[PATCH 5.10 003/130] ovl: simplify file splice

Greg Kroah-Hartman
2021-12-06T15:35:41Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit 82a763e61e2b601309d696d4fa514c77d64ee1be upstream.

generic_file_splice_read() and iter_file_splice_write() will call back into
f_op->iter_read() and f_op->iter_write() respectively. These already do
the real file lookup and cred override. So the code in ovl_splice_read()
and ovl_splice_write() is redundant.

In addition the ovl_file_accessed() call in ovl_splice_write() is
incorrect, though probably harmless.

Fix by calling generic_file_splice_read() and iter_file_splice_write()
directly.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Stan Hu <stanhu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/overlayfs/file.c | 46 ++--------------------------------------------
1 file changed, 2 insertions(+), 44 deletions(-)

--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -422,48 +422,6 @@ 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;
@@ -772,8 +730,8 @@ const struct file_operations ovl_file_op
#ifdef CONFIG_COMPAT
.compat_ioctl = ovl_compat_ioctl,
#endif
- .splice_read = ovl_splice_read,
- .splice_write = ovl_splice_write,
+ .splice_read = generic_file_splice_read,
+ .splice_write = iter_file_splice_write,

.copy_file_range = ovl_copy_file_range,
.remap_file_range = ovl_remap_file_range,