drivers/IB,usnic: reduce scope of mmap_sem

usnic_uiom_get_pages() uses gup_longterm() so we cannot really get rid of
mmap_sem altogether in the driver, but we can get rid of some complexity
that mmap_sem brings with only pinned_vm.  We can get rid of the wq
altogether as we no longer need to defer work to unpin pages as the
counter is now atomic.  We also share the lock.

Link: http://lkml.kernel.org/r/20190206175920.31082-6-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Parvi Kaustubhi <pkaustub@cisco.com>
Cc: Christian Benvenuti <benve@cisco.com>
Cc: Nelson Escobar <neescoba@cisco.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/drivers/infiniband/hw/usnic/usnic_ib_main.c b/drivers/infiniband/hw/usnic/usnic_ib_main.c
index c4a4cfe..577d930 100644 (file)
--- a/drivers/infiniband/hw/usnic/usnic_ib_main.c
+++ b/drivers/infiniband/hw/usnic/usnic_ib_main.c
@@ -684,7 +684,6 @@ out_unreg_netdev_notifier:
 out_pci_unreg:
        pci_unregister_driver(&usnic_ib_pci_driver);
 out_umem_fini:
-       usnic_uiom_fini();
 
        return err;
 }
@@ -697,7 +696,6 @@ static void __exit usnic_ib_destroy(void)
        unregister_inetaddr_notifier(&usnic_ib_inetaddr_notifier);
        unregister_netdevice_notifier(&usnic_ib_netdevice_notifier);
        pci_unregister_driver(&usnic_ib_pci_driver);
-       usnic_uiom_fini();
 }
 
 MODULE_DESCRIPTION("Cisco VIC (usNIC) Verbs Driver");

diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c
index 854436a..06862a6 100644 (file)
--- a/drivers/infiniband/hw/usnic/usnic_uiom.c
+++ b/drivers/infiniband/hw/usnic/usnic_uiom.c
@@ -47,8 +47,6 @@
 #include "usnic_uiom.h"
 #include "usnic_uiom_interval_tree.h"
 
-static struct workqueue_struct *usnic_uiom_wq;
-
 #define USNIC_UIOM_PAGE_CHUNK                                          \
        ((PAGE_SIZE - offsetof(struct usnic_uiom_chunk, page_list))     /\
        ((void *) &((struct usnic_uiom_chunk *) 0)->page_list[1] -      \
@@ -127,9 +125,9 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
        npages = PAGE_ALIGN(size + (addr & ~PAGE_MASK)) >> PAGE_SHIFT;
 
        uiomr->owning_mm = mm = current->mm;
-       down_write(&mm->mmap_sem);
+       down_read(&mm->mmap_sem);
 
-       locked = npages + atomic64_read(&current->mm->pinned_vm);
+       locked = atomic64_add_return(npages, &current->mm->pinned_vm);
        lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 
        if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
@@ -184,14 +182,13 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
        }
 
 out:
-       if (ret < 0)
+       if (ret < 0) {
                usnic_uiom_put_pages(chunk_list, 0);
-       else {
-               atomic64_set(&mm->pinned_vm, locked);
+               atomic64_sub(npages, &current->mm->pinned_vm);
+       } else
                mmgrab(uiomr->owning_mm);
-       }
 
-       up_write(&mm->mmap_sem);
+       up_read(&mm->mmap_sem);
        free_page((unsigned long) page_list);
        return ret;
 }
@@ -435,43 +432,12 @@ static inline size_t usnic_uiom_num_pages(struct usnic_uiom_reg *uiomr)
        return PAGE_ALIGN(uiomr->length + uiomr->offset) >> PAGE_SHIFT;
 }
 
-static void usnic_uiom_release_defer(struct work_struct *work)
-{
-       struct usnic_uiom_reg *uiomr =
-               container_of(work, struct usnic_uiom_reg, work);
-
-       down_write(&uiomr->owning_mm->mmap_sem);
-       atomic64_sub(usnic_uiom_num_pages(uiomr), &uiomr->owning_mm->pinned_vm);
-       up_write(&uiomr->owning_mm->mmap_sem);
-
-       __usnic_uiom_release_tail(uiomr);
-}
-
 void usnic_uiom_reg_release(struct usnic_uiom_reg *uiomr,
                            struct ib_ucontext *context)
 {
        __usnic_uiom_reg_release(uiomr->pd, uiomr, 1);
 
-       /*
-        * We may be called with the mm's mmap_sem already held.  This
-        * can happen when a userspace munmap() is the call that drops
-        * the last reference to our file and calls our release
-        * method.  If there are memory regions to destroy, we'll end
-        * up here and not be able to take the mmap_sem.  In that case
-        * we defer the vm_locked accounting to a workqueue.
-        */
-       if (context->closing) {
-               if (!down_write_trylock(&uiomr->owning_mm->mmap_sem)) {
-                       INIT_WORK(&uiomr->work, usnic_uiom_release_defer);
-                       queue_work(usnic_uiom_wq, &uiomr->work);
-                       return;
-               }
-       } else {
-               down_write(&uiomr->owning_mm->mmap_sem);
-       }
        atomic64_sub(usnic_uiom_num_pages(uiomr), &uiomr->owning_mm->pinned_vm);
-       up_write(&uiomr->owning_mm->mmap_sem);
-
        __usnic_uiom_release_tail(uiomr);
 }
 
@@ -600,17 +566,5 @@ int usnic_uiom_init(char *drv_name)
                return -EPERM;
        }
 
-       usnic_uiom_wq = create_workqueue(drv_name);
-       if (!usnic_uiom_wq) {
-               usnic_err("Unable to alloc wq for drv %s\n", drv_name);
-               return -ENOMEM;
-       }
-
        return 0;
 }
-
-void usnic_uiom_fini(void)
-{
-       flush_workqueue(usnic_uiom_wq);
-       destroy_workqueue(usnic_uiom_wq);
-}

diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.h b/drivers/infiniband/hw/usnic/usnic_uiom.h
index b86a973..c88cfa0 100644 (file)
--- a/drivers/infiniband/hw/usnic/usnic_uiom.h
+++ b/drivers/infiniband/hw/usnic/usnic_uiom.h
@@ -93,5 +93,4 @@ struct usnic_uiom_reg *usnic_uiom_reg_get(struct usnic_uiom_pd *pd,
 void usnic_uiom_reg_release(struct usnic_uiom_reg *uiomr,
                            struct ib_ucontext *ucontext);
 int usnic_uiom_init(char *drv_name);
-void usnic_uiom_fini(void);
 #endif /* USNIC_UIOM_H_ */