Display all possible partitions when the root filesystem failed to mount

Display all possible partitions when the root filesystem is not mounted.
This helps to track spell'o's and missing drivers.

Updated to work with newer kernels.

Example output:

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)

[akpm@linux-foundation.org: cleanups, fix printk warnings]
Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Cc: Dave Gilbert <linux@treblig.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/block/genhd.c b/block/genhd.c
index b5664440896c..93a2cf654597 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -213,6 +213,59 @@ struct gendisk *get_gendisk(dev_t dev, int *part)
         return  kobj ? to_disk(kobj) : NULL;
 }
 
+/*
+ * print 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.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)