Re: [LTP] [mm/page] ab19939a6a:

From: Cyril Hrubis
Date: Mon Sep 13 2021 - 04:11:07 EST

> FYI, we noticed the following commit (built with gcc-9):
> commit: ab19939a6a5010cba4e9cb04dd8bee03c72edcbd ("mm/page-writeback: Fix performance when BDI's share of ratio is 0.")
> master
> in testcase: ltp
> version: ltp-x86_64-14c1f76-1_20210907
> with following parameters:
> disk: 1HDD
> fs: xfs
> test: syscalls-03
> ucode: 0xe2
> test-description: The LTP testsuite contains a collection of tools for testing the Linux kernel and related features.
> test-url:

The msync04 test formats a device with a diffrent filesystems, for each
filesystem it maps a file, writes to the mapped page and the checks a
dirty bit in /proc/kpageflags before and after msync() on that page.

This seems to be broken after this patch for ntfs over FUSE and it looks
like the page does not have a dirty bit set right after it has been
written to.

Also I guess that we should increase the number of the pages we dirty or
attempt to retry since a single page may be flushed to the storage if we
are unlucky and the process is preempted between the write and the
initial check for the dirty bit.

Cyril Hrubis