pstore: use mount option instead sysfs to tweak kmsg_bytes

/sys/fs is a somewhat strange way to tweak what could more
obviously be tuned with a mount option.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 50 insertions, 37 deletions

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index f777f2902c49..977ed2723845 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -27,6 +27,7 @@
 #include <linux/string.h>
 #include <linux/mount.h>
 #include <linux/ramfs.h>
+#include <linux/parser.h>
 #include <linux/sched.h>
 #include <linux/magic.h>
 #include <linux/pstore.h>
@@ -112,10 +113,52 @@ static struct inode *pstore_get_inode(struct super_block *sb,
         return inode;
 }
 
+enum {
+        Opt_kmsg_bytes, Opt_err
+};
+
+static const match_table_t tokens = {
+        {Opt_kmsg_bytes, "kmsg_bytes=%u"},
+        {Opt_err, NULL}
+};
+
+static void parse_options(char *options)
+{
+        char            *p;
+        substring_t     args[MAX_OPT_ARGS];
+        int             option;
+
+        if (!options)
+                return;
+
+        while ((p = strsep(&options, ",")) != NULL) {
+                int token;
+
+                if (!*p)
+                        continue;
+
+                token = match_token(p, tokens, args);
+                switch (token) {
+                case Opt_kmsg_bytes:
+                        if (!match_int(&args[0], &option))
+                                pstore_set_kmsg_bytes(option);
+                        break;
+                }
+        }
+}
+
+static int pstore_remount(struct super_block *sb, int *flags, char *data)
+{
+        parse_options(data);
+
+        return 0;
+}
+
 static const struct super_operations pstore_ops = {
         .statfs         = simple_statfs,
         .drop_inode     = generic_delete_inode,
         .evict_inode    = pstore_evict_inode,
+        .remount_fs     = pstore_remount,
         .show_options   = generic_show_options,
 };
 
@@ -215,6 +258,8 @@ int pstore_fill_super(struct super_block *sb, void *data, int silent)
         sb->s_op                = &pstore_ops;
         sb->s_time_gran         = 1;
 
+        parse_options(data);
+
         inode = pstore_get_inode(sb, NULL, S_IFDIR | 0755, 0);
         if (!inode) {
                 err = -ENOMEM;
@@ -258,28 +303,7 @@ static struct file_system_type pstore_fs_type = {
 
 static int __init init_pstore_fs(void)
 {
-        int rc = 0;
-        struct kobject *pstorefs_kobj;
-
-        pstorefs_kobj = kobject_create_and_add("pstore", fs_kobj);
-        if (!pstorefs_kobj) {
-                rc = -ENOMEM;
-                goto done;
-        }
-
-        rc = sysfs_create_file(pstorefs_kobj, &pstore_kmsg_bytes_attr.attr);
-        if (rc)
-                goto done1;
-
-        rc = register_filesystem(&pstore_fs_type);
-        if (rc == 0)
-                goto done;
-
-        sysfs_remove_file(pstorefs_kobj, &pstore_kmsg_bytes_attr.attr);
-done1:
-        kobject_put(pstorefs_kobj);
-done:
-        return rc;
+        return register_filesystem(&pstore_fs_type);
 }
 module_init(init_pstore_fs)
 
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index 76c26d2fab29..8c9f23eb1645 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -1,7 +1,6 @@
+extern void     pstore_set_kmsg_bytes(int);
 extern void     pstore_get_records(void);
 extern int      pstore_mkfile(enum pstore_type_id, char *psname, u64 id,
                               char *data, size_t size,
                               struct timespec time, int (*erase)(u64));
 extern int      pstore_is_mounted(void);
-
-extern struct kobj_attribute pstore_kmsg_bytes_attr;
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 705fdf8abf6e..ce9ad84d5dd9 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -37,24 +37,14 @@
 static DEFINE_SPINLOCK(pstore_lock);
 static struct pstore_info *psinfo;
 
-/* How much of the console log to snapshot. /sys/fs/pstore/kmsg_bytes */
+/* How much of the console log to snapshot */
 static unsigned long kmsg_bytes = 10240;
 
-static ssize_t b_show(struct kobject *kobj,
-                      struct kobj_attribute *attr, char *buf)
+void pstore_set_kmsg_bytes(int bytes)
 {
-        return snprintf(buf, PAGE_SIZE, "%lu\n", kmsg_bytes);
+        kmsg_bytes = bytes;
 }
 
-static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
-                       const char *buf, size_t count)
-{
-        return (sscanf(buf, "%lu", &kmsg_bytes) > 0) ? count : 0;
-}
-
-struct kobj_attribute pstore_kmsg_bytes_attr =
-        __ATTR(kmsg_bytes, S_IRUGO | S_IWUSR, b_show, b_store);
-
 /* Tag each group of saved records with a sequence number */
 static int      oopscount;