From: Dave Gilbert 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) Signed-off-by: Jan Engelhardt Signed-off-by: Andrew Morton --- block/genhd.c | 53 ++++++++++++++++++++++++++++++++++++++++ include/linux/genhd.h | 1 init/do_mounts.c | 7 ++++- 3 files changed, 60 insertions(+), 1 deletion(-) diff -puN block/genhd.c~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount block/genhd.c --- a/block/genhd.c~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount +++ a/block/genhd.c @@ -213,6 +213,59 @@ 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) diff -puN include/linux/genhd.h~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount include/linux/genhd.h --- a/include/linux/genhd.h~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount +++ a/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); diff -puN init/do_mounts.c~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount init/do_mounts.c --- a/init/do_mounts.c~display-all-possible-partitions-when-the-root-filesystem-failed-to-mount +++ a/init/do_mounts.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -308,17 +309,21 @@ 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); _