[PATCH v3 3/7] fs: enforce locking in icount_read(), add some commentary

[Mateusz Guzik <mjguzik@gmail.com>]

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
---
 include/linux/fs.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0cf27085a579..07363fce4406 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2225,13 +2225,21 @@ static inline void mark_inode_dirty_sync(struct inode *inode)
 	__mark_inode_dirty(inode, I_DIRTY_SYNC);
 }
 
+/*
+ * returns the refcount on the inode. it can change arbitrarily.
+ */
 static inline int icount_read_once(const struct inode *inode)
 {
 	return atomic_read(&inode->i_count);
 }
 
+/*
+ * returns the refcount on the inode. The lock guarantees no new references
+ * are added, but references can be dropped as long as the result is > 0.
+ */
 static inline int icount_read(const struct inode *inode)
 {
+	lockdep_assert_held(&inode->i_lock);
 	return atomic_read(&inode->i_count);
 }
 
-- 
2.48.1