path: root/block
diff options
authorZhang, Yanmin <>2008-11-14 08:26:30 +0100
committerJens Axboe <>2008-11-18 15:08:56 +0100
commit561ec68e4de7947167937c49c451728e6b19e63b (patch)
tree4391af5bc00e5a2039e703df43ec3e84a21b63d5 /block
parent55e8e30c382d25c34f8aafcc78efec948571a941 (diff)
block: fix boot failure with CONFIG_DEBUG_BLOCK_EXT_DEVT=y and nash
We run into system boot failure with kernel 2.6.28-rc. We found it on a couple of machines, including T61 notebook, nehalem machine, and another HPC NX6325 notebook. All the machines use FedoraCore 8 or FedoraCore 9. With kernel prior to 2.6.28-rc, system boot doesn't fail. I debug it and locate the root cause. Pls. see As a matter of fact, there are 2 bugs. 1)root=/dev/sda1, system boot randomly fails. Mostly, boot for 5 times and fails once. nash has a bug. Some of its functions misuse return value 0. Sometimes, 0 means timeout and no uevent available. Sometimes, 0 means nash gets an uevent, but the uevent isn't block-related (for exmaple, usb). If by coincidence, kernel tells nash that uevents are available, but kernel also set timeout, nash might stops collecting other uevents in queue if current uevent isn't block-related. I work out a patch for nash to fix it. 2) root=LABEL=/, system always can't boot. initrd init reports switchroot fails. Here is an executation branch of nash when booting: (1) nash read /sys/block/sda/dev; Assume major is 8 (on my desktop) (2) nash query /proc/devices with the major number; It found line "8 sd"; (3) nash use 'sd' to search its own probe table to find device (DISK) type for the device and add it to its own list; (4) Later on, it probes all devices in its list to get filesystem labels; scsi register "8 sd" always. When major is 259, nash fails to find the device(DISK) type. I enables CONFIG_DEBUG_BLOCK_EXT_DEVT=y when compiling kernel, so 259 is picked up for device /dev/sda1, which causes nash to fail to find device (DISK) type. To fixing issue 2), I create a patch for nash and another patch for kernel. Below is the patch for kernel 2.6.28-rc4. It registers blkext, a new block device in proc/devices. With 2 patches on nash and 1 patch on kernel, I boot my machines for dozens of times without failure. Signed-off-by Zhang Yanmin <> Acked-by: Tejun Heo <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block')
1 files changed, 2 insertions, 0 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 4e5e7493f67..27549e470da 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -768,6 +768,8 @@ static int __init genhd_device_init(void)
bdev_map = kobj_map_init(base_probe, &block_class_lock);
+ register_blkdev(BLOCK_EXT_MAJOR, "blkext");
/* create top-level block dir */
block_depr = kobject_create_and_add("block", NULL);