ovl: simplify file splice

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>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index d1ae643..c2f574a 100644 (file)
--- 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_operations = {
 #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,