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Subject[PATCH v4 9/9] RDMA/umem_odp: optimize out the case when a range is updated to read only
Date
From: Jérôme Glisse <jglisse@redhat.com>

When range of virtual address is updated read only and corresponding
user ptr object are already read only it is pointless to do anything.
Optimize this case out.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: kvm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-rdma@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
---
drivers/infiniband/core/umem_odp.c | 22 +++++++++++++++++++---
include/rdma/ib_umem_odp.h | 1 +
2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index a4ec43093cb3..fa4e7fdcabfc 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -140,8 +140,15 @@ static void ib_umem_notifier_release(struct mmu_notifier *mn,
static int invalidate_range_start_trampoline(struct ib_umem_odp *item,
u64 start, u64 end, void *cookie)
{
+ bool update_to_read_only = *((bool *)cookie);
+
ib_umem_notifier_start_account(item);
- item->umem.context->invalidate_range(item, start, end);
+ /*
+ * If it is already read only and we are updating to read only then we
+ * do not need to change anything. So save time and skip this one.
+ */
+ if (!update_to_read_only || !item->read_only)
+ item->umem.context->invalidate_range(item, start, end);
return 0;
}

@@ -150,6 +157,7 @@ static int ib_umem_notifier_invalidate_range_start(struct mmu_notifier *mn,
{
struct ib_ucontext_per_mm *per_mm =
container_of(mn, struct ib_ucontext_per_mm, mn);
+ bool update_to_read_only;

if (range->blockable)
down_read(&per_mm->umem_rwsem);
@@ -166,10 +174,13 @@ static int ib_umem_notifier_invalidate_range_start(struct mmu_notifier *mn,
return 0;
}

+ update_to_read_only = mmu_notifier_range_update_to_read_only(range);
+
return rbt_ib_umem_for_each_in_range(&per_mm->umem_tree, range->start,
range->end,
invalidate_range_start_trampoline,
- range->blockable, NULL);
+ range->blockable,
+ &update_to_read_only);
}

static int invalidate_range_end_trampoline(struct ib_umem_odp *item, u64 start,
@@ -363,6 +374,9 @@ struct ib_umem_odp *ib_alloc_odp_umem(struct ib_ucontext_per_mm *per_mm,
goto out_odp_data;
}

+ /* Assume read only at first, each time GUP is call this is updated. */
+ odp_data->read_only = true;
+
odp_data->dma_list =
vzalloc(array_size(pages, sizeof(*odp_data->dma_list)));
if (!odp_data->dma_list) {
@@ -619,8 +633,10 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt,
goto out_put_task;
}

- if (access_mask & ODP_WRITE_ALLOWED_BIT)
+ if (access_mask & ODP_WRITE_ALLOWED_BIT) {
+ umem_odp->read_only = false;
flags |= FOLL_WRITE;
+ }

start_idx = (user_virt - ib_umem_start(umem)) >> page_shift;
k = start_idx;
diff --git a/include/rdma/ib_umem_odp.h b/include/rdma/ib_umem_odp.h
index 0b1446fe2fab..8256668c6170 100644
--- a/include/rdma/ib_umem_odp.h
+++ b/include/rdma/ib_umem_odp.h
@@ -76,6 +76,7 @@ struct ib_umem_odp {
struct completion notifier_completion;
int dying;
struct work_struct work;
+ bool read_only;
};

static inline struct ib_umem_odp *to_ib_umem_odp(struct ib_umem *umem)
--
2.17.2
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