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Gao Xiang ebdc993453 erofs: fix file-backed mounts no longer working on EROFS partitions
[ Upstream commit 7893cc1225 ]

Sheng Yong reported [1] that Android APEX images didn't work with commit
072a7c7cdb ("erofs: don't bother with s_stack_depth increasing for
now") because "EROFS-formatted APEX file images can be stored within an
EROFS-formatted Android system partition."

In response, I sent a quick fat-fingered [PATCH v3] to address the
report.  Unfortunately, the updated condition was incorrect:

         if (erofs_is_fileio_mode(sbi)) {
-            sb->s_stack_depth =
-                file_inode(sbi->dif0.file)->i_sb->s_stack_depth + 1;
-            if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
-                erofs_err(sb, "maximum fs stacking depth exceeded");
+            inode = file_inode(sbi->dif0.file);
+            if ((inode->i_sb->s_op == &erofs_sops && !sb->s_bdev) ||
+                inode->i_sb->s_stack_depth) {

The condition `!sb->s_bdev` is always true for all file-backed EROFS
mounts, making the check effectively a no-op.

The real fix tested and confirmed by Sheng Yong [2] at that time was
[PATCH v3 RESEND], which correctly ensures the following EROFS^2 setup
works:
    EROFS (on a block device) + EROFS (file-backed mount)

But sadly I screwed it up again by upstreaming the outdated [PATCH v3].

This patch applies the same logic as the delta between the upstream
[PATCH v3] and the real fix [PATCH v3 RESEND].

Reported-by: Sheng Yong <shengyong1@xiaomi.com>
Closes: https://lore.kernel.org/r/3acec686-4020-4609-aee4-5dae7b9b0093@gmail.com [1]
Fixes: 072a7c7cdb ("erofs: don't bother with s_stack_depth increasing for now")
Link: https://lore.kernel.org/r/243f57b8-246f-47e7-9fb1-27a771e8e9e8@gmail.com [2]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-01-17 16:35:30 +01:00
arch sparc/PCI: Correct 64-bit non-pref -> pref BAR resources 2026-01-17 16:35:29 +01:00
block block: don't merge bios with different app_tags 2026-01-17 16:35:28 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: seqiv - Do not use req->iv after crypto_aead_encrypt 2026-01-08 10:16:43 +01:00
Documentation dt-bindings: PCI: qcom,pcie-sm8550: Add missing required power-domains and resets 2026-01-02 12:57:27 +01:00
drivers irqchip/gic-v5: Fix gicv5_its_map_event() ITTE read endianness 2026-01-17 16:35:30 +01:00
fs erofs: fix file-backed mounts no longer working on EROFS partitions 2026-01-17 16:35:30 +01:00
include net: airoha: Fix npu rx DMA definitions 2026-01-17 16:35:25 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/io-wq: fix incorrect io_wq_for_each_worker() termination logic 2026-01-17 16:35:14 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel trace: ftrace_dump_on_oops[] is not exported, make it static 2026-01-17 16:35:29 +01:00
lib lib/crypto: aes: Fix missing MMU protection for AES S-box 2026-01-17 16:35:12 +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/damon/tests/core-kunit: handle alloc failures on damon_test_split_regions_of() 2026-01-08 10:17:21 +01:00
net arp: do not assume dev_hard_header() does not change skb->head 2026-01-17 16:35:30 +01:00
rust rust: maple_tree: rcu_read_lock() in destructor to silence lockdep 2026-01-08 10:17:11 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts mcb: Add missing modpost build support 2026-01-08 10:16:47 +01:00
security kernel/kexec: change the prototype of kimage_map_segment() 2026-01-08 10:17:10 +01:00
sound ALSA: hda/realtek: Add support for ASUS UM3406GA 2026-01-17 16:35:17 +01:00
tools selftests: drv-net: Bring back tool() to driver __init__s 2026-01-17 16:35:28 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Fix last_boosted_vcpu index assignment bug 2026-01-02 12:57:21 +01:00
.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 6.18.5 2026-01-11 15:26:20 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.