On Tue, Oct 18, 2005 at 07:26:46PM -0700, Andrew Morton wrote:
> Chris Mason <[email protected]> wrote:
> >
> > On Tue, Oct 18, 2005 at 06:15:48PM -0700, Andrew Morton wrote:
> > > > > Well according to my assertion (below), the inode in __sync_single_inode()
> > > > > cannot have a zero refcount, so the whole if() statement is never executed.
> > > >
> > > > generic_forget_inode->write_inode_now->__writeback_single_inode->
> > > > __sync_single_inode
> > >
> > > oshit.
> >
> > When does this ever happen? Just for private inodes released during
> > put_super right?
>
> I suppose so, yes.
It's not related to the bug, but prune_icache can jump in at any
time during generic_shutdown_super, except during the invalidate_inodes
runs. Something like this:
proc1 proc2
generic_shutdown_super
s->s_flags &= ~MS_ACTIVE
invalidate_inodes
put_super
shrink_icache_memory
prune_icache
invalidate_inode_pages
try_to_release_page
I doubt any FS triggers this. They would need to generate inodes
with pages during the put_super call, and get them onto the unused list.
But, I think prune_icache should just skip any inodes where the super
doesn't have MS_ACTIVE set.
At any rate, this wasn't the race I was looking for. Aside from the
bugs fixed by Andrea's patch, we were seeing inodes go negative thanks
to a bad interaction between a latency fix and a backport of something
else from mainline. Our latency code has a goto again, and mainline
has a big fat comment explaining why goto again isn't needed.
If the super->s_inodes list was long enough to reschedule in invalidate_list,
we would process the same inodes in multiple times without removing them.
The short version is that no additional patches should be needed for
mainline.
-chris
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