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>

9 files changed, 337 insertions, 243 deletions

diff --git a/fs/notify/Makefile b/fs/notify/Makefile
index 396a38779371..8f7f3b024a2e 100644
--- a/fs/notify/Makefile
+++ b/fs/notify/Makefile
@@ -1,4 +1,5 @@
-obj-$(CONFIG_FSNOTIFY)          += fsnotify.o notification.o group.o inode_mark.o
+obj-$(CONFIG_FSNOTIFY)          += fsnotify.o notification.o group.o inode_mark.o \
+                                   mark.o
 
 obj-y                   += dnotify/
 obj-y                   += inotify/
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index cac2eb896639..69f42df9ba45 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -95,7 +95,7 @@ static int dnotify_handle_event(struct fsnotify_group *group,
 
         to_tell = event->to_tell;
 
-        fsn_mark = fsnotify_find_mark(group, to_tell);
+        fsn_mark = fsnotify_find_inode_mark(group, to_tell);
         if (unlikely(!fsn_mark))
                 return 0;
         dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
@@ -143,14 +143,14 @@ static bool dnotify_should_send_event(struct fsnotify_group *group,
         if (!S_ISDIR(inode->i_mode))
                 return false;
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark)
                 return false;
 
         mask = (mask & ~FS_EVENT_ON_CHILD);
         send = (mask & fsn_mark->mask);
 
-        fsnotify_put_mark(fsn_mark); /* matches fsnotify_find_mark */
+        fsnotify_put_mark(fsn_mark); /* matches fsnotify_find_inode_mark */
 
         return send;
 }
@@ -193,7 +193,7 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
         if (!S_ISDIR(inode->i_mode))
                 return;
 
-        fsn_mark = fsnotify_find_mark(dnotify_group, inode);
+        fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
         if (!fsn_mark)
                 return;
         dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
@@ -346,12 +346,12 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
         mutex_lock(&dnotify_mark_mutex);
 
         /* add the new_fsn_mark or find an old one. */
-        fsn_mark = fsnotify_find_mark(dnotify_group, inode);
+        fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
         if (fsn_mark) {
                 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
                 spin_lock(&fsn_mark->lock);
         } else {
-                fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, 0);
+                fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, NULL, 0);
                 spin_lock(&new_fsn_mark->lock);
                 fsn_mark = new_fsn_mark;
                 dn_mark = new_dn_mark;
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 881067dc7923..aa5e92661142 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -118,7 +118,7 @@ static bool fanotify_should_send_event(struct fsnotify_group *group, struct inod
         if (data_type != FSNOTIFY_EVENT_PATH)
                 return false;
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark)
                 return false;
 
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 66e38fc052b2..05351936a725 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -305,7 +305,7 @@ static int fanotify_remove_mark(struct fsnotify_group *group,
         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__,
                  group, inode, mask);
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark)
                 return -ENOENT;
 
@@ -321,7 +321,7 @@ static int fanotify_remove_mark(struct fsnotify_group *group,
 
         fsnotify_recalc_group_mask(group);
 
-        /* matches the fsnotify_find_mark() */
+        /* matches the fsnotify_find_inode_mark() */
         fsnotify_put_mark(fsn_mark);
 
         return 0;
@@ -338,7 +338,7 @@ static int fanotify_add_mark(struct fsnotify_group *group,
         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__,
                  group, inode, mask);
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark) {
                 struct fsnotify_mark *new_fsn_mark;
 
@@ -348,7 +348,7 @@ static int fanotify_add_mark(struct fsnotify_group *group,
                         goto out;
 
                 fsnotify_init_mark(new_fsn_mark, fanotify_free_mark);
-                ret = fsnotify_add_mark(new_fsn_mark, group, inode, 0);
+                ret = fsnotify_add_mark(new_fsn_mark, group, inode, NULL, 0);
                 if (ret) {
                         fanotify_free_mark(new_fsn_mark);
                         goto out;
diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h
index 2ba59158969f..7c7a904b802d 100644
--- a/fs/notify/fsnotify.h
+++ b/fs/notify/fsnotify.h
@@ -20,6 +20,11 @@ extern __u32 fsnotify_vfsmount_mask;
 /* destroy all events sitting in this groups notification queue */
 extern void fsnotify_flush_notify(struct fsnotify_group *group);
 
+/* add a mark to an inode */
+extern int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
+                                   struct fsnotify_group *group, struct inode *inode,
+                                   int allow_dups);
+
 /* add a group to the inode group list */
 extern void fsnotify_add_inode_group(struct fsnotify_group *group);
 /* add a group to the vfsmount group list */
@@ -27,6 +32,8 @@ extern void fsnotify_add_vfsmount_group(struct fsnotify_group *group);
 /* final kfree of a group */
 extern void fsnotify_final_destroy_group(struct fsnotify_group *group);
 
+/* inode specific destruction of a mark */
+extern void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark);
 /* run the list of all marks associated with inode and flag them to be freed */
 extern void fsnotify_clear_marks_by_inode(struct inode *inode);
 /*
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;
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index cc8f6bcbb4a3..1d237e1bf7b1 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -97,7 +97,7 @@ static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_ev
 
         to_tell = event->to_tell;
 
-        fsn_mark = fsnotify_find_mark(group, to_tell);
+        fsn_mark = fsnotify_find_inode_mark(group, to_tell);
         /* race with watch removal?  We already passes should_send */
         if (unlikely(!fsn_mark))
                 return 0;
@@ -145,7 +145,7 @@ static bool inotify_should_send_event(struct fsnotify_group *group, struct inode
         struct fsnotify_mark *fsn_mark;
         bool send;
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark)
                 return false;
 
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index ad5a1ea7827e..a12315a7553d 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -566,7 +566,7 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
         if (unlikely(!mask))
                 return -EINVAL;
 
-        fsn_mark = fsnotify_find_mark(group, inode);
+        fsn_mark = fsnotify_find_inode_mark(group, inode);
         if (!fsn_mark)
                 return -ENOENT;
 
@@ -644,7 +644,7 @@ static int inotify_new_watch(struct fsnotify_group *group,
                 goto out_err;
 
         /* we are on the idr, now get on the inode */
-        ret = fsnotify_add_mark(&tmp_i_mark->fsn_mark, group, inode, 0);
+        ret = fsnotify_add_mark(&tmp_i_mark->fsn_mark, group, inode, NULL, 0);
         if (ret) {
                 /* we failed to get on the inode, get off the idr */
                 inotify_remove_from_idr(group, tmp_i_mark);
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
new file mode 100644
index 000000000000..e56e8768d676
--- /dev/null
+++ b/fs/notify/mark.c
@@ -0,0 +1,294 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; see the file COPYING.  If not, write to
+ *  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>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/writeback.h> /* for inode_lock */
+
+#include <asm/atomic.h>
+
+#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);
+}
+
+/*
+ * 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)
+{
+        struct fsnotify_group *group;
+        struct inode *inode;
+
+        spin_lock(&mark->lock);
+
+        group = mark->group;
+        inode = mark->i.inode;
+
+        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);
+
+        if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
+                fsnotify_destroy_inode_mark(mark);
+        else
+                BUG();
+
+        list_del_init(&mark->g_list);
+        mark->group = NULL;
+
+        fsnotify_put_mark(mark); /* for i_list and g_list */
+
+        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);
+}
+
+/*
+ * Attach an initialized mark to a given group and fs object.
+ * These marks may be used for the fsnotify backend to determine which
+ * event types should be delivered to which group.
+ */
+int fsnotify_add_mark(struct fsnotify_mark *mark,
+                      struct fsnotify_group *group, struct inode *inode,
+                      struct vfsmount *mnt, int allow_dups)
+{
+        int ret = 0;
+
+        BUG_ON(mnt);
+        BUG_ON(inode && mnt);
+        BUG_ON(!inode && !mnt);
+
+        /*
+         * if this group isn't being testing for inode type events we need
+         * to start testing
+         */
+        if (inode && unlikely(list_empty(&group->inode_group_list)))
+                fsnotify_add_inode_group(group);
+        else if (mnt && unlikely(list_empty(&group->vfsmount_group_list)))
+                fsnotify_add_vfsmount_group(group);
+
+        /*
+         * LOCKING ORDER!!!!
+         * mark->lock
+         * group->mark_lock
+         * inode->i_lock
+         */
+        spin_lock(&mark->lock);
+        spin_lock(&group->mark_lock);
+
+        mark->group = group;
+        list_add(&mark->g_list, &group->marks_list);
+        atomic_inc(&group->num_marks);
+        fsnotify_get_mark(mark); /* for i_list and g_list */
+
+        if (inode) {
+                ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
+                if (ret)
+                        goto err;
+        } else {
+                BUG();
+        }
+
+        spin_unlock(&group->mark_lock);
+        spin_unlock(&mark->lock);
+
+        if (inode)
+                __fsnotify_update_child_dentry_flags(inode);
+
+        return ret;
+err:
+        mark->group = NULL;
+        list_del_init(&mark->g_list);
+        atomic_dec(&group->num_marks);
+        fsnotify_put_mark(mark);
+
+        spin_unlock(&group->mark_lock);
+        spin_unlock(&mark->lock);
+
+        return ret;
+}
+
+/*
+ * 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);
+        }
+}
+
+void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
+{
+        assert_spin_locked(&old->lock);
+        new->i.inode = old->i.inode;
+        new->m.mnt = old->m.mnt;
+        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;
+}