linux-kernel - [PATCH v2 16/35] ovl: add ovl

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Message-Id: <20180507083807.28792-17-mszeredi@redhat.com>
Date:   Mon,  7 May 2018 10:37:48 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     linux-unionfs@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 16/35] ovl: add ovl_mmap()

Implement stacked mmap.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 fs/overlayfs/file.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 419aa3f9967b..b75ee0a3655e 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -252,6 +252,33 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	return ret;
 }
 
+static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	int ret;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	/* transfer ref: */
+	fput(vma->vm_file);
+	vma->vm_file = get_file(real.file);
+	fdput(real);
+
+	if (!vma->vm_file->f_op->mmap)
+		return -ENODEV;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	ret = call_mmap(vma->vm_file, vma);
+	revert_creds(old_cred);
+
+	ovl_file_accessed(file);
+
+	return ret;
+}
+
 const struct file_operations ovl_file_operations = {
 	.open		= ovl_open,
 	.release	= ovl_release,
@@ -259,4 +286,5 @@ const struct file_operations ovl_file_operations = {
 	.read_iter	= ovl_read_iter,
 	.write_iter	= ovl_write_iter,
 	.fsync		= ovl_fsync,
+	.mmap		= ovl_mmap,
 };
-- 
2.14.3