splice: fix unexpected size truncation

@splice_desc.total_len is 32 bit(unsigned int) which is used to store the
size passed from userspace which is 64 bit(size_t) so that the size is
unexpectedly truncated

That means vmsplice can not work if the size passed from userspace is >=
4G, for example, we noticed in vmsplice, splice-reader does not do
anything and splice-writer is waiting for available buffer forever if the
size is 4G

Fix it by extending @splice_desc.total_len to 64 bits as well

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/splice.h b/include/linux/splice.h
index 74575cbf2d6f..0e43906d2fda 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -24,7 +24,8 @@
  * Passed to the actors
  */
 struct splice_desc {
-        unsigned int len, total_len;    /* current and remaining length */
+        size_t total_len;               /* remaining length */
+        unsigned int len;               /* current length */
         unsigned int flags;             /* splice flags */
         /*
          * actor() private data