fsnotify_mask = mask;
}
+/*
+ * Update the group->mask by running all of the marks associated with this
+ * group and finding the bitwise | of all of the mark->mask. If we change
+ * the group->mask we need to update the global mask of events interesting
+ * to the system.
+ */
+void fsnotify_recalc_group_mask(struct fsnotify_group *group)
+{
+ __u32 mask = 0;
+ __u32 old_mask = group->mask;
+ struct fsnotify_mark_entry *entry;
+
+ spin_lock(&group->mark_lock);
+ list_for_each_entry(entry, &group->mark_entries, g_list)
+ mask |= entry->mask;
+ spin_unlock(&group->mark_lock);
+
+ group->mask = mask;
+
+ if (old_mask != mask)
+ fsnotify_recalc_global_mask();
+}
+
/*
* Take a reference to a group so things found under the fsnotify_grp_mutex
* can't get freed under us
/*
* Final freeing of a group
*/
-static void fsnotify_destroy_group(struct fsnotify_group *group)
+void fsnotify_final_destroy_group(struct fsnotify_group *group)
{
if (group->ops->free_group_priv)
group->ops->free_group_priv(group);
kfree(group);
}
+/*
+ * Trying to get rid of a group. We need to first get rid of any outstanding
+ * allocations and then free the group. Remember that fsnotify_clear_marks_by_group
+ * could miss marks that are being freed by inode and those marks could still
+ * hold a reference to this group (via group->num_marks) If we get into that
+ * situtation, the fsnotify_final_destroy_group will get called when that final
+ * mark is freed.
+ */
+static void fsnotify_destroy_group(struct fsnotify_group *group)
+{
+ /* clear all inode mark entries for this group */
+ fsnotify_clear_marks_by_group(group);
+
+ /* past the point of no return, matches the initial value of 1 */
+ if (atomic_dec_and_test(&group->num_marks))
+ fsnotify_final_destroy_group(group);
+}
+
/*
* Remove this group from the global list of groups that will get events
* this can be done even if there are still references and things still using
group->group_num = group_num;
group->mask = mask;
+ spin_lock_init(&group->mark_lock);
+ atomic_set(&group->num_marks, 0);
+ INIT_LIST_HEAD(&group->mark_entries);
+
group->ops = ops;
mutex_lock(&fsnotify_grp_mutex);
/* group not found, add a new one */
list_add_rcu(&group->group_list, &fsnotify_groups);
group->on_group_list = 1;
+ /* being on the fsnotify_groups list holds one num_marks */
+ atomic_inc(&group->num_marks);
mutex_unlock(&fsnotify_grp_mutex);
--- /dev/null
+/*
+ * 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:
+ *
+ * entry->lock
+ * group->mark_lock
+ * inode->i_lock
+ *
+ * entry->lock protects 2 things, entry->group and entry->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 mark_entries list anchored inside a given group
+ * and each entry 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_mark_entries list anchored inside a
+ * given inode and each entry 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_by_entry)
+ * - 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_mark_entries 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 <asm/atomic.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+void fsnotify_get_mark(struct fsnotify_mark_entry *entry)
+{
+ atomic_inc(&entry->refcnt);
+}
+
+void fsnotify_put_mark(struct fsnotify_mark_entry *entry)
+{
+ if (atomic_dec_and_test(&entry->refcnt))
+ entry->free_mark(entry);
+}
+
+/*
+ * Recalculate the mask of events relevant to a given inode locked.
+ */
+static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
+{
+ struct fsnotify_mark_entry *entry;
+ struct hlist_node *pos;
+ __u32 new_mask = 0;
+
+ assert_spin_locked(&inode->i_lock);
+
+ hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list)
+ new_mask |= entry->mask;
+ inode->i_fsnotify_mask = new_mask;
+}
+
+/*
+ * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
+ * any notifier is interested in hearing for this inode.
+ */
+void fsnotify_recalc_inode_mask(struct inode *inode)
+{
+ spin_lock(&inode->i_lock);
+ fsnotify_recalc_inode_mask_locked(inode);
+ spin_unlock(&inode->i_lock);
+}
+
+/*
+ * 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 entry->lock
+ */
+void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry)
+{
+ struct fsnotify_group *group;
+ struct inode *inode;
+
+ spin_lock(&entry->lock);
+
+ group = entry->group;
+ inode = entry->inode;
+
+ BUG_ON(group && !inode);
+ BUG_ON(!group && inode);
+
+ /* if !group something else already marked this to die */
+ if (!group) {
+ spin_unlock(&entry->lock);
+ return;
+ }
+
+ /* 1 from caller and 1 for being on i_list/g_list */
+ BUG_ON(atomic_read(&entry->refcnt) < 2);
+
+ spin_lock(&group->mark_lock);
+ spin_lock(&inode->i_lock);
+
+ hlist_del_init(&entry->i_list);
+ entry->inode = NULL;
+
+ list_del_init(&entry->g_list);
+ entry->group = NULL;
+
+ fsnotify_put_mark(entry); /* for i_list and g_list */
+
+ /*
+ * this mark is now off the inode->i_fsnotify_mark_entries list and we
+ * hold the inode->i_lock, so this is the perfect time to update the
+ * inode->i_fsnotify_mask
+ */
+ fsnotify_recalc_inode_mask_locked(inode);
+
+ spin_unlock(&inode->i_lock);
+ spin_unlock(&group->mark_lock);
+ spin_unlock(&entry->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 entry
+ * is being freed.
+ */
+ group->ops->freeing_mark(entry, group);
+
+ /*
+ * 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_entry *lentry, *entry;
+ LIST_HEAD(free_list);
+
+ spin_lock(&group->mark_lock);
+ list_for_each_entry_safe(entry, lentry, &group->mark_entries, g_list) {
+ list_add(&entry->free_g_list, &free_list);
+ list_del_init(&entry->g_list);
+ fsnotify_get_mark(entry);
+ }
+ spin_unlock(&group->mark_lock);
+
+ list_for_each_entry_safe(entry, lentry, &free_list, free_g_list) {
+ fsnotify_destroy_mark_by_entry(entry);
+ fsnotify_put_mark(entry);
+ }
+}
+
+/*
+ * Given an inode, destroy all of the marks associated with that inode.
+ */
+void fsnotify_clear_marks_by_inode(struct inode *inode)
+{
+ struct fsnotify_mark_entry *entry, *lentry;
+ struct hlist_node *pos, *n;
+ LIST_HEAD(free_list);
+
+ spin_lock(&inode->i_lock);
+ hlist_for_each_entry_safe(entry, pos, n, &inode->i_fsnotify_mark_entries, i_list) {
+ list_add(&entry->free_i_list, &free_list);
+ hlist_del_init(&entry->i_list);
+ fsnotify_get_mark(entry);
+ }
+ spin_unlock(&inode->i_lock);
+
+ list_for_each_entry_safe(entry, lentry, &free_list, free_i_list) {
+ fsnotify_destroy_mark_by_entry(entry);
+ fsnotify_put_mark(entry);
+ }
+}
+
+/*
+ * 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_entry *fsnotify_find_mark_entry(struct fsnotify_group *group,
+ struct inode *inode)
+{
+ struct fsnotify_mark_entry *entry;
+ struct hlist_node *pos;
+
+ assert_spin_locked(&inode->i_lock);
+
+ hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list) {
+ if (entry->group == group) {
+ fsnotify_get_mark(entry);
+ return entry;
+ }
+ }
+ return NULL;
+}
+
+/*
+ * Nothing fancy, just initialize lists and locks and counters.
+ */
+void fsnotify_init_mark(struct fsnotify_mark_entry *entry,
+ void (*free_mark)(struct fsnotify_mark_entry *entry))
+
+{
+ spin_lock_init(&entry->lock);
+ atomic_set(&entry->refcnt, 1);
+ INIT_HLIST_NODE(&entry->i_list);
+ entry->group = NULL;
+ entry->mask = 0;
+ entry->inode = NULL;
+ entry->free_mark = free_mark;
+}
+
+/*
+ * Attach an initialized mark entry 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_entry *entry,
+ struct fsnotify_group *group, struct inode *inode)
+{
+ struct fsnotify_mark_entry *lentry;
+ int ret = 0;
+
+ /*
+ * LOCKING ORDER!!!!
+ * entry->lock
+ * group->mark_lock
+ * inode->i_lock
+ */
+ spin_lock(&entry->lock);
+ spin_lock(&group->mark_lock);
+ spin_lock(&inode->i_lock);
+
+ entry->group = group;
+ entry->inode = inode;
+
+ lentry = fsnotify_find_mark_entry(group, inode);
+ if (!lentry) {
+ hlist_add_head(&entry->i_list, &inode->i_fsnotify_mark_entries);
+ list_add(&entry->g_list, &group->mark_entries);
+
+ fsnotify_get_mark(entry); /* 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(&entry->lock);
+
+ if (lentry) {
+ ret = -EEXIST;
+ fsnotify_put_mark(lentry);
+ }
+
+ return ret;
+}
struct fsnotify_group;
struct fsnotify_event;
+struct fsnotify_mark_entry;
/*
* Each group much define these ops. The fsnotify infrastructure will call
* these operations for each relevant group.
*
+ * should_send_event - given a group, inode, and mask this function determines
+ * if the group is interested in this event.
* handle_event - main call for a group to handle an fs event
* free_group_priv - called when a group refcnt hits 0 to clean up the private union
+ * freeing-mark - this means that a mark has been flagged to die when everything
+ * finishes using it. The function is supplied with what must be a
+ * valid group and inode to use to clean up.
*/
struct fsnotify_ops {
+ bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
void (*free_group_priv)(struct fsnotify_group *group);
+ void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
};
/*
const struct fsnotify_ops *ops; /* how this group handles things */
- /* prevents double list_del of group_list. protected by global fsnotify_gr_mutex */
+ /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
+ spinlock_t mark_lock; /* protect mark_entries list */
+ atomic_t num_marks; /* 1 for each mark entry and 1 for not being
+ * past the point of no return when freeing
+ * a group */
+ struct list_head mark_entries; /* all inode mark entries for this group */
+
+ /* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
bool on_group_list;
/* groups can define private fields here or use the void *private */
__u32 mask; /* the type of access, bitwise OR for FS_* event types */
};
+/*
+ * a mark is simply an entry attached to an in core inode which allows an
+ * fsnotify listener to indicate they are either no longer interested in events
+ * of a type matching mask or only interested in those events.
+ *
+ * these are flushed when an inode is evicted from core and may be flushed
+ * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
+ * (such as dnotify) will flush these when the open fd is closed and not at
+ * inode eviction or modification.
+ */
+struct fsnotify_mark_entry {
+ __u32 mask; /* mask this mark entry is for */
+ /* we hold ref for each i_list and g_list. also one ref for each 'thing'
+ * in kernel that found and may be using this mark. */
+ atomic_t refcnt; /* active things looking at this mark */
+ struct inode *inode; /* inode this entry is associated with */
+ struct fsnotify_group *group; /* group this mark entry is for */
+ struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */
+ struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */
+ spinlock_t lock; /* protect group, inode, and killme */
+ struct list_head free_i_list; /* tmp list used when freeing this mark */
+ struct list_head free_g_list; /* tmp list used when freeing this mark */
+ void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
+};
+
#ifdef CONFIG_FSNOTIFY
/* called from the vfs helpers */
/* main fsnotify call to send events */
extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
+extern void __fsnotify_inode_delete(struct inode *inode);
/* called from fsnotify listeners, such as fanotify or dnotify */
extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
__u32 mask,
const struct fsnotify_ops *ops);
+/* run all marks associated with this group and update group->mask */
+extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
/* drop reference on a group from fsnotify_obtain_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
struct fsnotify_event *event);
+/* functions used to manipulate the marks attached to inodes */
+
+/* run all marks associated with an inode and update inode->i_fsnotify_mask */
+extern void fsnotify_recalc_inode_mask(struct inode *inode);
+extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
+/* find (and take a reference) to a mark associated with group and inode */
+extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
+/* attach the mark to both the group and the inode */
+extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
+/* given a mark, flag it to be freed when all references are dropped */
+extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
+/* run all the marks in a group, and flag them to be freed */
+extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
+extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
+extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
+
/* put here because inotify does some weird stuff when destroying watches */
extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
void *data, int data_is);
static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
{}
+
+static inline void __fsnotify_inode_delete(struct inode *inode)
+{}
+
#endif /* CONFIG_FSNOTIFY */
#endif /* __KERNEL __ */
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