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Re: [libvirt] [PATCH v4 06/15] security_manager: Rework metadata locking



On 11/15/18 7:38 PM, John Ferlan wrote:
> 
> 
> On 11/14/18 7:44 AM, Michal Privoznik wrote:
>> Trying to use virlockd to lock metadata turns out to be too big
>> gun. Since we will always spawn a separate process for relabeling
>> we are safe to use thread unsafe POSIX locks and take out
>> virtlockd completely out of the picture.
>>
> 
> NB: This patch has a 1 second delay loop in the event the lock is
> already taken by another thread. Since it's not expected that threads
> holding the lock will need more than a second or two to process the
> various file security operations, it was felt this was a good starting
> point. The time taken to execute has two factors - the number of files
> to be locked and the time the operation required by the security driver
> to perform it's operation. Usage of virTimeBackOffStart may or may not
> help. Similarly a configurable delay time or delay maximum time is also
> possible, but was deemed unnecessary at this time.

Darn, I forgot to undo the virTimeBackOffStart. You know what? To avoid
sending v5 let me merge this version and investigate if using
virTimeBackOff is any better.

> 
> [fair enough statement??  - pick and choose if you want to add all, any
> part, or none of it... I think it's a fair representation for someone
> coming along and looking at this commit to consider if they wanted to
> make a change to help perceived performance if the delay loop becomes
> that type of problem. It's not that it wasn't considered, it just wasn't
> easily quantifiable].
> 
>> Signed-off-by: Michal Privoznik <mprivozn redhat com>
>> ---
>>  src/security/security_dac.c     |  12 +-
>>  src/security/security_manager.c | 225 +++++++++++++++++---------------
>>  src/security/security_manager.h |  17 ++-
>>  src/security/security_selinux.c |  11 +-
>>  4 files changed, 141 insertions(+), 124 deletions(-)
>>
> 
> Reviewed-by: John Ferlan <jferlan redhat com>

Thanks,
Michal


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