[PATCH RFC 05/12] vfs: factor file removal into a helper, no functional change

[Jonathan Flynn <jonathan.flynn@hammerspace.com>]

Move the body of vfs_unlink() into a static helper, __vfs_unlink(),
that calls the method it is passed in place of ->unlink(), or
->unlink() when passed NULL.  vfs_unlink() becomes a wrapper that
passes NULL, so every caller behaves exactly as before; its kerneldoc,
including the requirement that the caller hold the parent directory's
lock exclusive, does not change.

This prepares for a second removal method, called with the parent
directory's lock held shared, which a following patch adds.

Signed-off-by: Jonathan Flynn <jonathan.flynn@hammerspace.com>
---
 fs/namei.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index ce10a408d3..1b3a605ded 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5679,6 +5679,12 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
 	return filename_rmdir(AT_FDCWD, name);
 }
 
+static int __vfs_unlink(const struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry,
+			struct delegated_inode *delegated_inode,
+			int (*method)(struct inode *dir,
+				      struct dentry *dentry));
+
 /**
  * vfs_unlink - unlink a filesystem object
  * @idmap:	idmap of the mount the inode was found from
@@ -5706,6 +5712,20 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
  */
 int vfs_unlink(const struct mnt_idmap *idmap, struct inode *dir,
 	       struct dentry *dentry, struct delegated_inode *delegated_inode)
+{
+	return __vfs_unlink(idmap, dir, dentry, delegated_inode, NULL);
+}
+EXPORT_SYMBOL(vfs_unlink);
+
+/*
+ * The body of vfs_unlink().  @method, if not NULL, is called in place of
+ * dir->i_op->unlink(); vfs_unlink() passes NULL.
+ */
+static int __vfs_unlink(const struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry,
+			struct delegated_inode *delegated_inode,
+			int (*method)(struct inode *dir,
+				      struct dentry *dentry))
 {
 	struct inode *target = dentry->d_inode;
 	int error = may_delete_dentry(idmap, dir, dentry, false);
@@ -5730,7 +5750,10 @@ int vfs_unlink(const struct mnt_idmap *idmap, struct inode *dir,
 			error = try_break_deleg(target, 0, delegated_inode);
 			if (error)
 				goto out;
-			error = dir->i_op->unlink(dir, dentry);
+			if (method)
+				error = method(dir, dentry);
+			else
+				error = dir->i_op->unlink(dir, dentry);
 			if (!error) {
 				dont_mount(dentry);
 				detach_mounts(dentry);
@@ -5750,7 +5773,6 @@ int vfs_unlink(const struct mnt_idmap *idmap, struct inode *dir,
 
 	return error;
 }
-EXPORT_SYMBOL(vfs_unlink);
 
 /*
  * Make sure that the actual truncation of the file will occur outside its
-- 
2.43.0