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RDMA/odp: Lift umem_mutex out of ib_umem_odp_unmap_dma_pages() 

This fixes a race of the form:
    CPU0                               CPU1
mlx5_ib_invalidate_range()     mlx5_ib_invalidate_range()
				 // This one actually makes npages == 0
				 ib_umem_odp_unmap_dma_pages()
				 if (npages == 0 && !dying)
  // This one does nothing
  ib_umem_odp_unmap_dma_pages()
  if (npages == 0 && !dying)
     dying = 1;
                                    dying = 1;
				    schedule_work(&umem_odp->work);
     // Double schedule of the same work
     schedule_work(&umem_odp->work);  // BOOM

npages and dying must be read and written under the umem_mutex lock.

Since whenever ib_umem_odp_unmap_dma_pages() is called mlx5 must also call
mlx5_ib_update_xlt, and both need to be done in the same locking region,
hoist the lock out of unmap.

This avoids an expensive double critical section in
mlx5_ib_invalidate_range().

Fixes: 81713d3788 ("IB/mlx5: Add implicit MR support")
Link: https://lore.kernel.org/r/20191001153821.23621-4-jgg@ziepe.ca
Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2019-10-01 12:38:18 -03:00
parent f28b1932ea
commit 9dc775e7f5
2 changed files with 12 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/infiniband/core/umem_odp.c
View File

@ -451,8 +451,10 @@ void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
* that the hardware will not attempt to access the MR any more.
*/
if (!umem_odp->is_implicit_odp) {
mutex_lock(&umem_odp->umem_mutex);
ib_umem_odp_unmap_dma_pages(umem_odp, ib_umem_start(umem_odp),
ib_umem_end(umem_odp));
mutex_unlock(&umem_odp->umem_mutex);
kvfree(umem_odp->dma_list);
kvfree(umem_odp->page_list);
}
@ -719,6 +721,8 @@ void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
u64 addr;
struct ib_device *dev = umem_odp->umem.ibdev;
lockdep_assert_held(&umem_odp->umem_mutex);
virt = max_t(u64, virt, ib_umem_start(umem_odp));
bound = min_t(u64, bound, ib_umem_end(umem_odp));
/* Note that during the run of this function, the
@ -726,7 +730,6 @@ void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
* faults from completion. We might be racing with other
* invalidations, so we must make sure we free each page only
* once. */
mutex_lock(&umem_odp->umem_mutex);
for (addr = virt; addr < bound; addr += BIT(umem_odp->page_shift)) {
idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift;
if (umem_odp->page_list[idx]) {
@ -757,7 +760,6 @@ void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
umem_odp->npages--;
}
}
mutex_unlock(&umem_odp->umem_mutex);
}
EXPORT_SYMBOL(ib_umem_odp_unmap_dma_pages);

12
drivers/infiniband/hw/mlx5/odp.c
View File

@ -308,7 +308,6 @@ void mlx5_ib_invalidate_range(struct ib_umem_odp *umem_odp, unsigned long start,
idx - blk_start_idx + 1, 0,
MLX5_IB_UPD_XLT_ZAP |
MLX5_IB_UPD_XLT_ATOMIC);
mutex_unlock(&umem_odp->umem_mutex);
/*
* We are now sure that the device will not access the
* memory. We can safely unmap it, and mark it as dirty if
@ -319,10 +318,11 @@ void mlx5_ib_invalidate_range(struct ib_umem_odp *umem_odp, unsigned long start,
if (unlikely(!umem_odp->npages && mr->parent &&
!umem_odp->dying)) {
WRITE_ONCE(umem_odp->dying, 1);
umem_odp->dying = 1;
atomic_inc(&mr->parent->num_leaf_free);
schedule_work(&umem_odp->work);
}
mutex_unlock(&umem_odp->umem_mutex);
}
void mlx5_ib_internal_fill_odp_caps(struct mlx5_ib_dev *dev)
@ -585,15 +585,19 @@ void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr)
if (mr->parent != imr)
continue;
mutex_lock(&umem_odp->umem_mutex);
ib_umem_odp_unmap_dma_pages(umem_odp, ib_umem_start(umem_odp),
ib_umem_end(umem_odp));
if (umem_odp->dying)
if (umem_odp->dying) {
mutex_unlock(&umem_odp->umem_mutex);
continue;
}
WRITE_ONCE(umem_odp->dying, 1);
umem_odp->dying = 1;
atomic_inc(&imr->num_leaf_free);
schedule_work(&umem_odp->work);
mutex_unlock(&umem_odp->umem_mutex);
}
up_read(&per_mm->umem_rwsem);