From 2e13ba54a2682eea24918b87ad3edf70c2cf085b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Iago=20L=C3=B3pez=20Galeiras?= Date: Thu, 25 Jun 2015 15:00:57 -0700 Subject: [PATCH] fs, proc: introduce CONFIG_PROC_CHILDREN MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit 818411616baf ("fs, proc: introduce /proc//task//children entry") introduced the children entry for checkpoint restore and the file is only available on kernels configured with CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS) because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE. However, the children proc file is useful outside of checkpoint restore. I would like to use it in rkt. The rkt process exec() another program it does not control, and that other program will fork()+exec() a child process. I would like to find the pid of the child process from an external tool without iterating in /proc over all processes to find which one has a parent pid equal to rkt. This commit introduces CONFIG_PROC_CHILDREN and makes CONFIG_CHECKPOINT_RESTORE select it. This allows enabling /proc//task//children without needing to enable CONFIG_CHECKPOINT_RESTORE and CONFIG_EXPERT. Alban tested that /proc//task//children is present when the kernel is configured with CONFIG_PROC_CHILDREN=y but without CONFIG_CHECKPOINT_RESTORE Signed-off-by: Iago López Galeiras Tested-by: Alban Crequy Reviewed-by: Cyrill Gorcunov Cc: Oleg Nesterov Cc: Kees Cook Cc: Pavel Emelyanov Cc: Serge Hallyn Cc: KAMEZAWA Hiroyuki Cc: Alexander Viro Cc: Andy Lutomirski Cc: Djalal Harouni Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/Kconfig | 4 ++++ fs/proc/array.c | 4 ++-- fs/proc/base.c | 2 +- init/Kconfig | 1 + 4 files changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig index 2183fcf41d59..d751fcb637bb 100644 --- a/fs/proc/Kconfig +++ b/fs/proc/Kconfig @@ -71,3 +71,7 @@ config PROC_PAGE_MONITOR /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap, /proc/kpagecount, and /proc/kpageflags. Disabling these interfaces will reduce the size of the kernel by approximately 4kb. + +config PROC_CHILDREN + bool "Include /proc//task//children file" + default n diff --git a/fs/proc/array.c b/fs/proc/array.c index 3f57dac31ba6..ce065cf3104f 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -577,7 +577,7 @@ int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns, return 0; } -#ifdef CONFIG_CHECKPOINT_RESTORE +#ifdef CONFIG_PROC_CHILDREN static struct pid * get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos) { @@ -700,4 +700,4 @@ const struct file_operations proc_tid_children_operations = { .llseek = seq_lseek, .release = children_seq_release, }; -#endif /* CONFIG_CHECKPOINT_RESTORE */ +#endif /* CONFIG_PROC_CHILDREN */ diff --git a/fs/proc/base.c b/fs/proc/base.c index bd7a9affc14b..1d540b3f226f 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3109,7 +3109,7 @@ static const struct pid_entry tid_base_stuff[] = { ONE("stat", S_IRUGO, proc_tid_stat), ONE("statm", S_IRUGO, proc_pid_statm), REG("maps", S_IRUGO, proc_tid_maps_operations), -#ifdef CONFIG_CHECKPOINT_RESTORE +#ifdef CONFIG_PROC_CHILDREN REG("children", S_IRUGO, proc_tid_children_operations), #endif #ifdef CONFIG_NUMA diff --git a/init/Kconfig b/init/Kconfig index b999fa381bf9..6a930b7494ef 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1131,6 +1131,7 @@ endif # CGROUPS config CHECKPOINT_RESTORE bool "Checkpoint/restore support" if EXPERT + select PROC_CHILDREN default n help Enables additional kernel features in a sake of checkpoint/restore.