[Bug 202889] fsync on inode fails to persist its size, which is changed by pwrite

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=202889

--- Comment #3 from Seulbae Kim (seulbae@gatech.edu) ---
Hi Chao, Thank you for the quick response again!
And sorry, I missed a line in the PoC.. :(

This bug actually is a little bit tricky, because it's not ALWAYS being
reproduced..
Running the PoC repeatedly on a fresh VM instance, I get the wrong file size at
about 50% chance. However, when I run the same test case on a binary, which
utilizes the Linux Kernel Library for mounting, running PoC, remounting, and
retrieving the stat info from the files, I always get the wrong size for this
file, "foo/bar/xattr".

I've just re-tested the PoC on a new VM with kernel v5.0, and again, this bug
is reproduced 4 times out of 10 trials.

Do you have any idea about what is the cause of this nondeterministic behavior?

(In reply to Chao Yu from comment #1)
> Hi Seulbae,
> 
> Thanks for the report. :)
> 
> Your test program didn't handle any error paths, it should be fixed.
> 
> I try to reproduce this bug, but it looks there is no problem in my
> environment.
> 
> Could you add error handling and try again?

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