| Message ID | 20240522135444.1685642-9-haakon.bugge@oracle.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | rds: rdma: Add ability to force GFP_NOIO | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Guessing tree name failed - patch did not apply, async |
> -----Original Message----- > From: Håkon Bugge <haakon.bugge@oracle.com> > Sent: Wednesday, May 22, 2024 7:25 PM > To: linux-rdma@vger.kernel.org; linux-kernel@vger.kernel.org; > netdev@vger.kernel.org; rds-devel@oss.oracle.com > Cc: Jason Gunthorpe <jgg@ziepe.ca>; Leon Romanovsky <leon@kernel.org>; > Saeed Mahameed <saeedm@nvidia.com>; Tariq Toukan <tariqt@nvidia.com>; > David S . Miller <davem@davemloft.net>; Eric Dumazet > <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni > <pabeni@redhat.com>; Tejun Heo <tj@kernel.org>; Lai Jiangshan > <jiangshanlai@gmail.com>; Allison Henderson <allison.henderson@oracle.com>; > Manjunath Patil <manjunath.b.patil@oracle.com>; Mark Zhang > <markzhang@nvidia.com>; Håkon Bugge <haakon.bugge@oracle.com>; Chuck > Lever <chuck.lever@oracle.com>; Shiraz Saleem <shiraz.saleem@intel.com>; > Yang Li <yang.lee@linux.alibaba.com> > Subject: [PATCH v3 4/6] RDMA/cm: Brute force GFP_NOIO > > In ib_cm_init(), we call memalloc_noio_{save,restore} in a parenthetic fashion > when enabled by the module parameter force_noio. > > This in order to conditionally enable ib_cm to work aligned with block I/O devices. > Any work queued later on work-queues created during module initialization will > inherit the PF_MEMALLOC_{NOIO,NOFS} flag(s), due to commit ("workqueue: > Inherit NOIO and NOFS alloc flags"). > > We do this in order to enable ULPs using the RDMA stack to be used as a > network block I/O device. This to support a filesystem on top of a raw block > device which uses said ULP(s) 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 the ULP in > question, which calls the RDMA stack. Now, if regular GFP_KERNEL allocations > in ULP 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 the ULP 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). > > Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com> > --- > drivers/infiniband/core/cm.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c index > 07fb8d3c037f0..767eec38eb57d 100644 > --- a/drivers/infiniband/core/cm.c > +++ b/drivers/infiniband/core/cm.c > @@ -22,6 +22,7 @@ > #include <linux/workqueue.h> > #include <linux/kdev_t.h> > #include <linux/etherdevice.h> > +#include <linux/sched/mm.h> > > #include <rdma/ib_cache.h> > #include <rdma/ib_cm.h> > @@ -35,6 +36,11 @@ MODULE_DESCRIPTION("InfiniBand CM"); > MODULE_LICENSE("Dual BSD/GPL"); > > #define CM_DESTROY_ID_WAIT_TIMEOUT 10000 /* msecs */ > + > +static bool cm_force_noio; > +module_param_named(force_noio, cm_force_noio, bool, 0444); > +MODULE_PARM_DESC(force_noio, "Force the use of GFP_NOIO (Y/N)"); > + > static const char * const ibcm_rej_reason_strs[] = { > [IB_CM_REJ_NO_QP] = "no QP", > [IB_CM_REJ_NO_EEC] = "no EEC", > @@ -4504,6 +4510,10 @@ static void cm_remove_one(struct ib_device > *ib_device, void *client_data) static int __init ib_cm_init(void) { > int ret; > + unsigned int noio_flags; minor: please follow reverse xmas tree order > + > + if (cm_force_noio) > + noio_flags = memalloc_noio_save(); > > INIT_LIST_HEAD(&cm.device_list); > rwlock_init(&cm.device_lock); > @@ -4527,10 +4537,13 @@ static int __init ib_cm_init(void) > if (ret) > goto error3; > > - return 0; > + goto error2; > error3: > destroy_workqueue(cm.wq); > error2: > + if (cm_force_noio) > + memalloc_noio_restore(noio_flags); > + > return ret; > } > > -- > 2.31.1 >
diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c index 07fb8d3c037f0..767eec38eb57d 100644 --- a/drivers/infiniband/core/cm.c +++ b/drivers/infiniband/core/cm.c @@ -22,6 +22,7 @@ #include <linux/workqueue.h> #include <linux/kdev_t.h> #include <linux/etherdevice.h> +#include <linux/sched/mm.h> #include <rdma/ib_cache.h> #include <rdma/ib_cm.h> @@ -35,6 +36,11 @@ MODULE_DESCRIPTION("InfiniBand CM"); MODULE_LICENSE("Dual BSD/GPL"); #define CM_DESTROY_ID_WAIT_TIMEOUT 10000 /* msecs */ + +static bool cm_force_noio; +module_param_named(force_noio, cm_force_noio, bool, 0444); +MODULE_PARM_DESC(force_noio, "Force the use of GFP_NOIO (Y/N)"); + static const char * const ibcm_rej_reason_strs[] = { [IB_CM_REJ_NO_QP] = "no QP", [IB_CM_REJ_NO_EEC] = "no EEC", @@ -4504,6 +4510,10 @@ static void cm_remove_one(struct ib_device *ib_device, void *client_data) static int __init ib_cm_init(void) { int ret; + unsigned int noio_flags; + + if (cm_force_noio) + noio_flags = memalloc_noio_save(); INIT_LIST_HEAD(&cm.device_list); rwlock_init(&cm.device_lock); @@ -4527,10 +4537,13 @@ static int __init ib_cm_init(void) if (ret) goto error3; - return 0; + goto error2; error3: destroy_workqueue(cm.wq); error2: + if (cm_force_noio) + memalloc_noio_restore(noio_flags); + return ret; }
In ib_cm_init(), we call memalloc_noio_{save,restore} in a parenthetic fashion when enabled by the module parameter force_noio. This in order to conditionally enable ib_cm to work aligned with block I/O devices. Any work queued later on work-queues created during module initialization will inherit the PF_MEMALLOC_{NOIO,NOFS} flag(s), due to commit ("workqueue: Inherit NOIO and NOFS alloc flags"). We do this in order to enable ULPs using the RDMA stack to be used as a network block I/O device. This to support a filesystem on top of a raw block device which uses said ULP(s) 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 the ULP in question, which calls the RDMA stack. Now, if regular GFP_KERNEL allocations in ULP 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 the ULP 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). Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com> --- drivers/infiniband/core/cm.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)