fix handling of too many open zones at mount time v2

[Christoph Hellwig <hch@lst.de>]

Hi all,

because there is no actual write pointer when running the zoned allocator
on conventional devices or zones, we can see spurious extra open zones
when the last blocks in a written zone have been invalidated.  This
series adds code to handle that case and remove these spurious extra
zones.  It also fixes up the mountinfo code for open zones to be
more easy to parse, and adds a new sysfs file reporting the currently
open zones, which makes it easier to use the value in tests.

A test for the open zone behavior will be added to xfstests.

Changes since v1:
 - spelling and other documentation fixes
 - move two patches not directly related to the fix to a different
   series

Diffstat:
 xfs_trace.h      |    1 
 xfs_zone_alloc.c |  129 ++++++++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 110 insertions(+), 20 deletions(-)