diff mbox series

[1/2] mm/page_reporting: Add checks for page_reporting_order param value

Message ID 1664447081-14744-2-git-send-email-shradhagupta@linux.microsoft.com (mailing list archive)
State New
Headers show
Series Configurable order free page reporting in hyper-v | expand

Commit Message

Shradha Gupta Sept. 29, 2022, 10:24 a.m. UTC 
Current code allows the page_reporting_order parameter to be changed
via sysfs to any integer value.  The new value is used immediately
in page reporting code with no validation, which could cause incorrect
behavior.  Fix this by adding validation of the new value.
Export this parameter for use in the driver that is calling the
page_reporting_register().
This is needed by drivers like hv_balloon to know the order of the
pages reported. Traditionally the values provided in the kernel boot
line or subsequently changed via sysfs take priority therefore, if
page_reporting_order parameter's value is set, it takes precedence
over the value passed while registering with the driver.

Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
---
 mm/page_reporting.c | 50 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 5 deletions(-)

Comments

kernel test robot Oct. 1, 2022, 8 a.m. UTC | #1 
Hi Shradha,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v6.0-rc7 next-20220930]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Shradha-Gupta/Configurable-order-free-page-reporting-in-hyper-v/20220929-182918
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: arm-randconfig-r003-20220926
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/intel-lab-lkp/linux/commit/c3ac7f3e00c93db62e279104fae0b6df0c80d4af
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Shradha-Gupta/Configurable-order-free-page-reporting-in-hyper-v/20220929-182918
        git checkout c3ac7f3e00c93db62e279104fae0b6df0c80d4af
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> mm/page_reporting.c:17:5: warning: no previous prototype for function 'page_order_update_notify' [-Wmissing-prototypes]
   int page_order_update_notify(const char *val, const struct kernel_param *kp)
       ^
   mm/page_reporting.c:17:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int page_order_update_notify(const char *val, const struct kernel_param *kp)
   ^
   static 
   1 warning generated.


vim +/page_order_update_notify +17 mm/page_reporting.c

    16	
  > 17	int page_order_update_notify(const char *val, const struct kernel_param *kp)
    18	{
    19		/*
    20		 * If param is set beyond this limit, order is set to default
    21		 * pageblock_order value
    22		 */
    23		return  param_set_uint_minmax(val, kp, 0, MAX_ORDER-1);
    24	}
    25
kernel test robot Oct. 1, 2022, 9:49 a.m. UTC | #2 
Hi Shradha,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v6.0-rc7 next-20220930]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Shradha-Gupta/Configurable-order-free-page-reporting-in-hyper-v/20220929-182918
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: arc-randconfig-r043-20220928
compiler: arc-elf-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/c3ac7f3e00c93db62e279104fae0b6df0c80d4af
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Shradha-Gupta/Configurable-order-free-page-reporting-in-hyper-v/20220929-182918
        git checkout c3ac7f3e00c93db62e279104fae0b6df0c80d4af
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> mm/page_reporting.c:17:5: warning: no previous prototype for 'page_order_update_notify' [-Wmissing-prototypes]
      17 | int page_order_update_notify(const char *val, const struct kernel_param *kp)
         |     ^~~~~~~~~~~~~~~~~~~~~~~~


vim +/page_order_update_notify +17 mm/page_reporting.c

    16	
  > 17	int page_order_update_notify(const char *val, const struct kernel_param *kp)
    18	{
    19		/*
    20		 * If param is set beyond this limit, order is set to default
    21		 * pageblock_order value
    22		 */
    23		return  param_set_uint_minmax(val, kp, 0, MAX_ORDER-1);
    24	}
    25
diff mbox series

Patch

diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index 382958eef8a9..29d67c824fd2 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -11,10 +11,42 @@ 
 #include "page_reporting.h"
 #include "internal.h"
 
-unsigned int page_reporting_order = MAX_ORDER;
-module_param(page_reporting_order, uint, 0644);
+/* Initialize to an unsupported value */
+unsigned int page_reporting_order = -1;
+
+int page_order_update_notify(const char *val, const struct kernel_param *kp)
+{
+	/*
+	 * If param is set beyond this limit, order is set to default
+	 * pageblock_order value
+	 */
+	return  param_set_uint_minmax(val, kp, 0, MAX_ORDER-1);
+}
+
+const struct kernel_param_ops page_reporting_param_ops = {
+	.set = &page_order_update_notify,
+	/*
+	 * For the get op, use param_get_int instead of param_get_uint.
+	 * This is to make sure that when unset the initialized value of
+	 * -1 is shown correctly
+	 */
+	.get = &param_get_int,
+};
+
+module_param_cb(page_reporting_order, &page_reporting_param_ops,
+			&page_reporting_order, 0644);
 MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
 
+/*
+ * This symbol is also a kernel parameter. Export the page_reporting_order
+ * symbol so that other drivers can access it to control order values without
+ * having to introduce another configurable parameter. Only one driver can
+ * register with the page_reporting driver for the service, so we have just
+ * one control parameter for the use case(which can be accessed in both
+ * drivers)
+ */
+EXPORT_SYMBOL_GPL(page_reporting_order);
+
 #define PAGE_REPORTING_DELAY	(2 * HZ)
 static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
 
@@ -330,10 +362,18 @@  int page_reporting_register(struct page_reporting_dev_info *prdev)
 	}
 
 	/*
-	 * Update the page reporting order if it's specified by driver.
-	 * Otherwise, it falls back to @pageblock_order.
+	 * If the page_reporting_order value is not set, we check if
+	 * an order is provided from the driver that is performing the
+	 * registration. If that is not provided either, we default to
+	 * pageblock_order.
 	 */
-	page_reporting_order = prdev->order ? : pageblock_order;
+
+	if (page_reporting_order == -1) {
+		if (prdev->order > 0 && prdev->order <= MAX_ORDER)
+			page_reporting_order = prdev->order;
+		else
+			page_reporting_order = pageblock_order;
+	}
 
 	/* initialize state and work structures */
 	atomic_set(&prdev->state, PAGE_REPORTING_IDLE);