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Filipe Manana 3d9c5e1512 btrfs: fix race between setting last_dir_index_offset and inode logging 
[ Upstream commit 59a0dd4ab9 ]

At inode_logged() if we find that the inode was not logged before we
update its ->last_dir_index_offset to (u64)-1 with the goal that the
next directory log operation will see the (u64)-1 and then figure out
it must check what was the index of the last logged dir index key and
update ->last_dir_index_offset to that key's offset (this is done in
update_last_dir_index_offset()).

This however has a possibility for a time window where a race can happen
and lead to directory logging skipping dir index keys that should be
logged. The race happens like this:

1) Task A calls inode_logged(), sees ->logged_trans as 0 and then checks
   that the inode item was logged before, but before it sets the inode's
   ->last_dir_index_offset to (u64)-1...

2) Task B is at btrfs_log_inode() which calls inode_logged() early, and
   that has set ->last_dir_index_offset to (u64)-1;

3) Task B then enters log_directory_changes() which calls
   update_last_dir_index_offset(). There it sees ->last_dir_index_offset
   is (u64)-1 and that the inode was logged before (ctx->logged_before is
   true), and so it searches for the last logged dir index key in the log
   tree and it finds that it has an offset (index) value of N, so it sets
   ->last_dir_index_offset to N, so that we can skip index keys that are
   less than or equal to N (later at process_dir_items_leaf());

4) Task A now sets ->last_dir_index_offset to (u64)-1, undoing the update
   that task B just did;

5) Task B will now skip every index key when it enters
   process_dir_items_leaf(), since ->last_dir_index_offset is (u64)-1.

Fix this by making inode_logged() not touch ->last_dir_index_offset and
initializing it to 0 when an inode is loaded (at btrfs_alloc_inode()) and
then having update_last_dir_index_offset() treat a value of 0 as meaning
we must check the log tree and update with the index of the last logged
index key. This is fine since the minimum possible value for
->last_dir_index_offset is 1 (BTRFS_DIR_START_INDEX - 1 = 2 - 1 = 1).
This also simplifies the management of ->last_dir_index_offset and now
all accesses to it are done under the inode's log_mutex.

Fixes: 0f8ce49821 ("btrfs: avoid inode logging during rename and link when possible")
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-09-09 18:58:02 +02:00
arch x86/cpu/topology: Use initial APIC ID from XTOPOLOGY leaf on AMD/HYGON 2025-09-04 15:31:52 +02:00
block blk-zoned: Fix a lockdep complaint about recursive locking 2025-09-04 15:31:54 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: jitter - fix intermediary handling 2025-08-20 18:30:42 +02:00
Documentation dt-bindings: display/msm: qcom,mdp5: drop lut clock 2025-09-04 15:31:48 +02:00
drivers thermal/drivers/mediatek/lvts_thermal: Add mt7988 lvts commands 2025-09-04 15:31:56 +02:00
fs btrfs: fix race between setting last_dir_index_offset and inode logging 2025-09-09 18:58:02 +02:00
include bpf: Fix oob access in cgroup local storage 2025-09-09 18:58:01 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/futex: ensure io_futex_wait() cleans up properly on failure 2025-08-28 16:31:05 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel bpf: Fix oob access in cgroup local storage 2025-09-09 18:58:01 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:30:49 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/memory-failure: fix infinite UCE for VM_PFNMAP pfn 2025-08-28 16:31:05 +02:00
net net: rose: fix a typo in rose_clear_routes() 2025-09-04 15:31:55 +02:00
rust rust: alloc: fix rusttest by providing Cmalloc::aligned_layout too 2025-08-28 16:31:13 +02:00
samples samples: mei: Fix building on musl libc 2025-08-15 12:13:38 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-20 18:30:48 +02:00
security apparmor: Fix 8-byte alignment for initial dfa blob streams 2025-08-28 16:30:56 +02:00
sound ASoC: codecs: tx-macro: correct tx_macro_component_drv name 2025-09-04 15:31:44 +02:00
tools perf symbol-minimal: Fix ehdr reading in filename__read_build_id 2025-09-04 15:31:43 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
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 6.12.45 2025-09-04 15:31:56 +02:00
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.