Re: next-20250626: WARNING fs jbd2 transaction.c start_this_handle with ARM64_64K_PAGES

[Joseph Qi <jiangqi903@gmail.com>]

On 2025/7/5 15:10, Zhang Yi wrote:
> On 2025/7/3 18:47, Joseph Qi wrote:
>>
>>
>> On 2025/7/3 15:26, Naresh Kamboju wrote:
>>> On Thu, 26 Jun 2025 at 19:23, Zhang Yi <yi.zhang@huaweicloud.com> wrote:
>>>>
>>>> Hi, Naresh!
>>>>
>>>> On 2025/6/26 20:31, Naresh Kamboju wrote:
>>>>> Regressions noticed on arm64 devices while running LTP syscalls mmap16
>>>>> test case on the Linux next-20250616..next-20250626 with the extra build
>>>>> config fragment CONFIG_ARM64_64K_PAGES=y the kernel warning noticed.
>>>>>
>>>>> Not reproducible with 4K page size.
>>>>>
>>>>> Test environments:
>>>>> - Dragonboard-410c
>>>>> - Juno-r2
>>>>> - rk3399-rock-pi-4b
>>>>> - qemu-arm64
>>>>>
>>>>> Regression Analysis:
>>>>> - New regression? Yes
>>>>> - Reproducibility? Yes
>>>>>
>>>>> Test regression: next-20250626 LTP mmap16 WARNING fs jbd2
>>>>> transaction.c start_this_handle
>>>>>
>>>>> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
>>>>
>>>> Thank you for the report. The block size for this test is 1 KB, so I
>>>> suspect this is the issue with insufficient journal credits that we
>>>> are going to resolve.
>>>
>>> I have applied your patch set [1] and tested and the reported
>>> regressions did not fix.
>>> Am I missing anything ?
>>>
>>> [1] https://lore.kernel.org/linux-ext4/20250611111625.1668035-1-yi.zhang@huaweicloud.com/
>>>
>>
>> I can also reproduce the similar warning with xfstests generic/730 under
>> 64k page size + 4k block size.
>>
> 
> Hi, Joseph!
> 
> I cannot reproduce this issue on my machine. Theoretically, the 'rsv_credits'
> should be 113 under 64k page size + 4k block size, I don't think it would
> exceed the max user trans buffers. Could you please give more details?
> What is the configuration of your xfstests? and what does the specific error
> log look like?
> 
I'm testing on arm 64K ECS with xfstests local.config as follows:

export TEST_DEV=/dev/nvme1n1p1
export TEST_DIR=/mnt/test
export SCRATCH_DEV=/dev/nvme1n1p2
export SCRATCH_MNT=/mnt/scratch

Each disk part is 250G and formated with 4k block size.

The dmesg shows the following warning:

[  137.174661] JBD2: kworker/u32:0 wants too many credits credits:32 rsv_credits:1577 max:2695
...
[  137.175544] Call trace:
[  137.175545]  start_this_handle+0x3bc/0x3d8 (P)
[  137.175548]  jbd2__journal_start+0x10c/0x248
[  137.175550]  __ext4_journal_start_sb+0xe4/0x1b0
[  137.175553]  ext4_do_writepages+0x430/0x768
[  137.175556]  ext4_writepages+0x8c/0x118
[  137.175558]  do_writepages+0xac/0x180
[  137.175561]  __writeback_single_inode+0x48/0x328
[  137.175563]  writeback_sb_inodes+0x244/0x4a0
[  137.175564]  wb_writeback+0xec/0x3a0
[  137.175566]  wb_do_writeback+0xc0/0x250
[  137.175568]  wb_workfn+0x70/0x1b0
[  137.175570]  process_one_work+0x180/0x400
[  137.175573]  worker_thread+0x254/0x2c8
[  137.175575]  kthread+0x124/0x130
[  137.175577]  ret_from_fork+0x10/0x20
...