What is the “current” in Linux kernel source?

Question

I\'m studying about Linux kernel and I have a problem.

I see many Linux kernel source files have current->files. So what is the current?

Answer 1

It's a pointer to the current process (i.e. the process that issued the system call).

On x86, it's defined in arch/x86/include/current.h (similar files for other archs).

#ifndef _ASM_X86_CURRENT_H
#define _ASM_X86_CURRENT_H

#include 
#include 

#ifndef __ASSEMBLY__
struct task_struct;

DECLARE_PER_CPU(struct task_struct *, current_task);

static __always_inline struct task_struct *get_current(void)
{
    return percpu_read_stable(current_task);
}

#define current get_current()

#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_CURRENT_H */

More information in Linux Device Drivers chapter 2:

The current pointer refers to the user process currently executing. During the execution of a system call, such as open or read, the current process is the one that invoked the call. Kernel code can use process-specific information by using current, if it needs to do so. [...]