[PATCH 13/15] RDMA/mlx5: Do not store implicit children in the odp_mkeys xarray

Jason Gunthorpe
2019-10-09T16:36:18Z

These mkeys are entirely internal and are never used by the HW for
page fault. They should also never be used by userspace for prefetch.
Simplify & optimize things by not including them in the xarray.

Since the prefetch path can now never see a child mkey there is no need
for the second synchronize_srcu() during imr destroy.

Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
---
drivers/infiniband/hw/mlx5/odp.c | 36 ++++++--------------------------
1 file changed, 6 insertions(+), 30 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 71f8580b25b2ab..66523313c3e46c 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -146,9 +146,9 @@ void mlx5_odp_populate_klm(struct mlx5_klm *pklm, size_t idx, size_t nentries,

/*
* This must be called after the mr has been removed from implicit_children
- * and odp_mkeys and the SRCU synchronized. NOTE: The MR does not necessarily
- * have to be empty here, parallel page faults could have raced with the free
- * process and added pages to it.
+ * and the SRCU synchronized. NOTE: The MR does not necessarily have to be
+ * empty here, parallel page faults could have raced with the free process and
+ * added pages to it.
*/
static void free_implicit_child_mr(struct mlx5_ib_mr *mr, bool need_imr_xlt)
{
@@ -210,7 +210,6 @@ static void destroy_unused_implicit_child_mr(struct mlx5_ib_mr *mr)
mr)
goto out_unlock;

- __xa_erase(&mr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
atomic_inc(&imr->num_deferred_work);
call_srcu(&mr->dev->odp_srcu, &mr->odp_destroy.rcu,
free_implicit_child_mr_rcu);
@@ -401,13 +400,6 @@ static struct mlx5_ib_mr *implicit_get_child_mr(struct mlx5_ib_mr *imr,
if (IS_ERR(mr))
goto out_umem;

- err = xa_reserve(&imr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key),
- GFP_KERNEL);
- if (err) {
- ret = ERR_PTR(err);
- goto out_mr;
- }
-
mr->ibmr.pd = imr->ibmr.pd;
mr->access_flags = imr->access_flags;
mr->umem = &odp->umem;
@@ -424,7 +416,7 @@ static struct mlx5_ib_mr *implicit_get_child_mr(struct mlx5_ib_mr *imr,
MLX5_IB_UPD_XLT_ENABLE);
if (err) {
ret = ERR_PTR(err);
- goto out_release;
+ goto out_mr;
}

/*
@@ -433,26 +425,21 @@ static struct mlx5_ib_mr *implicit_get_child_mr(struct mlx5_ib_mr *imr,
*/
ret = xa_cmpxchg(&imr->implicit_children, idx, NULL, mr,
GFP_KERNEL);
- if (likely(!ret))
- xa_store(&imr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key),
- &mr->mmkey, GFP_ATOMIC);
if (unlikely(ret)) {
if (xa_is_err(ret)) {
ret = ERR_PTR(xa_err(ret));
- goto out_release;
+ goto out_mr;
}
/*
* Another thread beat us to creating the child mr, use
* theirs.
*/
- goto out_release;
+ goto out_mr;
}

mlx5_ib_dbg(imr->dev, "key %x mr %p\n", mr->mmkey.key, mr);
return mr;

-out_release:
- xa_release(&imr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
out_mr:
mlx5_mr_cache_free(imr->dev, mr);
out_umem:
@@ -535,14 +522,10 @@ void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr)
xa_lock(&imr->implicit_children);
xa_for_each (&imr->implicit_children, idx, mtt) {
__xa_erase(&imr->implicit_children, idx);
- __xa_erase(&dev->odp_mkeys, mlx5_base_mkey(mtt->mmkey.key));
list_add(&mtt->odp_destroy.elm, &destroy_list);
}
xa_unlock(&imr->implicit_children);

- /* Fence access to the child pointers via the pagefault thread */
- synchronize_srcu(&dev->odp_srcu);
-
/*
* num_deferred_work can only be incremented inside the odp_srcu, or
* under xa_lock while the child is in the xarray. Thus at this point
@@ -1655,13 +1638,6 @@ get_prefetchable_mr(struct ib_pd *pd, enum ib_uverbs_advise_mr_advice advice,
if (mr->ibmr.pd != pd)
return NULL;

- /*
- * Implicit child MRs are internal and userspace should not refer to
- * them.
- */
- if (mr->parent)
- return NULL;
-
odp = to_ib_umem_odp(mr->umem);

/* prefetch with write-access must be supported by the MR */
--
2.23.0