Re: [BUG] shmem: FALLOC_FL_PUNCH_HOLE vs fault-around race corrupts page cache / rss counters

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From: Baolin Wang

Date: Thu Oct 08 2026 - 03:59:18 EST

On 10/3/26 11:31 AM, Ayush Ranjan wrote:

Hi all,

Gentle ping on this.

Sorry for the late reply due to my vacation.

The reproducer in my previous mail [1] triggers

"Bad page cache ... still mapped when deleted" on 6.18.46 within a
couple of minutes on a 128-CPU bare-metal box, with no fork() and no
gVisor involved.

We continue to hit this in production at low frequency, so I am happy
to test patches or collect more data if that would help.

Now I can reproduce this issue on my machine with the latest mm-unstable branch, and I understand the race. I have confirmed that Andrew's patch can fix it. You can try Andrew's patch.