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