47ssize_t preadv(
int fd,
const struct iovec *iov,
int iovcnt, off_t offset)
49 return vfs_readv(fd, iov, iovcnt, &offset);
ssize_t preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
ssize_t vfs_readv(int fd, const struct iovec *iov, int iovcnt, off_t *offset)
供系统调用