xfs: Reference count per-ag structures
Reference count the per-ag structures to ensure that we keep get/put
pairs balanced. Assert that the reference counts are zero at unmount
time to catch leaks. In future, reference counts will enable us to
safely remove perag structures by allowing us to detect when they
are no longer in use.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 6702bd8..18ae43f 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -196,8 +196,8 @@
#define XFS_PAGB_NUM_SLOTS 128
#endif
-typedef struct xfs_perag
-{
+typedef struct xfs_perag {
+ atomic_t pag_ref; /* perag reference count */
char pagf_init; /* this agf's entry is initialized */
char pagi_init; /* this agi's entry is initialized */
char pagf_metadata; /* the agf is preferred to be metadata */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index c04dd83..f241fec 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -215,6 +215,7 @@
for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
spin_lock(&mp->m_perag_lock);
pag = radix_tree_delete(&mp->m_perag_tree, agno);
+ ASSERT(atomic_read(&pag->pag_ref) == 0);
spin_unlock(&mp->m_perag_lock);
ASSERT(pag);
kmem_free(pag->pagb_list);
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index cfa7a5d..16b2212 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -384,7 +384,7 @@
}
/*
- * perag get/put wrappers for eventual ref counting
+ * perag get/put wrappers for ref counting
*/
static inline struct xfs_perag *
xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
@@ -393,6 +393,12 @@
spin_lock(&mp->m_perag_lock);
pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+ if (pag) {
+ ASSERT(atomic_read(&pag->pag_ref) >= 0);
+ /* catch leaks in the positive direction during testing */
+ ASSERT(atomic_read(&pag->pag_ref) < 1000);
+ atomic_inc(&pag->pag_ref);
+ }
spin_unlock(&mp->m_perag_lock);
return pag;
}
@@ -400,7 +406,8 @@
static inline void
xfs_perag_put(struct xfs_perag *pag)
{
- /* nothing to see here, move along */
+ ASSERT(atomic_read(&pag->pag_ref) > 0);
+ atomic_dec(&pag->pag_ref);
}
/*
