[PATCH 11/13] fs: remove d_real_inode()

[Christian Brauner <brauner@kernel.org>]

All callers have been converted to d_real_data_inode() or
d_real_metadata_inode(). Remove d_real_inode() so that any user we
missed, or one that gets added in another tree, fails to build instead
of passing an ERR_PTR() from d_real() to d_inode().

Add a porting.rst entry.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 Documentation/filesystems/porting.rst | 10 ++++++++++
 include/linux/dcache.h                | 13 -------------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index c38f5df755bb5..28a24b702f2a6 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1422,3 +1422,13 @@ helpers take a const struct mnt_idmap *. mnt_idmap() and file_mnt_idmap()
 return one. The idmapping is immutable so nothing should have modified it
 anyway. References are taken and dropped via mnt_idmap_get() and
 mnt_idmap_put() as before, both accept a const pointer.
+
+---
+
+**mandatory**
+
+d_real_inode() is gone. d_real() can fail for D_REAL_DATA now and returns an
+ERR_PTR() then, e.g., when overlayfs can't look up the data of a metacopy file
+in a data-only layer. Use d_real_data_inode(), which returns the inode hosting
+the data or an ERR_PTR(), and handle the error. Use d_real_metadata_inode() for
+the inode hosting the metadata. That one never fails.
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 5b3b34d271bd0..2b15179e9baf9 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -654,19 +654,6 @@ static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type
 		return dentry;
 }
 
-/**
- * d_real_inode - Return the real inode hosting the data
- * @dentry: The dentry to query
- *
- * If dentry is on a union/overlay, then return the underlying, real inode.
- * Otherwise return d_inode().
- */
-static inline struct inode *d_real_inode(const struct dentry *dentry)
-{
-	/* This usage of d_real() results in const dentry */
-	return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA));
-}
-
 /**
  * d_real_data_inode - Return the real inode hosting the data
  * @dentry: The dentry to query

-- 
2.53.0