Merge branch 'work.icache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs inode freeing updates from Al Viro:
 "Introduction of separate method for RCU-delayed part of
  ->destroy_inode() (if any).

  Pretty much as posted, except that destroy_inode() stashes
  ->free_inode into the victim (anon-unioned with ->i_fops) before
  scheduling i_callback() and the last two patches (sockfs conversion
  and folding struct socket_wq into struct socket) are excluded - that
  pair should go through netdev once davem reopens his tree"

* 'work.icache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (58 commits)
  orangefs: make use of ->free_inode()
  shmem: make use of ->free_inode()
  hugetlb: make use of ->free_inode()
  overlayfs: make use of ->free_inode()
  jfs: switch to ->free_inode()
  fuse: switch to ->free_inode()
  ext4: make use of ->free_inode()
  ecryptfs: make use of ->free_inode()
  ceph: use ->free_inode()
  btrfs: use ->free_inode()
  afs: switch to use of ->free_inode()
  dax: make use of ->free_inode()
  ntfs: switch to ->free_inode()
  securityfs: switch to ->free_inode()
  apparmor: switch to ->free_inode()
  rpcpipe: switch to ->free_inode()
  bpf: switch to ->free_inode()
  mqueue: switch to ->free_inode()
  ufs: switch to ->free_inode()
  coda: switch to ->free_inode()
  ...

2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index efea228ccd8a..7b20c385cc02 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -118,6 +118,7 @@ set:		exclusive
 --------------------------- super_operations ---------------------------
 prototypes:
 	struct inode *(*alloc_inode)(struct super_block *sb);
+	void (*free_inode)(struct inode *);
 	void (*destroy_inode)(struct inode *);
 	void (*dirty_inode) (struct inode *, int flags);
 	int (*write_inode) (struct inode *, struct writeback_control *wbc);
@@ -139,6 +140,7 @@ locking rules:
 	All may block [not true, see below]
 			s_umount
 alloc_inode:
+free_inode:				called from RCU callback
 destroy_inode:
 dirty_inode:
 write_inode:
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index cf43bc4dbf31..b8d3ddd8b8db 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -638,3 +638,28 @@ in your dentry operations instead.
 	inode to d_splice_alias() will also do the right thing (equivalent of
 	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.