[PATCH RFC v2 04/28] vfs: allow mkdir to wait for delegation break on parent

[Jeff Layton <jlayton@kernel.org>]

In order to add directory delegation support, we need to break
delegations on the parent whenever there is going to be a change in the
directory.

Rename the existing vfs_mkdir to __vfs_mkdir, make it static and add a
new delegated_inode parameter. Add a new exported vfs_mkdir wrapper
around it that passes a NULL pointer for delegated_inode.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/namei.c | 67 +++++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 0fea12860036162c01a291558e068fde9c986142..7c9e237ed1b1a535934ffe5e523424bb035e7ae0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4318,29 +4318,9 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
 	return do_mknodat(AT_FDCWD, getname(filename), mode, dev);
 }
 
-/**
- * vfs_mkdir - create directory returning correct dentry if possible
- * @idmap:	idmap of the mount the inode was found from
- * @dir:	inode of the parent directory
- * @dentry:	dentry of the child directory
- * @mode:	mode of the child directory
- *
- * Create a directory.
- *
- * If the inode has been found through an idmapped mount the idmap of
- * the vfsmount must be passed through @idmap. This function will then take
- * care to map the inode according to @idmap before checking permissions.
- * On non-idmapped mounts or if permission checking is to be performed on the
- * raw inode simply pass @nop_mnt_idmap.
- *
- * In the event that the filesystem does not use the *@dentry but leaves it
- * negative or unhashes it and possibly splices a different one returning it,
- * the original dentry is dput() and the alternate is returned.
- *
- * In case of an error the dentry is dput() and an ERR_PTR() is returned.
- */
-struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
-			 struct dentry *dentry, umode_t mode)
+static struct dentry *__vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+				  struct dentry *dentry, umode_t mode,
+				  struct inode **delegated_inode)
 {
 	int error;
 	unsigned max_links = dir->i_sb->s_max_links;
@@ -4363,6 +4343,10 @@ struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	if (max_links && dir->i_nlink >= max_links)
 		goto err;
 
+	error = try_break_deleg(dir, delegated_inode);
+	if (error)
+		goto err;
+
 	de = dir->i_op->mkdir(idmap, dir, dentry, mode);
 	error = PTR_ERR(de);
 	if (IS_ERR(de))
@@ -4378,6 +4362,33 @@ struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	dput(dentry);
 	return ERR_PTR(error);
 }
+
+/**
+ * vfs_mkdir - create directory returning correct dentry if possible
+ * @idmap:	idmap of the mount the inode was found from
+ * @dir:	inode of the parent directory
+ * @dentry:	dentry of the child directory
+ * @mode:	mode of the child directory
+ *
+ * Create a directory.
+ *
+ * If the inode has been found through an idmapped mount the idmap of
+ * the vfsmount must be passed through @idmap. This function will then take
+ * care to map the inode according to @idmap before checking permissions.
+ * On non-idmapped mounts or if permission checking is to be performed on the
+ * raw inode simply pass @nop_mnt_idmap.
+ *
+ * In the event that the filesystem does not use the *@dentry but leaves it
+ * negative or unhashes it and possibly splices a different one returning it,
+ * the original dentry is dput() and the alternate is returned.
+ *
+ * In case of an error the dentry is dput() and an ERR_PTR() is returned.
+ */
+struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+			 struct dentry *dentry, umode_t mode)
+{
+	return __vfs_mkdir(idmap, dir, dentry, mode, NULL);
+}
 EXPORT_SYMBOL(vfs_mkdir);
 
 int do_mkdirat(int dfd, struct filename *name, umode_t mode)
@@ -4386,6 +4397,7 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode)
 	struct path path;
 	int error;
 	unsigned int lookup_flags = LOOKUP_DIRECTORY;
+	struct inode *delegated_inode = NULL;
 
 retry:
 	dentry = filename_create(dfd, name, &path, lookup_flags);
@@ -4396,12 +4408,17 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode)
 	error = security_path_mkdir(&path, dentry,
 			mode_strip_umask(path.dentry->d_inode, mode));
 	if (!error) {
-		dentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
-				  dentry, mode);
+		dentry = __vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
+				     dentry, mode, &delegated_inode);
 		if (IS_ERR(dentry))
 			error = PTR_ERR(dentry);
 	}
 	done_path_create(&path, dentry);
+	if (delegated_inode) {
+		error = break_deleg_wait(&delegated_inode);
+		if (!error)
+			goto retry;
+	}
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;

-- 
2.49.0