fs: use a helper for opening kernel internal files

cachefiles uses kernel_open_tmpfile() to open kernel internal tmpfile
without accounting for nr_files.

cachefiles uses open_with_fake_path() for the same reason without the
need for a fake path.

Fork open_with_fake_path() to kernel_file_open() which only does the
noaccount part and use it in cachefiles.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Message-Id: <20230615112229.2143178-3-amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/fs/open.c b/fs/open.c
index 4478adcc4f3a..322e017bf480 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1116,6 +1116,39 @@ struct file *dentry_create(const struct path *path, int flags, umode_t mode,
 }
 EXPORT_SYMBOL(dentry_create);
 
+/**
+ * kernel_file_open - open a file for kernel internal use
+ * @path:	path of the file to open
+ * @flags:	open flags
+ * @inode:	the inode
+ * @cred:	credentials for open
+ *
+ * Open a file for use by in-kernel consumers. The file is not accounted
+ * against nr_files and must not be installed into the file descriptor
+ * table.
+ *
+ * Return: Opened file on success, an error pointer on failure.
+ */
+struct file *kernel_file_open(const struct path *path, int flags,
+				struct inode *inode, const struct cred *cred)
+{
+	struct file *f;
+	int error;
+
+	f = alloc_empty_file_noaccount(flags, cred);
+	if (IS_ERR(f))
+		return f;
+
+	f->f_path = *path;
+	error = do_dentry_open(f, inode, NULL);
+	if (error) {
+		fput(f);
+		f = ERR_PTR(error);
+	}
+	return f;
+}
+EXPORT_SYMBOL_GPL(kernel_file_open);
+
 struct file *open_with_fake_path(const struct path *path, int flags,
 				struct inode *inode, const struct cred *cred)
 {