Re: [PATCH 2/5] xfs: fix sparse warning in xfs_extent_busy_clear

[Christoph Hellwig <hch@infradead.org>]

So while this works it looks pretty ugly.  I'd rewrite the nested loop
as what it is: a nested loop.  Something like the patch below.  Only
compile tested so far, but I'll kick off a real test later.

diff --git a/fs/xfs/xfs_extent_busy.c b/fs/xfs/xfs_extent_busy.c
index 2ccde32c9a9e97..1334360128662a 100644
--- a/fs/xfs/xfs_extent_busy.c
+++ b/fs/xfs/xfs_extent_busy.c
@@ -533,21 +533,6 @@ xfs_extent_busy_clear_one(
 	kmem_free(busyp);
 }
 
-static void
-xfs_extent_busy_put_pag(
-	struct xfs_perag	*pag,
-	bool			wakeup)
-		__releases(pag->pagb_lock)
-{
-	if (wakeup) {
-		pag->pagb_gen++;
-		wake_up_all(&pag->pagb_wait);
-	}
-
-	spin_unlock(&pag->pagb_lock);
-	xfs_perag_put(pag);
-}
-
 /*
  * Remove all extents on the passed in list from the busy extents tree.
  * If do_discard is set skip extents that need to be discarded, and mark
@@ -559,32 +544,43 @@ xfs_extent_busy_clear(
 	struct list_head	*list,
 	bool			do_discard)
 {
-	struct xfs_extent_busy	*busyp, *n;
-	struct xfs_perag	*pag = NULL;
-	xfs_agnumber_t		agno = NULLAGNUMBER;
-	bool			wakeup = false;
-
-	list_for_each_entry_safe(busyp, n, list, list) {
-		if (busyp->agno != agno) {
-			if (pag)
-				xfs_extent_busy_put_pag(pag, wakeup);
-			agno = busyp->agno;
-			pag = xfs_perag_get(mp, agno);
-			spin_lock(&pag->pagb_lock);
-			wakeup = false;
-		}
+	struct xfs_extent_busy	*busyp;
 
-		if (do_discard && busyp->length &&
-		    !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD)) {
-			busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
-		} else {
-			xfs_extent_busy_clear_one(mp, pag, busyp);
-			wakeup = true;
-		}
-	}
+	busyp = list_first_entry_or_null(list, typeof(*busyp), list);
+	if (!busyp)
+		return;
+
+	do {
+		struct xfs_perag	*pag = xfs_perag_get(mp, busyp->agno);
+		bool			wakeup = false;
+		struct xfs_extent_busy	*next;
 
-	if (pag)
-		xfs_extent_busy_put_pag(pag, wakeup);
+		spin_lock(&pag->pagb_lock);
+		for (;;) {
+			next = list_next_entry(busyp, list);
+
+			if (do_discard && busyp->length &&
+			    !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD)) {
+				busyp->flags = XFS_EXTENT_BUSY_DISCARDED;
+			} else {
+				xfs_extent_busy_clear_one(mp, pag, busyp);
+				wakeup = true;
+			}
+	
+			if (list_entry_is_head(next, list, list) ||
+			    next->agno != pag->pag_agno)
+				break;
+			busyp = next;
+		}
+		if (wakeup) {
+			pag->pagb_gen++;
+			wake_up_all(&pag->pagb_wait);
+		}
+		spin_unlock(&pag->pagb_lock);
+		xfs_perag_put(pag);
+	
+		busyp = next;
+	} while (!list_entry_is_head(busyp, list, list));
 }
 
 /*