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Filename Latest commit message Latest commit date
Qu Wenruo 670f5e40d7 btrfs: repair super block num_devices automatically
commit d201238ccd2f30b9bfcfadaeae0972e3a486a176 upstream.

[BUG]
There is a report that a btrfs has a bad super block num devices.

This makes btrfs to reject the fs completely.

  BTRFS error (device sdd3): super_num_devices 3 mismatch with num_devices 2 found here
  BTRFS error (device sdd3): failed to read chunk tree: -22
  BTRFS error (device sdd3): open_ctree failed

[CAUSE]
During btrfs device removal, chunk tree and super block num devs are
updated in two different transactions:

  btrfs_rm_device()
  |- btrfs_rm_dev_item(device)
  |  |- trans = btrfs_start_transaction()
  |  |  Now we got transaction X
  |  |
  |  |- btrfs_del_item()
  |  |  Now device item is removed from chunk tree
  |  |
  |  |- btrfs_commit_transaction()
  |     Transaction X got committed, super num devs untouched,
  |     but device item removed from chunk tree.
  |     (AKA, super num devs is already incorrect)
  |
  |- cur_devices->num_devices--;
  |- cur_devices->total_devices--;
  |- btrfs_set_super_num_devices()
     All those operations are not in transaction X, thus it will
     only be written back to disk in next transaction.

So after the transaction X in btrfs_rm_dev_item() committed, but before
transaction X+1 (which can be minutes away), a power loss happen, then
we got the super num mismatch.

This has been fixed by commit bbac58698a55 ("btrfs: remove device item
and update super block in the same transaction").

[FIX]
Make the super_num_devices check less strict, converting it from a hard
error to a warning, and reset the value to a correct one for the current
or next transaction commit.

As the number of device items is the critical information where the
super block num_devices is only a cached value (and also useful for
cross checking), it's safe to automatically update it. Other device
related problems like missing device are handled after that and may
require other means to resolve, like degraded mount. With this fix,
potentially affected filesystems won't fail mount and require the manual
repair by btrfs check.

Reported-by: Luca Béla Palkovics <luca.bela.palkovics@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CA+8xDSpvdm_U0QLBAnrH=zqDq_cWCOH5TiV46CKmp3igr44okQ@mail.gmail.com/
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-14 18:11:24 +02:00
arch ptrace: Reimplement PTRACE_KILL by always sending SIGKILL 2022-06-14 18:11:24 +02:00
block block: return ELEVATOR_DISCARD_MERGE if possible 2022-05-25 09:14:38 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: ecrdsa - Fix incorrect use of vli_cmp 2022-06-06 08:33:50 +02:00
Documentation docs: submitting-patches: Fix crossref to 'The canonical patch format' 2022-06-06 08:33:51 +02:00
drivers usb: core: hcd: Add support for deferring roothub registration 2022-06-14 18:11:24 +02:00
fs btrfs: repair super block num_devices automatically 2022-06-14 18:11:24 +02:00
include ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP 2022-06-14 18:11:24 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-15 14:18:35 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel ptrace: Reimplement PTRACE_KILL by always sending SIGKILL 2022-06-14 18:11:24 +02:00
lib assoc_array: Fix BUG_ON during garbage collect 2022-06-06 08:33:50 +02:00
LICENSES
mm zsmalloc: fix races between asynchronous zspage free and page migration 2022-06-06 08:33:50 +02:00
net bpf: Enlarge offset check value to INT_MAX in bpf_skb_{load,store}_bytes 2022-06-06 08:33:51 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:19:38 +02:00
security lockdown: also lock down previous kgdb use 2022-06-06 08:33:48 +02:00
sound ALSA: hda/realtek - Fix microphone noise on ASUS TUF B550M-PLUS 2022-06-14 18:11:23 +02:00
tools x86/xen: Mark cpu_bringup_and_idle() as dead_end_function 2022-05-25 09:14:38 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
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Kconfig
MAINTAINERS
Makefile Linux 5.4.197 2022-06-06 08:33:51 +02:00
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.