From bbdc2821db041fb07ffa52e4a0e1ebb5410790e9 Mon Sep 17 00:00:00 2001 From: Olaf Kirch Date: Tue, 29 Apr 2008 13:46:53 -0700 Subject: [PATCH] mlx4_core: Avoid recycling old FMR R_Keys too soon When a FMR is unmapped, mlx4 resets the map count to 0, and clears the upper part of the R_Key which is used as the sequence counter. This poses a problem for RDS, which uses ib_fmr_unmap as a fence operation. RDS assumes that after issuing an unmap, the old R_Keys will be invalid for a "reasonable" period of time. For instance, Oracle processes uses shared memory buffers allocated from a pool of buffers. When a process dies, we want to reclaim these buffers -- but we must make sure there are no pending RDMA operations to/from those buffers. The only way to achieve that is by using unmap and sync the TPT. However, when the sequence count is reset on unmap, there is a high likelihood that a new mapping will be given the same R_Key that was issued a few milliseconds ago. To prevent this, don't reset the sequence count when unmapping a FMR. Signed-off-by: Olaf Kirch Signed-off-by: Roland Dreier --- drivers/net/mlx4/mr.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/net/mlx4/mr.c b/drivers/net/mlx4/mr.c index 79b317b88c86..cb46446b2691 100644 --- a/drivers/net/mlx4/mr.c +++ b/drivers/net/mlx4/mr.c @@ -607,15 +607,9 @@ EXPORT_SYMBOL_GPL(mlx4_fmr_enable); void mlx4_fmr_unmap(struct mlx4_dev *dev, struct mlx4_fmr *fmr, u32 *lkey, u32 *rkey) { - u32 key; - if (!fmr->maps) return; - key = key_to_hw_index(fmr->mr.key); - key &= dev->caps.num_mpts - 1; - *lkey = *rkey = fmr->mr.key = hw_index_to_key(key); - fmr->maps = 0; *(u8 *) fmr->mpt = MLX4_MPT_STATUS_SW;