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

Pull epoll updates from Al Viro:
 "Deal with epoll loop check/removal races sanely (among other things).

  The solution merged last cycle (pinning a bunch of struct file
  instances) had been forced by the wrong data structures; untangling
  that takes a bunch of preparations, but it's worth doing - control
  flow in there is ridiculously overcomplicated. Memory footprint has
  also gone down, while we are at it.

  This is not all I want to do in the area, but since I didn't get
  around to posting the followups they'll have to wait for the next
  cycle"

* 'work.epoll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (27 commits)
  epoll: take epitem list out of struct file
  epoll: massage the check list insertion
  lift rcu_read_lock() into reverse_path_check()
  convert ->f_ep_links/->fllink to hlist
  ep_insert(): move creation of wakeup source past the fl_ep_links insertion
  fold ep_read_events_proc() into the only caller
  take the common part of ep_eventpoll_poll() and ep_item_poll() into helper
  ep_insert(): we only need tep->mtx around the insertion itself
  ep_insert(): don't open-code ep_remove() on failure exits
  lift locking/unlocking ep->mtx out of ep_{start,done}_scan()
  ep_send_events_proc(): fold into the caller
  lift the calls of ep_send_events_proc() into the callers
  lift the calls of ep_read_events_proc() into the callers
  ep_scan_ready_list(): prepare to splitup
  ep_loop_check_proc(): saner calling conventions
  get rid of ep_push_nested()
  ep_loop_check_proc(): lift pushing the cookie into callers
  clean reverse_path_check_proc() a bit
  reverse_path_check_proc(): don't bother with cookies
  reverse_path_check_proc(): sane arguments
  ...

fs/file_table.c

@@ -113,7 +113,6 @@ static struct file *__alloc_file(int flags, const struct cred *cred)
 	rwlock_init(&f->f_owner.lock);
 	spin_lock_init(&f->f_lock);
 	mutex_init(&f->f_pos_lock);
-	eventpoll_init_file(f);
 	f->f_flags = flags;
 	f->f_mode = OPEN_FMODE(flags);
 	/* f->f_version: 0 */

include/linux/eventpoll.h

@@ -22,14 +22,6 @@ struct file;
 struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
 #endif
 
-/* Used to initialize the epoll bits inside the "struct file" */
-static inline void eventpoll_init_file(struct file *file)
-{
-	INIT_LIST_HEAD(&file->f_ep_links);
-	INIT_LIST_HEAD(&file->f_tfile_llink);
-}
-
-
 /* Used to release the epoll bits inside the "struct file" */
 void eventpoll_release_file(struct file *file);
 
@@ -50,7 +42,7 @@ static inline void eventpoll_release(struct file *file)
 	 * because the file in on the way to be removed and nobody ( but
 	 * eventpoll ) has still a reference to this file.
 	 */
-	if (likely(list_empty(&file->f_ep_links)))
+	if (likely(!file->f_ep))
 		return;
 
 	/*
@@ -72,7 +64,6 @@ static inline int ep_op_has_event(int op)
 
 #else
 
-static inline void eventpoll_init_file(struct file *file) {}
 static inline void eventpoll_release(struct file *file) {}
 
 #endif

include/linux/fs.h

@@ -923,7 +923,7 @@ struct file {
 	const struct file_operations	*f_op;
 
 	/*
-	 * Protects f_ep_links, f_flags.
+	 * Protects f_ep, f_flags.
 	 * Must not be taken from IRQ context.
 	 */
 	spinlock_t		f_lock;
@@ -946,8 +946,7 @@ struct file {
 
 #ifdef CONFIG_EPOLL
 	/* Used by fs/eventpoll.c to link all the hooks to this file */
-	struct list_head	f_ep_links;
-	struct list_head	f_tfile_llink;
+	struct hlist_head	*f_ep;
 #endif /* #ifdef CONFIG_EPOLL */
 	struct address_space	*f_mapping;
 	errseq_t		f_wb_err;