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proc: allow to mark /proc files permanent outside of fs/proc/

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Add proc_make_permanent() function to mark PDE as permanent to speed up
open/read/close (one alloc/free and lock/unlock less).

Enable it for built-in code and for compiled-in modules.
This function becomes nop magically in modular code.

		Note, note, note!

If built-in code creates and deletes PDEs dynamically (not in init
hook), then proc_make_permanent() must not be used.

It is intended for simple code:

	static int __init xxx_module_init(void)
	{
		g_pde = proc_create_single();
		proc_make_permanent(g_pde);
		return 0;
	}
	static void __exit xxx_module_exit(void)
	{
		remove_proc_entry(g_pde);
	}

If module is built-in then exit hook never executed and PDE is
permanent so it is OK to mark it as such.

If module is module then rmmod will yank PDE, but proc_make_permanent()
is nop and core /proc code will do everything right.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Link: https://patch.msgid.link/20260425220844.1763933-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Alexey Dobriyan 2026-04-26 00:08:42 +02:00 committed by Christian Brauner
parent 254f49634e
commit 912289ee83
3 changed files with 25 additions and 0 deletions
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10
fs/proc/generic.c
View File

@ -841,3 +841,13 @@ ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
kfree(buf);
return ret == 0 ? size : ret;
}
/*
* Not exported to modules:
* modules' /proc files aren't permanent because modules aren't permanent.
*/
void impl_proc_make_permanent(struct proc_dir_entry *pde)
{
if (pde)
pde_make_permanent(pde);
}

3
fs/proc/internal.h
View File

@ -79,8 +79,11 @@ static inline bool pde_is_permanent(const struct proc_dir_entry *pde)
return pde->flags & PROC_ENTRY_PERMANENT;
}
/* This is for builtin code, not even for modules which are compiled in. */
static inline void pde_make_permanent(struct proc_dir_entry *pde)
{
/* Ensure magic flag does something. */
static_assert(PROC_ENTRY_PERMANENT != 0);
pde->flags |= PROC_ENTRY_PERMANENT;
}

12
include/linux/proc_fs.h
View File

@ -248,4 +248,16 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
bool proc_ns_file(const struct file *file);
#if defined CONFIG_PROC_FS && !defined MODULE
void impl_proc_make_permanent(struct proc_dir_entry *pde);
#endif
static inline void proc_make_permanent(struct proc_dir_entry *pde)
{
/* Don't give matches to modules. */
#if defined CONFIG_PROC_FS && !defined MODULE
impl_proc_make_permanent(pde);
#endif
}
#endif /* _LINUX_PROC_FS_H */