There is a risk that the fastmap anchor PEB is alternating between
just two PEBs, the current anchor and the previous anchor that was just
deleted. As the fastmap pools gets the first take on free PEBs, the
pools may leave no free PEBs to be selected as the new anchor,
resulting in the two PEBs alternating behaviour. If the anchor PEBs gets
a high erase count the PEBs will not be used by the pools but remain in
ubi->free, even more increasing the likelihood they will be used as
anchors.
Getting stuck using only a couple of PEBs continuously will result in an
uneven wear, eventually leading to failure.
To fix this:
- Choose the fastmap anchor when the most free PEBs are available. This is
during rebuilding of the fastmap pools, after the unused pool PEBs are
added to ubi->free but before the pools are populated again from the
free PEBs. Also reserve an additional second best PEB as a candidate
for the next time the fast map anchor is updated. If a better PEB is
found the next time the fast map anchor is updated, the candidate is
made available for building the pools.
- Enable anchor move within the anchor area again as it is useful for
distributing wear.
- The anchor candidate for the next fastmap update is the most suited free
PEB. Check this PEB's erase count during wear leveling. If the wear
leveling limit is exceeded, the PEB is considered unsuitable for now. As
all other non used anchor area PEBs should be even worse, free up the
used anchor area PEB with the lowest erase count.
Signed-off-by: Arne Edholm <arne.edholm@axis.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
When CONFIG_MTD_UBI_FASTMAP is enabled, fm_anchor will be assigned
a free PEB during ubi_wl_init() or ubi_update_fastmap(). However
if fastmap is not used or disabled on the MTD device, ubi_wl_entry
related with the PEB will not be freed during detach.
So Fix it by freeing the unused fastmap anchor during detach.
Fixes: f9c34bb529 ("ubi: Fix producing anchor PEBs")
Reported-by: syzbot+f317896aae32eb281a58@syzkaller.appspotmail.com
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
When a new fastmap is about to be written UBI must make sure it has a
free block for a fastmap anchor available. For this ubi_update_fastmap()
calls ubi_ensure_anchor_pebs(). This stopped working with 2e8f08deab
("ubi: Fix races around ubi_refill_pools()"), with this commit the wear
leveling code is blocked and can no longer produce free PEBs. UBI then
more often than not falls back to write the new fastmap anchor to the
same block it was already on which means the same erase block gets
erased during each fastmap write and wears out quite fast.
As the locking prevents us from producing the anchor PEB when we
actually need it, this patch changes the strategy for creating the
anchor PEB. We no longer create it on demand right before we want to
write a fastmap, but instead we create an anchor PEB right after we have
written a fastmap. This gives us enough time to produce a new anchor PEB
before it is needed. To make sure we have an anchor PEB for the very
first fastmap write we call ubi_ensure_anchor_pebs() during
initialisation as well.
Fixes: 2e8f08deab ("ubi: Fix races around ubi_refill_pools()")
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
Running stress test io_paral (A pressure ubi test in mtd-utils) on an
UBI device with fewer PEBs (fastmap enabled) may cause ENOSPC errors and
make UBI device read-only, but there are still free PEBs on the UBI
device. This problem can be easily reproduced by performing the following
steps on a 2-core machine:
$ modprobe nandsim first_id_byte=0x20 second_id_byte=0x33 parts=80
$ modprobe ubi mtd="0,0" fm_autoconvert
$ ./io_paral /dev/ubi0
We may see the following verbose:
(output)
[io_paral] update_volume():108: failed to write 380 bytes at offset
95920 of volume 2
[io_paral] update_volume():109: update: 97088 bytes
[io_paral] write_thread():227: function pwrite() failed with error 28
(No space left on device)
[io_paral] write_thread():229: cannot write 15872 bytes to offs 31744,
wrote -1
(dmesg)
ubi0 error: ubi_wl_get_peb [ubi]: Unable to get a free PEB from user WL
pool
ubi0 warning: ubi_eba_write_leb [ubi]: switch to read-only mode
CPU: 0 PID: 2027 Comm: io_paral Not tainted 5.3.0-rc2-00001-g5986cd0 #9
ubi0 warning: try_write_vid_and_data [ubi]: failed to write VID header
to LEB 2:5, PEB 18
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0
-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack+0x85/0xba
ubi_eba_write_leb+0xa1e/0xa40 [ubi]
vol_cdev_write+0x307/0x520 [ubi]
vfs_write+0xfa/0x280
ksys_pwrite64+0xc5/0xe0
__x64_sys_pwrite64+0x22/0x30
do_syscall_64+0xbf/0x440
In function ubi_wl_get_peb, the operation of filling the pool
(ubi_update_fastmap) with free PEBs and fetching a free PEB from the pool
is not atomic. After thread A filling the pool with free PEB, free PEB may
be taken away by thread B. When thread A checks the expression again, the
condition is still unsatisfactory. At this time, there may still be free
PEBs on UBI that can be filled into the pool.
This patch increases the number of attempts to obtain PEB. An extreme
case (No free PEBs left after creating test volumes) has been tested on
different type of machines for 100 times. The biggest number of attempts
are shown below:
x86_64 arm64
2-core 4 4
4-core 8 4
8-core 4 4
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation version 2 this program is distributed
in the hope that it will be useful but without any warranty without
even the implied warranty of merchantability or fitness for a
particular purpose see the gnu general public license for more
details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 97 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.025053186@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
At this point UBI volumes have already been free()'ed and fastmap can no
longer access these data structures.
Reported-by: Martin Townsend <mtownsend1973@gmail.com>
Fixes: 74cdaf2400 ("UBI: Fastmap: Fix memory leaks while closing the WL sub-system")
Cc: stable@vger.kernel.org
Signed-off-by: Richard Weinberger <richard@nod.at>
Fix misspelling of 'available' in function name.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
When writing a new Fastmap the first thing that happens
is refilling the pools in memory.
At this stage it is possible that new PEBs from the new pools
get already claimed and written with data.
If this happens before the new Fastmap data structure hits the
flash and we face power cut the freshly written PEB will not
scanned and unnoticed.
Solve the issue by locking the pools until Fastmap is written.
Cc: <stable@vger.kernel.org>
Fixes: dbb7d2a88d ("UBI: Add fastmap core")
Signed-off-by: Richard Weinberger <richard@nod.at>
If fastmap requests a free PEB for a pool and UBI is busy
with erasing PEBs we need to offer a function to wait for one.
We can reuse produce_free_peb() from the non-fastmap WL code
but with different locking semantics.
Cc: stable@vger.kernel.org # 4.1.x-
Reported-and-tested-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Richard Weinberger <richard@nod.at>
This function was added to fastmap in a very early stage
to have paranoid assertions.
With the current fastmap implementation this assert will never
trigger as fastmap PEBs are not seen by the WL sub-system.
Remove it to save us some CPU cycles.
Signed-off-by: Richard Weinberger <richard@nod.at>
Fastmap is tightly connected to the WL sub-system, many fastmap-specific
functionslive in wl.c.
To get rid of most #ifdefs in wl.c move this functions into a new file
and include it into wl.c
Signed-off-by: Richard Weinberger <richard@nod.at>
