* [PATCH] tracing/user_events: Use alloc_pages instead of kzalloc() for register pages
@ 2022-03-12 0:04 Steven Rostedt
2022-03-12 2:10 ` Masami Hiramatsu
0 siblings, 1 reply; 2+ messages in thread
From: Steven Rostedt @ 2022-03-12 0:04 UTC (permalink / raw)
To: LKML; +Cc: Beau Belgrave, Anders Roxell, Masami Hiramatsu, Linux Trace Devel
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
kzalloc virtual addresses do not work with SetPageReserved, use the actual
page virtual addresses instead via alloc_pages.
The issue is reported when booting with user_events and
DEBUG_VM_PGFLAGS=y.
Also make the number of events based on the ORDER.
Link: https://lore.kernel.org/all/CADYN=9+xY5Vku3Ws5E9S60SM5dCFfeGeRBkmDFbcxX0ZMoFing@mail.gmail.com/
Link: https://lore.kernel.org/all/20220311223028.1865-1-beaub@linux.microsoft.com/
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_events_user.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 4febc1d6ae72..e10ad057e797 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -30,9 +30,10 @@
/*
* Limits how many trace_event calls user processes can create:
- * Must be multiple of PAGE_SIZE.
+ * Must be a power of two of PAGE_SIZE.
*/
-#define MAX_PAGES 1
+#define MAX_PAGE_ORDER 0
+#define MAX_PAGES (1 << MAX_PAGE_ORDER)
#define MAX_EVENTS (MAX_PAGES * PAGE_SIZE)
/* Limit how long of an event name plus args within the subsystem. */
@@ -1622,16 +1623,17 @@ static void set_page_reservations(bool set)
static int __init trace_events_user_init(void)
{
+ struct page *pages;
int ret;
/* Zero all bits beside 0 (which is reserved for failures) */
bitmap_zero(page_bitmap, MAX_EVENTS);
set_bit(0, page_bitmap);
- register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL);
-
- if (!register_page_data)
+ pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER);
+ if (!pages)
return -ENOMEM;
+ register_page_data = page_address(pages);
set_page_reservations(true);
@@ -1640,7 +1642,7 @@ static int __init trace_events_user_init(void)
if (ret) {
pr_warn("user_events could not register with tracefs\n");
set_page_reservations(false);
- kfree(register_page_data);
+ __free_pages(pages, MAX_PAGE_ORDER);
return ret;
}
--
2.34.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tracing/user_events: Use alloc_pages instead of kzalloc() for register pages
2022-03-12 0:04 [PATCH] tracing/user_events: Use alloc_pages instead of kzalloc() for register pages Steven Rostedt
@ 2022-03-12 2:10 ` Masami Hiramatsu
0 siblings, 0 replies; 2+ messages in thread
From: Masami Hiramatsu @ 2022-03-12 2:10 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Beau Belgrave, Anders Roxell, Masami Hiramatsu, Linux Trace Devel
On Fri, 11 Mar 2022 19:04:57 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
>
> kzalloc virtual addresses do not work with SetPageReserved, use the actual
> page virtual addresses instead via alloc_pages.
Indeed. kzalloc allocates a slab object, we need a page.
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Thank you,
>
> The issue is reported when booting with user_events and
> DEBUG_VM_PGFLAGS=y.
>
> Also make the number of events based on the ORDER.
>
> Link: https://lore.kernel.org/all/CADYN=9+xY5Vku3Ws5E9S60SM5dCFfeGeRBkmDFbcxX0ZMoFing@mail.gmail.com/
> Link: https://lore.kernel.org/all/20220311223028.1865-1-beaub@linux.microsoft.com/
>
> Cc: Beau Belgrave <beaub@linux.microsoft.com>
> Reported-by: Anders Roxell <anders.roxell@linaro.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> kernel/trace/trace_events_user.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 4febc1d6ae72..e10ad057e797 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -30,9 +30,10 @@
>
> /*
> * Limits how many trace_event calls user processes can create:
> - * Must be multiple of PAGE_SIZE.
> + * Must be a power of two of PAGE_SIZE.
> */
> -#define MAX_PAGES 1
> +#define MAX_PAGE_ORDER 0
> +#define MAX_PAGES (1 << MAX_PAGE_ORDER)
> #define MAX_EVENTS (MAX_PAGES * PAGE_SIZE)
>
> /* Limit how long of an event name plus args within the subsystem. */
> @@ -1622,16 +1623,17 @@ static void set_page_reservations(bool set)
>
> static int __init trace_events_user_init(void)
> {
> + struct page *pages;
> int ret;
>
> /* Zero all bits beside 0 (which is reserved for failures) */
> bitmap_zero(page_bitmap, MAX_EVENTS);
> set_bit(0, page_bitmap);
>
> - register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL);
> -
> - if (!register_page_data)
> + pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER);
> + if (!pages)
> return -ENOMEM;
> + register_page_data = page_address(pages);
>
> set_page_reservations(true);
>
> @@ -1640,7 +1642,7 @@ static int __init trace_events_user_init(void)
> if (ret) {
> pr_warn("user_events could not register with tracefs\n");
> set_page_reservations(false);
> - kfree(register_page_data);
> + __free_pages(pages, MAX_PAGE_ORDER);
> return ret;
> }
>
> --
> 2.34.1
>
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 2+ messages in thread
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