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Anand Jain 6943d31a0b btrfs: do not skip re-registration for the mounted device 
commit d565fffa68 upstream.

There are reports that since version 6.7 update-grub fails to find the
device of the root on systems without initrd and on a single device.

This looks like the device name changed in the output of
/proc/self/mountinfo:

6.5-rc5 working

  18 1 0:16 / / rw,noatime - btrfs /dev/sda8 ...

6.7 not working:

  17 1 0:15 / / rw,noatime - btrfs /dev/root ...

and "update-grub" shows this error:

  /usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?)

This looks like it's related to the device name, but grub-probe
recognizes the "/dev/root" path and tries to find the underlying device.
However there's a special case for some filesystems, for btrfs in
particular.

The generic root device detection heuristic is not done and it all
relies on reading the device infos by a btrfs specific ioctl. This ioctl
returns the device name as it was saved at the time of device scan (in
this case it's /dev/root).

The change in 6.7 for temp_fsid to allow several single device
filesystem to exist with the same fsid (and transparently generate a new
UUID at mount time) was to skip caching/registering such devices.

This also skipped mounted device. One step of scanning is to check if
the device name hasn't changed, and if yes then update the cached value.

This broke the grub-probe as it always read the device /dev/root and
couldn't find it in the system. A temporary workaround is to create a
symlink but this does not survive reboot.

The right fix is to allow updating the device path of a mounted
filesystem even if this is a single device one.

In the fix, check if the device's major:minor number matches with the
cached device. If they do, then we can allow the scan to happen so that
device_list_add() can take care of updating the device path. The file
descriptor remains unchanged.

This does not affect the temp_fsid feature, the UUID of the mounted
filesystem remains the same and the matching is based on device major:minor
which is unique per mounted filesystem.

This covers the path when the device (that exists for all mounted
devices) name changes, updating /dev/root to /dev/sdx. Any other single
device with filesystem and is not mounted is still skipped.

Note that if a system is booted and initial mount is done on the
/dev/root device, this will be the cached name of the device. Only after
the command "btrfs device scan" it will change as it triggers the
rename.

The fix was verified by users whose systems were affected.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=218353
Link: https://lore.kernel.org/lkml/CAKLYgeJ1tUuqLcsquwuFqjDXPSJpEiokrWK2gisPKDZLs8Y2TQ@mail.gmail.com/
Fixes: bc27d6f0aa ("btrfs: scan but don't register device on single device filesystem")
CC: stable@vger.kernel.org # 6.7+
Tested-by: Alex Romosan <aromosan@gmail.com>
Tested-by: CHECK_1234543212345@protonmail.com
Signed-off-by: Anand Jain <anand.jain@oracle.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>
 		2024-04-03 15:32:35 +02:00
Documentation x86/Kconfig: Remove CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT 2024-04-03 15:32:32 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD 2024-04-03 15:32:34 +02:00
block Revert "block/mq-deadline: use correct way to throttling write requests" 2024-04-03 15:32:22 +02:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto Revert "crypto: pkcs7 - remove sha1 support" 2024-04-03 15:32:31 +02:00
drivers pwm: img: fix pwm clock lookup 2024-04-03 15:32:35 +02:00
fs btrfs: do not skip re-registration for the mounted device 2024-04-03 15:32:35 +02:00
include Revert "crypto: pkcs7 - remove sha1 support" 2024-04-03 15:32:31 +02:00
init modules: wait do_free_init correctly 2024-03-26 18:17:17 -04:00
io_uring io_uring/waitid: always remove waitid entry for cancel all 2024-04-03 15:32:24 +02:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel printk: Update @console_may_schedule in console_trylock_spinning() 2024-04-03 15:32:33 +02:00
lib pci_iounmap(): Fix MMIO mapping leak 2024-04-03 15:32:02 +02:00
mm memtest: use {READ,WRITE}_ONCE in memory scanning 2024-04-03 15:32:22 +02:00
net netfilter: nf_tables: reject constant set with timeout 2024-04-03 15:32:31 +02:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-09 15:57:48 -08:00
scripts kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1 2024-04-03 15:32:18 +02:00
security lsm: handle the NULL buffer case in lsm_fill_user_ctx() 2024-04-03 15:32:22 +02:00
sound ASoC: amd: yc: Revert "add new YC platform variant (0x63) support" 2024-04-03 15:32:32 +02:00
tools selftests/mm: Fix build with _FORTIFY_SOURCE 2024-04-03 15:32:35 +02:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:32:03 +02:00
.clang-format clang-format: Update with v6.7-rc4's `for_each` macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
…
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap drm fixes for 6.8 final 2024-03-08 12:44:56 -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: supplement of zswap maintainers update 2024-01-25 23:52:21 -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 drm fixes for 6.8 final 2024-03-08 12:44:56 -08:00
Makefile Linux 6.8.2 2024-03-26 18:23:34 -04:00
README
…

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.