* [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
@ 2025-04-09 19:20 Alexey Dobriyan
2025-04-09 20:27 ` Mateusz Guzik
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Alexey Dobriyan @ 2025-04-09 19:20 UTC (permalink / raw)
To: akpm, brauner; +Cc: Mateusz Guzik, linux-kernel, linux-fsdevel
From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
From: Alexey Dobriyan <adobriyan@gmail.com>
Date: Sat, 5 Apr 2025 14:50:10 +0300
Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
fs/proc/
From: Mateusz Guzik <mjguzik@gmail.com>
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.
Use it on /proc/filesystems to add a user.
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.
[adobriyan@gmail.com: unexport function (usual exporting is a bug)]
[adobriyan@gmail.com: rewrite changelog]
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
fs/filesystems.c | 4 +++-
fs/proc/generic.c | 12 ++++++++++++
fs/proc/internal.h | 3 +++
include/linux/proc_fs.h | 10 ++++++++++
4 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/filesystems.c b/fs/filesystems.c
index 58b9067b2391..81dcd0ddadb6 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -252,7 +252,9 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
static int __init proc_filesystems_init(void)
{
- proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
+ struct proc_dir_entry *pde =
+ proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
+ proc_make_permanent(pde);
return 0;
}
module_init(proc_filesystems_init);
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index a3e22803cddf..0342600c0172 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -826,3 +826,15 @@ 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);
+void impl_proc_make_permanent(struct proc_dir_entry *pde)
+{
+ if (pde) {
+ pde_make_permanent(pde);
+ }
+}
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 96122e91c645..885b1cd38020 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -80,8 +80,11 @@ 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;
}
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index ea62201c74c4..2d59f29b49eb 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -247,4 +247,14 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
bool proc_ns_file(const struct file *file);
+static inline void proc_make_permanent(struct proc_dir_entry *pde)
+{
+ /* Don't give matches to modules. */
+#if defined CONFIG_PROC_FS && !defined MODULE
+ /* This mess is created by defining "struct proc_dir_entry" elsewhere. */
+ void impl_proc_make_permanent(struct proc_dir_entry *pde);
+ impl_proc_make_permanent(pde);
+#endif
+}
+
#endif /* _LINUX_PROC_FS_H */
--
2.47.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
2025-04-09 19:20 [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/ Alexey Dobriyan
@ 2025-04-09 20:27 ` Mateusz Guzik
2025-04-09 21:35 ` Andrew Morton
2025-09-17 3:44 ` Mateusz Guzik
2 siblings, 0 replies; 6+ messages in thread
From: Mateusz Guzik @ 2025-04-09 20:27 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: akpm, brauner, linux-kernel, linux-fsdevel
On Wed, Apr 9, 2025 at 9:20 PM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
> From: Alexey Dobriyan <adobriyan@gmail.com>
> Date: Sat, 5 Apr 2025 14:50:10 +0300
> Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
> fs/proc/
>
> From: Mateusz Guzik <mjguzik@gmail.com>
>
> 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.
>
> Use it on /proc/filesystems to add a user.
>
> 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.
>
> [adobriyan@gmail.com: unexport function (usual exporting is a bug)]
> [adobriyan@gmail.com: rewrite changelog]
>
> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
> fs/filesystems.c | 4 +++-
> fs/proc/generic.c | 12 ++++++++++++
> fs/proc/internal.h | 3 +++
> include/linux/proc_fs.h | 10 ++++++++++
> 4 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/fs/filesystems.c b/fs/filesystems.c
> index 58b9067b2391..81dcd0ddadb6 100644
> --- a/fs/filesystems.c
> +++ b/fs/filesystems.c
> @@ -252,7 +252,9 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
>
> static int __init proc_filesystems_init(void)
> {
> - proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + struct proc_dir_entry *pde =
> + proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + proc_make_permanent(pde);
> return 0;
> }
> module_init(proc_filesystems_init);
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index a3e22803cddf..0342600c0172 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -826,3 +826,15 @@ 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);
> +void impl_proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + if (pde) {
> + pde_make_permanent(pde);
> + }
> +}
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 96122e91c645..885b1cd38020 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -80,8 +80,11 @@ 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;
> }
>
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index ea62201c74c4..2d59f29b49eb 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -247,4 +247,14 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
>
> bool proc_ns_file(const struct file *file);
>
> +static inline void proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + /* Don't give matches to modules. */
> +#if defined CONFIG_PROC_FS && !defined MODULE
> + /* This mess is created by defining "struct proc_dir_entry" elsewhere. */
> + void impl_proc_make_permanent(struct proc_dir_entry *pde);
> + impl_proc_make_permanent(pde);
> +#endif
> +}
> +
> #endif /* _LINUX_PROC_FS_H */
This diff should not be changing /proc/filesystems, that's for the
other patch to do.
So I think this patch is all you and my name needs to be dropped from
it, along with marking /proc/filesystems as permanent.
Given that you kept the name (proc_make_permanent), the
fs/filesystems.c side of things is identical so my first patch can be
just swapped for this one.
Alternatively I can resend the patchset with this (augmented as
described above).
--
Mateusz Guzik <mjguzik gmail.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
2025-04-09 19:20 [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/ Alexey Dobriyan
2025-04-09 20:27 ` Mateusz Guzik
@ 2025-04-09 21:35 ` Andrew Morton
2025-04-09 22:04 ` Mateusz Guzik
2025-05-07 9:48 ` Alexey Dobriyan
2025-09-17 3:44 ` Mateusz Guzik
2 siblings, 2 replies; 6+ messages in thread
From: Andrew Morton @ 2025-04-09 21:35 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: brauner, Mateusz Guzik, linux-kernel, linux-fsdevel
On Wed, 9 Apr 2025 22:20:13 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
> >From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
> From: Alexey Dobriyan <adobriyan@gmail.com>
> Date: Sat, 5 Apr 2025 14:50:10 +0300
> Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
> fs/proc/
>
> From: Mateusz Guzik <mjguzik@gmail.com>
>
> Add proc_make_permanent() function to mark PDE as permanent to speed up
> open/read/close (one alloc/free and lock/unlock less).
When proposing a speedup it is preferable to provide some benchmarking
results to help others understand the magnitude of that speedup.
> ...
>
> index 58b9067b2391..81dcd0ddadb6 100644
> --- a/fs/filesystems.c
> +++ b/fs/filesystems.c
> @@ -252,7 +252,9 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
>
> static int __init proc_filesystems_init(void)
> {
> - proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + struct proc_dir_entry *pde =
> + proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
To avoid the 80-column nasties, this is more pleasing:
struct proc_dir_entry *pde;
pde = proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + proc_make_permanent(pde);
> return 0;
> }
> module_init(proc_filesystems_init);
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index a3e22803cddf..0342600c0172 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -826,3 +826,15 @@ 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);
This declaration is unneeded, isn't it?
> +void impl_proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + if (pde) {
> + pde_make_permanent(pde);
> + }
Please let's be running checkpatch more often?
> +}
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 96122e91c645..885b1cd38020 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -80,8 +80,11 @@ 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);
Looks odd. What is this doing? The comment does a poor job of
explaining this!
> pde->flags |= PROC_ENTRY_PERMANENT;
> }
>
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index ea62201c74c4..2d59f29b49eb 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -247,4 +247,14 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
>
> bool proc_ns_file(const struct file *file);
>
> +static inline void proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + /* Don't give matches to modules. */
This comment is also mysterious (to me). Please expand upon it.
> +#if defined CONFIG_PROC_FS && !defined MODULE
> + /* This mess is created by defining "struct proc_dir_entry" elsewhere. */
Also mysterious.
> + void impl_proc_make_permanent(struct proc_dir_entry *pde);
Forward-declaring a function within a function in this manner is quite
unusual. Let's be conventional, please.
> + impl_proc_make_permanent(pde);
> +#endif
> +}
> +
> #endif /* _LINUX_PROC_FS_H */
> --
> 2.47.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
2025-04-09 21:35 ` Andrew Morton
@ 2025-04-09 22:04 ` Mateusz Guzik
2025-05-07 9:48 ` Alexey Dobriyan
1 sibling, 0 replies; 6+ messages in thread
From: Mateusz Guzik @ 2025-04-09 22:04 UTC (permalink / raw)
To: Andrew Morton; +Cc: Alexey Dobriyan, brauner, linux-kernel, linux-fsdevel
On Wed, Apr 9, 2025 at 11:35 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 9 Apr 2025 22:20:13 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > >From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
> > From: Alexey Dobriyan <adobriyan@gmail.com>
> > Date: Sat, 5 Apr 2025 14:50:10 +0300
> > Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
> > fs/proc/
> >
> > From: Mateusz Guzik <mjguzik@gmail.com>
> >
> > Add proc_make_permanent() function to mark PDE as permanent to speed up
> > open/read/close (one alloc/free and lock/unlock less).
>
> When proposing a speedup it is preferable to provide some benchmarking
> results to help others understand the magnitude of that speedup.
>
It's all in the original submission:
https://lore.kernel.org/linux-fsdevel/20250329192821.822253-3-mjguzik@gmail.com/
--
Mateusz Guzik <mjguzik gmail.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
2025-04-09 21:35 ` Andrew Morton
2025-04-09 22:04 ` Mateusz Guzik
@ 2025-05-07 9:48 ` Alexey Dobriyan
1 sibling, 0 replies; 6+ messages in thread
From: Alexey Dobriyan @ 2025-05-07 9:48 UTC (permalink / raw)
To: Andrew Morton; +Cc: brauner, Mateusz Guzik, linux-kernel, linux-fsdevel
On Wed, Apr 09, 2025 at 02:35:46PM -0700, Andrew Morton wrote:
> On Wed, 9 Apr 2025 22:20:13 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > >From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
> > From: Alexey Dobriyan <adobriyan@gmail.com>
> > Date: Sat, 5 Apr 2025 14:50:10 +0300
> > Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
> > fs/proc/
> >
> > From: Mateusz Guzik <mjguzik@gmail.com>
> >
> > Add proc_make_permanent() function to mark PDE as permanent to speed up
> > open/read/close (one alloc/free and lock/unlock less).
>
> When proposing a speedup it is preferable to provide some benchmarking
> results to help others understand the magnitude of that speedup.
>
> > ...
> >
> > index 58b9067b2391..81dcd0ddadb6 100644
> > --- a/fs/filesystems.c
> > +++ b/fs/filesystems.c
> > @@ -252,7 +252,9 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
> >
> > static int __init proc_filesystems_init(void)
> > {
> > - proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> > + struct proc_dir_entry *pde =
> > + proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
>
> To avoid the 80-column nasties, this is more pleasing:
It is inferior style, see below. BTW, how the kernel is still on 80 columns?
> struct proc_dir_entry *pde;
>
> pde = proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
>
>
> > + proc_make_permanent(pde);
> > return 0;
> > }
> > module_init(proc_filesystems_init);
> > diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> > index a3e22803cddf..0342600c0172 100644
> > --- a/fs/proc/generic.c
> > +++ b/fs/proc/generic.c
> > @@ -826,3 +826,15 @@ 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);
>
> This declaration is unneeded, isn't it?
It is necessary, but I need to make a comment, yes.
> > +void impl_proc_make_permanent(struct proc_dir_entry *pde)
> > +{
> > + if (pde) {
> > + pde_make_permanent(pde);
> > + }
>
> Please let's be running checkpatch more often?
No! I'd rather change kernel coding style.
> > --- a/fs/proc/internal.h
> > +++ b/fs/proc/internal.h
> > @@ -80,8 +80,11 @@ 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);
>
> Looks odd. What is this doing? The comment does a poor job of
> explaining this!
>
> > pde->flags |= PROC_ENTRY_PERMANENT;
> > }
> >
> > diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> > index ea62201c74c4..2d59f29b49eb 100644
> > --- a/include/linux/proc_fs.h
> > +++ b/include/linux/proc_fs.h
> > @@ -247,4 +247,14 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
> >
> > bool proc_ns_file(const struct file *file);
> >
> > +static inline void proc_make_permanent(struct proc_dir_entry *pde)
> > +{
> > + /* Don't give matches to modules. */
>
> This comment is also mysterious (to me). Please expand upon it.
>
> > +#if defined CONFIG_PROC_FS && !defined MODULE
> > + /* This mess is created by defining "struct proc_dir_entry" elsewhere. */
>
> Also mysterious.
>
> > + void impl_proc_make_permanent(struct proc_dir_entry *pde);
>
> Forward-declaring a function within a function in this manner is quite
> unusual. Let's be conventional, please.
>
> > + impl_proc_make_permanent(pde);
> > +#endif
> > +}
This patch tries to create semi-exported interface which does nothing
if module built as module is using it it but does something it built-in or
module built-in does. This is why all complications and prorotypes.
But let me change coding style first.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/
2025-04-09 19:20 [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/ Alexey Dobriyan
2025-04-09 20:27 ` Mateusz Guzik
2025-04-09 21:35 ` Andrew Morton
@ 2025-09-17 3:44 ` Mateusz Guzik
2 siblings, 0 replies; 6+ messages in thread
From: Mateusz Guzik @ 2025-09-17 3:44 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: akpm, brauner, linux-kernel, linux-fsdevel
Hi. This fell through the cracks.
Can you please resubmit your patch with my name dropped from it? It's
basically all you.
Alternatively perhaps Christian will be happy to do the edits?
After this is sorted out I'll resend my thing altering how the content
of the file is generated.
On Wed, Apr 9, 2025 at 9:20 PM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> From 06e2ff406942fef65b9c397a7f44478dd4b61451 Mon Sep 17 00:00:00 2001
> From: Alexey Dobriyan <adobriyan@gmail.com>
> Date: Sat, 5 Apr 2025 14:50:10 +0300
> Subject: [PATCH 1/1] proc: allow to mark /proc files permanent outside of
> fs/proc/
>
> From: Mateusz Guzik <mjguzik@gmail.com>
>
> 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.
>
> Use it on /proc/filesystems to add a user.
>
> 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.
>
> [adobriyan@gmail.com: unexport function (usual exporting is a bug)]
> [adobriyan@gmail.com: rewrite changelog]
>
> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
> fs/filesystems.c | 4 +++-
> fs/proc/generic.c | 12 ++++++++++++
> fs/proc/internal.h | 3 +++
> include/linux/proc_fs.h | 10 ++++++++++
> 4 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/fs/filesystems.c b/fs/filesystems.c
> index 58b9067b2391..81dcd0ddadb6 100644
> --- a/fs/filesystems.c
> +++ b/fs/filesystems.c
> @@ -252,7 +252,9 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
>
> static int __init proc_filesystems_init(void)
> {
> - proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + struct proc_dir_entry *pde =
> + proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
> + proc_make_permanent(pde);
> return 0;
> }
> module_init(proc_filesystems_init);
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index a3e22803cddf..0342600c0172 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -826,3 +826,15 @@ 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);
> +void impl_proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + if (pde) {
> + pde_make_permanent(pde);
> + }
> +}
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 96122e91c645..885b1cd38020 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -80,8 +80,11 @@ 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;
> }
>
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index ea62201c74c4..2d59f29b49eb 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -247,4 +247,14 @@ static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
>
> bool proc_ns_file(const struct file *file);
>
> +static inline void proc_make_permanent(struct proc_dir_entry *pde)
> +{
> + /* Don't give matches to modules. */
> +#if defined CONFIG_PROC_FS && !defined MODULE
> + /* This mess is created by defining "struct proc_dir_entry" elsewhere. */
> + void impl_proc_make_permanent(struct proc_dir_entry *pde);
> + impl_proc_make_permanent(pde);
> +#endif
> +}
> +
> #endif /* _LINUX_PROC_FS_H */
> --
> 2.47.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-09-17 3:44 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-04-09 19:20 [PATCH] proc: allow to mark /proc files permanent outside of fs/proc/ Alexey Dobriyan
2025-04-09 20:27 ` Mateusz Guzik
2025-04-09 21:35 ` Andrew Morton
2025-04-09 22:04 ` Mateusz Guzik
2025-05-07 9:48 ` Alexey Dobriyan
2025-09-17 3:44 ` Mateusz Guzik
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