linux-kernel - [REGRESSION][STABLE] ext4: too many credits wanted / file system issue in v6.16.1

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Message-ID: <3d7f77d2-b1f8-4d49-b36a-927a943efc2f@heusel.eu>
Date: Tue, 19 Aug 2025 22:47:30 +0200
From: Christian Heusel <christian@...sel.eu>
To: Zhang Yi <yi.zhang@...wei.com>, Sasha Levin <sashal@...nel.org>, 
	Theodore Ts'o <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, 
	regressions@...ts.linux.dev, stable@...r.kernel.org, heftig@...hlinux.org, 
	Luca Boccassi <bluca@...ian.org>
Subject: [REGRESSION][STABLE] ext4: too many credits wanted / file system
 issue in v6.16.1

Hello everyone,

the systemd CI has [recently noticed][0] an issue within the ext4 file
system after the Arch Linux kernel was upgraded to 6.16.1. The issue is
exclusive to the stable tree and does not occur on 6.16 and not on
6.17-rc2. I have also tested 6.16.2-rc1 and it still contains the bug.

I was able to bisect the issue between 6.16 and 6.16.1 to the following
commit:

    b9c561f3f29c2 ("ext4: fix insufficient credits calculation in ext4_meta_trans_blocks()")

The issue can be reproduced by running the tests from
[TEST-58-REPART.sh][1] by running the [systemd integration tests][2].
But if there are any suggestions I can also test myself as the initial
setup for the integration tests is a bit involved.

It is not yet clear to me whether this has real-world impact besides the
test, but the systemd devs said that it's not a particularily demanding
workflow, so I guess it is expected to work and could cause issues on
other systems too.

Also does anybody have an idea which backport could be missing?

Cheers,
Chris

[0]: https://github.com/systemd/systemd/actions/runs/17053272497/job/48345703316#step:14:233
[1]: https://github.com/systemd/systemd/blob/main/test/units/TEST-58-REPART.sh
[2]: https://github.com/systemd/systemd/blob/main/test/integration-tests/README.md

---

#regzbot introduced: b9c561f3f29c2
#regzbot title: [STABLE] ext4: too many credits wanted / file system issue in v6.16.1
#regzbot link: https://github.com/systemd/systemd/actions/runs/17053272497/job/48345703316#step:14:233

---

git bisect start
# status: waiting for both good and bad commits
# good: [038d61fd642278bab63ee8ef722c50d10ab01e8f] Linux 6.16
git bisect good 038d61fd642278bab63ee8ef722c50d10ab01e8f
# status: waiting for bad commit, 1 good commit known
# bad: [3e0969c9a8c57ff3c6139c084673ebedfc1cf14f] Linux 6.16.1
git bisect bad 3e0969c9a8c57ff3c6139c084673ebedfc1cf14f
# good: [288f1562e3f6af6d9b461eba49e75c84afa1b92c] media: v4l2-ctrls: Fix H264 SEPARATE_COLOUR_PLANE check
git bisect good 288f1562e3f6af6d9b461eba49e75c84afa1b92c
# bad: [f427460a1586c2e0865f9326b71ed6e5a0f404f2] f2fs: turn off one_time when forcibly set to foreground GC
git bisect bad f427460a1586c2e0865f9326b71ed6e5a0f404f2
# bad: [5f57327f41a5bbb85ea382bc389126dd7b8f2d7b] scsi: elx: efct: Fix dma_unmap_sg() nents value
git bisect bad 5f57327f41a5bbb85ea382bc389126dd7b8f2d7b
# good: [9143c604415328d5dcd4d37b8adab8417afcdd21] leds: pca955x: Avoid potential overflow when filling default_label (take 2)
git bisect good 9143c604415328d5dcd4d37b8adab8417afcdd21
# good: [9c4f20b7ac700e4b4377f85e36165a4f6ca85995] RDMA/hns: Fix accessing uninitialized resources
git bisect good 9c4f20b7ac700e4b4377f85e36165a4f6ca85995
# good: [0b21d1962bec2e660c22c4c4231430f97163dcf8] perf tests bp_account: Fix leaked file descriptor
git bisect good 0b21d1962bec2e660c22c4c4231430f97163dcf8
# good: [3dbe96d5481acd40d6090f174d2be8433d88716d] clk: thead: th1520-ap: Correctly refer the parent of osc_12m
git bisect good 3dbe96d5481acd40d6090f174d2be8433d88716d
# bad: [c6714f30ef88096a8da9fcafb6034dc4e9aa467d] clk: sunxi-ng: v3s: Fix de clock definition
git bisect bad c6714f30ef88096a8da9fcafb6034dc4e9aa467d
# bad: [b9c561f3f29c2d6e1c1d3ffc202910bef250b7d8] ext4: fix insufficient credits calculation in ext4_meta_trans_blocks()
git bisect bad b9c561f3f29c2d6e1c1d3ffc202910bef250b7d8
# first bad commit: [b9c561f3f29c2d6e1c1d3ffc202910bef250b7d8] ext4: fix insufficient credits calculation in ext4_meta_trans_blocks()

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