Commit Graph

50 Commits

Author SHA1 Message Date
Pavel Emelyanov
ba25f9dcc4 Use helpers to obtain task pid in printks
The task_struct->pid member is going to be deprecated, so start
using the helpers (task_pid_nr/task_pid_vnr/task_pid_nr_ns) in
the kernel.

The first thing to start with is the pid, printed to dmesg - in
this case we may safely use task_pid_nr(). Besides, printks produce
more (much more) than a half of all the explicit pid usage.

[akpm@linux-foundation.org: git-drm went and changed lots of stuff]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-19 11:53:43 -07:00
Christoph Lameter
4ba9b9d0ba Slab API: remove useless ctor parameter and reorder parameters
Slab constructors currently have a flags parameter that is never used.  And
the order of the arguments is opposite to other slab functions.  The object
pointer is placed before the kmem_cache pointer.

Convert

        ctor(void *object, struct kmem_cache *s, unsigned long flags)

to

        ctor(struct kmem_cache *s, void *object)

throughout the kernel

[akpm@linux-foundation.org: coupla fixes]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:42:45 -07:00
David Woodhouse
e3d18658d4 Merge branch 'master' of git://git.infradead.org/~dedekind/ubi-2.6 2007-10-14 14:29:00 +01:00
Artem Bityutskiy
cc5f4f2875 UBI: return correct error code
Fix the following warning:

drivers/mtd/ubi/eba.c: In function 'ubi_eba_init_scan':
drivers/mtd/ubi/eba.c:1116: warning: 'err' may be used uninitialized in this function

Pointed-to-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:21 +03:00
Artem Bityutskiy
5abde384e3 UBI: remove useless inlines
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:21 +03:00
Artem Bityutskiy
e8823bd63d UBI: fix atomic LEB change problems
When the UBI device is nearly full, i.e. all LEBs are mapped, we have
only one spare LEB left - the one we reserved for WL purposes. Well,
I do not count the LEBs which were reserved for bad PEB handling -
suppose NOR flash for simplicity. If an "atomic LEB change operation"
is run, and the WL unit is moving a LEB, we have no spare LEBs to
finish the operation and fail, which is not good. Moreover, if there
are 2 or more simultanious "atomic LEB change" requests, only one of
them has chances to succeed, the other will fail with -ENOSPC. Not
good either.

This patch does 2 things:
1. Reserves one PEB for the "atomic LEB change" operation.
2. Serealize the operations so that only on of them may run
   at a time (by means of a mutex).

Pointed-to-by: Brijesh Singh <brijesh.s.singh@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:21 +03:00
Artem Bityutskiy
6986646ba7 UBI: use byte hexdump
More handy since word hexdump prints in host endian.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:21 +03:00
Artem Bityutskiy
e88d6e10e5 UBI: do not use vmalloc on I/O path
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>
2007-10-14 13:10:21 +03:00
Artem Bityutskiy
33818bbb84 UBI: allocate memory with GFP_NOFS
Use GFP_NOFS flag when allocating memory on I/O path, because otherwise
we may deadlock the filesystem which works on top of us. We observed
the deadlocks with UBIFS. Example:

VFS->FS lock a lock->UBI->kmalloc()->VFS writeback->FS locks the same
lock again.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Artem Bityutskiy
ef6075fbfc UBI: use linux print_hex_dump(), not home-grown one
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Jesper Juhl
0169b49d52 UBI: don't use array index before testing if it is negative
I can't find anything guaranteeing that 'ubi_num' cannot be <0 in
drivers/mtd/ubi/kapi.c::ubi_open_volume(), and in fact the code
even tests for that and errors out if so. Unfortunately the test
for "ubi_num < 0" happens after we've already used 'ubi_num' as
an array index - bad thing to do if it is negative.
This patch moves the test earlier in the function and then moves
the indexing using that variable after the check. A bit safer :-)

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Artem Bityutskiy
8d2d4011f1 UBI: add more prints
I hit those situations and found out lack of print messages. Add more prints
when erase problems occur.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Artem Bityutskiy
8bc2296196 UBI: fix sparse warnings
Fix "symbol shadows an earlier one" warnings. Although they are harmless
but it does not hurt to fix them and make sparse happy.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Florin Malita
dcec4c3bdc UBI: fix leak in ubi_scan_erase_peb
Coverity (1769) found the following problem: if the erase counter
overflow check triggers, ec_hdr is leaked.

Moving the allocation after the overflow check should take care of it.

Signed-off-by: Florin Malita <fmalita@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-10-14 13:10:20 +03:00
Mariusz Kozlowski
d9b0744d6c [UBI] drivers/mtd/ubi/scan.c: kmalloc + memset conversion to kzalloc
To be able to convert kmalloc + memset(..., 1, ...) to kzalloc this patch
reverses the logic around 'buf'.

Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
2007-08-01 11:04:05 +01:00
Paul Mundt
20c2df83d2 mm: Remove slab destructors from kmem_cache_create().
Slab destructors were no longer supported after Christoph's
c59def9f22 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2007-07-20 10:11:58 +09:00
Paul Mundt
add0b43ca6 UBI: fix compile warning
cdev.c whines in current git:

drivers/mtd/ubi/cdev.c: In function `major_to_device':
drivers/mtd/ubi/cdev.c:67: warning: control reaches end of non-void function

Shut it up.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:59:17 +03:00
Artem Bityutskiy
784c145444 UBI: fix error handling in erase worker
Do not switch to read-only mode in case of -EINTR and some
other obvious cases. Switch to RO mode only when we do not
know what is the error.

Reported-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:59:09 +03:00
Artem Bityutskiy
63b6c1ed56 UBI: fix comments
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:59:01 +03:00
Artem Bityutskiy
503990ebb2 UBI: remove unneeded error checks
Pointed to by viro.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:58:53 +03:00
Fernando Luis Vázquez Cao
2db61c95c0 UBI: cleanup usage of try_module_get
The use of try_module_get(THIS_MODULE) in ubi_get_device_info does not
offer real protection against unexpected driver unloads, since we could
be preempted before try_modules_get gets executed. It is the caller who
should manipulate the refcounts. Besides, ubi_get_device_info is an
exported symbol which guarantees protection when accessed through
symbol_get.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:58:45 +03:00
Vinit Agnihotri
d08c3b78b8 UBI: fix overflow bug
I was experiencing overflows in multiplications for
volume->used_bytes in vmt.c & vtbl.c, while creating & resizing large volumes.

vol->used_bytes is long long however its 2 operands vol->used_ebs &
vol->usable_leb_size
are int. So their multiplication for larger values causes integer overflows.
Typecasting them solves the problem.

My machine & flash details:

64Bit dual-core AMD opteron, 1 GB RAM, linux 2.6.18.3.
mtd size = 6GB, volume size= 5GB, peb_size = 4MB.

heres patch which does the fix.

Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:58:12 +03:00
Artem Bityutskiy
2f3cdb55ee UBI: bugfix in max_sqnum calculation
Do not zero max_sqnum after a new volume has been found.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:58:02 +03:00
Brijesh Singh
76eafe479e UBI: bugfix in sqnum calculation
Hi,I came across problem of having two leb with same sequence no.This
happens when we continuously write one block again and again and reboot
machine before background thread erases those blocks.
The problem here was,when we find two blocks with same sequence no,we take
the higher one,but we were not updating max seq no,so next block may have
the same seqnum.
This patch solves this problem.

Signed-off-by: Brijesh Singh <brijesh.s.singh@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:57:52 +03:00
Brijesh Singh
2f176f7987 UBI: fix signed-unsigned multiplication
There is signed multiplication assigned to unsigned ei.addr in io.c.
This causes wrong addresses for big multiplication.This patch solves the
problem.

Signed-off-by: Brijesh Singh <brijesh.s.singh@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:57:34 +03:00
Artem Bityutskiy
84a9258062 UBI: fix bug in atomic_leb_change()
atomic_leb_change() is only allowed for dynamic volumes, so set
the volume type correctly.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:56:24 +03:00
Vinit Agnihotri
a6ded48e34 UBI: fix message
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>
2007-07-18 16:56:13 +03:00
Artem Bityutskiy
b89044bfa0 UBI: fix debugging stuff
Do not check volumes which are currently in use because thay may be
in inconsistent state.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:56:05 +03:00
Artem Bityutskiy
94784d9164 UBI: bugfix in error path
When volume creation fails, we have to set ubi->volumes[vol_id]
back to NULL.

This patch also tweaks some debugging stuff.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:55:55 +03:00
Vignesh Babu
7753f1692f UBI: use is_power_of_2()
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>
2007-07-18 16:55:26 +03:00
Vinit Agnihotri
d7f0c4dc31 UBI: fix freeing ubi->vtbl while unloading
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>
2007-07-18 16:54:15 +03:00
Artem Bityutskiy
a443db48e0 UBI: bugfix in ubi_leb_change()
Do not call 'ubi_wl_put_peb()' if the LEB was unmapped.

Reported-by: Gabor Loki <loki@inf.u-szeged.hu>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:57 +03:00
Christoph Hellwig
3261ebd7d4 UBI: kill homegrown endian macros
Kill UBI's homegrown endianess handling and replace it with
the standard kernel endianess handling.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:49 +03:00
Christoph Hellwig
bf07803a68 UBI: cleanup ioctl handling
- don't do access_ok + get/put user but use the proper macro
- remove useless checks

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:36 +03:00
Artem Bityutskiy
16d8cd7ce4 UBI: error path bugfix
No need to unlock the lock, this will be done at out_unlock.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:27 +03:00
Artem Bityutskiy
f800f09bf4 UBI: minor comma fix
Use coma at the the last elements of structure initializer.

Daniel Stone's explanation:

Because it turns:
-   .attr   = foo
+   .attr   = foo,
+   .bar    = baz

into:
+   .bar    = baz,

i.e., far less likely to screw up a merge.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:17 +03:00
Artem Bityutskiy
92ad8f3750 UBI: use vmalloc for large buffers
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>
2007-07-18 16:53:08 +03:00
Artem Bityutskiy
79b510c0f2 UBI: add few more comments
Add few comments above ubi_scan_add_used() to explain why it is so
complex. Requested by Satyam Sharma <satyam.sharma@gmail.com>.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:53:00 +03:00
Artem Bityutskiy
941dfb07ed UBI: set correct gluebi device size
In case of static volumes, make emulated MTD device size to
be equivalent to data size, rather then volume size.

Reported-by: John Smith <john@arrows.demon.co.uk>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:52:51 +03:00
Artem Bityutskiy
4ab60a0d7c UBI: do not let to read too much
In case of static volumes it is prohibited to read more data
then available.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:52:42 +03:00
Artem Bityutskiy
78d87c95b8 UBI: fix error path in create_vtbl()
There were several bugs in volume table creation error path. Thanks to
Satyam Sharma <satyam.sharma@gmail.com> and Florin Malita <fmalita@gmail.com>
for finding and analysing them: http://lkml.org/lkml/2007/5/3/274

This patch makes ubi_scan_add_to_list() static and renames it to
add_to_list(), just because it is not needed outside scan.c anymore.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:52:32 +03:00
Florin Malita
c4e90ec013 UBI: fix dereference after kfree
Coverity (CID 1614) spotted new_seb being dereferenced after kfree() in
create_vtbl's write_error path.

Signed-off-by: Florin Malita <fmalita@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:52:22 +03:00
Artem Bityutskiy
341e1a0cf2 UBI: fix memory leak in checking code
Reported-by: Eric Sesterhenn / Snakebyte <snakebyte@gmx.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-07-18 16:52:13 +03:00
Jeff Garzik
a6343afb6e drivers/*: mark variables with uninitialized_var()
Mark variables in drivers/* with uninitialized_var() if such a warning
appears, and analysis proves that the var is initialized properly on all
paths it is used.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-07-17 16:23:19 -04:00
Jeff Garzik
2ab934b8af drivers/mtd/ubi/eba: minor cleanup: tighten scope of a local var
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-07-17 16:18:00 -04:00
Rafael J. Wysocki
8314418629 Freezer: make kernel threads nonfreezable by default
Currently, the freezer treats all tasks as freezable, except for the kernel
threads that explicitly set the PF_NOFREEZE flag for themselves.  This
approach is problematic, since it requires every kernel thread to either
set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't
care for the freezing of tasks at all.

It seems better to only require the kernel threads that want to or need to
be frozen to use some freezer-related code and to remove any
freezer-related code from the other (nonfreezable) kernel threads, which is
done in this patch.

The patch causes all kernel threads to be nonfreezable by default (ie.  to
have PF_NOFREEZE set by default) and introduces the set_freezable()
function that should be called by the freezable kernel threads in order to
unset PF_NOFREEZE.  It also makes all of the currently freezable kernel
threads call set_freezable(), so it shouldn't cause any (intentional)
change of behaviour to appear.  Additionally, it updates documentation to
describe the freezing of tasks more accurately.

[akpm@linux-foundation.org: build fixes]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Nigel Cunningham <nigel@nigel.suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:02 -07:00
Christoph Lameter
a35afb830f Remove SLAB_CTOR_CONSTRUCTOR
SLAB_CTOR_CONSTRUCTOR is always specified. No point in checking it.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven French <sfrench@us.ibm.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@ucw.cz>
Cc: David Chinner <dgc@sgi.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-17 05:23:04 -07:00
Christoph Lameter
50953fe9e0 slab allocators: Remove SLAB_DEBUG_INITIAL flag
I have never seen a use of SLAB_DEBUG_INITIAL.  It is only supported by
SLAB.

I think its purpose was to have a callback after an object has been freed
to verify that the state is the constructor state again?  The callback is
performed before each freeing of an object.

I would think that it is much easier to check the object state manually
before the free.  That also places the check near the code object
manipulation of the object.

Also the SLAB_DEBUG_INITIAL callback is only performed if the kernel was
compiled with SLAB debugging on.  If there would be code in a constructor
handling SLAB_DEBUG_INITIAL then it would have to be conditional on
SLAB_DEBUG otherwise it would just be dead code.  But there is no such code
in the kernel.  I think SLUB_DEBUG_INITIAL is too problematic to make real
use of, difficult to understand and there are easier ways to accomplish the
same effect (i.e.  add debug code before kfree).

There is a related flag SLAB_CTOR_VERIFY that is frequently checked to be
clear in fs inode caches.  Remove the pointless checks (they would even be
pointless without removeal of SLAB_DEBUG_INITIAL) from the fs constructors.

This is the last slab flag that SLUB did not support.  Remove the check for
unimplemented flags from SLUB.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-07 12:12:57 -07:00
Artem Bityutskiy
d468a03002 UBI: remove unused variable
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2007-04-27 15:11:44 +03:00
Artem B. Bityutskiy
801c135ce7 UBI: Unsorted Block Images
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>
2007-04-27 14:23:33 +03:00