On Sat, Sep 06, 2025 at 02:57:05PM +1000, NeilBrown wrote:
> From: NeilBrown <neil@xxxxxxxxxx>
>
> proc_setup_self() and proc_setup_thread_self() are only called from
> proc_fill_super() which is before the filesystem is "live". So there is
> no need to lock the root directory when adding "self" and "thread-self".
>
> The locking rules are expected to change, so this locking will become
> anachronistic if we don't remove it.
Please, leave that one alone. FWIW, in tree-in-dcache branch (will push
tomorrow or on Sunday, once I sort the fucking #work.f_path out) there's
this:
commit fcac614cd72f0dfc45168817a139653877649507
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Mon Feb 26 01:55:36 2024 -0500
procfs: make /self and /thread_self dentries persistent
... 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@xxxxxxxxxxxxxxxxxx>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c667702dc69b..2d6a541ede27 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 96122e91c645..dadc621556d9 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -369,6 +369,7 @@ 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 06a297a27ba3..923ae40f19b9 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -261,17 +261,11 @@ 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(fs_info);
+ }
}
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 ea62201c74c4..de0edb431eac 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -63,8 +63,6 @@ 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;
