In check_disk() we should only check the entire device if it
not a whole disk. It is a whole disk with an EFI label on it,
it is possible that libblkid will misidentify the device as a
filesystem. I had a case yesterday where 2 bytes in the EFI
GUID happened we set to the right values such that libblkid
decided there was a minux filesystem there. If it's a whole
device we look for a EFI label.
If we are able to read the backup EFI label from a device but
the primary is corrupt. Then don't bother trying to stat
the partitions in /dev/ the kernel will not create devices
using the backup label when the primary is damaged.
Add code to determine if we have a udev path instead of a
normal device path. In this case use the -part# partition
naming scheme instead of the /dev/disk# scheme. This is
important because we always want to access devices using
the full path provided at configuration time.
Readded support for zpool_relabel_disk() now that we have
the full libefi library in place we do have access to this
functionality.
Lots of additional paranoia to ensure EFI label are written
correctly. These changes include:
1) Removing the O_NDELAY flag when opening a file descriptor
for libefi. This flag should really only be used when you
do not intend to do any file IO. Under Solaris only ioctl()'s
were performed under linux we do perform reads and writes.
2) Use O_DIRECT to ensure any caching is bypassed while
writing or reading the EFI labels. This change forces the
use of sector aligned memory buffers which are allocated
using posix_memalign().
3) Add additional efi_debug error messages to efi_ioctl().
4) While doing a fsync is good to ensure the EFI label is on
disk we can, and should go one step futher by issuing the
BLKFLSBUF ioctl(). This signals the kernel to instruct the
drive to flush it's on-disk cache.
5) Because of some initial strangeness I observed in testing
with some flakey drives be extra paranoid in zpool_label_disk().
After we've written the device without error, flushed the drive
caches, correctly detected the new partitions created by the
kernel. Then additionally read back the EFI label from user
space to make sure it is intact and correct. I don't think we
can ever be to careful here.
NOTE: The was recently some concern expressed that writing EFI
labels from user space on Linux was not the right way to do this.
That instead two kernel ioctl()s should be used to create and
remove partitions. After some investigation it's clear to me
using those ioctl() would be a bad idea. The in fact don't
actually write partition tables to the disk, they only create
the partition devices in the kernel. So what you really want
to do is write the label out from user space, then prompt the
kernel to re-read the partition from disk to create the partitions.
This is in fact exactly what newer version of parted do.
