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>

2 files changed, 16 insertions, 28 deletions

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 48e854cf416f..f32ca5fbb26b 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -39,13 +39,6 @@
 
 #include "uverbs.h"
 
-struct ib_umem_account_work {
-        struct work_struct work;
-        struct mm_struct  *mm;
-        unsigned long      diff;
-};
-
-
 static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int dirty)
 {
         struct ib_umem_chunk *chunk, *tmp;
@@ -192,16 +185,15 @@ out:
 }
 EXPORT_SYMBOL(ib_umem_get);
 
-static void ib_umem_account(struct work_struct *_work)
+static void ib_umem_account(struct work_struct *work)
 {
-        struct ib_umem_account_work *work =
-                container_of(_work, struct ib_umem_account_work, work);
-
-        down_write(&work->mm->mmap_sem);
-        work->mm->locked_vm -= work->diff;
-        up_write(&work->mm->mmap_sem);
-        mmput(work->mm);
-        kfree(work);
+        struct ib_umem *umem = container_of(work, struct ib_umem, work);
+
+        down_write(&umem->mm->mmap_sem);
+        umem->mm->locked_vm -= umem->diff;
+        up_write(&umem->mm->mmap_sem);
+        mmput(umem->mm);
+        kfree(umem);
 }
 
 /**
@@ -210,7 +202,6 @@ static void ib_umem_account(struct work_struct *_work)
  */
 void ib_umem_release(struct ib_umem *umem)
 {
-        struct ib_umem_account_work *work;
         struct ib_ucontext *context = umem->context;
         struct mm_struct *mm;
         unsigned long diff;
@@ -222,7 +213,6 @@ void ib_umem_release(struct ib_umem *umem)
                 return;
 
         diff = PAGE_ALIGN(umem->length + umem->offset) >> PAGE_SHIFT;
-        kfree(umem);
 
         /*
          * We may be called with the mm's mmap_sem already held.  This
@@ -233,17 +223,11 @@ void ib_umem_release(struct ib_umem *umem)
          * we defer the vm_locked accounting to the system workqueue.
          */
         if (context->closing && !down_write_trylock(&mm->mmap_sem)) {
-                work = kmalloc(sizeof *work, GFP_KERNEL);
-                if (!work) {
-                        mmput(mm);
-                        return;
-                }
+                INIT_WORK(&umem->work, ib_umem_account);
+                umem->mm   = mm;
+                umem->diff = diff;
 
-                INIT_WORK(&work->work, ib_umem_account);
-                work->mm   = mm;
-                work->diff = diff;
-
-                schedule_work(&work->work);
+                schedule_work(&umem->work);
                 return;
         } else
                 down_write(&mm->mmap_sem);
@@ -251,6 +235,7 @@ void ib_umem_release(struct ib_umem *umem)
         current->mm->locked_vm -= diff;
         up_write(&mm->mmap_sem);
         mmput(mm);
+        kfree(umem);
 }
 EXPORT_SYMBOL(ib_umem_release);
 
diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index 06307f7e43e0..b3a36f7d79e5 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 {