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Date: Fri, 11 Mar 2011 16:29:16 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Chen Gong <gong.chen@...ux.intel.com>
Cc: Wu Fengguang <fengguang.wu@...el.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>,
Clark Williams <williams@...hat.com>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Subject: Re: [PATCH V2] page-types.c: auto debugfs mount for hwpoison
operation
On Tue, 08 Mar 2011 13:01:09 +0800
Chen Gong <gong.chen@...ux.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@...ux.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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