babu@wipro.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
ubi->vtbl is allocated using vmalloc() in vtbl.c empty_create_lvol(),
but it is freed in build.c with kfree()
Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI allocates temporary buffers of PEB size, which may be 256KiB.
Use vmalloc instead of kmalloc for such big temporary buffers.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.
In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.
More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html
Partitioning/Re-partitioning
An UBI volume occupies a certain number of erase blocks. This is
limited by a configured maximum volume size, which could also be
viewed as the partition size. Each individual UBI volume's size can
be changed independently of the other UBI volumes, provided that the
sum of all volume sizes doesn't exceed a certain limit.
UBI supports dynamic volumes and static volumes. Static volumes are
read-only and their contents are protected by CRC check sums.
Bad eraseblocks handling
UBI transparently handles bad eraseblocks. When a physical
eraseblock becomes bad, it is substituted by a good physical
eraseblock, and the user does not even notice this.
Scrubbing
On a NAND flash bit flips can occur on any write operation,
sometimes also on read. If bit flips persist on the device, at first
they can still be corrected by ECC, but once they accumulate,
correction will become impossible. Thus it is best to actively scrub
the affected eraseblock, by first copying it to a free eraseblock
and then erasing the original. The UBI layer performs this type of
scrubbing under the covers, transparently to the UBI volume users.
Erase Counts
UBI maintains an erase count header per eraseblock. This frees
higher-level layers (like file systems) from doing this and allows
for centralized erase count management instead. The erase counts are
used by the wear-levelling algorithm in the UBI layer. The algorithm
itself is exchangeable.
Booting from NAND
For booting directly from NAND flash the hardware must at least be
capable of fetching and executing a small portion of the NAND
flash. Some NAND flash controllers have this kind of support. They
usually limit the window to a few kilobytes in erase block 0. This
"initial program loader" (IPL) must then contain sufficient logic to
load and execute the next boot phase.
Due to bad eraseblocks, which may be randomly scattered over the
flash device, it is problematic to store the "secondary program
loader" (SPL) statically. Also, due to bit-flips it may become
corrupted over time. UBI allows to solve this problem gracefully by
storing the SPL in a small static UBI volume.
UBI volumes vs. static partitions
UBI volumes are still very similar to static MTD partitions:
* both consist of eraseblocks (logical eraseblocks in case of UBI
volumes, and physical eraseblocks in case of static partitions;
* both support three basic operations - read, write, erase.
But UBI volumes have the following advantages over traditional
static MTD partitions:
* there are no eraseblock wear-leveling constraints in case of UBI
volumes, so the user should not care about this;
* there are no bit-flips and bad eraseblocks in case of UBI volumes.
So, UBI volumes may be considered as flash devices with relaxed
restrictions.
Where can it be found?
Documentation, kernel code and applications can be found in the MTD
gits.
What are the applications for?
The applications help to create binary flash images for two purposes: pfi
files (partial flash images) for in-system update of UBI volumes, and plain
binary images, with or without OOB data in case of NAND, for a manufacturing
step. Furthermore some tools are/and will be created that allow flash content
analysis after a system has crashed..
Who did UBI?
The original ideas, where UBI is based on, were developed by Andreas
Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
were involved too. The implementation of the kernel layer was done by Artem
B. Bityutskiy. The user-space applications and tools were written by Oliver
Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
Schmidt made some testing work as well as core functionality improvements.
Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
