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

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Date: Tue, 14 May 2024 10:53:05 +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 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 ... ?

> 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
>