xfs: unwind xfs_extent_busy_clear

The current structure of xfs_extent_busy_clear that locks the first busy
extent in each AG and unlocks when switching to a new AG makes sparse
unhappy as the lock critical section tracking can't cope with taking the
lock conditionally and inside a loop.

Rewrite xfs_extent_busy_clear so that it has an outer loop only advancing
when moving to a new AG, and an inner loop that consumes busy extents for
the given AG to make life easier for sparse and to also make this logic
more obvious to humans.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

diff --git a/fs/xfs/xfs_extent_busy.c b/fs/xfs/xfs_extent_busy.c
index 6fbffa46e5e94bc9a31fcdd0904e48b6b7dd0b5a..a73e7c73b664c6bd5bafffb494c1a84924508ab1 100644 (file)
--- a/fs/xfs/xfs_extent_busy.c
+++ b/fs/xfs/xfs_extent_busy.c
@@ -540,21 +540,6 @@ xfs_extent_busy_clear_one(
        return true;
 }
 
-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
@@ -566,27 +551,33 @@ 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, *next;
 
-               if (xfs_extent_busy_clear_one(pag, busyp, do_discard))
-                       wakeup = true;
-       }
+       busyp = list_first_entry_or_null(list, typeof(*busyp), list);
+       if (!busyp)
+               return;
+
+       do {
+               bool                    wakeup = false;
+               struct xfs_perag        *pag;
 
-       if (pag)
-               xfs_extent_busy_put_pag(pag, wakeup);
+               pag = xfs_perag_get(mp, busyp->agno);
+               spin_lock(&pag->pagb_lock);
+               do {
+                       next = list_next_entry(busyp, list);
+                       if (xfs_extent_busy_clear_one(pag, busyp, do_discard))
+                               wakeup = true;
+                       busyp = next;
+               } while (!list_entry_is_head(busyp, list, list) &&
+                        busyp->agno == pag->pag_agno);
+
+               if (wakeup) {
+                       pag->pagb_gen++;
+                       wake_up_all(&pag->pagb_wait);
+               }
+               spin_unlock(&pag->pagb_lock);
+               xfs_perag_put(pag);
+       } while (!list_entry_is_head(busyp, list, list));
 }
 
 /*