netdev - Re: [PATCH net v3 1/7] net/rds: Give fr_state a chance to transition to FRMR_IS

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Message-ID: <88c45c78-13fb-9774-6397-397b5d08c78e@oracle.com>
Date:   Tue, 16 Jul 2019 17:26:04 -0700
From:   santosh.shilimkar@...cle.com
To:     Gerd Rausch <gerd.rausch@...cle.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, rds-devel@....oracle.com
Cc:     David Miller <davem@...emloft.net>
Subject: Re: [PATCH net v3 1/7] net/rds: Give fr_state a chance to transition
 to FRMR_IS_FREE

On 7/16/19 3:28 PM, Gerd Rausch wrote:
> In the context of FRMR (ib_frmr.c):
> 
> Memory regions make it onto the "clean_list" via "rds_ib_flush_mr_pool",
> after the memory region has been posted for invalidation via
> "rds_ib_post_inv".
> 
> At that point in time, "fr_state" may still be in state "FRMR_IS_INUSE",
> since the only place where "fr_state" transitions to "FRMR_IS_FREE"
> is in "rds_ib_mr_cqe_handler", which is triggered by a tasklet.
> 
> So in case we notice that "fr_state != FRMR_IS_FREE" (see below),
> we wait for "fr_inv_done" to trigger with a maximum of 10msec.
> Then we check again, and only put the memory region onto the drop_list
> (via "rds_ib_free_frmr") in case the situation remains unchanged.
> 
> This avoids the problem of memory-regions bouncing between "clean_list"
> and "drop_list" before they even have a chance to be properly invalidated.
> 
> Signed-off-by: Gerd Rausch <gerd.rausch@...cle.com>
> ---
Thanks for the update.

Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>