VFS: rename kern_path_locked() and related functions.

kern_path_locked() is now only used to prepare for removing an object
from the filesystem (and that is the only credible reason for wanting a
positive locked dentry).  Thus it corresponds to kern_path_create() and
so should have a corresponding name.

Unfortunately the name "kern_path_create" is somewhat misleading as it
doesn't actually create anything.  The recently added
simple_start_creating() provides a better pattern I believe.  The
"start" can be matched with "end" to bracket the creating or removing.

So this patch changes names:

 kern_path_locked -> start_removing_path
 kern_path_create -> start_creating_path
 user_path_create -> start_creating_user_path
 user_path_locked_at -> start_removing_user_path_at
 done_path_create -> end_creating_path

and also introduces end_removing_path() which is identical to
end_creating_path().

__start_removing_path (which was __kern_path_locked) is enhanced to
call mnt_want_write() for consistency with the start_creating_path().

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

Documentation/filesystems/porting.rst

@@ -1285,3 +1285,15 @@ rather than a VMA, as the VMA at this stage is not yet valid.
 The vm_area_desc provides the minimum required information for a filesystem
 to initialise state upon memory mapping of a file-backed region, and output
 parameters for the file system to set this state.
+
+---
+
+**mandatory**
+
+Several functions are renamed:
+
+-  kern_path_locked -> start_removing_path
+-  kern_path_create -> start_creating_path
+-  user_path_create -> start_creating_user_path
+-  user_path_locked_at -> start_removing_user_path_at
+-  done_path_create -> end_creating_path

arch/powerpc/platforms/cell/spufs/syscalls.c

@@ -67,11 +67,11 @@ static long do_spu_create(const char __user *pathname, unsigned int flags,
 	struct dentry *dentry;
 	int ret;
 
-	dentry = user_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_user_path(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
 	ret = PTR_ERR(dentry);
 	if (!IS_ERR(dentry)) {
 		ret = spufs_create(&path, dentry, flags, mode, neighbor);
-		done_path_create(&path, dentry);
+		end_creating_path(&path, dentry);
 	}
 
 	return ret;

drivers/base/devtmpfs.c

@@ -176,15 +176,15 @@ static int dev_mkdir(const char *name, umode_t mode)
 	struct dentry *dentry;
 	struct path path;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_path(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
 	dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode);
 	if (!IS_ERR(dentry))
 		/* mark as kernel-created inode */
 		d_inode(dentry)->i_private = &thread;
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return PTR_ERR_OR_ZERO(dentry);
 }
 
@@ -222,10 +222,10 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
 	struct path path;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, nodename, &path, 0);
 	if (dentry == ERR_PTR(-ENOENT)) {
 		create_path(nodename);
-		dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
+		dentry = start_creating_path(AT_FDCWD, nodename, &path, 0);
 	}
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
@@ -246,7 +246,7 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
 		/* mark as kernel-created inode */
 		d_inode(dentry)->i_private = &thread;
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return err;
 }
 
@@ -256,7 +256,7 @@ static int dev_rmdir(const char *name)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_locked(name, &parent);
+	dentry = start_removing_path(name, &parent);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	if (d_inode(dentry)->i_private == &thread)
@@ -265,9 +265,7 @@ static int dev_rmdir(const char *name)
 	else
 		err = -EPERM;
 
-	dput(dentry);
-	inode_unlock(d_inode(parent.dentry));
-	path_put(&parent);
+	end_removing_path(&parent, dentry);
 	return err;
 }
 
@@ -325,7 +323,7 @@ static int handle_remove(const char *nodename, struct device *dev)
 	int deleted = 0;
 	int err = 0;
 
-	dentry = kern_path_locked(nodename, &parent);
+	dentry = start_removing_path(nodename, &parent);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -349,10 +347,8 @@ static int handle_remove(const char *nodename, struct device *dev)
 		if (!err || err == -ENOENT)
 			deleted = 1;
 	}
-	dput(dentry);
-	inode_unlock(d_inode(parent.dentry));
+	end_removing_path(&parent, dentry);
 
-	path_put(&parent);
 	if (deleted && strchr(nodename, '/'))
 		delete_path(nodename);
 	return err;

fs/bcachefs/fs-ioctl.c

@@ -255,7 +255,7 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,
 		snapshot_src = inode_inum(to_bch_ei(src_path.dentry->d_inode));
 	}
 
-	dst_dentry = user_path_create(arg.dirfd,
+	dst_dentry = start_creating_user_path(arg.dirfd,
 			(const char __user *)(unsigned long)arg.dst_ptr,
 			&dst_path, lookup_flags);
 	error = PTR_ERR_OR_ZERO(dst_dentry);
@@ -314,7 +314,7 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,
 	d_instantiate(dst_dentry, &inode->v);
 	fsnotify_mkdir(dir, dst_dentry);
 err3:
-	done_path_create(&dst_path, dst_dentry);
+	end_creating_path(&dst_path, dst_dentry);
 err2:
 	if (arg.src_ptr)
 		path_put(&src_path);
@@ -334,7 +334,7 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
 	if (arg.flags)
 		return -EINVAL;
 
-	victim = user_path_locked_at(arg.dirfd, name, &path);
+	victim = start_removing_user_path_at(arg.dirfd, name, &path);
 	if (IS_ERR(victim))
 		return PTR_ERR(victim);
 
@@ -351,9 +351,7 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
 		d_invalidate(victim);
 	}
 err:
-	inode_unlock(dir);
-	dput(victim);
-	path_put(&path);
+	end_removing_path(&path, victim);
 	return ret;
 }
 

fs/init.c

@@ -149,7 +149,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
 	else if (!(S_ISBLK(mode) || S_ISCHR(mode)))
 		return -EINVAL;
 
-	dentry = kern_path_create(AT_FDCWD, filename, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, filename, &path, 0);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -158,7 +158,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
 	if (!error)
 		error = vfs_mknod(mnt_idmap(path.mnt), path.dentry->d_inode,
 				  dentry, mode, new_decode_dev(dev));
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 
@@ -173,7 +173,7 @@ int __init init_link(const char *oldname, const char *newname)
 	if (error)
 		return error;
 
-	new_dentry = kern_path_create(AT_FDCWD, newname, &new_path, 0);
+	new_dentry = start_creating_path(AT_FDCWD, newname, &new_path, 0);
 	error = PTR_ERR(new_dentry);
 	if (IS_ERR(new_dentry))
 		goto out;
@@ -191,7 +191,7 @@ int __init init_link(const char *oldname, const char *newname)
 	error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
 			 new_dentry, NULL);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 out:
 	path_put(&old_path);
 	return error;
@@ -203,14 +203,14 @@ int __init init_symlink(const char *oldname, const char *newname)
 	struct path path;
 	int error;
 
-	dentry = kern_path_create(AT_FDCWD, newname, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, newname, &path, 0);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	error = security_path_symlink(&path, dentry, oldname);
 	if (!error)
 		error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
 				    dentry, oldname);
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 
@@ -225,7 +225,8 @@ int __init init_mkdir(const char *pathname, umode_t mode)
 	struct path path;
 	int error;
 
-	dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_path(AT_FDCWD, pathname, &path,
+				     LOOKUP_DIRECTORY);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	mode = mode_strip_umask(d_inode(path.dentry), mode);
@@ -236,7 +237,7 @@ int __init init_mkdir(const char *pathname, umode_t mode)
 		if (IS_ERR(dentry))
 			error = PTR_ERR(dentry);
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 

fs/namei.c

@@ -2758,7 +2758,8 @@ static int filename_parentat(int dfd, struct filename *name,
 }
 
 /* does lookup, returns the object with parent locked */
-static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path *path)
+static struct dentry *__start_removing_path(int dfd, struct filename *name,
+					   struct path *path)
 {
 	struct path parent_path __free(path_put) = {};
 	struct dentry *d;
@@ -2770,15 +2771,26 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
 		return ERR_PTR(error);
 	if (unlikely(type != LAST_NORM))
 		return ERR_PTR(-EINVAL);
+	/* don't fail immediately if it's r/o, at least try to report other errors */
+	error = mnt_want_write(parent_path.mnt);
 	inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
 	d = lookup_one_qstr_excl(&last, parent_path.dentry, 0);
-	if (IS_ERR(d)) {
-		inode_unlock(parent_path.dentry->d_inode);
-		return d;
-	}
+	if (IS_ERR(d))
+		goto unlock;
+	if (error)
+		goto fail;
 	path->dentry = no_free_ptr(parent_path.dentry);
 	path->mnt = no_free_ptr(parent_path.mnt);
 	return d;
+
+fail:
+	dput(d);
+	d = ERR_PTR(error);
+unlock:
+	inode_unlock(parent_path.dentry->d_inode);
+	if (!error)
+		mnt_drop_write(parent_path.mnt);
+	return d;
 }
 
 /**
@@ -2816,24 +2828,26 @@ struct dentry *kern_path_parent(const char *name, struct path *path)
 	return d;
 }
 
-struct dentry *kern_path_locked(const char *name, struct path *path)
+struct dentry *start_removing_path(const char *name, struct path *path)
 {
 	struct filename *filename = getname_kernel(name);
-	struct dentry *res = __kern_path_locked(AT_FDCWD, filename, path);
+	struct dentry *res = __start_removing_path(AT_FDCWD, filename, path);
 
 	putname(filename);
 	return res;
 }
 
-struct dentry *user_path_locked_at(int dfd, const char __user *name, struct path *path)
+struct dentry *start_removing_user_path_at(int dfd,
+					   const char __user *name,
+					   struct path *path)
 {
 	struct filename *filename = getname(name);
-	struct dentry *res = __kern_path_locked(dfd, filename, path);
+	struct dentry *res = __start_removing_path(dfd, filename, path);
 
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(user_path_locked_at);
+EXPORT_SYMBOL(start_removing_user_path_at);
 
 int kern_path(const char *name, unsigned int flags, struct path *path)
 {
@@ -4223,37 +4237,38 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	return dentry;
 }
 
-struct dentry *kern_path_create(int dfd, const char *pathname,
-				struct path *path, unsigned int lookup_flags)
+struct dentry *start_creating_path(int dfd, const char *pathname,
+				   struct path *path, unsigned int lookup_flags)
 {
 	struct filename *filename = getname_kernel(pathname);
 	struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
 
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(kern_path_create);
+EXPORT_SYMBOL(start_creating_path);
 
-void done_path_create(struct path *path, struct dentry *dentry)
+void end_creating_path(struct path *path, struct dentry *dentry)
 {
 	if (!IS_ERR(dentry))
 		dput(dentry);
 	inode_unlock(path->dentry->d_inode);
 	mnt_drop_write(path->mnt);
 	path_put(path);
 }
-EXPORT_SYMBOL(done_path_create);
+EXPORT_SYMBOL(end_creating_path);
 
-inline struct dentry *user_path_create(int dfd, const char __user *pathname,
-				struct path *path, unsigned int lookup_flags)
+inline struct dentry *start_creating_user_path(
+	int dfd, const char __user *pathname,
+	struct path *path, unsigned int lookup_flags)
 {
 	struct filename *filename = getname(pathname);
 	struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
 
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(user_path_create);
+EXPORT_SYMBOL(start_creating_user_path);
 
 /**
  * vfs_mknod - create device node or file
@@ -4361,7 +4376,7 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 			break;
 	}
 out2:
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4465,7 +4480,7 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode)
 		if (IS_ERR(dentry))
 			error = PTR_ERR(dentry);
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4819,7 +4834,7 @@ int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
 	if (!error)
 		error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
 				    dentry, from->name);
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4988,7 +5003,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 	error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
 			 new_dentry, &delegated_inode);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 	if (delegated_inode) {
 		error = break_deleg_wait(&delegated_inode);
 		if (!error) {

fs/ocfs2/refcounttree.c

@@ -4418,7 +4418,7 @@ int ocfs2_reflink_ioctl(struct inode *inode,
 		return error;
 	}
 
-	new_dentry = user_path_create(AT_FDCWD, newname, &new_path, 0);
+	new_dentry = start_creating_user_path(AT_FDCWD, newname, &new_path, 0);
 	error = PTR_ERR(new_dentry);
 	if (IS_ERR(new_dentry)) {
 		mlog_errno(error);
@@ -4435,7 +4435,7 @@ int ocfs2_reflink_ioctl(struct inode *inode,
 				  d_inode(new_path.dentry),
 				  new_dentry, preserve);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 out:
 	path_put(&old_path);