fsnotify: split generic and inode specific mark code

currently all marking is done by functions in inode-mark.c.  Some of this
is pretty generic and should be instead done in a generic function and we
should only put the inode specific code in inode-mark.c

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 19 insertions, 227 deletions

diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index ba6f9833561b..c925579ba011 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -16,72 +16,6 @@
  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
-/*
- * fsnotify inode mark locking/lifetime/and refcnting
- *
- * REFCNT:
- * The mark->refcnt tells how many "things" in the kernel currently are
- * referencing this object.  The object typically will live inside the kernel
- * with a refcnt of 2, one for each list it is on (i_list, g_list).  Any task
- * which can find this object holding the appropriete locks, can take a reference
- * and the object itself is guarenteed to survive until the reference is dropped.
- *
- * LOCKING:
- * There are 3 spinlocks involved with fsnotify inode marks and they MUST
- * be taken in order as follows:
- *
- * mark->lock
- * group->mark_lock
- * inode->i_lock
- *
- * mark->lock protects 2 things, mark->group and mark->inode.  You must hold
- * that lock to dereference either of these things (they could be NULL even with
- * the lock)
- *
- * group->mark_lock protects the marks_list anchored inside a given group
- * and each mark is hooked via the g_list.  It also sorta protects the
- * free_g_list, which when used is anchored by a private list on the stack of the
- * task which held the group->mark_lock.
- *
- * inode->i_lock protects the i_fsnotify_marks list anchored inside a
- * given inode and each mark is hooked via the i_list. (and sorta the
- * free_i_list)
- *
- *
- * LIFETIME:
- * Inode marks survive between when they are added to an inode and when their
- * refcnt==0.
- *
- * The inode mark can be cleared for a number of different reasons including:
- * - The inode is unlinked for the last time.  (fsnotify_inode_remove)
- * - The inode is being evicted from cache. (fsnotify_inode_delete)
- * - The fs the inode is on is unmounted.  (fsnotify_inode_delete/fsnotify_unmount_inodes)
- * - Something explicitly requests that it be removed.  (fsnotify_destroy_mark)
- * - The fsnotify_group associated with the mark is going away and all such marks
- *   need to be cleaned up. (fsnotify_clear_marks_by_group)
- *
- * Worst case we are given an inode and need to clean up all the marks on that
- * inode.  We take i_lock and walk the i_fsnotify_marks safely.  For each
- * mark on the list we take a reference (so the mark can't disappear under us).
- * We remove that mark form the inode's list of marks and we add this mark to a
- * private list anchored on the stack using i_free_list;  At this point we no
- * longer fear anything finding the mark using the inode's list of marks.
- *
- * We can safely and locklessly run the private list on the stack of everything
- * we just unattached from the original inode.  For each mark on the private list
- * we grab the mark-> and can thus dereference mark->group and mark->inode.  If
- * we see the group and inode are not NULL we take those locks.  Now holding all
- * 3 locks we can completely remove the mark from other tasks finding it in the
- * future.  Remember, 10 things might already be referencing this mark, but they
- * better be holding a ref.  We drop our reference we took before we unhooked it
- * from the inode.  When the ref hits 0 we can free the mark.
- *
- * Very similarly for freeing by group, except we use free_g_list.
- *
- * This has the very interesting property of being able to run concurrently with
- * any (or all) other directions.
- */
-
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -95,17 +29,6 @@
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
 
-void fsnotify_get_mark(struct fsnotify_mark *mark)
-{
-	atomic_inc(&mark->refcnt);
-}
-
-void fsnotify_put_mark(struct fsnotify_mark *mark)
-{
-	if (atomic_dec_and_test(&mark->refcnt))
-		mark->free_mark(mark);
-}
-
 /*
  * Recalculate the mask of events relevant to a given inode locked.
  */
@@ -135,44 +58,18 @@ void fsnotify_recalc_inode_mask(struct inode *inode)
 	__fsnotify_update_child_dentry_flags(inode);
 }
 
-/*
- * Any time a mark is getting freed we end up here.
- * The caller had better be holding a reference to this mark so we don't actually
- * do the final put under the mark->lock
- */
-void fsnotify_destroy_mark(struct fsnotify_mark *mark)
+void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
 {
-	struct fsnotify_group *group;
-	struct inode *inode;
-
-	spin_lock(&mark->lock);
+	struct inode *inode = mark->i.inode;
 
-	group = mark->group;
-	inode = mark->i.inode;
+	assert_spin_locked(&mark->lock);
+	assert_spin_locked(&mark->group->mark_lock);
 
-	BUG_ON(group && !inode);
-	BUG_ON(!group && inode);
-
-	/* if !group something else already marked this to die */
-	if (!group) {
-		spin_unlock(&mark->lock);
-		return;
-	}
-
-	/* 1 from caller and 1 for being on i_list/g_list */
-	BUG_ON(atomic_read(&mark->refcnt) < 2);
-
-	spin_lock(&group->mark_lock);
 	spin_lock(&inode->i_lock);
 
 	hlist_del_init(&mark->i.i_list);
 	mark->i.inode = NULL;
 
-	list_del_init(&mark->g_list);
-	mark->group = NULL;
-
-	fsnotify_put_mark(mark); /* for i_list and g_list */
-
 	/*
 	 * this mark is now off the inode->i_fsnotify_marks list and we
 	 * hold the inode->i_lock, so this is the perfect time to update the
@@ -181,61 +78,6 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 	fsnotify_recalc_inode_mask_locked(inode);
 
 	spin_unlock(&inode->i_lock);
-	spin_unlock(&group->mark_lock);
-	spin_unlock(&mark->lock);
-
-	/*
-	 * Some groups like to know that marks are being freed.  This is a
-	 * callback to the group function to let it know that this mark
-	 * is being freed.
-	 */
-	if (group->ops->freeing_mark)
-		group->ops->freeing_mark(mark, group);
-
-	/*
-	 * __fsnotify_update_child_dentry_flags(inode);
-	 *
-	 * I really want to call that, but we can't, we have no idea if the inode
-	 * still exists the second we drop the mark->lock.
-	 *
-	 * The next time an event arrive to this inode from one of it's children
-	 * __fsnotify_parent will see that the inode doesn't care about it's
-	 * children and will update all of these flags then.  So really this
-	 * is just a lazy update (and could be a perf win...)
-	 */
-
-
-	iput(inode);
-
-	/*
-	 * it's possible that this group tried to destroy itself, but this
-	 * this mark was simultaneously being freed by inode.  If that's the
-	 * case, we finish freeing the group here.
-	 */
-	if (unlikely(atomic_dec_and_test(&group->num_marks)))
-		fsnotify_final_destroy_group(group);
-}
-
-/*
- * Given a group, destroy all of the marks associated with that group.
- */
-void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
-{
-	struct fsnotify_mark *lmark, *mark;
-	LIST_HEAD(free_list);
-
-	spin_lock(&group->mark_lock);
-	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
-		list_add(&mark->free_g_list, &free_list);
-		list_del_init(&mark->g_list);
-		fsnotify_get_mark(mark);
-	}
-	spin_unlock(&group->mark_lock);
-
-	list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
-		fsnotify_destroy_mark(mark);
-		fsnotify_put_mark(mark);
-	}
 }
 
 /*
@@ -261,8 +103,12 @@ void fsnotify_clear_marks_by_inode(struct inode *inode)
 	}
 }
 
-static struct fsnotify_mark *fsnotify_find_mark_locked(struct fsnotify_group *group,
-						       struct inode *inode)
+/*
+ * given a group and inode, find the mark associated with that combination.
+ * if found take a reference to that mark and return it, else return NULL
+ */
+struct fsnotify_mark *fsnotify_find_inode_mark_locked(struct fsnotify_group *group,
+						      struct inode *inode)
 {
 	struct fsnotify_mark *mark;
 	struct hlist_node *pos;
@@ -282,50 +128,26 @@ static struct fsnotify_mark *fsnotify_find_mark_locked(struct fsnotify_group *gr
  * given a group and inode, find the mark associated with that combination.
  * if found take a reference to that mark and return it, else return NULL
  */
-struct fsnotify_mark *fsnotify_find_mark(struct fsnotify_group *group,
-					 struct inode *inode)
+struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
+					       struct inode *inode)
 {
 	struct fsnotify_mark *mark;
 
 	spin_lock(&inode->i_lock);
-	mark = fsnotify_find_mark_locked(group, inode);
+	mark = fsnotify_find_inode_mark_locked(group, inode);
 	spin_unlock(&inode->i_lock);
 
 	return mark;
 }
 
-void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
-{
-	assert_spin_locked(&old->lock);
-	new->i.inode = old->i.inode;
-	new->group = old->group;
-	new->mask = old->mask;
-	new->free_mark = old->free_mark;
-}
-
-/*
- * Nothing fancy, just initialize lists and locks and counters.
- */
-void fsnotify_init_mark(struct fsnotify_mark *mark,
-			void (*free_mark)(struct fsnotify_mark *mark))
-{
-	spin_lock_init(&mark->lock);
-	atomic_set(&mark->refcnt, 1);
-	INIT_HLIST_NODE(&mark->i.i_list);
-	mark->group = NULL;
-	mark->mask = 0;
-	mark->i.inode = NULL;
-	mark->free_mark = free_mark;
-}
-
 /*
  * Attach an initialized mark mark to a given group and inode.
  * These marks may be used for the fsnotify backend to determine which
  * event types should be delivered to which group and for which inodes.
  */
-int fsnotify_add_mark(struct fsnotify_mark *mark,
-		      struct fsnotify_group *group, struct inode *inode,
-		      int allow_dups)
+int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
+			    struct fsnotify_group *group, struct inode *inode,
+			    int allow_dups)
 {
 	struct fsnotify_mark *lmark = NULL;
 	int ret = 0;
@@ -336,56 +158,26 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
 
 	mark->flags = FSNOTIFY_MARK_FLAG_INODE;
 
-	/*
-	 * if this group isn't being testing for inode type events we need
-	 * to start testing
-	 */
-	if (unlikely(list_empty(&group->inode_group_list)))
-		fsnotify_add_inode_group(group);
-	/*
-	 * XXX This is where we could also do the fsnotify_add_vfsmount_group
-	 * if we are setting and vfsmount mark....
-
-	if (unlikely(list_empty(&group->vfsmount_group_list)))
-		fsnotify_add_vfsmount_group(group);
-	 */
+	assert_spin_locked(&mark->lock);
+	assert_spin_locked(&group->mark_lock);
 
-	/*
-	 * LOCKING ORDER!!!!
-	 * mark->lock
-	 * group->mark_lock
-	 * inode->i_lock
-	 */
-	spin_lock(&mark->lock);
-	spin_lock(&group->mark_lock);
 	spin_lock(&inode->i_lock);
 
 	if (!allow_dups)
-		lmark = fsnotify_find_mark_locked(group, inode);
+		lmark = fsnotify_find_inode_mark_locked(group, inode);
 	if (!lmark) {
-		mark->group = group;
 		mark->i.inode = inode;
 
 		hlist_add_head(&mark->i.i_list, &inode->i_fsnotify_marks);
-		list_add(&mark->g_list, &group->marks_list);
-
-		fsnotify_get_mark(mark); /* for i_list and g_list */
-
-		atomic_inc(&group->num_marks);
 
 		fsnotify_recalc_inode_mask_locked(inode);
 	}
 
 	spin_unlock(&inode->i_lock);
-	spin_unlock(&group->mark_lock);
-	spin_unlock(&mark->lock);
 
 	if (lmark) {
 		ret = -EEXIST;
 		iput(inode);
-		fsnotify_put_mark(lmark);
-	} else {
-		__fsnotify_update_child_dentry_flags(inode);
 	}
 
 	return ret;