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authorIago López Galeiras <iago@endocode.com>2015-06-25 15:00:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-25 17:00:37 -0700
commit2e13ba54a2682eea24918b87ad3edf70c2cf085b (patch)
treefaa1c51d66968fada40fc971c3c17d1a242c7857
parentc2c0bb44620dece7ec97e28167e32c343da22867 (diff)
downloadlinux-linaro-stable-2e13ba54a2682eea24918b87ad3edf70c2cf085b.tar.gz
fs, proc: introduce CONFIG_PROC_CHILDREN
Commit 818411616baf ("fs, proc: introduce /proc/<pid>/task/<tid>/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/<pid>/task/<tid>/children without needing to enable CONFIG_CHECKPOINT_RESTORE and CONFIG_EXPERT. Alban tested that /proc/<pid>/task/<tid>/children is present when the kernel is configured with CONFIG_PROC_CHILDREN=y but without CONFIG_CHECKPOINT_RESTORE Signed-off-by: Iago López Galeiras <iago@endocode.com> Tested-by: Alban Crequy <alban@endocode.com> Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Djalal Harouni <djalal@endocode.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/Kconfig4
-rw-r--r--fs/proc/array.c4
-rw-r--r--fs/proc/base.c2
-rw-r--r--init/Kconfig1
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/<pid>/task/<tid>/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.