vfs: merge .d_select_inode() into .d_real()

The two methods essentially do the same: find the real dentry/inode
belonging to an overlay dentry.  The difference is in the usage:

vfs_open() uses ->d_select_inode() and expects the function to perform
copy-up if necessary based on the open flags argument.

file_dentry() uses ->d_real() passing in the overlay dentry as well as the
underlying inode.

vfs_rename() uses ->d_select_inode() but passes zero flags.  ->d_real()
with a zero inode would have worked just as well here.

This patch merges the functionality of ->d_select_inode() into ->d_real()
by adding an 'open_flags' argument to the latter.

[Al Viro] Make the signature of d_real() match that of ->d_real() again.
And constify the inode argument, while we are at it.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

3 files changed, 25 insertions, 28 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 1dbeab6cf96e..e08cd94d7b26 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -325,36 +325,25 @@ static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
 	return true;
 }
 
-struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
+int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
 {
-	int err;
+	int err = 0;
 	struct path realpath;
 	enum ovl_path_type type;
 
-	if (d_is_dir(dentry))
-		return d_backing_inode(dentry);
-
 	type = ovl_path_real(dentry, &realpath);
 	if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
 		err = ovl_want_write(dentry);
-		if (err)
-			return ERR_PTR(err);
-
-		if (file_flags & O_TRUNC)
-			err = ovl_copy_up_truncate(dentry);
-		else
-			err = ovl_copy_up(dentry);
-		ovl_drop_write(dentry);
-		if (err)
-			return ERR_PTR(err);
-
-		ovl_path_upper(dentry, &realpath);
+		if (!err) {
+			if (file_flags & O_TRUNC)
+				err = ovl_copy_up_truncate(dentry);
+			else
+				err = ovl_copy_up(dentry);
+			ovl_drop_write(dentry);
+		}
 	}
 
-	if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
-		return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);
-
-	return d_backing_inode(realpath.dentry);
+	return err;
 }
 
 static const struct inode_operations ovl_file_inode_operations = {
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 4bd9b5ba8f42..6b9fd25c5ad4 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -179,7 +179,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
 		     const char *name, void *value, size_t size);
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 int ovl_removexattr(struct dentry *dentry, const char *name);
-struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags);
+int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags);
 
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 			    struct ovl_entry *oe);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ce02f46029da..035c176edf00 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -304,7 +304,9 @@ static void ovl_dentry_release(struct dentry *dentry)
 	}
 }
 
-static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)
+static struct dentry *ovl_d_real(struct dentry *dentry,
+				 const struct inode *inode,
+				 unsigned int open_flags)
 {
 	struct dentry *real;
 
@@ -314,6 +316,16 @@ static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)
 		goto bug;
 	}
 
+	if (d_is_negative(dentry))
+		return dentry;
+
+	if (open_flags) {
+		int err = ovl_open_maybe_copy_up(dentry, open_flags);
+
+		if (err)
+			return ERR_PTR(err);
+	}
+
 	real = ovl_dentry_upper(dentry);
 	if (real && (!inode || inode == d_inode(real)))
 		return real;
@@ -326,9 +338,7 @@ static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)
 		return real;
 
 	/* Handle recursion */
-	if (real->d_flags & DCACHE_OP_REAL)
-		return real->d_op->d_real(real, inode);
-
+	return d_real(real, inode, open_flags);
 bug:
 	WARN(1, "ovl_d_real(%pd4, %s:%lu\n): real dentry not found\n", dentry,
 	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
@@ -378,13 +388,11 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 
 static const struct dentry_operations ovl_dentry_operations = {
 	.d_release = ovl_dentry_release,
-	.d_select_inode = ovl_d_select_inode,
 	.d_real = ovl_d_real,
 };
 
 static const struct dentry_operations ovl_reval_dentry_operations = {
 	.d_release = ovl_dentry_release,
-	.d_select_inode = ovl_d_select_inode,
 	.d_real = ovl_d_real,
 	.d_revalidate = ovl_dentry_revalidate,
 	.d_weak_revalidate = ovl_dentry_weak_revalidate,