kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-26 19:14:18 +00:00
Code Issues Releases Packages Activity
No description
1,312,670 commits 117 branches 5,805 tags 5.9 GiB
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Qu Wenruo 653b704e7d btrfs: fix mount failure due to remount races 
[ Upstream commit 951a3f59d2 ]

[BUG]
The following reproducer can cause btrfs mount to fail:

  dev="/dev/test/scratch1"
  mnt1="/mnt/test"
  mnt2="/mnt/scratch"

  mkfs.btrfs -f $dev
  mount $dev $mnt1
  btrfs subvolume create $mnt1/subvol1
  btrfs subvolume create $mnt1/subvol2
  umount $mnt1

  mount $dev $mnt1 -o subvol=subvol1
  while mount -o remount,ro $mnt1; do mount -o remount,rw $mnt1; done &
  bg=$!

  while mount $dev $mnt2 -o subvol=subvol2; do umount $mnt2; done

  kill $bg
  wait
  umount -R $mnt1
  umount -R $mnt2

The script will fail with the following error:

  mount: /mnt/scratch: /dev/mapper/test-scratch1 already mounted on /mnt/test.
        dmesg(1) may have more information after failed mount system call.
  umount: /mnt/test: target is busy.
  umount: /mnt/scratch/: not mounted

And there is no kernel error message.

[CAUSE]
During the btrfs mount, to support mounting different subvolumes with
different RO/RW flags, we need to detect that and retry if needed:

  Retry with matching RO flags if the initial mount fail with -EBUSY.

The problem is, during that retry we do not hold any super block lock
(s_umount), this means there can be a remount process changing the RO
flags of the original fs super block.

If so, we can have an EBUSY error during retry.  And this time we treat
any failure as an error, without any retry and cause the above EBUSY
mount failure.

[FIX]
The current retry behavior is racy because we do not have a super block
thus no way to hold s_umount to prevent the race with remount.

Solve the root problem by allowing fc->sb_flags to mismatch from the
sb->s_flags at btrfs_get_tree_super().

Then at the re-entry point btrfs_get_tree_subvol(), manually check the
fc->s_flags against sb->s_flags, if it's a RO->RW mismatch, then
reconfigure with s_umount lock hold.

Reported-by: Enno Gotthold <egotthold@suse.com>
Reported-by: Fabian Vogt <fvogt@suse.com>
[ Special thanks for the reproducer and early analysis pointing to btrfs. ]
Fixes: f044b31867 ("btrfs: handle the ro->rw transition for mounting different subvolumes")
Link: https://bugzilla.suse.com/show_bug.cgi?id=1231836
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: Sasha Levin <sashal@kernel.org>
History 2024-12-14 20:04:13 +01:00
arch irqchip/gicv3-its: Add workaround for hip09 ITS erratum 162100801 2024-12-14 20:04:09 +01:00
block block: RCU protect disk->conv_zones_bitmap 2024-12-14 20:03:35 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ecdsa - Avoid signed integer overflow on signature decoding 2024-12-14 20:03:36 +01:00
Documentation irqchip/gicv3-its: Add workaround for hip09 ITS erratum 162100801 2024-12-14 20:04:09 +01:00
drivers drm/amd/display: Add option to retrieve detile buffer size 2024-12-14 20:04:11 +01:00
fs btrfs: fix mount failure due to remount races 2024-12-14 20:04:13 +01:00
include misc: eeprom: eeprom_93cx6: Add quirk for extra read clock cycle 2024-12-14 20:04:09 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring/tctx: work around xa_store() allocation error issue 2024-12-14 20:04:10 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel sched/deadline: Fix warning in migrate_enable for boosted tasks 2024-12-14 20:04:12 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 20:03:32 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm memblock: allow zero threshold in validate_numa_converage() 2024-12-14 20:03:34 +01:00
net netpoll: Use rcu_access_pointer() in __netpoll_setup 2024-12-14 20:03:58 +01:00
rust rust: enable arbitrary_self_types and remove Receiver 2024-12-14 20:03:34 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:03:46 +01:00
scripts setlocalversion: work around "git describe" performance 2024-12-14 20:04:10 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-05 14:02:46 +01:00
sound ASoC: amd: yc: Add quirk for microphone on Lenovo Thinkpad T14s Gen 6 21M1CTO1WW 2024-12-14 20:04:08 +01:00
tools verification/dot2: Improve dot parser robustness 2024-12-14 20:04:03 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile rust: allow clippy::needless_lifetimes 2024-12-14 20:03:20 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.