pidfs: remove pidfs_pid_valid()

The validation is now completely handled in path_from_stashed().

Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-9-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/pidfs.c

@@ -804,58 +804,8 @@ static int pidfs_export_permission(struct handle_to_path_ctx *ctx,
 	return 0;
 }
 
-static inline bool pidfs_pid_valid(struct pid *pid, const struct path *path,
-				   unsigned int flags)
-{
-	enum pid_type type;
-
-	if (flags & PIDFD_STALE)
-		return true;
-
-	/*
-	 * Make sure that if a pidfd is created PIDFD_INFO_EXIT
-	 * information will be available. So after an inode for the
-	 * pidfd has been allocated perform another check that the pid
-	 * is still alive. If it is exit information is available even
-	 * if the task gets reaped before the pidfd is returned to
-	 * userspace. The only exception are indicated by PIDFD_STALE:
-	 *
-	 * (1) The kernel is in the middle of task creation and thus no
-	 *     task linkage has been established yet.
-	 * (2) The caller knows @pid has been registered in pidfs at a
-	 *     time when the task was still alive.
-	 *
-	 * In both cases exit information will have been reported.
-	 */
-	if (flags & PIDFD_THREAD)
-		type = PIDTYPE_PID;
-	else
-		type = PIDTYPE_TGID;
-
-	/*
-	 * Since pidfs_exit() is called before struct pid's task linkage
-	 * is removed the case where the task got reaped but a dentry
-	 * was already attached to struct pid and exit information was
-	 * recorded and published can be handled correctly.
-	 */
-	if (unlikely(!pid_has_task(pid, type))) {
-		struct pidfs_attr *attr;
-
-		attr = READ_ONCE(pid->attr);
-		if (!attr)
-			return false;
-		if (!READ_ONCE(attr->exit_info))
-			return false;
-	}
-
-	return true;
-}
-
 static struct file *pidfs_export_open(struct path *path, unsigned int oflags)
 {
-	if (!pidfs_pid_valid(d_inode(path->dentry)->i_private, path, oflags))
-		return ERR_PTR(-ESRCH);
-
 	/*
 	 * Clear O_LARGEFILE as open_by_handle_at() forces it and raise
 	 * O_RDWR as pidfds always are.
@@ -993,9 +943,6 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags)
 	if (ret < 0)
 		return ERR_PTR(ret);
 
-	if (!pidfs_pid_valid(pid, &path, flags))
-		return ERR_PTR(-ESRCH);
-
 	flags &= ~PIDFD_STALE;
 	flags |= O_RDWR;
 	pidfd_file = dentry_open(&path, flags, current_cred());