Don't bother with redoing rw_verify_area() from default_file_splice_from()

default_file_splice_from() ends up calling vfs_write() (via very convoluted
callchain).  It's an overkill, since we already have done rw_verify_area()
in the caller by the time we call vfs_write() we are under set_fs(KERNEL_DS),
so access_ok() is also pointless.  Add a new helper (__kernel_write()),
use it instead of kernel_write() in there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 718bd0056384..29e394e49ddd 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -31,6 +31,7 @@
 #include <linux/security.h>
 #include <linux/gfp.h>
 #include <linux/socket.h>
+#include "internal.h"
 
 /*
  * Attempt to steal a page from a pipe buffer. This should perhaps go into
@@ -1048,9 +1049,10 @@ static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 {
         int ret;
         void *data;
+        loff_t tmp = sd->pos;
 
         data = buf->ops->map(pipe, buf, 0);
-        ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
+        ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
         buf->ops->unmap(pipe, buf, data);
 
         return ret;