Re: [RFC PATCH] shrink_dcache_parent() deadlock

[Al Viro <viro@ZenIV.linux.org.uk>]

On Tue, Jan 10, 2012 at 07:59:07AM +1100, Dave Chinner wrote:
> > Comments?
> 
> Looks OK to me.

OK, grabbed.  And there's *more* fixes for obvious shite - by now I'm
really sick and tired of what people are doing with failure exits;
this morning catch just from looking through d_alloc_root() callers:
	isofs - inode leak
	ext4 - dentry leak + completely bogus handling of ext4_mb_init()
failure (stuff that hadn't been allocated gets freed, stuff that was
allocated isn't)
	ceph - d_alloc_root() can fail.  NULL pointer derefs galore...
)

Frankly, d_alloc_root() had been a bad API; it should've been doing
iput() on allocation failure.  I've added a trivial helper in the
local tree (d_make_root(inode) - same as d_alloc_root(inode) and do
iput(inode) if result turns out to be NULL).  Looks like *all* callers
of d_alloc_root() either turn out to be buggy or trivially convert to
d_make_root().  With a lot of boilerplate crap removed...

Hell knows...  Originally I thought about leaving both side-by-side, but
it really starts looking as if there's no reason to keep d_alloc_root()
at all...  I still have a couple of callers to check, though.