[PATCH 5.4 45/61] ovl: add splice file read write helper

Sasha Levin
2021-08-24T17:17:46Z

From: Murphy Zhou <jencce.kernel@gmail.com>

[ Upstream commit 1a980b8cbf0059a5308eea61522f232fd03002e2 ]

Now overlayfs falls back to use default file splice read
and write, which is not compatiple with overlayfs, returning
EFAULT. xfstests generic/591 can reproduce part of this.

Tested this patch with xfstests auto group tests.

Signed-off-by: Murphy Zhou <jencce.kernel@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/overlayfs/file.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 7a08a576f7b2..ab5e92897270 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -9,6 +9,9 @@
#include <linux/xattr.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
+#include <linux/splice.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
#include "overlayfs.h"

static char ovl_whatisit(struct inode *inode, struct inode *realinode)
@@ -293,6 +296,48 @@ out_unlock:
return ret;
}

+static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ ssize_t ret;
+ struct fd real;
+ const struct cred *old_cred;
+
+ ret = ovl_real_fdget(in, &real);
+ if (ret)
+ return ret;
+
+ old_cred = ovl_override_creds(file_inode(in)->i_sb);
+ ret = generic_file_splice_read(real.file, ppos, pipe, len, flags);
+ revert_creds(old_cred);
+
+ ovl_file_accessed(in);
+ fdput(real);
+ return ret;
+}
+
+static ssize_t
+ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags)
+{
+ struct fd real;
+ const struct cred *old_cred;
+ ssize_t ret;
+
+ ret = ovl_real_fdget(out, &real);
+ if (ret)
+ return ret;
+
+ old_cred = ovl_override_creds(file_inode(out)->i_sb);
+ ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);
+ revert_creds(old_cred);
+
+ ovl_file_accessed(out);
+ fdput(real);
+ return ret;
+}
+
static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
struct fd real;
@@ -649,6 +694,8 @@ const struct file_operations ovl_file_operations = {
.fadvise = ovl_fadvise,
.unlocked_ioctl = ovl_ioctl,
.compat_ioctl = ovl_compat_ioctl,
+ .splice_read = ovl_splice_read,
+ .splice_write = ovl_splice_write,

.copy_file_range = ovl_copy_file_range,
.remap_file_range = ovl_remap_file_range,
--
2.30.2