IB: Put rlimit accounting struct in struct ib_umem

When memory pinned with ib_umem_get() is released, ib_umem_release()
needs to subtract the amount of memory being unpinned from
mm->locked_vm.  However, ib_umem_release() may be called with
mm->mmap_sem already held for writing if the memory is being released
as part of an munmap() call, so it is sometimes necessary to defer
this accounting into a workqueue.

However, the work struct used to defer this accounting is dynamically
allocated before it is queued, so there is the possibility of failing
that allocation.  If the allocation fails, then ib_umem_release has no
choice except to bail out and leave the process with a permanently
elevated locked_vm.

Fix this by allocating the structure to defer accounting as part of
the original struct ib_umem, so there's no possibility of failing a
later allocation if creating the struct ib_umem and pinning memory
succeeds.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index 06307f7e43e..b3a36f7d79e 100644
--- a/include/rdma/ib_umem.h
+++ b/include/rdma/ib_umem.h
@@ -45,6 +45,9 @@ struct ib_umem {
         int                     page_size;
         int                     writable;
         struct list_head        chunk_list;
+        struct work_struct      work;
+        struct mm_struct       *mm;
+        unsigned long           diff;
 };
 
 struct ib_umem_chunk {