Re: [PATCH 10/16] show partitions on mount error

Jan Engelhardt
2007-04-02T07:02:17Z

Hi,

On Apr 1 2007 22:47, Andrew Morton wrote:
>On Sun, 1 Apr 2007 20:15:53 +0200 (MEST) Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
>>
>> Display all possible partitions when the root filesystem is not mounted.
>> This helps to track spell'o's and missing drivers.
>>
>> +void printk_all_partitions(void)
>
>I made this __init.

Seems reasonable.
I have done some additional cleanups, see patch below.

>It would be nice to include a sample of the resulting output for people
>to review.

Loaded with PXELINUX...

LABEL l
KERNEL bzImage
APPEND root=/dev/foobar

or root=/dev/sdb both produce:

[...]
VFS: Cannot open root device "foobar" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:
0800 8388608 sda driver: sd
0801 192748 sda1
0802 8193150 sda2
0810 4194304 sdb driver: sd
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

With root=/dev/sdb, the list of possible filesystems is also displayed
(a patch that was merged a (long)while back).

---

Integrated __init annotation, and deindented the loop by one level.
Replaces original patch.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>

Index: linux-2.6.21-rc5/block/genhd.c
===================================================================
--- linux-2.6.21-rc5.orig/block/genhd.c
+++ linux-2.6.21-rc5/block/genhd.c
@@ -215,6 +215,59 @@ struct gendisk *get_gendisk(dev_t dev, i
return kobj ? to_disk(kobj) : NULL;
}

+/*
+ * printk a full list of all partitions - intended for
+ * places where the root filesystem can't be mounted and thus
+ * to give the victim some idea of what went wrong
+ */
+void __init printk_all_partitions(void)
+{
+ int n;
+ struct gendisk *sgp;
+ mutex_lock(&block_subsys_lock);
+
+ /* For each block device... */
+ list_for_each_entry(sgp, &block_subsys.kset.list, kobj.entry) {
+ char buf[BDEVNAME_SIZE];
+ /*
+ * Don't show empty devices or things that have been surpressed
+ */
+ if (get_capacity(sgp) == 0 ||
+ (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO))
+ continue;
+
+ /*
+ * Note, unlike /proc/partitions, I am showing the numbers in
+ * hex - the same format as the root= option takes.
+ */
+ printk("%02x%02x %10llu %s",
+ sgp->major, sgp->first_minor,
+ (unsigned long long)get_capacity(sgp) >> 1,
+ disk_name(sgp, 0, buf));
+ if (sgp->driverfs_dev != NULL &&
+ sgp->driverfs_dev->driver != NULL)
+ printk(" driver: %s\n",
+ sgp->driverfs_dev->driver->name);
+ else
+ printk(" (driver?)\n");
+
+ /* now show the partitions */
+ for (n = 0; n < sgp->minors - 1; ++n) {
+ if (sgp->part[n] == NULL)
+ continue;
+ if (sgp->part[n]->nr_sects == 0)
+ continue;
+ printk(" %02x%02x %10llu %s\n",
+ sgp->major, n + 1 + sgp->first_minor,
+ (unsigned long long)sgp->part[n]->nr_sects >> 1,
+ disk_name(sgp, n + 1, buf));
+ } /* partition subloop */
+ } /* Block device loop */
+
+ mutex_unlock(&block_subsys_lock);
+ return;
+}
+
#ifdef CONFIG_PROC_FS
/* iterator */
static void *part_start(struct seq_file *part, loff_t *pos)
Index: linux-2.6.21-rc5/include/linux/genhd.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/genhd.h
+++ linux-2.6.21-rc5/include/linux/genhd.h
@@ -413,6 +413,7 @@ char *disk_name (struct gendisk *hd, int
extern int rescan_partitions(struct gendisk *disk, struct block_device *bdev);
extern void add_partition(struct gendisk *, int, sector_t, sector_t, int);
extern void delete_partition(struct gendisk *, int);
+extern void printk_all_partitions(void);

extern struct gendisk *alloc_disk_node(int minors, int node_id);
extern struct gendisk *alloc_disk(int minors);
Index: linux-2.6.21-rc5/init/do_mounts.c
===================================================================
--- linux-2.6.21-rc5.orig/init/do_mounts.c
+++ linux-2.6.21-rc5/init/do_mounts.c
@@ -7,6 +7,7 @@
#include <linux/root_dev.h>
#include <linux/security.h>
#include <linux/delay.h>
+#include <linux/genhd.h>
#include <linux/mount.h>
#include <linux/device.h>

@@ -307,17 +308,21 @@ retry:
/*
* Allow the user to distinguish between failed sys_open
* and bad superblock on root device.
+ * and give them a list of the available devices
*/
#ifdef CONFIG_BLOCK
__bdevname(ROOT_DEV, b);
#endif
printk("VFS: Cannot open root device \"%s\" or %s\n",
root_device_name, b);
- printk("Please append a correct \"root=\" boot option\n");
+ printk("Please append a correct \"root=\" boot option; here are the available partitions:\n");

+ printk_all_partitions();
panic("VFS: Unable to mount root fs on %s", b);
}

+ printk("List of all partitions:\n");
+ printk_all_partitions();
printk("No filesystem could mount root, tried: ");
for (p = fs_names; *p; p += strlen(p)+1)
printk(" %s", p);
#<EOF>