Re: [PATCH V2] target: iscsi: simplify the connection closing mechanism

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On Tue, Dec 07, 2021 at 01:59:08PM -0600, Mike Christie wrote:
> On 11/11/21 7:37 AM, Maurizio Lombardi wrote:
> > When the connection reinstatement is performed, the target driver
> > executes a complex scheme of complete()/wait_for_completion() that is not
> > really needed.
> > 
> > Considering that:
> > 
> > 1) The callers of iscsit_connection_reinstatement_rcfr() and
> >    iscsit_cause_connection_reinstatement() hold a reference
> >    to the conn structure.> > 2) iscsit_close_connection() will sleep when calling
> >    iscsit_check_conn_usage_count() until the conn structure's refcount
> >    reaches zero.
> > 
> > we can optimize the driver the following way:
> > 
> > * The threads that must sleep until the connection is closed
> >   will all wait for the "conn_wait_comp" completion,
> >   iscsit_close_connection() will then call complete_all() to wake them up.
> >   No need to have multiple completion structures.
> > 
> > * The conn_post_wait_comp completion is not necessary and can be removed
> >   because iscsit_close_connection() sleeps until all the other threads
> >   release the conn structure.
> >   (see the iscsit_check_conn_usage_count() function)
> > 
> > V2: do not set connection_reinstatement to 1 in iscsit_close_connection(),
> >     leave iscsit_cause_connection_reinstatement() deal with reentrancy.
> > 
> 
> What was the issue with setting it to 1?
>

At first I thought that setting it to 1 could introduce a race condition,
then I realized that it's not the case, setting it to 1 simply has no effect
and therefore the assignment can be removed.

Maurizio




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