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fork: introduce kernel_clone()

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The old _do_fork() helper doesn't follow naming conventions of in-kernel
helpers for syscalls. The process creation cleanup in [1] didn't change the
name to something more reasonable mainly because _do_fork() was used in quite a
few places. So sending this as a separate series seemed the better strategy.

This commit does two things:
1. renames _do_fork() to kernel_clone() but keeps _do_fork() as a simple static
   inline wrapper around kernel_clone().
2. Changes the return type from long to pid_t. This aligns kernel_thread() and
   kernel_clone(). Also, the return value from kernel_clone that is surfaced in
   fork(), vfork(), clone(), and clone3() is taken from pid_vrn() which returns
   a pid_t too.

Follow-up patches will switch each caller of _do_fork() and each place where it
is referenced over to kernel_clone(). After all these changes are done, we can
remove _do_fork() completely and will only be left with kernel_clone().

[1]: 9ba27414f2 ("Merge tag 'fork-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux")

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200819104655.436656-2-christian.brauner@ubuntu.com
This commit is contained in:
Christian Brauner 2020-08-19 12:46:45 +02:00
parent 9123e3a74e
commit cad6967ac1
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 13 additions and 9 deletions
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6
include/linux/sched/task.h
View File

@ -83,7 +83,11 @@ extern void do_group_exit(int);
extern void exit_files(struct task_struct *); extern void exit_files(struct task_struct *);
extern void exit_itimers(struct signal_struct *); extern void exit_itimers(struct signal_struct *);
extern long _do_fork(struct kernel_clone_args *kargs); extern pid_t kernel_clone(struct kernel_clone_args *kargs);
static inline long _do_fork(struct kernel_clone_args *kargs)
{
return kernel_clone(kargs);
}
struct task_struct *fork_idle(int); struct task_struct *fork_idle(int);
struct mm_struct *copy_init_mm(void); struct mm_struct *copy_init_mm(void);
extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags); extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);

16
kernel/fork.c
View File

@ -2384,14 +2384,14 @@ struct mm_struct *copy_init_mm(void)
* *
* args->exit_signal is expected to be checked for sanity by the caller. * args->exit_signal is expected to be checked for sanity by the caller.
*/ */
long _do_fork(struct kernel_clone_args *args) pid_t kernel_clone(struct kernel_clone_args *args)
{ {
u64 clone_flags = args->flags; u64 clone_flags = args->flags;
struct completion vfork; struct completion vfork;
struct pid *pid; struct pid *pid;
struct task_struct *p; struct task_struct *p;
int trace = 0; int trace = 0;
long nr; pid_t nr;
/* /*
* For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
@ -2477,7 +2477,7 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
.stack_size = (unsigned long)arg, .stack_size = (unsigned long)arg,
}; };
return _do_fork(&args); return kernel_clone(&args);
} }
#ifdef __ARCH_WANT_SYS_FORK #ifdef __ARCH_WANT_SYS_FORK
@ -2488,7 +2488,7 @@ SYSCALL_DEFINE0(fork)
.exit_signal = SIGCHLD, .exit_signal = SIGCHLD,
}; };
return _do_fork(&args); return kernel_clone(&args);
#else #else
/* can not support in nommu mode */ /* can not support in nommu mode */
return -EINVAL; return -EINVAL;
@ -2504,7 +2504,7 @@ SYSCALL_DEFINE0(vfork)
.exit_signal = SIGCHLD, .exit_signal = SIGCHLD,
}; };
return _do_fork(&args); return kernel_clone(&args);
} }
#endif #endif
@ -2542,7 +2542,7 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
.tls = tls, .tls = tls,
}; };
return _do_fork(&args); return kernel_clone(&args);
} }
#endif #endif
@ -2700,7 +2700,7 @@ SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
if (!clone3_args_valid(&kargs)) if (!clone3_args_valid(&kargs))
return -EINVAL; return -EINVAL;
return _do_fork(&kargs); return kernel_clone(&kargs);
} }
#endif #endif
@ -2863,7 +2863,7 @@ int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
/* /*
* unshare allows a process to 'unshare' part of the process * unshare allows a process to 'unshare' part of the process
* context which was originally shared using clone. copy_* * context which was originally shared using clone. copy_*
* functions used by _do_fork() cannot be used here directly * functions used by kernel_clone() cannot be used here directly
* because they modify an inactive task_struct that is being * because they modify an inactive task_struct that is being
* constructed. Here we are modifying the current, active, * constructed. Here we are modifying the current, active,
* task_struct. * task_struct.