[PATCH 4/6] fsnotify: replace inode pointer with tag

[Amir Goldstein <amir73il@xxxxxxxxx>]

The event inode field is used only for comparison in queue merges and
cannot be dereferenced after handle_event(), because it does not hold a
refcount on the inode.

Replace it with an abstract tag do to the same thing. We are going to
set this tag for values other than inode pointer in fanotify.

Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
 fs/notify/fanotify/fanotify.c        | 2 +-
 fs/notify/inotify/inotify_fsnotify.c | 2 +-
 include/linux/fsnotify_backend.h     | 8 +++-----
 3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index b4cd90afece1..34454390e4b6 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -26,7 +26,7 @@ static bool should_merge(struct fsnotify_event *old_fsn,
 	old = FANOTIFY_E(old_fsn);
 	new = FANOTIFY_E(new_fsn);
 
-	if (old_fsn->inode != new_fsn->inode || old->pid != new->pid ||
+	if (old_fsn->tag != new_fsn->tag || old->pid != new->pid ||
 	    old->fh_type != new->fh_type || old->fh_len != new->fh_len)
 		return false;
 
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index d510223d302c..cbaaec234fcd 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -39,7 +39,7 @@ static bool event_compare(struct fsnotify_event *old_fsn,
 	if (old->mask & FS_IN_IGNORED)
 		return false;
 	if ((old->mask == new->mask) &&
-	    (old_fsn->inode == new_fsn->inode) &&
+	    (old_fsn->tag == new_fsn->tag) &&
 	    (old->name_len == new->name_len) &&
 	    (!old->name_len || !strcmp(old->name, new->name)))
 		return true;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 77edd866926f..caf8bbc1be08 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -132,8 +132,7 @@ struct fsnotify_ops {
  */
 struct fsnotify_event {
 	struct list_head list;
-	/* inode may ONLY be dereferenced during handle_event(). */
-	struct inode *inode;	/* either the inode the event happened to or its parent */
+	unsigned long tag;	/* identifier for queue merges */
 };
 
 /*
@@ -499,11 +498,10 @@ extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
 
-static inline void fsnotify_init_event(struct fsnotify_event *event,
-				       struct inode *inode)
+static inline void fsnotify_init_event(struct fsnotify_event *event, void *tag)
 {
 	INIT_LIST_HEAD(&event->list);
-	event->inode = inode;
+	event->tag = (unsigned long)tag;
 }
 
 #else
-- 
2.17.1