Change in vdsm[master]: sriov: Make the hook safe for concurrency

[Dan Kenigsberg]

Dan Kenigsberg has submitted this change and it was merged.

Change subject: sriov: Make the hook safe for concurrency
......................................................................

sriov: Make the hook safe for concurrency

The current model uses a cache that is not locked and could
be overwritten by a second VM creation effectively preventing
the return of the chown to root:root.

This patch solves that by creating with exclusivity a file for
each virtual function that is attached (thus avoiding locking)
but having concurrency safety due to the OS guarantee that the
not more than a single processes can perform an open when the
flags O_CREAT | O_EXCL are set.

Change-Id: I2c6ad7f2ee53911312700396000e0aca07a917e9
Signed-off-by: Antoni S. Puimedon 
---
M vdsm_hooks/sriov/after_vm_destroy.py
M vdsm_hooks/sriov/before_vm_start.py
2 files changed, 40 insertions(+), 46 deletions(-)

Approvals:
  Antoni Segura Puimedon: Verified
  Dan Kenigsberg: Looks good to me, approved

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Gerrit-MessageType: merged
Gerrit-Change-Id: I2c6ad7f2ee53911312700396000e0aca07a917e9
Gerrit-PatchSet: 1
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Antoni Segura Puimedon 
Gerrit-Reviewer: Antoni Segura Puimedon 
Gerrit-Reviewer: Dan Kenigsberg 
Gerrit-Reviewer: Dan Yasny 
Gerrit-Reviewer: Mark Wu 
Gerrit-Reviewer: Shu Ming 
Gerrit-Reviewer: oVirt Jenkins CI Server