1 files changed, 219 insertions, 143 deletions

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 1f77c00af566..2d47f10f8bed 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
+ * Copyright (c) 2008 Dave Chinner
  * All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or
@@ -28,13 +29,13 @@
 #include "xfs_trans_priv.h"
 #include "xfs_error.h"
 
-STATIC void xfs_ail_insert(xfs_ail_t *, xfs_log_item_t *);
-STATIC xfs_log_item_t * xfs_ail_delete(xfs_ail_t *, xfs_log_item_t *);
-STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_t *);
-STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_t *, xfs_log_item_t *);
+STATIC void xfs_ail_insert(struct xfs_ail *, xfs_log_item_t *);
+STATIC xfs_log_item_t * xfs_ail_delete(struct xfs_ail *, xfs_log_item_t *);
+STATIC xfs_log_item_t * xfs_ail_min(struct xfs_ail *);
+STATIC xfs_log_item_t * xfs_ail_next(struct xfs_ail *, xfs_log_item_t *);
 
 #ifdef DEBUG
-STATIC void xfs_ail_check(xfs_ail_t *, xfs_log_item_t *);
+STATIC void xfs_ail_check(struct xfs_ail *, xfs_log_item_t *);
 #else
 #define	xfs_ail_check(a,l)
 #endif /* DEBUG */
@@ -50,20 +51,20 @@ STATIC void xfs_ail_check(xfs_ail_t *, xfs_log_item_t *);
  * lsn of the last item in the AIL.
  */
 xfs_lsn_t
-xfs_trans_tail_ail(
-	xfs_mount_t	*mp)
+xfs_trans_ail_tail(
+	struct xfs_ail	*ailp)
 {
 	xfs_lsn_t	lsn;
 	xfs_log_item_t	*lip;
 
-	spin_lock(&mp->m_ail_lock);
-	lip = xfs_ail_min(&mp->m_ail);
+	spin_lock(&ailp->xa_lock);
+	lip = xfs_ail_min(ailp);
 	if (lip == NULL) {
 		lsn = (xfs_lsn_t)0;
 	} else {
 		lsn = lip->li_lsn;
 	}
-	spin_unlock(&mp->m_ail_lock);
+	spin_unlock(&ailp->xa_lock);
 
 	return lsn;
 }
@@ -85,16 +86,125 @@ xfs_trans_tail_ail(
  * any of the objects, so the lock is not needed.
  */
 void
-xfs_trans_push_ail(
-	xfs_mount_t		*mp,
-	xfs_lsn_t		threshold_lsn)
+xfs_trans_ail_push(
+	struct xfs_ail	*ailp,
+	xfs_lsn_t	threshold_lsn)
 {
-	xfs_log_item_t		*lip;
+	xfs_log_item_t	*lip;
+
+	lip = xfs_ail_min(ailp);
+	if (lip && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {
+		if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0)
+			xfsaild_wakeup(ailp, threshold_lsn);
+	}
+}
+
+/*
+ * AIL traversal cursor initialisation.
+ *
+ * The cursor keeps track of where our current traversal is up
+ * to by tracking the next ƣtem in the list for us. However, for
+ * this to be safe, removing an object from the AIL needs to invalidate
+ * any cursor that points to it. hence the traversal cursor needs to
+ * be linked to the struct xfs_ail so that deletion can search all the
+ * active cursors for invalidation.
+ *
+ * We don't link the push cursor because it is embedded in the struct
+ * xfs_ail and hence easily findable.
+ */
+STATIC void
+xfs_trans_ail_cursor_init(
+	struct xfs_ail		*ailp,
+	struct xfs_ail_cursor	*cur)
+{
+	cur->item = NULL;
+	if (cur == &ailp->xa_cursors)
+		return;
+
+	cur->next = ailp->xa_cursors.next;
+	ailp->xa_cursors.next = cur;
+}
+
+/*
+ * Set the cursor to the next item, because when we look
+ * up the cursor the current item may have been freed.
+ */
+STATIC void
+xfs_trans_ail_cursor_set(
+	struct xfs_ail		*ailp,
+	struct xfs_ail_cursor	*cur,
+	struct xfs_log_item	*lip)
+{
+	if (lip)
+		cur->item = xfs_ail_next(ailp, lip);
+}
+
+/*
+ * Get the next item in the traversal and advance the cursor.
+ * If the cursor was invalidated (inidicated by a lip of 1),
+ * restart the traversal.
+ */
+struct xfs_log_item *
+xfs_trans_ail_cursor_next(
+	struct xfs_ail		*ailp,
+	struct xfs_ail_cursor	*cur)
+{
+	struct xfs_log_item	*lip = cur->item;
+
+	if ((__psint_t)lip & 1)
+		lip = xfs_ail_min(ailp);
+	xfs_trans_ail_cursor_set(ailp, cur, lip);
+	return lip;
+}
+
+/*
+ * Now that the traversal is complete, we need to remove the cursor
+ * from the list of traversing cursors. Avoid removing the embedded
+ * push cursor, but use the fact it is alway present to make the
+ * list deletion simple.
+ */
+void
+xfs_trans_ail_cursor_done(
+	struct xfs_ail		*ailp,
+	struct xfs_ail_cursor	*done)
+{
+	struct xfs_ail_cursor	*prev = NULL;
+	struct xfs_ail_cursor	*cur;
+
+	done->item = NULL;
+	if (done == &ailp->xa_cursors)
+		return;
+	prev = &ailp->xa_cursors;
+	for (cur = prev->next; cur; prev = cur, cur = prev->next) {
+		if (cur == done) {
+			prev->next = cur->next;
+			break;
+		}
+	}
+	ASSERT(cur);
+}
+
+/*
+ * Invalidate any cursor that is pointing to this item. This is
+ * called when an item is removed from the AIL. Any cursor pointing
+ * to this object is now invalid and the traversal needs to be
+ * terminated so it doesn't reference a freed object. We set the
+ * cursor item to a value of 1 so we can distinguish between an
+ * invalidation and the end of the list when getting the next item
+ * from the cursor.
+ */
+STATIC void
+xfs_trans_ail_cursor_clear(
+	struct xfs_ail		*ailp,
+	struct xfs_log_item	*lip)
+{
+	struct xfs_ail_cursor	*cur;
 
-	lip = xfs_ail_min(&mp->m_ail);
-	if (lip && !XFS_FORCED_SHUTDOWN(mp)) {
-		if (XFS_LSN_CMP(threshold_lsn, mp->m_ail.xa_target) > 0)
-			xfsaild_wakeup(mp, threshold_lsn);
+	/* need to search all cursors */
+	for (cur = &ailp->xa_cursors; cur; cur = cur->next) {
+		if (cur->item == lip)
+			cur->item = (struct xfs_log_item *)
+					((__psint_t)cur->item | 1);
 	}
 }
 
@@ -103,25 +213,27 @@ xfs_trans_push_ail(
  * Return the current tree generation number for use
  * in calls to xfs_trans_next_ail().
  */
-STATIC xfs_log_item_t *
-xfs_trans_first_push_ail(
-	xfs_mount_t	*mp,
-	int		*gen,
-	xfs_lsn_t	lsn)
+xfs_log_item_t *
+xfs_trans_ail_cursor_first(
+	struct xfs_ail		*ailp,
+	struct xfs_ail_cursor	*cur,
+	xfs_lsn_t		lsn)
 {
-	xfs_log_item_t	*lip;
+	xfs_log_item_t		*lip;
 
-	lip = xfs_ail_min(&mp->m_ail);
-	*gen = (int)mp->m_ail.xa_gen;
+	xfs_trans_ail_cursor_init(ailp, cur);
+	lip = xfs_ail_min(ailp);
 	if (lsn == 0)
-		return lip;
+		goto out;
 
-	list_for_each_entry(lip, &mp->m_ail.xa_ail, li_ail) {
+	list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
 		if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
-			return lip;
+			goto out;
 	}
-
-	return NULL;
+	lip = NULL;
+out:
+	xfs_trans_ail_cursor_set(ailp, cur, lip);
+	return lip;
 }
 
 /*
@@ -129,29 +241,29 @@ xfs_trans_first_push_ail(
  */
 long
 xfsaild_push(
-	xfs_mount_t	*mp,
+	struct xfs_ail	*ailp,
 	xfs_lsn_t	*last_lsn)
 {
 	long		tout = 1000; /* milliseconds */
 	xfs_lsn_t	last_pushed_lsn = *last_lsn;
-	xfs_lsn_t	target =  mp->m_ail.xa_target;
+	xfs_lsn_t	target =  ailp->xa_target;
 	xfs_lsn_t	lsn;
 	xfs_log_item_t	*lip;
-	int		gen;
-	int		restarts;
 	int		flush_log, count, stuck;
+	xfs_mount_t	*mp = ailp->xa_mount;
+	struct xfs_ail_cursor	*cur = &ailp->xa_cursors;
 
-#define	XFS_TRANS_PUSH_AIL_RESTARTS	10
-
-	spin_lock(&mp->m_ail_lock);
-	lip = xfs_trans_first_push_ail(mp, &gen, *last_lsn);
+	spin_lock(&ailp->xa_lock);
+	xfs_trans_ail_cursor_init(ailp, cur);
+	lip = xfs_trans_ail_cursor_first(ailp, cur, *last_lsn);
 	if (!lip || XFS_FORCED_SHUTDOWN(mp)) {
 		/*
 		 * AIL is empty or our push has reached the end.
 		 */
-		spin_unlock(&mp->m_ail_lock);
+		xfs_trans_ail_cursor_done(ailp, cur);
+		spin_unlock(&ailp->xa_lock);
 		last_pushed_lsn = 0;
-		goto out;
+		return tout;
 	}
 
 	XFS_STATS_INC(xs_push_ail);
@@ -169,7 +281,7 @@ xfsaild_push(
 	 */
 	tout = 10;
 	lsn = lip->li_lsn;
-	flush_log = stuck = count = restarts = 0;
+	flush_log = stuck = count = 0;
 	while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
 		int	lock_result;
 		/*
@@ -184,7 +296,7 @@ xfsaild_push(
 		 * skip to the next item in the list.
 		 */
 		lock_result = IOP_TRYLOCK(lip);
-		spin_unlock(&mp->m_ail_lock);
+		spin_unlock(&ailp->xa_lock);
 		switch (lock_result) {
 		case XFS_ITEM_SUCCESS:
 			XFS_STATS_INC(xs_push_ail_success);
@@ -221,7 +333,7 @@ xfsaild_push(
 			break;
 		}
 
-		spin_lock(&mp->m_ail_lock);
+		spin_lock(&ailp->xa_lock);
 		/* should we bother continuing? */
 		if (XFS_FORCED_SHUTDOWN(mp))
 			break;
@@ -244,14 +356,13 @@ xfsaild_push(
 		if (stuck > 100)
 			break;
 
-		lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
+		lip = xfs_trans_ail_cursor_next(ailp, cur);
 		if (lip == NULL)
 			break;
-		if (restarts > XFS_TRANS_PUSH_AIL_RESTARTS)
-			break;
 		lsn = lip->li_lsn;
 	}
-	spin_unlock(&mp->m_ail_lock);
+	xfs_trans_ail_cursor_done(ailp, cur);
+	spin_unlock(&ailp->xa_lock);
 
 	if (flush_log) {
 		/*
@@ -274,8 +385,7 @@ xfsaild_push(
 		 */
 		tout += 20;
 		last_pushed_lsn = 0;
-	} else if ((restarts > XFS_TRANS_PUSH_AIL_RESTARTS) ||
-		   ((stuck * 100) / count > 90)) {
+	} else if ((stuck * 100) / count > 90) {
 		/*
 		 * Either there is a lot of contention on the AIL or we
 		 * are stuck due to operations in progress. "Stuck" in this
@@ -287,7 +397,6 @@ xfsaild_push(
 		 */
 		tout += 10;
 	}
-out:
 	*last_lsn = last_pushed_lsn;
 	return tout;
 }	/* xfsaild_push */
@@ -303,7 +412,7 @@ out:
  */
 void
 xfs_trans_unlocked_item(
-	xfs_mount_t	*mp,
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip)
 {
 	xfs_log_item_t	*min_lip;
@@ -315,7 +424,7 @@ xfs_trans_unlocked_item(
 	 * over some potentially valid data.
 	 */
 	if (!(lip->li_flags & XFS_LI_IN_AIL) ||
-	    XFS_FORCED_SHUTDOWN(mp)) {
+	    XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {
 		return;
 	}
 
@@ -331,10 +440,10 @@ xfs_trans_unlocked_item(
 	 * the call to xfs_log_move_tail() doesn't do anything if there's
 	 * not enough free space to wake people up so we're safe calling it.
 	 */
-	min_lip = xfs_ail_min(&mp->m_ail);
+	min_lip = xfs_ail_min(ailp);
 
 	if (min_lip == lip)
-		xfs_log_move_tail(mp, 1);
+		xfs_log_move_tail(ailp->xa_mount, 1);
 }	/* xfs_trans_unlocked_item */
 
 
@@ -347,41 +456,37 @@ xfs_trans_unlocked_item(
  * we move in the AIL is the minimum one, update the tail lsn in the
  * log manager.
  *
- * Increment the AIL's generation count to indicate that the tree
- * has changed.
- *
  * This function must be called with the AIL lock held.  The lock
  * is dropped before returning.
  */
 void
-xfs_trans_update_ail(
-	xfs_mount_t	*mp,
+xfs_trans_ail_update(
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip,
-	xfs_lsn_t	lsn) __releases(mp->m_ail_lock)
+	xfs_lsn_t	lsn) __releases(ailp->xa_lock)
 {
-	xfs_log_item_t		*dlip=NULL;
+	xfs_log_item_t		*dlip = NULL;
 	xfs_log_item_t		*mlip;	/* ptr to minimum lip */
 
-	mlip = xfs_ail_min(&mp->m_ail);
+	mlip = xfs_ail_min(ailp);
 
 	if (lip->li_flags & XFS_LI_IN_AIL) {
-		dlip = xfs_ail_delete(&mp->m_ail, lip);
+		dlip = xfs_ail_delete(ailp, lip);
 		ASSERT(dlip == lip);
+		xfs_trans_ail_cursor_clear(ailp, dlip);
 	} else {
 		lip->li_flags |= XFS_LI_IN_AIL;
 	}
 
 	lip->li_lsn = lsn;
-
-	xfs_ail_insert(&mp->m_ail, lip);
-	mp->m_ail.xa_gen++;
+	xfs_ail_insert(ailp, lip);
 
 	if (mlip == dlip) {
-		mlip = xfs_ail_min(&mp->m_ail);
-		spin_unlock(&mp->m_ail_lock);
-		xfs_log_move_tail(mp, mlip->li_lsn);
+		mlip = xfs_ail_min(ailp);
+		spin_unlock(&ailp->xa_lock);
+		xfs_log_move_tail(ailp->xa_mount, mlip->li_lsn);
 	} else {
-		spin_unlock(&mp->m_ail_lock);
+		spin_unlock(&ailp->xa_lock);
 	}
 
 
@@ -403,29 +508,30 @@ xfs_trans_update_ail(
  * is dropped before returning.
  */
 void
-xfs_trans_delete_ail(
-	xfs_mount_t	*mp,
-	xfs_log_item_t	*lip) __releases(mp->m_ail_lock)
+xfs_trans_ail_delete(
+	struct xfs_ail	*ailp,
+	xfs_log_item_t	*lip) __releases(ailp->xa_lock)
 {
 	xfs_log_item_t		*dlip;
 	xfs_log_item_t		*mlip;
 
 	if (lip->li_flags & XFS_LI_IN_AIL) {
-		mlip = xfs_ail_min(&mp->m_ail);
-		dlip = xfs_ail_delete(&mp->m_ail, lip);
+		mlip = xfs_ail_min(ailp);
+		dlip = xfs_ail_delete(ailp, lip);
 		ASSERT(dlip == lip);
+		xfs_trans_ail_cursor_clear(ailp, dlip);
 
 
 		lip->li_flags &= ~XFS_LI_IN_AIL;
 		lip->li_lsn = 0;
-		mp->m_ail.xa_gen++;
 
 		if (mlip == dlip) {
-			mlip = xfs_ail_min(&mp->m_ail);
-			spin_unlock(&mp->m_ail_lock);
-			xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
+			mlip = xfs_ail_min(ailp);
+			spin_unlock(&ailp->xa_lock);
+			xfs_log_move_tail(ailp->xa_mount,
+						(mlip ? mlip->li_lsn : 0));
 		} else {
-			spin_unlock(&mp->m_ail_lock);
+			spin_unlock(&ailp->xa_lock);
 		}
 	}
 	else {
@@ -433,13 +539,13 @@ xfs_trans_delete_ail(
 		 * If the file system is not being shutdown, we are in
 		 * serious trouble if we get to this stage.
 		 */
-		if (XFS_FORCED_SHUTDOWN(mp))
-			spin_unlock(&mp->m_ail_lock);
-		else {
+		struct xfs_mount	*mp = ailp->xa_mount;
+
+		spin_unlock(&ailp->xa_lock);
+		if (!XFS_FORCED_SHUTDOWN(mp)) {
 			xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
 		"%s: attempting to delete a log item that is not in the AIL",
 					__func__);
-			spin_unlock(&mp->m_ail_lock);
 			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
 		}
 	}
@@ -448,56 +554,6 @@ xfs_trans_delete_ail(
 
 
 /*
- * Return the item in the AIL with the smallest lsn.
- * Return the current tree generation number for use
- * in calls to xfs_trans_next_ail().
- */
-xfs_log_item_t *
-xfs_trans_first_ail(
-	xfs_mount_t	*mp,
-	int		*gen)
-{
-	xfs_log_item_t	*lip;
-
-	lip = xfs_ail_min(&mp->m_ail);
-	*gen = (int)mp->m_ail.xa_gen;
-
-	return lip;
-}
-
-/*
- * If the generation count of the tree has not changed since the
- * caller last took something from the AIL, then return the elmt
- * in the tree which follows the one given.  If the count has changed,
- * then return the minimum elmt of the AIL and bump the restarts counter
- * if one is given.
- */
-xfs_log_item_t *
-xfs_trans_next_ail(
-	xfs_mount_t	*mp,
-	xfs_log_item_t	*lip,
-	int		*gen,
-	int		*restarts)
-{
-	xfs_log_item_t	*nlip;
-
-	ASSERT(mp && lip && gen);
-	if (mp->m_ail.xa_gen == *gen) {
-		nlip = xfs_ail_next(&mp->m_ail, lip);
-	} else {
-		nlip = xfs_ail_min(&mp->m_ail);
-		*gen = (int)mp->m_ail.xa_gen;
-		if (restarts != NULL) {
-			XFS_STATS_INC(xs_push_ail_restarts);
-			(*restarts)++;
-		}
-	}
-
-	return (nlip);
-}
-
-
-/*
  * The active item list (AIL) is a doubly linked list of log
  * items sorted by ascending lsn.  The base of the list is
  * a forw/back pointer pair embedded in the xfs mount structure.
@@ -515,15 +571,35 @@ int
 xfs_trans_ail_init(
 	xfs_mount_t	*mp)
 {
-	INIT_LIST_HEAD(&mp->m_ail.xa_ail);
-	return xfsaild_start(mp);
+	struct xfs_ail	*ailp;
+	int		error;
+
+	ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
+	if (!ailp)
+		return ENOMEM;
+
+	ailp->xa_mount = mp;
+	INIT_LIST_HEAD(&ailp->xa_ail);
+	spin_lock_init(&ailp->xa_lock);
+	error = xfsaild_start(ailp);
+	if (error)
+		goto out_free_ailp;
+	mp->m_ail = ailp;
+	return 0;
+
+out_free_ailp:
+	kmem_free(ailp);
+	return error;
 }
 
 void
 xfs_trans_ail_destroy(
 	xfs_mount_t	*mp)
 {
-	xfsaild_stop(mp);
+	struct xfs_ail	*ailp = mp->m_ail;
+
+	xfsaild_stop(ailp);
+	kmem_free(ailp);
 }
 
 /*
@@ -534,7 +610,7 @@ xfs_trans_ail_destroy(
  */
 STATIC void
 xfs_ail_insert(
-	xfs_ail_t	*ailp,
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip)
 /* ARGSUSED */
 {
@@ -568,7 +644,7 @@ xfs_ail_insert(
 /*ARGSUSED*/
 STATIC xfs_log_item_t *
 xfs_ail_delete(
-	xfs_ail_t	*ailp,
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip)
 /* ARGSUSED */
 {
@@ -585,7 +661,7 @@ xfs_ail_delete(
  */
 STATIC xfs_log_item_t *
 xfs_ail_min(
-	xfs_ail_t	*ailp)
+	struct xfs_ail	*ailp)
 /* ARGSUSED */
 {
 	if (list_empty(&ailp->xa_ail))
@@ -601,7 +677,7 @@ xfs_ail_min(
  */
 STATIC xfs_log_item_t *
 xfs_ail_next(
-	xfs_ail_t	*ailp,
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip)
 /* ARGSUSED */
 {
@@ -617,7 +693,7 @@ xfs_ail_next(
  */
 STATIC void
 xfs_ail_check(
-	xfs_ail_t 	*ailp,
+	struct xfs_ail	*ailp,
 	xfs_log_item_t	*lip)
 {
 	xfs_log_item_t	*prev_lip;