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Coly Li 1dda32aed6 bcache: avoid journal no-space deadlock by reserving 1 journal bucket 
commit 32feee36c3 upstream.

The journal no-space deadlock was reported time to time. Such deadlock
can happen in the following situation.

When all journal buckets are fully filled by active jset with heavy
write I/O load, the cache set registration (after a reboot) will load
all active jsets and inserting them into the btree again (which is
called journal replay). If a journaled bkey is inserted into a btree
node and results btree node split, new journal request might be
triggered. For example, the btree grows one more level after the node
split, then the root node record in cache device super block will be
upgrade by bch_journal_meta() from bch_btree_set_root(). But there is no
space in journal buckets, the journal replay has to wait for new journal
bucket to be reclaimed after at least one journal bucket replayed. This
is one example that how the journal no-space deadlock happens.

The solution to avoid the deadlock is to reserve 1 journal bucket in
run time, and only permit the reserved journal bucket to be used during
cache set registration procedure for things like journal replay. Then
the journal space will never be fully filled, there is no chance for
journal no-space deadlock to happen anymore.

This patch adds a new member "bool do_reserve" in struct journal, it is
inititalized to 0 (false) when struct journal is allocated, and set to
1 (true) by bch_journal_space_reserve() when all initialization done in
run_cache_set(). In the run time when journal_reclaim() tries to
allocate a new journal bucket, free_journal_buckets() is called to check
whether there are enough free journal buckets to use. If there is only
1 free journal bucket and journal->do_reserve is 1 (true), the last
bucket is reserved and free_journal_buckets() will return 0 to indicate
no free journal bucket. Then journal_reclaim() will give up, and try
next time to see whetheer there is free journal bucket to allocate. By
this method, there is always 1 jouranl bucket reserved in run time.

During the cache set registration, journal->do_reserve is 0 (false), so
the reserved journal bucket can be used to avoid the no-space deadlock.

Reported-by: Nikhil Kshirsagar <nkshirsagar@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220524102336.10684-5-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-09 10:30:53 +02:00
arch xtensa/simdisk: fix proc_read_simdisk() 2022-06-09 10:30:52 +02:00
block block: Fix potential deadlock in blk_ia_range_sysfs_show() 2022-06-09 10:30:44 +02:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto crypto: cryptd - Protect per-CPU resource by disabling BH. 2022-06-09 10:30:30 +02:00
Documentation landlock: Reduce the maximum number of layers to 16 2022-06-09 10:30:47 +02:00
drivers bcache: avoid journal no-space deadlock by reserving 1 journal bucket 2022-06-09 10:30:53 +02:00
fs ksmbd: fix outstanding credits related bugs 2022-06-09 10:30:51 +02:00
include nodemask.h: fix compilation error with GCC12 2022-06-09 10:30:52 +02:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-06-09 10:30:49 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:30:30 +02:00
kernel kprobes: Fix build errors with CONFIG_KRETPROBES=n 2022-06-09 10:30:51 +02:00
lib lib/string_helpers: fix not adding strarray to device's resource list 2022-06-09 10:30:49 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/memremap: fix missing call to untrack_pfn() in pagemap_range() 2022-06-09 10:30:52 +02:00
net mac80211: upgrade passive scan to active scan on DFS channels after beacon rx 2022-06-09 10:30:50 +02:00
samples samples/landlock: Format with clang-format 2022-06-09 10:30:46 +02:00
scripts scripts/faddr2line: Fix overlapping text section failures 2022-06-09 10:30:10 +02:00
security ima: remove the IMA_TEMPLATE Kconfig option 2022-06-09 10:30:49 +02:00
sound ASoC: rt5514: Fix event generation for "DSP Voice Wake Up" control 2022-06-09 10:30:52 +02:00
tools landlock: Fix same-layer rule unions 2022-06-09 10:30:48 +02:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM: Free new dirty bitmap if creating a new memslot fails 2022-05-20 13:02:05 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap hotfixes for 5.18-rc7 2022-05-13 10:22:37 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'arm/fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc 2022-05-18 14:07:43 -10:00
Makefile Linux 5.18.2 2022-06-06 08:49:00 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.