Re: [Xen-devel] [PATCH 1/2 linux-next] Revert "ufs: fix deadlocks introduced by sb mutex merge"

[Jan Kara <jack@xxxxxxx>]

On Fri 05-06-15 23:03:48, Al Viro wrote:
> On Fri, Jun 05, 2015 at 07:50:18PM +0100, Al Viro wrote:
> > Basically, we have
> >     i_mutex: file size changes, contents-affecting syscalls.  Per-inode.
> >     truncate_mutex: block pointers changes.  Per-inode.
> >     s_lock: block and inode bitmaps changes.  Per-filesystem.
> > 
> > For UFS it's slightly more complicated due to tail packing they are doing 
> > for
> > short files, but most of that complexity is due to having that stuff handled
> > way too deep in call chain.
> 
> Oh, lovely... commit 10e5dc
> Author: Evgeniy Dushistov <dushistov@xxxxxxx>
> Date:   Sat Jul 1 04:36:24 2006 -0700
> 
>     [PATCH] ufs: truncate should allocate block for last byte
> 
> had removed ->truncate() method and missed the fact that vmtrucate() had
> callers outside of ->setattr(), such as handling of ->prepare_write() partial
> failures and short copies on write(2) in general.
> 
> Then we had a long and convoluted series of conversions that ended up with
> vmtruncate() lifted into ufs_write_failed() and replaced with
> truncate_pagecache() in there.
> 
> Through all that, everybody (me included) had not noticed that we *still*
> do not free blocks allocated by ufs_write_begin() failing halfway through.
> While we are at it, ufs_write_end() ought to call ufs_write_failed() in
> case when we'd been called after a short copy (and do the same block freeing).
> 
> Joy...  Folks, is anybody actively maintaining fs/ufs these days?

Looking into the changelog there wasn't anyone seriously looking into UFS
for at least 5-6 years... Fabian did some cleanups recently but they were
mostly cosmetic. So I don't think it's really maintained. OTOH clearly
there are some users since occasionally someone comes with a bug report.
Welcome to the world where we have ~50 on disk / network filesystems :-|

                                                                Honza
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR

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