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Filipe Manana 1ab78aabdc btrfs: do not update last_log_commit when logging inode due to a new name 
commit bfe3d755ef upstream.

When logging that a new name exists, we skip updating the inode's
last_log_commit field to prevent a later explicit fsync against the inode
from doing nothing (as updating last_log_commit makes btrfs_inode_in_log()
return true). We are detecting, at btrfs_log_inode(), that logging a new
name is happening by checking the logging mode is not LOG_INODE_EXISTS,
but that is not enough because we may log parent directories when logging
a new name of a file in LOG_INODE_ALL mode - we need to check that the
logging_new_name field of the log context too.

An example scenario where this results in an explicit fsync against a
directory not persisting changes to the directory is the following:

  $ mkfs.btrfs -f /dev/sdc
  $ mount /dev/sdc /mnt

  $ touch /mnt/foo

  $ sync

  $ mkdir /mnt/dir

  # Write some data to our file and fsync it.
  $ xfs_io -c "pwrite -S 0xab 0 64K" -c "fsync" /mnt/foo

  # Add a new link to our file. Since the file was logged before, we
  # update it in the log tree by calling btrfs_log_new_name().
  $ ln /mnt/foo /mnt/dir/bar

  # fsync the root directory - we expect it to persist the dentry for
  # the new directory "dir".
  $ xfs_io -c "fsync" /mnt

  <power fail>

After mounting the fs the entry for directory "dir" does not exists,
despite the explicit fsync on the root directory.

Here's why this happens:

1) When we fsync the file we log the inode, so that it's present in the
   log tree;

2) When adding the new link we enter btrfs_log_new_name(), and since the
   inode is in the log tree we proceed to updating the inode in the log
   tree;

3) We first set the inode's last_unlink_trans to the current transaction
   (early in btrfs_log_new_name());

4) We then eventually enter btrfs_log_inode_parent(), and after logging
   the file's inode, we call btrfs_log_all_parents() because the inode's
   last_unlink_trans matches the current transaction's ID (updated in the
   previous step);

5) So btrfs_log_all_parents() logs the root directory by calling
   btrfs_log_inode() for the root's inode with a log mode of LOG_INODE_ALL
   so that new dentries are logged;

6) At btrfs_log_inode(), because the log mode is LOG_INODE_ALL, we
   update root inode's last_log_commit to the last transaction that
   changed the inode (->last_sub_trans field of the inode), which
   corresponds to the current transaction's ID;

7) Then later when user space explicitly calls fsync against the root
   directory, we enter btrfs_sync_file(), which calls skip_inode_logging()
   and that returns true, since its call to btrfs_inode_in_log() returns
   true and there are no ordered extents (it's a directory, never has
   ordered extents). This results in btrfs_sync_file() returning without
   syncing the log or committing the current transaction, so all the
   updates we did when logging the new name, including logging the root
   directory,  are not persisted.

So fix this by but updating the inode's last_log_commit if we are sure
we are not logging a new name (if ctx->logging_new_name is false).

A test case for fstests will follow soon.

Reported-by: Vyacheslav Kovalevsky <slava.kovalevskiy.2014@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/03c5d7ec-5b3d-49d1-95bc-8970a7f82d87@gmail.com/
Fixes: 130341be7f ("btrfs: always update the logged transaction when logging new names")
CC: stable@vger.kernel.org # 6.1+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-11-24 10:36:03 +01:00
arch LoongArch: Use physical addresses for CSR_MERRENTRY/CSR_TLBRENTRY 2025-11-24 10:36:02 +01:00
block blk-cgroup: fix possible deadlock while configuring policy 2025-11-13 15:34:07 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:33:42 +02:00
Documentation dpll: spec: add missing module-name and clock-id to pin-get reply 2025-11-13 15:33:59 -05:00
drivers EDAC/altera: Use INTTEST register for Ethernet and USB SBE injection 2025-11-24 10:36:02 +01:00
fs btrfs: do not update last_log_commit when logging inode due to a new name 2025-11-24 10:36:03 +01:00
include dma-mapping: benchmark: Restore padding to ensure uABI remained consistent 2025-11-24 10:35:59 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/zctx: check chained notif contexts 2025-11-13 15:34:03 -05:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel PM: hibernate: Use atomic64_t for compressed_size variable 2025-11-24 10:36:03 +01:00
lib lib/crypto: curve25519-hacl64: Fix older clang KASAN workaround for GCC 2025-11-13 15:34:40 -05:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm codetag: debug: handle existing CODETAG_EMPTY in mark_objexts_empty for slabobj_ext 2025-11-24 10:36:01 +01:00
net wifi: mac80211: reject address change while connecting 2025-11-24 10:36:00 +01:00
rust rust: Add -fno-isolate-erroneous-paths-dereference to bindgen_skip_c_flags 2025-11-24 10:35:49 +01:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr 2025-11-13 15:34:32 -05:00
sound ALSA: usb-audio: Fix potential overflow of PCM transfer buffer 2025-11-24 10:36:01 +01:00
tools selftests/user_events: fix type cast for write_index packed member in perf_test 2025-11-24 10:36:02 +01:00
usr kbuild: uapi: Strip comments before size type check 2025-11-13 15:34:35 -05:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.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 rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.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 Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.58 2025-11-13 15:34:41 -05:00
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.