oops..forgot that was paywalled
They say its going to be fixed in the MArch 23rd release of 9.1 and may release of 9.2 so we will soon see...
herei s bug details.
Title SMB byte lock downgrades do not work on ONTAP
Bug Severity 2 - System barely usable
Product Data ONTAP
Bug Type Unknown
Formatted An issue in ONTAP causes Server Message Block (SMB) byte lock downgrades
to work incorrectly on ONTAP. When an SMB client establishes an exclusive
byte lock on a file offset range, and then subsequently wants to downgrade
the byte lock to a shared byte lock on the same file offset range -- while at
the same time does not want any other SMB client to acquire an exclusive byte
lock on the same file offset range -- the following occurs:
1. The SMB client will acquire a shared byte lock on the same file offset range
and this will be granted without any waiting period since the SMB client
already has an exclusive byte lock.
2. The SMB client will release the byte lock for that file offset
range. At this point the SMB server should release the exclusive byte lock.
Instead ONTAP misbehaves by releasing the shared byte lock that was established
on that file offset range.
3. While the application assumes that the file is left with a shared byte lock,
ONTAP has left an exclusive byte lock on that file offset range. This causes
other applications wanting to establish the shared byte lock to indefinitely
wait until the byte lock is released by the first application.
Formatted There are no workarounds available within the ONTAP software. The Windows
application that is trying to perform the byte lock downgrades can work around
this issue by changing its locking sequence to release the exclusive byte lock
first before establishing the shared byte lock for the file offset range.
Formatted This issue has been seen with customers using SnapManager for Hyper-V to create a
VSS snapshot for VHDX files stored on SMB shares.
Note that the locking and unlocking offset ranges for the exclusive and the
shared byte lock sequences need not be exact matching ranges. They can be
overlapping each other and experience the same issue.