new helper: open_with_fake_path() (2abc77af) · Commits · 戴 / test

open a file by given inode, faking ->f_path. Use with shitloads of caution - at the very least you'd damn better make sure that some dentry alias of that inode is pinned down by the path in question. Again, this is no general-purpose interface and I hope it will eventually go away. Right now overlayfs wants something like that, but nothing else should. Any out-of-tree code with bright idea of using this one *will* eventually get hurt, with zero notice and great delight on my part. I refuse to use EXPORT_SYMBOL_GPL(), especially in situations when it's really EXPORT_SYMBOL_DONT_USE_IT(), but don't take that export as "you are welcome to use it". Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

fs/open.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -925,6 +925,24 @@ struct file dentry_open(const struct path path, int flags,
		}
		EXPORT_SYMBOL(dentry_open);

		struct file open_with_fake_path(const struct path path, int flags,
		struct inode inode, const struct cred cred)
		{
		struct file *f = alloc_empty_file(flags, cred);
		if (!IS_ERR(f)) {
		int error;

		f->f_path = *path;
		error = do_dentry_open(f, inode, NULL);
		if (error) {
		fput(f);
		f = ERR_PTR(error);
		}
		}
		return f;
		}
		EXPORT_SYMBOL(open_with_fake_path);

		static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
		{
		int lookup_flags = 0;

include/linux/fs.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -2424,6 +2424,8 @@ extern struct file filp_open(const char , int, umode_t);
		extern struct file file_open_root(struct dentry , struct vfsmount *,
		const char *, int, umode_t);
		extern struct file * dentry_open(const struct path , int, const struct cred );
		extern struct file * open_with_fake_path(const struct path *, int,
		struct inode, const struct cred );
		static inline struct file file_clone_open(struct file file)
		{
		return dentry_open(&file->f_path, file->f_flags, file->f_cred);

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