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: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Currently UBI has one small flaw - when we read EC or VID header, but find only
0xFF bytes, we return UBI_IO_FF and do not report whether we had bit-flips or
not. In case of the VID header, the scanning code adds this PEB to the free list,
even though there were bit-flips.

Imagine the following situation: we start writing VID header to a PEB and have a
power cut, so the PEB becomes unstable. When we scan and read the PEB, we get
a bit-flip. Currently, UBI would just ignore this and treat the PEB as free. This
patch changes UBI behavior and now UBI will schedule this PEB for erasure.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

The 'UBI_IO_PEB_EMPTY' and 'UBI_IO_PEB_FREE' are essentially the same
and mean that there are only 0xFF bytes instead of headers. Simplify
UBI a little by turning them into a single 'UBI_IO_FF' error code.

Also, stop maintaining commentaries in 'ubi_io_read_vid_hdr()' which are
almost identical to commentaries in 'ubi_io_read_ec_hdr()'.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When an erroneous PEB is scheduling for scrubbing, we end up with the
following oops:

[<c0162404>] (prot_queue_del+0x0/0x50) from [<c01635b4>] (ubi_wl_scrub_peb+0xec/0x13c)
[<c01634c8>] (ubi_wl_scrub_peb+0x0/0x13c) from [<c01603bc>] (ubi_eba_read_leb+0x200/0x428)
[<c01601bc>] (ubi_eba_read_leb+0x0/0x428) from [<c015e3c0>] (ubi_leb_read+0xe8/0x138)
[<c015e2d8>] (ubi_leb_read+0x0/0x138) from [<c00d6918>] (ubifs_start_scan+0x7c/0xf4)
[<c00d689c>] (ubifs_start_scan+0x0/0xf4) from [<c00e3650>] (ubifs_recover_leb+0x3c/0x730)
[<c00e3614>] (ubifs_recover_leb+0x0/0x730) from [<c00e444c>] (ubifs_recover_log_leb+0xc8/0x2dc)
[<c00e4384>] (ubifs_recover_log_leb+0x0/0x2dc) from [<c00d7c20>] (ubifs_replay_journal+0xb90/0x13a4)
[<c00d7090>] (ubifs_replay_journal+0x0/0x13a4) from [<c00cdd68>] (ubifs_fill_super+0xb84/0x1054)
[<c00cd1e4>] (ubifs_fill_super+0x0/0x1054) from [<c00ced04>] (ubifs_get_sb+0xc4/0x2ac)
[<c00cec40>] (ubifs_get_sb+0x0/0x2ac) from [<c007f04c>] (vfs_kern_mount+0x58/0x94)
[<c007eff4>] (vfs_kern_mount+0x0/0x94) from [<c007f0e8>] (do_kern_mount+0x40/0xe8)
[<c007f0a8>] (do_kern_mount+0x0/0xe8) from [<c0095628>] (do_new_mount+0x68/0x8c)
[<c00955c0>] (do_new_mount+0x0/0x8c) from [<c00957a8>] (do_mount+0x15c/0x1b8)
[<c009564c>] (do_mount+0x0/0x1b8) from [<c0095890>] (sys_mount+0x8c/0xd4)
[<c0095804>] (sys_mount+0x0/0xd4) from [<c0023c00>] (ret_fast_syscall+0x0/0x2c)
Kernel panic - not syncing: Fatal exception

The problem is that 'ubi_wl_scrub_peb()' does not expect that PEBs may
be in the erroneous tree, which is a bug. This patch fixes the bug
and adds corresponding check to 'ubi_wl_scrub_peb()'. Now it will simply
ignore erroneous PEBs, instead of causing an oops.
Reported-by: NMatthieu CASTET <matthieu.castet@parrot.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NShinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI debugging functions were a little bit over-engineered and
returned more error codes than needed, and the callers had to
do useless checks. Simplify the return codes.

Impact: only debugging code is affected, which means that for
        non-developers this is a no-op patch.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

The 'paranoid_check_empty()' is bogus because, which is easilly
seen on NOR flash, which has long erase cycles, and which may
easilly end-up with half-erased eraseblocks. In this case the
paranoid check fails. I is just wrong to assume that PEBs which
do not have EC headers always contain all 0xFF. Such assumption
should not be made on the I/O level, which is quite low.

Thus, just kill the check.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch adds code which makes sure eraseblocks contain all 0xFF
bytes before starting using them. The verification is done only when
debugging checks are enabled.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Some of the typos were indicated by Adrian Hunter,
some by 'aspell'.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

'kmem_cache_free()' oopeses if NULL is passed, and there is
one error-path place where UBI may call it with NULL object.
This problem was pointed to by Adrian Hunter.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When marking a PEB as bad, print how many PEBs are left reserved.
This is very useful information.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Print not only the PEB number, but also the LEB number and volume id,
which is very useful for bug hunting.
Signed-off-by: NArtem 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: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch fixes the error path in the WL worker - in same cases
UBI oopses when 'goto out_error' happens and e1 or e2 are NULL.
This patch also cleans up the error paths a little. And I have
tested nearly all error paths in the WL worker.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch is a clean-up and a preparation for the following
patches. It introduece constants for the return values of the
'ubi_eba_copy_leb()' function.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

- (better, more, bigger ...) then -> (...) than
Signed-off-by: NFrederik Schwarzer <schwarzerf@gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

UBI has 2 RB-trees to implement PEB protection, which is too
much for simply prevent PEB from being moved for some time.
This patch implements this using lists. The benefits:

1. No need to allocate protection entry on each PEB get.
2. No need to maintain balanced trees and walk them.
Signed-off-by: NXiaochuan-Xu <xiaochuan-xu@cqu.edu.cn>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch modifies @struct ubi_wl_entry and adds union which
contains only one element so far. This is just a preparation
for further changes which will kill the protection tree and
make UBI use a list instead.
Signed-off-by: NXiaochuan-Xu <xiaochuan-xu@cqu.edu.cn>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When a PEB is moved and a write error happens, UBI switches
to R/O mode, which is wrong, because we just copy the data
and may select a different PEB and re-try this. This patch
fixes WL worker's behavior.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Make sure the resources had not already been freed before
freeing them in the error path of the WL worker function.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Minor code re-structuring and commentaries fixes to improve readability.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

If ubi_thread() exits but kthread_should_stop() is not true
then kthread_stop() will never return and cleanup thread
will forever stay in "D" state.
Signed-off-by: NVitaliy Gusev <vgusev@openvz.org>
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>

If bit-flips happen often, UBI prints to many messages. Lessen
the amount by only printing the messages when the PEB has been
scrubbed. Also, print torturing messages.
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>

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>

drivers/mtd/ubi/wl.c:746: warning: 'pe' may be used uninitialized in this function
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

Old gcc complains:

CC      drivers/mtd/ubi/wl.o
drivers/mtd/ubi/wl.c: In function 'wear_leveling_worker':
drivers/mtd/ubi/wl.c:746: warning: 'pe' may be used uninitialized in this function
CC      drivers/mtd/ubi/scan.o
drivers/mtd/ubi/scan.c: In function 'ubi_scan':
drivers/mtd/ubi/scan.c:772: warning: 'ec' may be used uninitialized in this function
drivers/mtd/ubi/scan.c:772: note: 'ec' was declared here
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>

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>

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

The flush function should finish all the pending jobs. But if
somebody else is doing a work, this function should wait and let
it finish.

This patche uses rw semaphore for synchronization purpose - it
just looks quite convinient.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When the WL worker is moving an LEB, the volume might go away
occasionally. UBI does not handle these situations correctly.

This patch introduces a new mutex which serializes wear-levelling
worker and the the 'ubi_wl_put_peb()' function. Now, if one puts
an LEB, and its PEB is being moved, it will wait on the mutex.
And because we unmap all LEBs when removing volumes, this will make
the volume remove function to wait while the LEB movement
finishes.

Below is an example of an oops which should be fixed by this patch:

Pid: 9167, comm: io_paral Not tainted (2.6.24-rc5-ubi-2.6.git #2)
EIP: 0060:[<f884a379>] EFLAGS: 00010246 CPU: 0
EIP is at prot_tree_del+0x2a/0x63 [ubi]
EAX: f39a90e0 EBX: 00000000 ECX: 00000000 EDX: 00000134
ESI: f39a90e0 EDI: f39a90e0 EBP: f2d55ddc ESP: f2d55dd4
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process io_paral (pid: 9167, ti=f2d54000 task=f72a8030 task.ti=f2d54000)
Stack: f39a95f8 ef6aae50 f2d55e08 f884a511 f88538e1 f884ecea 00000134 00000000
       f39a9604 f39a95f0 efea8280 00000000 f39a90e0 f2d55e40 f8847261 f8850c3c
       f884eaad 00000001 000000b9 00000134 00000172 000000b9 00000134 00000001
Call Trace:
 [<c0105227>] show_trace_log_lvl+0x1a/0x30
 [<c01052e2>] show_stack_log_lvl+0xa5/0xca
 [<c01053d6>] show_registers+0xcf/0x21b
 [<c0105648>] die+0x126/0x224
 [<c0119a62>] do_page_fault+0x27f/0x60d
 [<c037dd62>] error_code+0x72/0x78
 [<f884a511>] ubi_wl_put_peb+0xf0/0x191 [ubi]
 [<f8847261>] ubi_eba_unmap_leb+0xaf/0xcc [ubi]
 [<f8843c21>] ubi_remove_volume+0x102/0x1e8 [ubi]
 [<f8846077>] ubi_cdev_ioctl+0x22a/0x383 [ubi]
 [<c017d768>] do_ioctl+0x68/0x71
 [<c017d7c6>] vfs_ioctl+0x55/0x271
 [<c017da15>] sys_ioctl+0x33/0x52
 [<c0104152>] sysenter_past_esp+0x5f/0xa5
 =======================
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Explain better the purpose of thie 'move_to_put' stuff.
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>

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: NPavel Emelyanov <xemul@openvz.org>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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>