Commits on Jul 13, 2018

1. Add support for autoexpand property …

   While the autoexpand property may seem like a small feature it
   depends on a significant amount of system infrastructure.  Enough
   of that infrastructure is now in place with a few modifications
   for Linux it can be supported.
   
   Auto-expand works as follows; when a block device is modified
   (re-sized, closed after being open r/w, etc) a change uevent is
   generated for udev.  The ZED, which is monitoring udev events,
   passes the change event along to zfs_deliver_dle() if the disk
   or partition contains a zfs_member as identified by blkid.
   
   From here the device is matched against all imported pool vdevs
   using the vdev_guid which was read from the label by blkid.  If
   a match is found the ZED reopens the pool vdev.  This re-opening
   is important because it allows the vdev to be briefly closed so
   the disk partition table can be re-read.  Otherwise, it wouldn't
   be possible to report thee maximum possible expansion size.
   
   Finally, if the property autoexpand=on a vdev expansion will be
   attempted.  After performing some sanity checks on the disk to
   verify that it is safe to expand,  the primary partition (-part1)
   will be expanded and the partition table updated.  The partition
   is then re-opened (again) to detect the updated size which allows
   the new capacity to be used.
   
   In order to make all of the above possible the following changes
   were required:
   
   * Updated the zpool_expand_001_pos and zpool_expand_003_pos tests.
     These tests now create a pool which is layered on a loopback,
     scsi_debug, and file vdev.  This allows for testing of non-
     partitioned block device (loopback), a partition block device
     (scsi_debug), and a file which does not receive udev change
     events.  This provided for better test coverage, and by removing
     the layering on ZFS volumes there issues surrounding layering
     one pool on another are avoided.
   
   * zpool_find_vdev_by_physpath() updated to accept a vdev guid.
     This allows for matching by guid rather than path which is a
     more reliable way for the ZED to reference a vdev.
   
   * Fixed zfs_zevent_wait() signal handling which could result
     in the ZED spinning when a signal was not handled.
   
   * Removed vdev_disk_rrpart() functionality which can be abandoned
     in favor of kernel provided blkdev_reread_part() function.
   
   * Added a rwlock which is held as a writer while a disk is being
     reopened.  This is important to prevent errors from occurring
     for any configuration related IOs which bypass the SCL_ZIO lock.
     The zpool_reopen_007_pos.ksh test case was added to verify IO
     error are never observed when reopening.  This is not expected
     to impact IO performance.
   
   Additional fixes which aren't critical but were discovered and
   resolved in the course of developing this functionality.
   
   * Added PHYS_PATH="/dev/zvol/dataset" to the vdev configuration for
     ZFS volumes.  This is as good as a unique physical path, while the
     volumes are not used in the test cases anymore for other reasons
     this improvement was included.
   
   Signed-off-by: Sara Hartse <sara.hartse@delphix.com>
   Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
   Issue openzfs#120
   Issue openzfs#2437
   Issue openzfs#5771
   Issue openzfs#7366
   Issue openzfs#7582

   

   behlendorf committed Jul 13, 2018
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