Merge branch 'stable-fodder' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs stable fodder fixes from Al Viro:

 - acct_on() fix for deadlock caught by overlayfs folks

 - autofs RCU use-after-free SNAFU (->d_manage() can be called
   locklessly, so we need to RCU-delay freeing the objects it looks at)

 - (hopefully) the end of "do we need freeing this dentry RCU-delayed"
   whack-a-mole.

* 'stable-fodder' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  autofs: fix use-after-free in lockless ->d_manage()
  dcache: sort the freeing-without-RCU-delay mess for good.
  acct_on(): don't mess with freeze protection

diff --cc Documentation/filesystems/porting
index b8d3ddd8b8db3281fb4171aa57a99bac0a67193c,a60fa516d4cbb1eacdd00cae0008645c10d403cf..d392d4b0c39327d0609f8248a125c74e04b5d82e
--- 1/Documentation/filesystems/porting
--- 2/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@@ -639,27 -639,7 +639,32 @@@ in your dentry operations instead
        d_add(dentry, NULL); return NULL;), so that kind of special cases
        also doesn't need a separate treatment.
  --
 +[strongly recommended]
 +      take the RCU-delayed parts of ->destroy_inode() into a new method -
 +      ->free_inode().  If ->destroy_inode() becomes empty - all the better,
 +      just get rid of it.  Synchronous work (e.g. the stuff that can't
 +      be done from an RCU callback, or any WARN_ON() where we want the
 +      stack trace) *might* be movable to ->evict_inode(); however,
 +      that goes only for the things that are not needed to balance something
 +      done by ->alloc_inode().  IOW, if it's cleaning up the stuff that
 +      might have accumulated over the life of in-core inode, ->evict_inode()
 +      might be a fit.
 +
 +      Rules for inode destruction:
 +              * if ->destroy_inode() is non-NULL, it gets called
 +              * if ->free_inode() is non-NULL, it gets scheduled by call_rcu()
 +              * combination of NULL ->destroy_inode and NULL ->free_inode is
 +                treated as NULL/free_inode_nonrcu, to preserve the compatibility.
 +
 +      Note that the callback (be it via ->free_inode() or explicit call_rcu()
 +      in ->destroy_inode()) is *NOT* ordered wrt superblock destruction;
 +      as the matter of fact, the superblock and all associated structures
 +      might be already gone.  The filesystem driver is guaranteed to be still
 +      there, but that's it.  Freeing memory in the callback is fine; doing
 +      more than that is possible, but requires a lot of care and is best
 +      avoided.
++--
+ [mandatory]
+       DCACHE_RCUACCESS is gone; having an RCU delay on dentry freeing is the
+       default.  DCACHE_NORCU opts out, and only d_alloc_pseudo() has any
+       business doing so.