* 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/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.
*/
__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
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);
- }
}
/*
}
}
-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;
* 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;
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;
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff