Btrfs fixes for 6.19-rc7

Hi,

please pull the following btrfs fixes. Thanks.

- protect reading super block vs setting block size externally (found by syzbot)

- make sure no transaction is started in read-only mode even with some rescue mount option combinations

- fix checksum calculation of backup super blocks when block-group-tree is enabled

- more extensive mount-time checks of device items that could be left after device replace and attempting degraded mount

- fix build warning with -Wmaybe-uninitialized on loongarch64-gcc 12

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The following changes since commit 437cc6057e01d98ee124496f045ede36224af326:

btrfs: remove zoned statistics from sysfs (2026-01-14 22:08:04 +0100)

are available in the Git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git tags/for-6.19-rc6-tag

for you to fetch changes up to 34308187395ff01f2d54007eb8b222f843bdf445:

btrfs: add extra device item checks at mount (2026-01-20 17:18:48 +0100)

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Edward Adam Davis (1):
btrfs: sync read disk super and set block size

Mark Harmstone (1):
btrfs: fix missing fields in superblock backup with BLOCK_GROUP_TREE

Qiang Ma (1):
btrfs: fix Wmaybe-uninitialized warning in replay_one_buffer()

Qu Wenruo (2):
btrfs: reject new transactions if the fs is fully read-only
btrfs: add extra device item checks at mount

 fs/btrfs/disk-io.c  | 19 ++++++++++++++++++-
 fs/btrfs/fs.h       |  8 ++++++++
 fs/btrfs/tree-log.c |  2 +-
 fs/btrfs/volumes.c  | 42 ++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h  |  4 ++++
 5 files changed, 73 insertions(+), 2 deletions(-)