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Zhaoyang Huang ccaba78582 Revert "f2fs: remove non-uptodate folio from the page cache in move_data_block"
This reverts commit 9609dd7047.

The kernel panics are keeping to be reported especially when the f2fs
partition get almost full. By investigation, we find that the reason is
one f2fs page got freed to buddy without being deleted from LRU and the
root cause is the race happened in [2] which is enrolled by this commit.

There are 3 race processes in this scenario, please find below for their
main activities.

The changed code in move_data_block() lets the GC path evict the tail-end
folio from the page cache through folio_end_dropbehind().  Once
folio_unmap_invalidate() removes the folio from mapping->i_pages, the
page-cache references for all pages in the folio are dropped.  The folio
is then kept alive only by temporary external references, which allows a
later split to operate on a folio whose subpages are no longer protected
by page-cache references.

After the page-cache references are gone, split_folio_to_order() can
split the big folio into individual pages and put the resulting subpages
back on the LRU.  For tail pages beyond EOF, split removes them from the
page cache and drops their page-cache references.  A tail page can then
remain on the LRU with PG_lru set while holding only the split caller's
temporary reference.  When free_folio_and_swap_cache() drops that final
reference, the page enters the final folio_put() release path.

In parallel, folio_isolate_lru() can observe the same tail page with a
non-zero refcount and PG_lru set.  It clears PG_lru before taking its own
reference.  If this races with the final folio_put() from the split path,
__folio_put() sees PG_lru already cleared and skips lruvec_del_folio().
The page is then freed back to the allocator while its lru links are
still present in the LRU list.  A later LRU operation on a neighboring
page detects the stale link and reports list corruption.

[1]
[   22.486082] list_del corruption. next->prev should be fffffffec10e0ac8, but was dead000000000122. (next=fffffffec10e0a88)
[   22.486130] ------------[ cut here ]------------
[   22.486134] kernel BUG at lib/list_debug.c:67!
[   22.486141] Internal error: Oops - BUG: 00000000f2000800 [#1]  SMP
[   22.488502] Tainted: [W]=WARN, [O]=OOT_MODULE
[   22.488506] Hardware name: Spreadtrum UMS9230 1H10 SoC (DT)
[   22.488511] pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   22.488517] pc : __list_del_entry_valid_or_report+0x14c/0x154
[   22.488531] lr : __list_del_entry_valid_or_report+0x14c/0x154
[   22.488539] sp : ffffffc08006b830
[   22.488542] x29: ffffffc08006b868 x28: 0000000000003020 x27: 0000000000000000
[   22.488553] x26: 0000000000000000 x25: 0000000000000004 x24: fffffffec10e0ac0
[   22.488564] x23: 00000000000000e8 x22: 0000000000000024 x21: dead000000000122
[   22.488574] x20: fffffffec10e0a88 x19: fffffffec10e0ac8 x18: ffffffc080061060
[   22.488585] x17: 20747562202c3863 x16: 6130653031636566 x15: 0000000000000058
[   22.488595] x14: 0000000000000004 x13: ffffff80f91e0000 x12: 0000000000000003
[   22.488605] x11: 0000000000000003 x10: 0000000000000001 x9 : ffe85721f0e25f00
[   22.488615] x8 : ffe85721f0e25f00 x7 : 0000000000000000 x6 : 6c65645f7473696c
[   22.488625] x5 : ffffffed39b23026 x4 : 0000000000000000 x3 : 0000000000000010
[   22.488636] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 000000000000006d
[   22.488647] Call trace:
[   22.488651]  __list_del_entry_valid_or_report+0x14c/0x154 (P)
[   22.488661]  __folio_put+0x2bc/0x434
[   22.488670]  folio_put+0x28/0x58
[   22.488678]  do_garbage_collect+0x1a34/0x2584
[   22.488689]  f2fs_gc+0x230/0x9b4
[   22.488697]  f2fs_fallocate+0xb90/0xdf4
[   22.488706]  vfs_fallocate+0x1b4/0x2bc
[   22.488716]  __arm64_sys_fallocate+0x44/0x78
[   22.488725]  invoke_syscall+0x58/0xe4
[   22.488732]  do_el0_svc+0x48/0xdc
[   22.488739]  el0_svc+0x3c/0x98
[   22.488747]  el0t_64_sync_handler+0x20/0x130
[   22.488754]  el0t_64_sync+0x1c4/0x1c8

[2]
CPU0 (f2fs GC)              CPU1 (split_folio_to_order)          CPU2 (folio_isolate_lru)

F: pagecache refs = n
F: extra refs = GC + split
F: PG_lru set
move_data_block()
folio = f2fs_grab_cache_folio(F)
...
__folio_set_dropbehind(F)
folio_unlock(F)
folio_end_dropbehind(F)
  folio_unmap_invalidate(F)
    __filemap_remove_folio(F)
    folio_put_refs(F, n)
folio_put(F)
                            split_folio_to_order(F)
                              folio_ref_freeze(F, 1)
                              ...
                              lru_add_split_folio(T)
                                list_add_tail(&T->lru, &F->lru)
                                folio_set_lru(T)
                              __filemap_remove_folio(T)
                              folio_put_refs(T, 1)
                              /* T refcount == 1, PageLRU set */
                                                                  folio_isolate_lru(T)
                                                                    folio_test_clear_lru(T)
                            free_folio_and_swap_cache(T)
                              folio_put(T)
                                /* refcount: 1 -> 0 */
                                __folio_put(T)
                                  __page_cache_release(T)
                                    folio_test_lru(T) == false
                                    /* skip lruvec_del_folio(T) */
                                  free_frozen_pages(T)
                                                                  folio_get(T)
                                                                  lruvec_del_folio(T)
later:
  list_del(adjacent->lru)
    next == &T->lru
    next->prev == LIST_POISON / PCP freelist
    BUG

Cc: stable@vger.kernel.org
Fixes: 9609dd7047 ("f2fs: remove non-uptodate folio from the page cache in move_data_block")
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
2026-06-22 19:52:37 +00:00
arch ACPI support fixes for 7.1-rc4 2026-05-14 14:06:31 -07:00
block block: only read from sqe on initial invocation of blkdev_uring_cmd() 2026-05-05 01:37:12 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto This push contains the following changes: 2026-05-02 12:31:43 -07:00
Documentation f2fs: doc: fix the wrong description for critical_task_priority 2026-05-22 03:49:06 +00:00
drivers hid-for-linus-2026051401 2026-05-14 14:30:01 -07:00
fs Revert "f2fs: remove non-uptodate folio from the page cache in move_data_block" 2026-06-22 19:52:37 +00:00
include f2fs: validate orphan inode entry count 2026-06-22 19:52:36 +00:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260508 2026-05-08 13:12:48 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel audit/stable-7.1 PR 20260513 2026-05-14 08:53:24 -07:00
lib Probes fixes for v7.1-rc3 2026-05-12 10:18:02 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm liveupdate fixes for v7.1-rc4 2026-05-13 08:24:50 -07:00
net Including fixes from netfilter. 2026-05-14 08:57:43 -07:00
rust Rust fixes for v7.1 2026-05-09 11:24:02 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts First round of Kbuild fixes for 7.1 2026-04-25 17:04:15 -07:00
security selinux: shrink critical section in sel_write_load() 2026-05-05 16:02:28 -04:00
sound ASoC: Fixes for v7.1 2026-05-06 16:10:00 +02:00
tools Including fixes from netfilter. 2026-05-14 08:57:43 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-05-12 22:16:16 +02:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add Askar 2026-04-15 02:15:02 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap MAINTAINERS: Update mail for Peter Rosin 2026-05-04 21:02:58 +02:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Including fixes from netfilter. 2026-05-14 08:57:43 -07:00
Makefile Linux 7.1-rc3 2026-05-10 14:08:09 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
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* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
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* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


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============

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* New Kernel Developer - Getting started with kernel development
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For Specific Users
==================

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--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
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* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

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-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
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---------------

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-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
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--------------------

Configure, tune, and troubleshoot Linux systems:

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----------

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---------------

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-----------------------

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* ABI Documentation: Documentation/ABI/README
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-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
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* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
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=========================

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