RDMA/umem: Don't hold mmap_sem for too long

DMA mapping is time consuming operation and doesn't need to be performed
with mmap_sem semaphore is held.

The semaphore only needs to be held for accounting and get_user_pages
related activities.

Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 498f59b..abe9924 100644 (file)
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -84,7 +84,6 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
        struct ib_umem *umem;
        struct page **page_list;
        struct vm_area_struct **vma_list;
-       unsigned long locked;
        unsigned long lock_limit;
        unsigned long cur_base;
        unsigned long npages;
@@ -149,15 +148,16 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
 
        npages = ib_umem_num_pages(umem);
 
-       down_write(&current->mm->mmap_sem);
-
-       locked     = npages + current->mm->pinned_vm;
        lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 
-       if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
+       down_write(&current->mm->mmap_sem);
+       current->mm->pinned_vm += npages;
+       if ((current->mm->pinned_vm > lock_limit) && !capable(CAP_IPC_LOCK)) {
+               up_write(&current->mm->mmap_sem);
                ret = -ENOMEM;
                goto out;
        }
+       up_write(&current->mm->mmap_sem);
 
        cur_base = addr & PAGE_MASK;
 
@@ -176,14 +176,16 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
        need_release = 1;
        sg_list_start = umem->sg_head.sgl;
 
+       down_read(&current->mm->mmap_sem);
        while (npages) {
                ret = get_user_pages_longterm(cur_base,
                                     min_t(unsigned long, npages,
                                           PAGE_SIZE / sizeof (struct page *)),
                                     gup_flags, page_list, vma_list);
-
-               if (ret < 0)
+               if (ret < 0) {
+                       up_read(&current->mm->mmap_sem);
                        goto out;
+               }
 
                umem->npages += ret;
                cur_base += ret * PAGE_SIZE;
@@ -199,6 +201,7 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
                /* preparing for next loop */
                sg_list_start = sg;
        }
+       up_read(&current->mm->mmap_sem);
 
        umem->nmap = ib_dma_map_sg_attrs(context->device,
                                  umem->sg_head.sgl,
@@ -215,13 +218,14 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
 
 out:
        if (ret < 0) {
+               down_write(&current->mm->mmap_sem);
+               current->mm->pinned_vm -= ib_umem_num_pages(umem);
+               up_write(&current->mm->mmap_sem);
                if (need_release)
                        __ib_umem_release(context->device, umem, 0);
                kfree(umem);
-       } else
-               current->mm->pinned_vm = locked;
+       }
 
-       up_write(&current->mm->mmap_sem);
        if (vma_list)
                free_page((unsigned long) vma_list);
        free_page((unsigned long) page_list);