[PATCH v4 09/54] procfs: make /self and /thread_self dentries persistent

Al Viro
2025-11-18T05:17:51Z

... and there's no need to remember those pointers anywhere - ->kill_sb()
no longer needs to bother since kill_anon_super() will take care of
them anyway and proc_pid_readdir() only wants the inumbers, which
we had in a couple of static variables all along.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/proc/base.c | 6 ++----
fs/proc/internal.h | 1 +
fs/proc/root.c | 14 ++++----------
fs/proc/self.c | 10 +++-------
fs/proc/thread_self.c | 11 +++--------
include/linux/proc_fs.h | 2 --
6 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 6299878e3d97..869677a26332 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3585,14 +3585,12 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
return 0;

if (pos == TGID_OFFSET - 2) {
- struct inode *inode = d_inode(fs_info->proc_self);
- if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
+ if (!dir_emit(ctx, "self", 4, self_inum, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
if (pos == TGID_OFFSET - 1) {
- struct inode *inode = d_inode(fs_info->proc_thread_self);
- if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
+ if (!dir_emit(ctx, "thread-self", 11, thread_self_inum, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index d1598576506c..c1e8eb984da8 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -373,6 +373,7 @@ static inline void proc_tty_init(void) {}
extern struct proc_dir_entry proc_root;

extern void proc_self_init(void);
+extern unsigned self_inum, thread_self_inum;

/*
* task_[no]mmu.c
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 1e24e085c7d5..d8ca41d823e4 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -347,17 +347,11 @@ static void proc_kill_sb(struct super_block *sb)
{
struct proc_fs_info *fs_info = proc_sb_info(sb);

- if (!fs_info) {
- kill_anon_super(sb);
- return;
- }
-
- dput(fs_info->proc_self);
- dput(fs_info->proc_thread_self);
-
kill_anon_super(sb);
- put_pid_ns(fs_info->pid_ns);
- kfree_rcu(fs_info, rcu);
+ if (fs_info) {
+ put_pid_ns(fs_info->pid_ns);
+ kfree_rcu(fs_info, rcu);
+ }
}

static struct file_system_type proc_fs_type = {
diff --git a/fs/proc/self.c b/fs/proc/self.c
index b46fbfd22681..62d2c0cfe35c 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -31,12 +31,11 @@ static const struct inode_operations proc_self_inode_operations = {
.get_link = proc_self_get_link,
};

-static unsigned self_inum __ro_after_init;
+unsigned self_inum __ro_after_init;

int proc_setup_self(struct super_block *s)
{
struct inode *root_inode = d_inode(s->s_root);
- struct proc_fs_info *fs_info = proc_sb_info(s);
struct dentry *self;
int ret = -ENOMEM;

@@ -51,18 +50,15 @@ int proc_setup_self(struct super_block *s)
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
inode->i_op = &proc_self_inode_operations;
- d_add(self, inode);
+ d_make_persistent(self, inode);
ret = 0;
- } else {
- dput(self);
}
+ dput(self);
}
inode_unlock(root_inode);

if (ret)
pr_err("proc_fill_super: can't allocate /proc/self\n");
- else
- fs_info->proc_self = self;

return ret;
}
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
index 0e5050d6ab64..d6113dbe58e0 100644
--- a/fs/proc/thread_self.c
+++ b/fs/proc/thread_self.c
@@ -31,12 +31,11 @@ static const struct inode_operations proc_thread_self_inode_operations = {
.get_link = proc_thread_self_get_link,
};

-static unsigned thread_self_inum __ro_after_init;
+unsigned thread_self_inum __ro_after_init;

int proc_setup_thread_self(struct super_block *s)
{
struct inode *root_inode = d_inode(s->s_root);
- struct proc_fs_info *fs_info = proc_sb_info(s);
struct dentry *thread_self;
int ret = -ENOMEM;

@@ -51,19 +50,15 @@ int proc_setup_thread_self(struct super_block *s)
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
inode->i_op = &proc_thread_self_inode_operations;
- d_add(thread_self, inode);
+ d_make_persistent(thread_self, inode);
ret = 0;
- } else {
- dput(thread_self);
}
+ dput(thread_self);
}
inode_unlock(root_inode);

if (ret)
pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
- else
- fs_info->proc_thread_self = thread_self;
-
return ret;
}

diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index f139377f4b31..19d1c5e5f335 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -66,8 +66,6 @@ enum proc_pidonly {

struct proc_fs_info {
struct pid_namespace *pid_ns;
- struct dentry *proc_self; /* For /proc/self */
- struct dentry *proc_thread_self; /* For /proc/thread-self */
kgid_t pid_gid;
enum proc_hidepid hide_pid;
enum proc_pidonly pidonly;
--
2.47.3