[RFC PATCH v6 3/9] vfs: prepare vfs_creat|mkdir_no_perm for reuse in lookup_open()

[Jori Koolstra <jkoolstra@xs4all.nl>]

To implement O_CREAT|O_DIRECTORY we will have to repeat some of the
logic that is now in vfs_mkdir() (e.g. do error checks in the same
order). Separate this out in vfs_mkdir_no_perm(), which does all the
non-permission related work of vfs_mkdir(). Permission checking for the
lookup_open() path is timed differently because we may just be doing an
open and no create. Similar considerations give rise to
vfs_create_no_perm().

Moving the fsnotify_* calls also allows us to deal with this in one
place for each type of operation. This does mean that we also need
to move the fsnotify_* calls into atomic_open() for the atomic open
case, but this actually reduces duplicate code in open_last_lookups()
and dentry_create().

Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
---
 fs/namei.c | 105 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 68 insertions(+), 37 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 4cd132fe3981..2a35dd72ee96 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4171,6 +4171,24 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
 	return mode;
 }
 
+static inline
+int vfs_create_no_perm(struct mnt_idmap *idmap, struct dentry *dentry,
+		       umode_t mode, struct delegated_inode *di, bool excl)
+{
+	struct inode *dir = d_inode(dentry->d_parent);
+	int error;
+
+	error = try_break_deleg(dir, di);
+	if (error)
+		return error;
+
+	error = dir->i_op->create(idmap, dir, dentry, mode, excl);
+	if (!error)
+		fsnotify_create(dir, dentry);
+
+	return error;
+}
+
 /**
  * vfs_create - create new file
  * @idmap:	idmap of the mount the inode was found from
@@ -4203,13 +4221,8 @@ int vfs_create(struct mnt_idmap *idmap, struct dentry *dentry, umode_t mode,
 	error = security_inode_create(dir, dentry, mode);
 	if (error)
 		return error;
-	error = try_break_deleg(dir, di);
-	if (error)
-		return error;
-	error = dir->i_op->create(idmap, dir, dentry, mode, true);
-	if (!error)
-		fsnotify_create(dir, dentry);
-	return error;
+
+	return vfs_create_no_perm(idmap, dentry, mode, di, /*excl=*/ true);
 }
 EXPORT_SYMBOL(vfs_create);
 
@@ -4386,10 +4399,17 @@ static struct dentry *atomic_open(const struct path *path, struct dentry *dentry
 				error = -ENOENT;
 		}
 	}
+
 	if (error) {
 		dput(dentry);
 		dentry = ERR_PTR(error);
+	} else {
+		if (file->f_mode & FMODE_CREATED)
+			fsnotify_create(dir, dentry);
+		if (file->f_mode & FMODE_OPENED)
+			fsnotify_open(file);
 	}
+
 	return dentry;
 }
 
@@ -4522,6 +4542,8 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 						mode, open_flag & O_EXCL);
 		if (error)
 			goto out_dput;
+
+		fsnotify_create(dir_inode, dentry);
 	}
 
 	return dentry;
@@ -4610,13 +4632,9 @@ static const char *open_last_lookups(struct nameidata *nd,
 		inode_lock(dir->d_inode);
 	else
 		inode_lock_shared(dir->d_inode);
+
 	dentry = lookup_open(nd, file, op, got_write, &delegated_inode);
-	if (!IS_ERR(dentry)) {
-		if (file->f_mode & FMODE_CREATED)
-			fsnotify_create(dir->d_inode, dentry);
-		if (file->f_mode & FMODE_OPENED)
-			fsnotify_open(file);
-	}
+
 	if (open_flag & O_CREAT)
 		inode_unlock(dir->d_inode);
 	else
@@ -5051,13 +5069,6 @@ struct file *dentry_create(struct path *path, int flags, umode_t mode,
 		if (unlikely(create_error) && error == -ENOENT)
 			error = create_error;
 
-		if (!error) {
-			if (file->f_mode & FMODE_CREATED)
-				fsnotify_create(dir->d_inode, dentry);
-			if (file->f_mode & FMODE_OPENED)
-				fsnotify_open(file);
-		}
-
 		path->dentry = dentry;
 
 	} else {
@@ -5209,6 +5220,39 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
 	return filename_mknodat(AT_FDCWD, name, mode, dev);
 }
 
+static inline
+struct dentry *vfs_mkdir_no_perm(struct mnt_idmap *idmap, struct inode *dir,
+				 struct dentry *dentry, umode_t mode,
+				 struct delegated_inode *di)
+{
+	int error;
+	struct dentry *de;
+	unsigned max_links = dir->i_sb->s_max_links;
+
+	error = -EMLINK;
+	if (max_links && dir->i_nlink >= max_links)
+		goto err;
+
+	error = try_break_deleg(dir, di);
+	if (error)
+		goto err;
+
+	de = dir->i_op->mkdir(idmap, dir, dentry, mode);
+	if (IS_ERR(de)) {
+		error = PTR_ERR(de);
+		goto err;
+	}
+	if (de) {
+		dput(dentry);
+		dentry = de;
+	}
+	fsnotify_mkdir(dir, dentry);
+	return dentry;
+
+err:
+	return ERR_PTR(error);
+}
+
 /**
  * vfs_mkdir - create directory returning correct dentry if possible
  * @idmap:		idmap of the mount the inode was found from
@@ -5236,7 +5280,6 @@ struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 			 struct delegated_inode *delegated_inode)
 {
 	int error;
-	unsigned max_links = dir->i_sb->s_max_links;
 	struct dentry *de;
 
 	error = may_create_dentry(idmap, dir, dentry);
@@ -5252,24 +5295,12 @@ struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	if (error)
 		goto err;
 
-	error = -EMLINK;
-	if (max_links && dir->i_nlink >= max_links)
+	de = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode);
+	if (IS_ERR(de)) {
+		error = PTR_ERR(de);
 		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))
-		goto err;
-	if (de) {
-		dput(dentry);
-		dentry = de;
 	}
-	fsnotify_mkdir(dir, dentry);
-	return dentry;
+	return de;
 
 err:
 	end_creating(dentry);
-- 
2.54.0