* Re: [PATCH] proc: Make inline name size calculation automatic
@ 2018-06-14 20:09 Alexey Dobriyan
2018-06-14 20:30 ` David Howells
0 siblings, 1 reply; 6+ messages in thread
From: Alexey Dobriyan @ 2018-06-14 20:09 UTC (permalink / raw)
To: dhowells; +Cc: viro, linux-fsdevel, linux-kernel
> Require a minimum inline name size of 33+1 to allow for names that look
> like two hex numbers with a dash between.
Hi, David.
Why 34? /proc will fallback to separate allocation for name anyway.
I sent nearly identical patch earlier.
https://marc.info/?l=linux-kernel&m=152667374404900&w=4
If you compare, the differences are:
* no BUILD_BUG_ON,
* 64 bytes is too litle even on 32-bit,
* 512 bytes is probably too much even on 64-bit.
> - .name = proc_root.inline_name,
> - .inline_name = "/proc",
> + .name = "/proc",
This will "uninline" 5 bytes wasting space.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: Make inline name size calculation automatic
2018-06-14 20:09 [PATCH] proc: Make inline name size calculation automatic Alexey Dobriyan
@ 2018-06-14 20:30 ` David Howells
2018-06-15 17:15 ` Alexey Dobriyan
2018-06-17 21:57 ` [PATCH] proc: fixup PDE allocation bloat Alexey Dobriyan
0 siblings, 2 replies; 6+ messages in thread
From: David Howells @ 2018-06-14 20:30 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: dhowells, viro, linux-fsdevel, linux-kernel
Alexey Dobriyan <adobriyan@gmail.com> wrote:
> > Require a minimum inline name size of 33+1 to allow for names that look
> > like two hex numbers with a dash between.
>
> Why 34? /proc will fallback to separate allocation for name anyway.
See above comment. I ran find on /proc and there were a bunch of files whose
names were "<hex>-<hex>". Allow for 16-char hex addresses and add a NUL char
to that and you get 34.
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: Make inline name size calculation automatic
2018-06-14 20:30 ` David Howells
@ 2018-06-15 17:15 ` Alexey Dobriyan
2018-06-17 21:57 ` [PATCH] proc: fixup PDE allocation bloat Alexey Dobriyan
1 sibling, 0 replies; 6+ messages in thread
From: Alexey Dobriyan @ 2018-06-15 17:15 UTC (permalink / raw)
To: David Howells; +Cc: viro, linux-fsdevel, linux-kernel
On Thu, Jun 14, 2018 at 09:30:42PM +0100, David Howells wrote:
> Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > > Require a minimum inline name size of 33+1 to allow for names that look
> > > like two hex numbers with a dash between.
> >
> > Why 34? /proc will fallback to separate allocation for name anyway.
>
> See above comment. I ran find on /proc and there were a bunch of files whose
> names were "<hex>-<hex>". Allow for 16-char hex addresses and add a NUL char
> to that and you get 34.
Those must be /proc/*/map_files symlinks. If that's the case,
they don't have PDEs allocated.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] proc: fixup PDE allocation bloat
2018-06-14 20:30 ` David Howells
2018-06-15 17:15 ` Alexey Dobriyan
@ 2018-06-17 21:57 ` Alexey Dobriyan
2018-07-20 0:06 ` Shakeel Butt
1 sibling, 1 reply; 6+ messages in thread
From: Alexey Dobriyan @ 2018-06-17 21:57 UTC (permalink / raw)
To: dhowells, viro, akpm; +Cc: linux-fsdevel, linux-kernel
commit 24074a35c5c975c94cd9691ae962855333aac47f
("proc: Make inline name size calculation automatic")
started to put PDE allocations into kmalloc-256 which is unnecessary as
~40 character names are very rare.
Put allocation back into kmalloc-192 cache for 64-bit non-debug builds.
Put BUILD_BUG_ON to know when PDE size is gotten out of control.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
fs/proc/inode.c | 6 ++++--
fs/proc/internal.h | 17 +++++++----------
2 files changed, 11 insertions(+), 12 deletions(-)
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -105,8 +105,10 @@ void __init proc_init_kmemcache(void)
kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
SLAB_ACCOUNT|SLAB_PANIC, NULL);
proc_dir_entry_cache = kmem_cache_create_usercopy(
- "proc_dir_entry", SIZEOF_PDE_SLOT, 0, SLAB_PANIC,
- OFFSETOF_PDE_NAME, SIZEOF_PDE_INLINE_NAME, NULL);
+ "proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
+ offsetof(struct proc_dir_entry, inline_name),
+ SIZEOF_PDE_INLINE_NAME, NULL);
+ BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
}
static int proc_show_options(struct seq_file *seq, struct dentry *root)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -65,16 +65,13 @@ struct proc_dir_entry {
char inline_name[];
} __randomize_layout;
-#define OFFSETOF_PDE_NAME offsetof(struct proc_dir_entry, inline_name)
-#define SIZEOF_PDE_SLOT \
- (OFFSETOF_PDE_NAME + 34 <= 64 ? 64 : \
- OFFSETOF_PDE_NAME + 34 <= 128 ? 128 : \
- OFFSETOF_PDE_NAME + 34 <= 192 ? 192 : \
- OFFSETOF_PDE_NAME + 34 <= 256 ? 256 : \
- OFFSETOF_PDE_NAME + 34 <= 512 ? 512 : \
- 0)
-
-#define SIZEOF_PDE_INLINE_NAME (SIZEOF_PDE_SLOT - OFFSETOF_PDE_NAME)
+#ifdef CONFIG_64BIT
+#define SIZEOF_PDE (sizeof(spinlock_t) <= 4 ? 192 : 256)
+#else
+#define SIZEOF_PDE (sizeof(spinlock_t) <= 4 ? 128 : 192)
+#endif
+
+#define SIZEOF_PDE_INLINE_NAME (SIZEOF_PDE - sizeof(struct proc_dir_entry))
extern struct kmem_cache *proc_dir_entry_cache;
void pde_free(struct proc_dir_entry *pde);
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: fixup PDE allocation bloat
2018-06-17 21:57 ` [PATCH] proc: fixup PDE allocation bloat Alexey Dobriyan
@ 2018-07-20 0:06 ` Shakeel Butt
2018-08-17 13:28 ` Alexey Dobriyan
0 siblings, 1 reply; 6+ messages in thread
From: Shakeel Butt @ 2018-07-20 0:06 UTC (permalink / raw)
To: adobriyan; +Cc: dhowells, Alexander Viro, Andrew Morton, linux-fsdevel, LKML
On Sun, Jun 17, 2018 at 2:57 PM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> commit 24074a35c5c975c94cd9691ae962855333aac47f
> ("proc: Make inline name size calculation automatic")
> started to put PDE allocations into kmalloc-256 which is unnecessary as
> ~40 character names are very rare.
>
> Put allocation back into kmalloc-192 cache for 64-bit non-debug builds.
>
> Put BUILD_BUG_ON to know when PDE size is gotten out of control.
>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>
> fs/proc/inode.c | 6 ++++--
> fs/proc/internal.h | 17 +++++++----------
> 2 files changed, 11 insertions(+), 12 deletions(-)
>
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -105,8 +105,10 @@ void __init proc_init_kmemcache(void)
> kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
> SLAB_ACCOUNT|SLAB_PANIC, NULL);
> proc_dir_entry_cache = kmem_cache_create_usercopy(
> - "proc_dir_entry", SIZEOF_PDE_SLOT, 0, SLAB_PANIC,
> - OFFSETOF_PDE_NAME, SIZEOF_PDE_INLINE_NAME, NULL);
> + "proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
Hi Alexey, can you comment if proc_dir_entry_cache should or shouldn't
have SLAB_ACCOUNT flag?
Shakeel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] proc: fixup PDE allocation bloat
2018-07-20 0:06 ` Shakeel Butt
@ 2018-08-17 13:28 ` Alexey Dobriyan
0 siblings, 0 replies; 6+ messages in thread
From: Alexey Dobriyan @ 2018-08-17 13:28 UTC (permalink / raw)
To: Shakeel Butt; +Cc: dhowells, Alexander Viro, Andrew Morton, linux-fsdevel, LKML
On Thu, Jul 19, 2018 at 05:06:55PM -0700, Shakeel Butt wrote:
> On Sun, Jun 17, 2018 at 2:57 PM Alexey Dobriyan <adobriyan@gmail.com> wrote:
> >
> > commit 24074a35c5c975c94cd9691ae962855333aac47f
> > ("proc: Make inline name size calculation automatic")
> > started to put PDE allocations into kmalloc-256 which is unnecessary as
> > ~40 character names are very rare.
> >
> > Put allocation back into kmalloc-192 cache for 64-bit non-debug builds.
> >
> > Put BUILD_BUG_ON to know when PDE size is gotten out of control.
> >
> > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> > ---
> >
> > fs/proc/inode.c | 6 ++++--
> > fs/proc/internal.h | 17 +++++++----------
> > 2 files changed, 11 insertions(+), 12 deletions(-)
> >
> > --- a/fs/proc/inode.c
> > +++ b/fs/proc/inode.c
> > @@ -105,8 +105,10 @@ void __init proc_init_kmemcache(void)
> > kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
> > SLAB_ACCOUNT|SLAB_PANIC, NULL);
> > proc_dir_entry_cache = kmem_cache_create_usercopy(
> > - "proc_dir_entry", SIZEOF_PDE_SLOT, 0, SLAB_PANIC,
> > - OFFSETOF_PDE_NAME, SIZEOF_PDE_INLINE_NAME, NULL);
> > + "proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
>
> Hi Alexey, can you comment if proc_dir_entry_cache should or shouldn't
> have SLAB_ACCOUNT flag?
It should not (but see below):
SLAB_ACCOUNT is for allocations which can be done by userspace directly:
open(2) directly allocates "struct file".
But /proc entries aren't like that: say, /proc/cpuinfo is created by kernel
and userspace can't do anything about it.
Some subsystems create /proc entries based on userspace actions and
those aren't related to hardware (example: xt_hashlimit.c) but those are
few so kernel doesn't bother accounting those.
Or in other words: user can't mkdir(1) and touch(1) and ln(1) inside /proc
at will and therefore PDEs aren't accounted.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-08-17 16:32 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2018-06-14 20:09 [PATCH] proc: Make inline name size calculation automatic Alexey Dobriyan
2018-06-14 20:30 ` David Howells
2018-06-15 17:15 ` Alexey Dobriyan
2018-06-17 21:57 ` [PATCH] proc: fixup PDE allocation bloat Alexey Dobriyan
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2018-08-17 13:28 ` Alexey Dobriyan
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