Re: [PATCH 16/21] fs: Protect inode->i_state with the inode->i_lock

[Christoph Hellwig]

On Sun, Oct 24, 2010 at 10:13:10AM -0400, Christoph Hellwig wrote:
> On Sat, Oct 23, 2010 at 10:37:52PM +0100, Al Viro wrote:
> > 	* invalidate_inodes() - collect I_FREEING/I_WILL_FREE on a separate
> > list, then (after we'd evicted the stuff we'd decided to evict) wait until
> > they get freed by whatever's freeing them already.
> 
> Note that we would only have to do this for the umount case.  For others
> it's pretty pointless.

Now that I've looked into it I think we basically fine right now.

If we're in umount there should be no other I_FREEING inodes.

 - concurrent prune_icache is prevented by iprune_sem.
 - concurrent other invalidate_inodes should not happen because we're
   in unmount and the filesystem should not be reachable any more,
   and even if it did iprune_sem would protect us.
 - how could a concurrent iput_final happen?  filesystem is not
   accessible anymore, and iput of fs internal inodes is single-threaded
   with the rest of the actual umount process.

So just skipping over I_FREEING inodes here should be fine for
non-umount callers, and for umount we could even do a WARN_ON.
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