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pid: add pidfd_get_task() helper

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The number of system calls making use of pidfds is constantly
increasing. Some of those new system calls duplicate the code to turn a
pidfd into task_struct it refers to. Give them a simple helper for this.

Link: https://lore.kernel.org/r/20211004125050.1153693-2-christian.brauner@ubuntu.com
Link: https://lore.kernel.org/r/20211011133245.1703103-2-brauner@kernel.org
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Matthew Bobrowski <repnop@google.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Reviewed-by: Matthew Bobrowski <repnop@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2021-10-11 15:32:44 +02:00
parent 64570fbc14
commit e9bdcdbf69
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 37 additions and 0 deletions
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1
include/linux/pid.h
View File

@ -78,6 +78,7 @@ struct file;
extern struct pid *pidfd_pid(const struct file *file);
struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags);
struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags);
int pidfd_create(struct pid *pid, unsigned int flags);
static inline struct pid *get_pid(struct pid *pid)

36
kernel/pid.c
View File

@ -539,6 +539,42 @@ struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
return pid;
}
/**
* pidfd_get_task() - Get the task associated with a pidfd
*
* @pidfd: pidfd for which to get the task
* @flags: flags associated with this pidfd
*
* Return the task associated with @pidfd. The function takes a reference on
* the returned task. The caller is responsible for releasing that reference.
*
* Currently, the process identified by @pidfd is always a thread-group leader.
* This restriction currently exists for all aspects of pidfds including pidfd
* creation (CLONE_PIDFD cannot be used with CLONE_THREAD) and pidfd polling
* (only supports thread group leaders).
*
* Return: On success, the task_struct associated with the pidfd.
* On error, a negative errno number will be returned.
*/
struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags)
{
unsigned int f_flags;
struct pid *pid;
struct task_struct *task;
pid = pidfd_get_pid(pidfd, &f_flags);
if (IS_ERR(pid))
return ERR_CAST(pid);
task = get_pid_task(pid, PIDTYPE_TGID);
put_pid(pid);
if (!task)
return ERR_PTR(-ESRCH);
*flags = f_flags;
return task;
}
/**
* pidfd_create() - Create a new pid file descriptor.
*