drivers/IB,hfi1: do not se mmap_sem

This driver already uses gup_fast() and thus we can just drop the mmap_sem
protection around the pinned_vm counter.  Note that the window between
when hfi1_can_pin_pages() is called and the actual counter is incremented
remains the same as mmap_sem was _only_ used for when ->pinned_vm was
touched.

Link: http://lkml.kernel.org/r/20190206175920.31082-5-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.det>
Reviewed-by: Ira Weiny <ira.weiny@intel.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/hfi1/user_pages.c b/drivers/infiniband/hw/hfi1/user_pages.c
index 40a6e43..24b592c 100644 (file)
--- a/drivers/infiniband/hw/hfi1/user_pages.c
+++ b/drivers/infiniband/hw/hfi1/user_pages.c
@@ -91,9 +91,7 @@ bool hfi1_can_pin_pages(struct hfi1_devdata *dd, struct mm_struct *mm,
        /* Convert to number of pages */
        size = DIV_ROUND_UP(size, PAGE_SIZE);
 
-       down_read(&mm->mmap_sem);
        pinned = atomic64_read(&mm->pinned_vm);
-       up_read(&mm->mmap_sem);
 
        /* First, check the absolute limit against all pinned pages. */
        if (pinned + npages >= ulimit && !can_lock)
@@ -111,9 +109,7 @@ int hfi1_acquire_user_pages(struct mm_struct *mm, unsigned long vaddr, size_t np
        if (ret < 0)
                return ret;
 
-       down_write(&mm->mmap_sem);
        atomic64_add(ret, &mm->pinned_vm);
-       up_write(&mm->mmap_sem);
 
        return ret;
 }
@@ -130,8 +126,6 @@ void hfi1_release_user_pages(struct mm_struct *mm, struct page **p,
        }
 
        if (mm) { /* during close after signal, mm can be NULL */
-               down_write(&mm->mmap_sem);
                atomic64_sub(npages, &mm->pinned_vm);
-               up_write(&mm->mmap_sem);
        }
 }