linux-kernel - [RFC PATCH 1/7] IB/mlx5: Change ib_umem_odp_map_dma_single_page() to retain umem

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Date:   Wed,  7 Sep 2022 11:42:59 +0900
From:   Daisuke Matsuda <matsuda-daisuke@...itsu.com>
To:     linux-rdma@...r.kernel.org, leonro@...dia.com, jgg@...dia.com,
        zyjzyj2000@...il.com
Cc:     nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        rpearsonhpe@...il.com, yangx.jy@...itsu.com, lizhijian@...itsu.com,
        y-goto@...itsu.com, Daisuke Matsuda <matsuda-daisuke@...itsu.com>
Subject: [RFC PATCH 1/7] IB/mlx5: Change ib_umem_odp_map_dma_single_page() to retain umem_mutex

ib_umem_odp_map_dma_single_page(), which has been used only by the mlx5
driver, holds umem_mutex on success and releases on failure. This
behavior is not convenient for other drivers to use it, so change it to
always retain mutex on return.

Signed-off-by: Daisuke Matsuda <matsuda-daisuke@...itsu.com>
---
 drivers/infiniband/core/umem_odp.c | 6 ++----
 drivers/infiniband/hw/mlx5/odp.c   | 4 +++-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index c459c4d011cf..92617a021439 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -328,8 +328,8 @@ static int ib_umem_odp_map_dma_single_page(
  *
  * Maps the range passed in the argument to DMA addresses.
  * The DMA addresses of the mapped pages is updated in umem_odp->dma_list.
- * Upon success the ODP MR will be locked to let caller complete its device
- * page table update.
+ * The umem mutex is locked and not released in this function. The caller should
+ * complete its device page table update before releasing the lock.
  *
  * Returns the number of pages mapped in success, negative error code
  * for failure.
@@ -456,8 +456,6 @@ int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,
 	/* upon success lock should stay on hold for the callee */
 	if (!ret)
 		ret = dma_index - start_idx;
-	else
-		mutex_unlock(&umem_odp->umem_mutex);
 
 out_put_mm:
 	mmput(owning_mm);
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index bc97958818bb..a0de27651586 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -572,8 +572,10 @@ static int pagefault_real_mr(struct mlx5_ib_mr *mr, struct ib_umem_odp *odp,
 		access_mask |= ODP_WRITE_ALLOWED_BIT;
 
 	np = ib_umem_odp_map_dma_and_lock(odp, user_va, bcnt, access_mask, fault);
-	if (np < 0)
+	if (np < 0) {
+		mutex_unlock(&odp->umem_mutex);
 		return np;
+	}
 
 	/*
 	 * No need to check whether the MTTs really belong to this MR, since
-- 
2.31.1