[rds-devel] [PATCH v2 0/6] rds: rdma: Add ability to force GFP_NOIO

[Håkon Bugge]

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
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                            | 21 +++++++
 net/rds/af_rds.c                              | 59 ++++++++++++++++++-
 7 files changed, 141 insertions(+), 12 deletions(-)

--
2.45.0