[PATCH] root mount failure emit filesystems attempted

[PATCH] root mount failure emit filesystems attempted

[Andy Whitcroft]

root mount failure emit filesystems attempted

When we fail to mount from a valid root device list out the filesystems
we have tried to mount it with.  This gives the user vital diagnostics
as to what is missing from their kernel.

For example in the fragment below the kernel does not have CRAMFS
compiled into the kernel and yet appears to recognise it at the RAMDISK
detect stage.  Later the mount fails as we don't have the filesystem.

  RAMDISK: cramfs filesystem found at block 0
  RAMDISK: Loading 1604KiB [1 disk] into ram disk... done.
  XFS: bad magic number
  XFS: SB validate failed
  No filesystem could mount root, tried: reiserfs ext3 ext2 msdos vfat
    iso9660 jfs xfs
  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,1)
  
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
---
 do_mounts.c |    5 +++++
 1 files changed, 5 insertions(+)
diff -upN reference/init/do_mounts.c current/init/do_mounts.c
--- reference/init/do_mounts.c
+++ current/init/do_mounts.c
@@ -310,6 +310,11 @@ retry:
 
 		panic("VFS: Unable to mount root fs on %s", b);
 	}
+
+	printk("No filesystem could mount root, tried: ");
+	for (p = fs_names; *p; p += strlen(p)+1)
+		printk(" %s", p);
+	printk("\n");
 	panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
 out:
 	putname(fs_names);

Re: [PATCH] root mount failure emit filesystems attempted

[Jan Engelhardt]

>
>root mount failure emit filesystems attempted

Something better was already submitted earlier, but it did not get merged.

URL:      http://tinyurl.com/pa4ap

Long URL: http://groups.google.com/group/linux.kernel/browse_thread/thread/81bfec7e96bd60cd/b3a7f8421fb7ca53?q=show+partitions+diff&rnum=1#b3a7f8421fb7ca53

What it does:
When we fail to mount from a valid root device list out the 
block devices available.

>When we fail to mount from a valid root device list out the filesystems
>we have tried to mount it with.  This gives the user vital diagnostics
>as to what is missing from their kernel.

I think both should be merged. An updated version of the print-partitions 
patch that works with 2.6.17-rc3 is below.

>  No filesystem could mount root, tried: reiserfs ext3 ext2 msdos vfat
>    iso9660 jfs xfs
>  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,1)

Your patch: Acked-by: Jan Engelhardt <jengelh@gmx.de>


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

diff --fast -Ndpru linux-2.6.17-rc3~/block/genhd.c linux-2.6.17-rc3+/block/genhd.c
--- linux-2.6.17-rc3~/block/genhd.c	2006-04-27 04:19:25.000000000 +0200
+++ linux-2.6.17-rc3+/block/genhd.c	2006-05-01 18:50:14.326821000 +0200
@@ -214,6 +214,52 @@ 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 printk_all_partitions(void)
+{
+	int n;
+        struct gendisk* sgp;
+	down(&block_subsys_sem);
+
+        /* 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) && !(sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)) {
+			/* Note, unlike /proc/partitions I'm showing the numbers in hex
+			   in the same format as the root= option */
+			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) && (sgp->driverfs_dev->driver)) {
+			  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])
+					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 */
+		} /* Non 0 size, not surpressed */
+	} /* Block device loop */
+
+	up(&block_subsys_sem);
+  
+}
+
 #ifdef CONFIG_PROC_FS
 /* iterator */
 static void *part_start(struct seq_file *part, loff_t *pos)
diff --fast -Ndpru linux-2.6.17-rc3~/include/linux/genhd.h linux-2.6.17-rc3+/include/linux/genhd.h
--- linux-2.6.17-rc3~/include/linux/genhd.h	2006-04-27 04:19:25.000000000 +0200
+++ linux-2.6.17-rc3+/include/linux/genhd.h	2006-05-01 18:50:14.326821000 +0200
@@ -401,6 +401,7 @@ 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);
 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);
diff --fast -Ndpru linux-2.6.17-rc3~/init/do_mounts.c linux-2.6.17-rc3+/init/do_mounts.c
--- linux-2.6.17-rc3~/init/do_mounts.c	2006-04-27 04:19:25.000000000 +0200
+++ linux-2.6.17-rc3+/init/do_mounts.c	2006-05-01 18:50:14.326821000 +0200
@@ -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/nfs_fs.h>
@@ -302,14 +303,18 @@ 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
 		 */
 		__bdevname(ROOT_DEV, b);
 		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 partitions available:\n");
 
+		printk_all_partitions();
 		panic("VFS: Unable to mount root fs on %s", b);
 	}
+	printk("List of all partitions:\n");
+	printk_all_partitions();
 	panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
 out:
 	putname(fs_names);
#<<eof>>

Jan Engelhardt
--