fix iov_iter_advance() for ITER_PIPE

iov_iter_advance() needs to decrement iter->count by the number of bytes we'd moved beyond. Normal flavours do that, but ITER_PIPE doesn't and ITER_PIPE generic_file_read_iter() for O_DIRECT files ends up with a bogus fallback to page cache read, resulting in incorrect values for file offset and bytes read. Signed-off-by: Abhi Das <[email protected]> Signed-off-by: Al Viro <[email protected]>
kyagi · Nov 17, 2016 · 680bb94 · 680bb94
1 parent 4a59015
commit 680bb94
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
@@ -683,10 +683,11 @@ static void pipe_advance(struct iov_iter *i, size_t size)
 	struct pipe_inode_info *pipe = i->pipe;
 	struct pipe_buffer *buf;
 	int idx = i->idx;
-	size_t off = i->iov_offset;
+	size_t off = i->iov_offset, orig_sz;
 
 	if (unlikely(i->count < size))
 		size = i->count;
+	orig_sz = size;
 
 	if (size) {
 		if (off) /* make it relative to the beginning of buffer */
@@ -713,6 +714,7 @@ static void pipe_advance(struct iov_iter *i, size_t size)
 			pipe->nrbufs--;
 		}
 	}
+	i->count -= orig_sz;
 }
 
 void iov_iter_advance(struct iov_iter *i, size_t size)