xfs: fix per-ag reference counting in inode reclaim tree walking

The walk fails to decrement the per-ag reference count when the
non-blocking walk fails to obtain the per-ag reclaim lock, leading
to an assert failure on debug kernels when unmounting a filesystem.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

2 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 37d33254981d..afb0d7cfad1c 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -853,6 +853,7 @@ restart:
                 if (trylock) {
                         if (!mutex_trylock(&pag->pag_ici_reclaim_lock)) {
                                 skipped++;
+                                xfs_perag_put(pag);
                                 continue;
                         }
                         first_index = pag->pag_ici_reclaim_cursor;
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index b1498ab5a399..19e9dfa1c254 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -275,6 +275,7 @@ xfs_free_perag(
                 pag = radix_tree_delete(&mp->m_perag_tree, agno);
                 spin_unlock(&mp->m_perag_lock);
                 ASSERT(pag);
+                ASSERT(atomic_read(&pag->pag_ref) == 0);
                 call_rcu(&pag->rcu_head, __xfs_free_perag);
         }
 }