Move partition scanning from userspace to module.

Currently, zpool online -e (dynamic vdev expansion) doesn't work on
whole disks because we're invoking ioctl(BLKRRPART) from userspace
while ZFS still has a partition open on the disk, which results in
EBUSY.

This patch moves the BLKRRPART invocation from the zpool utility to the
module. Specifically, this is done just before opening the device in
vdev_disk_open() which is called inside vdev_reopen(). This requires
jumping through some hoops to get to the disk device from the partition
device, and to make sure we can still open the partition after the
BLKRRPART call.

Note that this new code path is triggered on dynamic vdev expansion
only; other actions, like creating a new pool, are unchanged and still
call BLKRRPART from userspace.

This change also depends on API changes which are available in 2.6.37
and latter kernels.  The build system has been updated to detect this,
but there is no compatibility mode for older kernels.  This means that
online expansion will NOT be available in older kernels.  However, it
will still be possible to expand the vdev offline.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #808

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index fa9f36cc6..833930571 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -2097,6 +2097,9 @@ zpool_relabel_disk(libzfs_handle_t *hdl, const char *path, const char *msg)
 	 * It's possible that we might encounter an error if the device
 	 * does not have any unallocated space left. If so, we simply
 	 * ignore that error and continue on.
+	 *
+	 * Also, we don't call efi_rescan() - that would just return EBUSY.
+	 * The module will do it for us in vdev_disk_open().
 	 */
 	error = efi_use_whole_disk(fd);
 	(void) close(fd);
@@ -3847,7 +3850,7 @@ zpool_label_disk(libzfs_handle_t *hdl, zpool_handle_t *zhp, char *name)
 	vtoc->efi_parts[8].p_size = resv;
 	vtoc->efi_parts[8].p_tag = V_RESERVED;
 
-	if ((rval = efi_write(fd, vtoc)) != 0) {
+	if ((rval = efi_write(fd, vtoc)) != 0 || (rval = efi_rescan(fd)) != 0) {
 		/*
 		 * Some block drivers (like pcata) may not support EFI
 		 * GPT labels.  Print out a helpful error message dir-