[PATCH 5/6] drivers/IB,usnic: reduce scope of mmap_sem

Davidlohr Bueso
2019-01-21T17:43:25Z

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.

Cc: benve@cisco.com
Cc: neescoba@cisco.com
Cc: pkaustub@cisco.com
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
drivers/infiniband/hw/usnic/usnic_ib_main.c | 2 --
drivers/infiniband/hw/usnic/usnic_uiom.c | 54 +++--------------------------
drivers/infiniband/hw/usnic/usnic_uiom.h | 1 -
3 files changed, 4 insertions(+), 53 deletions(-)

diff --git a/drivers/infiniband/hw/usnic/usnic_ib_main.c b/drivers/infiniband/hw/usnic/usnic_ib_main.c
index 3201dd1899c7..1d363b706314 100644
--- a/drivers/infiniband/hw/usnic/usnic_ib_main.c
+++ b/drivers/infiniband/hw/usnic/usnic_ib_main.c
@@ -691,7 +691,6 @@ static int __init usnic_ib_init(void)
out_pci_unreg:
pci_unregister_driver(&usnic_ib_pci_driver);
out_umem_fini:
- usnic_uiom_fini();

return err;
}
@@ -704,7 +703,6 @@ 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 854436a2b437..505252298b52 100644
--- 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] - \
@@ -129,7 +127,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
uiomr->owning_mm = mm = current->mm;
down_write(&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)) {
@@ -184,12 +182,11 @@ 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);
free_page((unsigned long) page_list);
@@ -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 b86a9731071b..c88cfa087e3a 100644
--- 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_ */
--
2.16.4