Re: ftruncate fails

[Dominique Martinet <asmadeus@codewreck.org>]

Itaru Kitayama wrote on Mon, Apr 08, 2024 at 11:22:56AM +0900:
>> FVP and just mount -t 9p FM /mnt

FVP is the arm "fixed virutal platforms"?
I've never used it and the doc I just found doesn't clarify much but it
looks like each individual "model" provides its own emulation program,
so they each might have a different 9p server.. doesn't look like
qemu-based either.

We have had other reports of problems with 9p recently (since 6.9-rc1)
so I'll keep digging with qemu for now, but writing down to try FVP
eventually.

> >> - Does this reproduce right after boot/mounting the 9p filesystem?
> > 
> > Not immediately after the boot/mounting.
> 
> My reproducer wasn’t explaining what a kselftests was showing.
> 
> If you build the “mm” subsystem and execute one of the programs,
> gup_longterm from the 9p mounted directory, you’ll notice the
> ftruncate error.

Okay, the failure from gup_longterm isn't what you describe in your
first mail (no bus error, ENOENT on ftruncate)
I think it is a new bug though:

openat(AT_FDCWD, "gup_longterm.c_tmpfile_vKvLVC", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
unlink("gup_longterm.c_tmpfile_vKvLVC") = 0
fstatfs(3, 0x7ffcf7f74920)              = -1 ENOENT (No such file or directory)
ftruncate(3, 4096)                      = -1 ENOENT (No such file or directory)

I think that used to work, we need to fix this.


If you can reproduce the bus error though I'd be very interested.
-- 
Dominique Martinet | Asmadeus