[PATCH] page-types.c: add a new argument of debugfs path

[PATCH] page-types.c: add a new argument of debugfs path

[Chen Gong]

page-types.c doesn't supply a way to specify the debugfs path and
the original debugfs path is not usual on most machines. Add a
new argument to set the debugfs path easily.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
---
 Documentation/vm/page-types.c |   33 ++++++++++++++++++++++++---------
 1 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
index cc96ee2..1ebe87d 100644
--- a/Documentation/vm/page-types.c
+++ b/Documentation/vm/page-types.c
@@ -184,7 +184,7 @@ static int		kpageflags_fd;
 static int		opt_hwpoison;
 static int		opt_unpoison;
 
-static const char	hwpoison_debug_fs[] = "/debug/hwpoison";
+static char		hwpoison_debug_fs[256] = "/sys/kernel/debug";
 static int		hwpoison_inject_fd;
 static int		hwpoison_forget_fd;
 
@@ -464,28 +464,37 @@ static uint64_t kpageflags_flags(uint64_t flags)
 	return flags;
 }
 
+static void prepare_debugfs(const char *optarg)
+{
+	/*
+	 * avoid too long filename.
+	 * "/hwpoison/unpoison-pfn" occupies 22 characters
+	 */
+	strncpy(hwpoison_debug_fs, optarg, 255 - 22);
+}
+
 /*
  * page actions
  */
 
 static void prepare_hwpoison_fd(void)
 {
-	char buf[100];
+	char buf[256];
 
 	if (opt_hwpoison && !hwpoison_inject_fd) {
-		sprintf(buf, "%s/corrupt-pfn", hwpoison_debug_fs);
+		sprintf(buf, "%s/hwpoison/corrupt-pfn", hwpoison_debug_fs);
 		hwpoison_inject_fd = checked_open(buf, O_WRONLY);
 	}
 
 	if (opt_unpoison && !hwpoison_forget_fd) {
-		sprintf(buf, "%s/unpoison-pfn", hwpoison_debug_fs);
+		sprintf(buf, "%s/hwpoison/unpoison-pfn", hwpoison_debug_fs);
 		hwpoison_forget_fd = checked_open(buf, O_WRONLY);
 	}
 }
 
 static int hwpoison_page(unsigned long offset)
 {
-	char buf[100];
+	char buf[256];
 	int len;
 
 	len = sprintf(buf, "0x%lx\n", offset);
@@ -499,7 +508,7 @@ static int hwpoison_page(unsigned long offset)
 
 static int unpoison_page(unsigned long offset)
 {
-	char buf[100];
+	char buf[256];
 	int len;
 
 	len = sprintf(buf, "0x%lx\n", offset);
@@ -686,6 +695,7 @@ static void usage(void)
 "page-types [options]\n"
 "            -r|--raw                   Raw mode, for kernel developers\n"
 "            -d|--describe flags        Describe flags\n"
+"            -D|--debugfs debugfs-path  specify the debugfs path\n"
 "            -a|--addr    addr-spec     Walk a range of pages\n"
 "            -b|--bits    bits-spec     Walk pages with specified bits\n"
 "            -p|--pid     pid           Walk process address space\n"
@@ -917,6 +927,7 @@ static const struct option opts[] = {
 	{ "addr"      , 1, NULL, 'a' },
 	{ "bits"      , 1, NULL, 'b' },
 	{ "describe"  , 1, NULL, 'd' },
+	{ "debugfs"   , 1, NULL, 'D' },
 	{ "list"      , 0, NULL, 'l' },
 	{ "list-each" , 0, NULL, 'L' },
 	{ "no-summary", 0, NULL, 'N' },
@@ -933,7 +944,7 @@ int main(int argc, char *argv[])
 	page_size = getpagesize();
 
 	while ((c = getopt_long(argc, argv,
-				"rp:f:a:b:d:lLNXxh", opts, NULL)) != -1) {
+				"rp:f:a:b:d:D:lLNXxh", opts, NULL)) != -1) {
 		switch (c) {
 		case 'r':
 			opt_raw = 1;
@@ -953,6 +964,9 @@ int main(int argc, char *argv[])
 		case 'd':
 			describe_flags(optarg);
 			exit(0);
+		case 'D':
+			prepare_debugfs(optarg);
+			break;
 		case 'l':
 			opt_list = 1;
 			break;
@@ -964,11 +978,9 @@ int main(int argc, char *argv[])
 			break;
 		case 'X':
 			opt_hwpoison = 1;
-			prepare_hwpoison_fd();
 			break;
 		case 'x':
 			opt_unpoison = 1;
-			prepare_hwpoison_fd();
 			break;
 		case 'h':
 			usage();
@@ -979,6 +991,9 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (opt_hwpoison == 1 || opt_unpoison == 1)
+		prepare_hwpoison_fd();
+
 	if (opt_list && opt_pid)
 		printf("voffset\t");
 	if (opt_list == 1)
-- 
1.7.3.1.120.g38a18

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Re: [PATCH] page-types.c: add a new argument of debugfs path

[KOSAKI Motohiro]

> page-types.c doesn't supply a way to specify the debugfs path and
> the original debugfs path is not usual on most machines. Add a
> new argument to set the debugfs path easily.
> 
> Signed-off-by: Chen Gong <gong.chen@linux.intel.com>

Hi

Why do we need to set debugfs path manually? Instead I'd suggested to
read /proc/mount and detect it automatically.

Thanks.



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Re: [PATCH] page-types.c: add a new argument of debugfs path

[Wu Fengguang]

On Mon, Mar 07, 2011 at 05:42:39PM +0800, KOSAKI Motohiro wrote:
> > page-types.c doesn't supply a way to specify the debugfs path and
> > the original debugfs path is not usual on most machines. Add a
> > new argument to set the debugfs path easily.
> > 
> > Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
> 
> Hi
> 
> Why do we need to set debugfs path manually? Instead I'd suggested to
> read /proc/mount and detect it automatically.

Good idea! And could reuse tools/perf/util/debugfs.c for finding out
and even audo-mounting debugfs. 

Thanks,
Fengguang

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Re: [PATCH V2] page-types.c: auto debugfs mount for hwpoison operation

[Chen Gong]

page-types.c doesn't supply a way to specify the debugfs path and
the original debugfs path is not usual on most machines. This patch
supplies a way to auto mount debugfs if needed.

This patch is heavily inspired by tools/perf/utils/debugfs.c

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
---
  Documentation/vm/page-types.c |  105 
+++++++++++++++++++++++++++++++++++++++--
  1 files changed, 101 insertions(+), 4 deletions(-)

diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
index cc96ee2..303b4ed 100644
--- a/Documentation/vm/page-types.c
+++ b/Documentation/vm/page-types.c
@@ -32,8 +32,20 @@
  #include <sys/types.h>
  #include <sys/errno.h>
  #include <sys/fcntl.h>
+#include <sys/mount.h>
+#include <sys/statfs.h>
+#include "../../include/linux/magic.h"


+#ifndef MAX_PATH
+# define MAX_PATH 256
+#endif
+
+#ifndef STR
+# define _STR(x) #x
+# define STR(x) _STR(x)
+#endif
+
  /*
   * pagemap kernel ABI bits
   */
@@ -152,6 +164,12 @@ static const char *page_flag_names[] = {
  };


+static const char *debugfs_known_mountpoints[] = {
+	"/sys/kernel/debug",
+	"/debug",
+	0,
+};
+
  /*
   * data structures
   */
@@ -184,7 +202,7 @@ static int		kpageflags_fd;
  static int		opt_hwpoison;
  static int		opt_unpoison;

-static const char	hwpoison_debug_fs[] = "/debug/hwpoison";
+static char		hwpoison_debug_fs[MAX_PATH+1];
  static int		hwpoison_inject_fd;
  static int		hwpoison_forget_fd;

@@ -464,21 +482,100 @@ static uint64_t kpageflags_flags(uint64_t flags)
  	return flags;
  }

+/* verify that a mountpoint is actually a debugfs instance */
+int debugfs_valid_mountpoint(const char *debugfs)
+{
+	struct statfs st_fs;
+
+	if (statfs(debugfs, &st_fs) < 0)
+		return -ENOENT;
+	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
+		return -ENOENT;
+
+	return 0;
+}
+
+/* find the path to the mounted debugfs */
+const char *debugfs_find_mountpoint(void)
+{
+	const char **ptr;
+	char type[100];
+	FILE *fp;
+
+	ptr = debugfs_known_mountpoints;
+	while (*ptr) {
+		if (debugfs_valid_mountpoint(*ptr) == 0) {
+			strcpy(hwpoison_debug_fs, *ptr);
+			return hwpoison_debug_fs;
+		}
+		ptr++;
+	}
+
+	/* give up and parse /proc/mounts */
+	fp = fopen("/proc/mounts", "r");
+	if (fp == NULL)
+		perror("Can't open /proc/mounts for read");
+
+	while (fscanf(fp, "%*s %"
+		      STR(MAX_PATH)
+		      "s %99s %*s %*d %*d\n",
+		      hwpoison_debug_fs, type) == 2) {
+		if (strcmp(type, "debugfs") == 0)
+			break;
+	}
+	fclose(fp);
+
+	if (strcmp(type, "debugfs") != 0)
+		return NULL;
+
+	return hwpoison_debug_fs;
+}
+
+/* mount the debugfs somewhere if it's not mounted */
+
+void debugfs_mount()
+{
+	const char **ptr;
+
+	/* see if it's already mounted */
+	if (debugfs_find_mountpoint())
+		return;
+
+	ptr = debugfs_known_mountpoints;
+	while (*ptr) {
+		if (mount(NULL, *ptr, "debugfs", 0, NULL) == 0) {
+			/* save the mountpoint */
+			strcpy(hwpoison_debug_fs, *ptr);
+			break;
+		}
+		ptr++;
+	}
+
+	if (*ptr == NULL) {
+		perror("mount debugfs");
+		exit(EXIT_FAILURE);
+	}
+}
+
  /*
   * page actions
   */

  static void prepare_hwpoison_fd(void)
  {
-	char buf[100];
+	char buf[MAX_PATH + 1];
+
+	debugfs_mount();

  	if (opt_hwpoison && !hwpoison_inject_fd) {
-		sprintf(buf, "%s/corrupt-pfn", hwpoison_debug_fs);
+		snprintf(buf, MAX_PATH, "%s/hwpoison/corrupt-pfn",
+			hwpoison_debug_fs);
  		hwpoison_inject_fd = checked_open(buf, O_WRONLY);
  	}

  	if (opt_unpoison && !hwpoison_forget_fd) {
-		sprintf(buf, "%s/unpoison-pfn", hwpoison_debug_fs);
+		snprintf(buf, MAX_PATH, "%s/hwpoison/unpoison-pfn",
+			hwpoison_debug_fs);
  		hwpoison_forget_fd = checked_open(buf, O_WRONLY);
  	}
  }
-- 
1.7.3.1.120.g38a18


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Re: [PATCH V2] page-types.c: auto debugfs mount for hwpoison operation

[KOSAKI Motohiro]

> page-types.c doesn't supply a way to specify the debugfs path and
> the original debugfs path is not usual on most machines. This patch
> supplies a way to auto mount debugfs if needed.
> 
> This patch is heavily inspired by tools/perf/utils/debugfs.c
> 
> Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
> ---
>   Documentation/vm/page-types.c |  105 
> +++++++++++++++++++++++++++++++++++++++--
>   1 files changed, 101 insertions(+), 4 deletions(-)


Cute!
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>



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Re: [PATCH V2] page-types.c: auto debugfs mount for hwpoison operation

[Wu Fengguang]

On Tue, Mar 08, 2011 at 01:01:09PM +0800, Chen Gong wrote:
> page-types.c doesn't supply a way to specify the debugfs path and
> the original debugfs path is not usual on most machines. This patch
> supplies a way to auto mount debugfs if needed.
> 
> This patch is heavily inspired by tools/perf/utils/debugfs.c
> 
> Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
> ---
>   Documentation/vm/page-types.c |  105 
> +++++++++++++++++++++++++++++++++++++++--
>   1 files changed, 101 insertions(+), 4 deletions(-)

Thanks!

Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>

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Re: [PATCH V2] page-types.c: auto debugfs mount for hwpoison operation

[Andrew Morton]

On Tue, 08 Mar 2011 13:01:09 +0800
Chen Gong <gong.chen@linux.intel.com> wrote:

> page-types.c doesn't supply a way to specify the debugfs path and
> the original debugfs path is not usual on most machines. This patch
> supplies a way to auto mount debugfs if needed.
> 
> This patch is heavily inspired by tools/perf/utils/debugfs.c
> 
> Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
> ---
>   Documentation/vm/page-types.c |  105 
> +++++++++++++++++++++++++++++++++++++++--
>   1 files changed, 101 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
> index cc96ee2..303b4ed 100644
> --- a/Documentation/vm/page-types.c
> +++ b/Documentation/vm/page-types.c
> @@ -32,8 +32,20 @@
>   #include <sys/types.h>
>   #include <sys/errno.h>
>   #include <sys/fcntl.h>
> +#include <sys/mount.h>
> +#include <sys/statfs.h>
> +#include "../../include/linux/magic.h"

Your email client is space-stuffing the patches.

> 
> +#ifndef MAX_PATH
> +# define MAX_PATH 256
> +#endif
> +
> +#ifndef STR
> +# define _STR(x) #x
> +# define STR(x) _STR(x)
> +#endif
> +
>   /*
>    * pagemap kernel ABI bits
>    */
> @@ -152,6 +164,12 @@ static const char *page_flag_names[] = {
>   };
> 
> 
> +static const char *debugfs_known_mountpoints[] = {
> +	"/sys/kernel/debug",
> +	"/debug",
> +	0,
> +};
> +
>   /*
>    * data structures
>    */
> @@ -184,7 +202,7 @@ static int		kpageflags_fd;
>   static int		opt_hwpoison;
>   static int		opt_unpoison;
> 
> -static const char	hwpoison_debug_fs[] = "/debug/hwpoison";
> +static char		hwpoison_debug_fs[MAX_PATH+1];
>   static int		hwpoison_inject_fd;
>   static int		hwpoison_forget_fd;
> 
> @@ -464,21 +482,100 @@ static uint64_t kpageflags_flags(uint64_t flags)
>   	return flags;
>   }
> 
> +/* verify that a mountpoint is actually a debugfs instance */
> +int debugfs_valid_mountpoint(const char *debugfs)

page-types.c carefully makes its symbols static.  Let's continue to do
that.

--- a/Documentation/vm/page-types.c~documentation-vm-page-typesc-auto-debugfs-mount-for-hwpoison-operation-fix
+++ a/Documentation/vm/page-types.c
@@ -483,7 +483,7 @@ static uint64_t kpageflags_flags(uint64_
 }
 
 /* verify that a mountpoint is actually a debugfs instance */
-int debugfs_valid_mountpoint(const char *debugfs)
+static int debugfs_valid_mountpoint(const char *debugfs)
 {
 	struct statfs st_fs;
 
@@ -496,7 +496,7 @@ int debugfs_valid_mountpoint(const char 
 }
 
 /* find the path to the mounted debugfs */
-const char *debugfs_find_mountpoint(void)
+static const char *debugfs_find_mountpoint(void)
 {
 	const char **ptr;
 	char type[100];
@@ -533,7 +533,7 @@ const char *debugfs_find_mountpoint(void
 
 /* mount the debugfs somewhere if it's not mounted */
 
-void debugfs_mount()
+static void debugfs_mount()
 {
 	const char **ptr;
 
_

> +{
> +	struct statfs st_fs;
> +
> +	if (statfs(debugfs, &st_fs) < 0)
> +		return -ENOENT;
> +	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
> +		return -ENOENT;
> +
> +	return 0;
> +}
> +
> +/* find the path to the mounted debugfs */
> +const char *debugfs_find_mountpoint(void)
> +{
> +	const char **ptr;
> +	char type[100];
> +	FILE *fp;
> +
> +	ptr = debugfs_known_mountpoints;
> +	while (*ptr) {
> +		if (debugfs_valid_mountpoint(*ptr) == 0) {
> +			strcpy(hwpoison_debug_fs, *ptr);
> +			return hwpoison_debug_fs;
> +		}
> +		ptr++;
> +	}
> +
> +	/* give up and parse /proc/mounts */
> +	fp = fopen("/proc/mounts", "r");
> +	if (fp == NULL)
> +		perror("Can't open /proc/mounts for read");
> +
> +	while (fscanf(fp, "%*s %"
> +		      STR(MAX_PATH)
> +		      "s %99s %*s %*d %*d\n",
> +		      hwpoison_debug_fs, type) == 2) {
> +		if (strcmp(type, "debugfs") == 0)
> +			break;
> +	}
> +	fclose(fp);
> +
> +	if (strcmp(type, "debugfs") != 0)
> +		return NULL;
> +
> +	return hwpoison_debug_fs;
> +}
> +
> +/* mount the debugfs somewhere if it's not mounted */
> +
> +void debugfs_mount()
> +{
> +	const char **ptr;
> +
> +	/* see if it's already mounted */
> +	if (debugfs_find_mountpoint())
> +		return;
> +
> +	ptr = debugfs_known_mountpoints;
> +	while (*ptr) {
> +		if (mount(NULL, *ptr, "debugfs", 0, NULL) == 0) {
> +			/* save the mountpoint */
> +			strcpy(hwpoison_debug_fs, *ptr);
> +			break;
> +		}
> +		ptr++;
> +	}
> +
> +	if (*ptr == NULL) {
> +		perror("mount debugfs");
> +		exit(EXIT_FAILURE);
> +	}
> +}

The application now silently mounts debugfs.  Perhaps it should inform
the operator when it did this?


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