xfs: split inode AG walking into separate code for reclaim

The reclaim walk requires different locking and has a slightly
different walk algorithm, so separate it out so that it can be
optimised separately.

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

1 files changed, 26 insertions, 0 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 912101d280bf..d66e87c7c3a6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -219,6 +219,32 @@ xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
         return pag;
 }
 
+/*
+ * search from @first to find the next perag with the given tag set.
+ */
+struct xfs_perag *
+xfs_perag_get_tag(
+        struct xfs_mount        *mp,
+        xfs_agnumber_t          first,
+        int                     tag)
+{
+        struct xfs_perag        *pag;
+        int                     found;
+        int                     ref;
+
+        rcu_read_lock();
+        found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
+                                        (void **)&pag, first, 1, tag);
+        if (found <= 0) {
+                rcu_read_unlock();
+                return NULL;
+        }
+        ref = atomic_inc_return(&pag->pag_ref);
+        rcu_read_unlock();
+        trace_xfs_perag_get_tag(mp, pag->pag_agno, ref, _RET_IP_);
+        return pag;
+}
+
 void
 xfs_perag_put(struct xfs_perag *pag)
 {