[PATCH 2/2] proc: rewrite next_tgid()

Alexey Dobriyan
2026-04-16T16:44:03Z

* deduplicate "iter.tgid += 1" line,
Right now it is done once inside next_tgid() itself and second time
inside "for" loop.

* deduplicate next_tgid() call itself with different loop style:

auto it = make_tgid_iter();
while (next_tgid(&it)) {
...
}

gcc seems to inline it twice:

$ ./scripts/bloat-o-meter ../vmlinux-000 ../obj/vmlinux
add/remove: 0/1 grow/shrink: 1/0 up/down: 100/-245 (-145)
Function old new delta
proc_pid_readdir 531 631 +100
next_tgid 245 - -245

* make tgid_iter.pid_ns const
it never changes during readdir anyway
---
fs/proc/base.c | 57 +++++++++++++++++++++++++++++---------------------
1 file changed, 33 insertions(+), 24 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index f2db455dbbfd..f38ac943ec32 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3543,30 +3543,43 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
struct tgid_iter {
unsigned int tgid;
struct task_struct *task;
- struct pid_namespace *pid_ns;
+ struct pid_namespace *const pid_ns;
};

-static struct tgid_iter next_tgid(struct tgid_iter iter)
+static
+struct tgid_iter
+make_tgid_iter(unsigned int init_tgid, struct pid_namespace *pid_ns)
{
- struct pid *pid;
+ return (struct tgid_iter){
+ .tgid = init_tgid - 1,
+ .pid_ns = pid_ns,
+ };
+}
+
+static bool next_tgid(struct tgid_iter *it)
+{
+ if (it->task) {
+ put_task_struct(it->task);
+ it->task = NULL;
+ }

- if (iter.task)
- put_task_struct(iter.task);
rcu_read_lock();
-retry:
- iter.task = NULL;
- pid = find_ge_pid(iter.tgid, iter.pid_ns);
- if (pid) {
- iter.tgid = pid_nr_ns(pid, iter.pid_ns);
- iter.task = pid_task(pid, PIDTYPE_TGID);
- if (!iter.task) {
- iter.tgid += 1;
- goto retry;
+ while (1) {
+ it->tgid += 1;
+ const auto pid = find_ge_pid(it->tgid, it->pid_ns);
+ if (pid) {
+ it->tgid = pid_nr_ns(pid, it->pid_ns);
+ it->task = pid_task(pid, PIDTYPE_TGID);
+ if (it->task) {
+ get_task_struct(it->task);
+ rcu_read_unlock();
+ return true;
+ }
+ } else {
+ rcu_read_unlock();
+ return false;
}
- get_task_struct(iter.task);
}
- rcu_read_unlock();
- return iter;
}

#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)
@@ -3574,7 +3587,6 @@ static struct tgid_iter next_tgid(struct tgid_iter iter)
/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file *file, struct dir_context *ctx)
{
- struct tgid_iter iter;
struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb);
struct pid_namespace *pid_ns = proc_pid_ns(file_inode(file)->i_sb);
loff_t pos = ctx->pos;
@@ -3592,12 +3604,9 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
return 0;
ctx->pos = pos = pos + 1;
}
- iter.tgid = pos - TGID_OFFSET;
- iter.task = NULL;
- iter.pid_ns = pid_ns;
- for (iter = next_tgid(iter);
- iter.task;
- iter.tgid += 1, iter = next_tgid(iter)) {
+
+ auto iter = make_tgid_iter(pos - TGID_OFFSET, pid_ns);
+ while (next_tgid(&iter)) {