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Subjectpstore: use mount option instead sysfs to tweak kmsg_bytes
Date
/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>

---

Christoph Hellwig wrote:
> - the kmsg_bytes attribute really should be a mount option. no need
> have this in a completely different namespace, and require all the
> kobject mess around it.

Al: If this looks OK, will you run it through your vfs tree please?

diff --git a/Documentation/ABI/testing/pstore b/Documentation/ABI/testing/pstore
index f1fb2a0..8232d2f 100644
--- a/Documentation/ABI/testing/pstore
+++ b/Documentation/ABI/testing/pstore
@@ -1,6 +1,6 @@
Where: /dev/pstore/...
-Date: January 2011
-Kernel Version: 2.6.38
+Date: March 2011
+Kernel Version: 2.6.39
Contact: tony.luck@intel.com
Description: Generic interface to platform dependent persistent storage.

@@ -11,7 +11,7 @@ Description: Generic interface to platform dependent persistent storage.
of the console log is captured, but other interesting
data can also be saved.

- # mount -t pstore - /dev/pstore
+ # mount -t pstore -o kmsg_bytes=8000 - /dev/pstore

$ ls -l /dev/pstore
total 0
@@ -33,3 +33,9 @@ Description: Generic interface to platform dependent persistent storage.
will be saved elsewhere and erased from persistent store
soon after boot to free up space ready for the next
catastrophe.
+
+ The 'kmsg_bytes' mount option changes the target amount of
+ data saved on each oops/panic. Pstore saves (possibly
+ multiple) files based on the record size of the underlying
+ persistent storage until at least this amount is reached.
+ Default is 10 Kbytes.
diff --git a/Documentation/ABI/testing/sysfs-fs-pstore b/Documentation/ABI/testing/sysfs-fs-pstore
deleted file mode 100644
index 8e659d8..0000000
--- a/Documentation/ABI/testing/sysfs-fs-pstore
+++ /dev/null
@@ -1,7 +0,0 @@
-What: /sys/fs/pstore/kmsg_bytes
-Date: January 2011
-Kernel Version: 2.6.38
-Contact: "Tony Luck" <tony.luck@intel.com>
-Description:
- Controls amount of console log that will be saved
- to persistent store on oops/panic.
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index f777f29..52cb6d4 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 76c26d2..8c9f23e 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 705fdf8..ce9ad84 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;


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