Re: system hang on a syncfs test with nfs_export enabled

[Chengguang Xu <cgxu519@mykernel.net>]

 ---- 在 星期四, 2020-04-30 20:22:06 Amir Goldstein <amir73il@gmail.com> 撰写 ----
 > On Thu, Apr 30, 2020 at 12:48 PM Chengguang Xu <cgxu519@mykernel.net> wrote:
 > >
 > >  ---- 在 星期四, 2020-04-30 17:15:20 Chengguang Xu <cgxu519@mykernel.net> 撰写 ----
 > >  > Hi
 > >  >
 > >  > I'm doing some tests for my new version of syncfs improvement patch and I found an
 > >  > interesting problem when combining dirty data && godown && nfs_export.
 > >  >
 > >  > My expectation  is  Pass or Fail  all tests listed below, Test2 looks a bit strange and in my
 > >  > opinion there is no strong connection between nfs_export/index and dirty data.
 > >  > Any idea?
 > >  >
 > >  >
 > >  > Test env and step like below:
 > >  >
 > >  > Test1:
 > >  > Compile module with nfs_export enabled
 > >  > Run xfstest generic/474   ==> PASS
 > >  >
 > >  > Test2:
 > >  > Compile module with nfs_export enabled
 > >  > Comment syncfs step in the test
 > >  > Run xfstest generic/474   ==> Hang
 > >  >
 > >  > Test3:
 > >  > Compile module with nfs_export disabled
 > >  > Run xfstest generic/474   ==> PASS
 > >  >
 > >  > Test4:
 > >  > Compile module with nfs_export disabled
 > >  > Comment syncfs step in the test
 > >  > Run xfstest generic/474   ==> FAIL
 > >  >
 > >
 > > Additional information:
 > >
 > > Overlayfs version: latest next branch of miklos tree (5.7-rc2)
 > > Underlying fs: xfs
 > >
 > 
 > Please test also against 5.7-rc2. Maybe we introduced some
 > regression in -next.
 > 
 > Please dump waiting processes stack by echo w > /proc/sysrq-trigger
 > to see where in kernel does the test hang.
 > 
 > I cannot think of anything in nfs_export/index that should affect
 > generic/474, but we will find out soon...
 > 

I‘m on vacation this week and it seems hard to reproduce the problem on my laptop, maybe there were some config problems.
I'll do more analyses next week on my testing machine.


Thanks,
cgxu