Re: [PATCH] fs/9p: fix inode nlink accounting

[asmadeus@codewreck.org]

Eric Van Hensbergen wrote on Sun, Jan 07, 2024 at 07:07:52PM +0000:
> I was running some regressions and noticed a (race-y) kernel warning that
> happens when nlink becomes less than zero.  Looking through the code
> it looks like we aren't good about protecting the inode lock when
> manipulating nlink and some code that was added several years ago to
> protect against bugs in underlying file systems nlink handling didn't
> look quite right either.  I took a look at what NFS was doing and tried to
> follow similar approaches in the 9p code.

I was about to say the set/inc/etc_nlink helpers could probably just be
using atomic (there's an atomic_dec_if_postive that we could have used
for the v9fs_dec_count warning), but this isn't our code so not much to
do about that -- I agree it needs a lock.

I didn't take the time to check if you missed any, but it won't be worse
than what we have right now:
Acked-by: Dominique Martinet <asmadeus@codewreck.org>

-- 
Dominique Martinet | Asmadeus