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Xiaole He b355d300f5 f2fs: fix age extent cache insertion skip on counter overflow 
commit 27bf6a637b upstream.

The age extent cache uses last_blocks (derived from
allocated_data_blocks) to determine data age. However, there's a
conflict between the deletion
marker (last_blocks=0) and legitimate last_blocks=0 cases when
allocated_data_blocks overflows to 0 after reaching ULLONG_MAX.

In this case, valid extents are incorrectly skipped due to the
"if (!tei->last_blocks)" check in __update_extent_tree_range().

This patch fixes the issue by:
1. Reserving ULLONG_MAX as an invalid/deletion marker
2. Limiting allocated_data_blocks to range [0, ULLONG_MAX-1]
3. Using F2FS_EXTENT_AGE_INVALID for deletion scenarios
4. Adjusting overflow age calculation from ULLONG_MAX to (ULLONG_MAX-1)

Reproducer (using a patched kernel with allocated_data_blocks
initialized to ULLONG_MAX - 3 for quick testing):

Step 1: Mount and check initial state
  # dd if=/dev/zero of=/tmp/test.img bs=1M count=100
  # mkfs.f2fs -f /tmp/test.img
  # mkdir -p /mnt/f2fs_test
  # mount -t f2fs -o loop,age_extent_cache /tmp/test.img /mnt/f2fs_test
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 18446744073709551612 # ULLONG_MAX - 3
  Inner Struct Count: tree: 1(0), node: 0

Step 2: Create files and write data to trigger overflow
  # touch /mnt/f2fs_test/{1,2,3,4}.txt; sync
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 18446744073709551613 # ULLONG_MAX - 2
  Inner Struct Count: tree: 5(0), node: 1

  # dd if=/dev/urandom of=/mnt/f2fs_test/1.txt bs=4K count=1; sync
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 18446744073709551614 # ULLONG_MAX - 1
  Inner Struct Count: tree: 5(0), node: 2

  # dd if=/dev/urandom of=/mnt/f2fs_test/2.txt bs=4K count=1; sync
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 18446744073709551615 # ULLONG_MAX
  Inner Struct Count: tree: 5(0), node: 3

  # dd if=/dev/urandom of=/mnt/f2fs_test/3.txt bs=4K count=1; sync
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 0 # Counter overflowed!
  Inner Struct Count: tree: 5(0), node: 4

Step 3: Trigger the bug - next write should create node but gets skipped
  # dd if=/dev/urandom of=/mnt/f2fs_test/4.txt bs=4K count=1; sync
  # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age"
  Allocated Data Blocks: 1
  Inner Struct Count: tree: 5(0), node: 4

  Expected: node: 5 (new extent node for 4.txt)
  Actual: node: 4 (extent insertion was incorrectly skipped due to
  last_blocks = allocated_data_blocks = 0 in __get_new_block_age)

After this fix, the extent node is correctly inserted and node count
becomes 5 as expected.

Fixes: 71644dff48 ("f2fs: add block_age-based extent cache")
Cc: stable@kernel.org
Signed-off-by: Xiaole He <hexiaole1994@126.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-02 12:57:17 +01:00
arch crash: let architecture decide crash memory export to iomem_resource 2026-01-02 12:57:11 +01:00
block block: Remove queue freezing from several sysfs store callbacks 2026-01-02 12:57:11 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: scatterwalk - Fix memcpy_sglist() to always succeed 2026-01-02 12:57:08 +01:00
Documentation dt-bindings: slimbus: fix warning from example 2026-01-02 12:57:14 +01:00
drivers scsi: ufs: core: Add ufshcd_update_evt_hist() for UFS suspend error 2026-01-02 12:57:16 +01:00
fs f2fs: fix age extent cache insertion skip on counter overflow 2026-01-02 12:57:17 +01:00
include mptcp: pm: ignore unknown endpoint flags 2026-01-02 12:57:12 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring: fix filename leak in __io_openat_prep() 2026-01-02 12:57:06 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel crash: let architecture decide crash memory export to iomem_resource 2026-01-02 12:57:11 +01:00
lib lib/crypto: x86/blake2s: Fix 32-bit arg treated as 64-bit 2026-01-02 12:57:07 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction 2026-01-02 12:57:12 +01:00
net mptcp: avoid deadlock on fallback while reinjecting 2026-01-02 12:57:12 +01:00
rust rust: io: add typedef for phys_addr_t 2026-01-02 12:57:05 +01:00
samples samples: rust: fix endianness issue in rust_driver_pci 2026-01-02 12:57:05 +01:00
scripts kbuild: Use objtree for module signing key path 2026-01-02 12:56:40 +01:00
security tpm2-sessions: Fix out of range indexing in name_size 2026-01-02 12:57:11 +01:00
sound ASoC: ops: fix snd_soc_get_volsw for sx controls 2026-01-02 12:56:59 +01:00
tools selftests: mptcp: pm: ensure unknown flags are ignored 2026-01-02 12:57:12 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-04 09:16:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.2 2025-12-18 14:03:43 +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.