linux-kernel - Re: [PATCH 0/6] rds: rdma: Add ability to force GFP

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Date: Tue, 14 May 2024 14:02:22 +0200
From: Zhu Yanjun <zyjzyj2000@...il.com>
To: Håkon Bugge <haakon.bugge@...cle.com>,
 linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, rds-devel@....oracle.com
Cc: Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
 Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Tejun Heo <tj@...nel.org>,
 Lai Jiangshan <jiangshanlai@...il.com>,
 Allison Henderson <allison.henderson@...cle.com>,
 Manjunath Patil <manjunath.b.patil@...cle.com>,
 Mark Zhang <markzhang@...dia.com>, Chuck Lever <chuck.lever@...cle.com>,
 Shiraz Saleem <shiraz.saleem@...el.com>, Yang Li <yang.lee@...ux.alibaba.com>
Subject: Re: [PATCH 0/6] rds: rdma: Add ability to force GFP_NOIO

On 14.05.24 10:53, Zhu Yanjun wrote:
> On 13.05.24 14:53, Håkon Bugge wrote:
>> This series enables RDS and the RDMA stack to be used as a block I/O
>> device. This to support a filesystem on top of a raw block device
> 
> This is to support a filesystem ... ?

Sorry. my bad. I mean, normally rds is used to act as a communication 
protocol between Oracle databases. Now in this patch series, it seems 
that rds acts as a communication protocol to support a filesystem. So I 
am curious which filesystem that rds is supporting?

Thanks a lot.
Zhu Yanjun

> 
>> which uses RDS and the RDMA stack as the network transport layer.
>>
>> Under intense memory pressure, we get memory reclaims. Assume the
>> filesystem reclaims memory, goes to the raw block device, which calls
>> into RDS, which calls the RDMA stack. Now, if regular GFP_KERNEL
>> allocations in RDS or the RDMA stack require reclaims to be fulfilled,
>> we end up in a circular dependency.
>>
>> We break this circular dependency by:
>>
>> 1. Force all allocations in RDS and the relevant RDMA stack to use
>>     GFP_NOIO, by means of a parenthetic use of
>>     memalloc_noio_{save,restore} on all relevant entry points.
>>
>> 2. Make sure work-queues inherits current->flags
>>     wrt. PF_MEMALLOC_{NOIO,NOFS}, such that work executed on the
>>     work-queue inherits the same flag(s).
>>
>> Håkon Bugge (6):
>>    workqueue: Inherit NOIO and NOFS alloc flags
>>    rds: Brute force GFP_NOIO
>>    RDMA/cma: Brute force GFP_NOIO
>>    RDMA/cm: Brute force GFP_NOIO
>>    RDMA/mlx5: Brute force GFP_NOIO
>>    net/mlx5: Brute force GFP_NOIO
>>
>>   drivers/infiniband/core/cm.c                  | 15 ++++-
>>   drivers/infiniband/core/cma.c                 | 20 ++++++-
>>   drivers/infiniband/hw/mlx5/main.c             | 22 +++++--
>>   .../net/ethernet/mellanox/mlx5/core/main.c    | 14 ++++-
>>   include/linux/workqueue.h                     |  2 +
>>   kernel/workqueue.c                            | 17 ++++++
>>   net/rds/af_rds.c                              | 60 ++++++++++++++++++-
>>   7 files changed, 138 insertions(+), 12 deletions(-)
>>
>> -- 
>> 2.39.3
>>
> 

-- 
Best