From 4d45e75a9955ade5c2f49bd96fc4173b2cec9a72 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Thu, 15 Oct 2020 20:13:00 -0700
Subject: mm: remove the now-unnecessary mmget_still_valid() hack

The preceding patches have ensured that core dumping properly takes the
mmap_lock.  Thanks to that, we can now remove mmget_still_valid() and all
its users.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/r/20200827114932.3572699-8-jannh@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 drivers/vfio/pci/vfio_pci.c | 38 ++++++++++++++++++--------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

(limited to 'drivers/vfio')

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 1ab1f5cda4ac..b0f4b92a87ed 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1480,31 +1480,29 @@ static int vfio_pci_zap_and_vma_lock(struct vfio_pci_device *vdev, bool try)
 		} else {
 			mmap_read_lock(mm);
 		}
-		if (mmget_still_valid(mm)) {
-			if (try) {
-				if (!mutex_trylock(&vdev->vma_lock)) {
-					mmap_read_unlock(mm);
-					mmput(mm);
-					return 0;
-				}
-			} else {
-				mutex_lock(&vdev->vma_lock);
+		if (try) {
+			if (!mutex_trylock(&vdev->vma_lock)) {
+				mmap_read_unlock(mm);
+				mmput(mm);
+				return 0;
 			}
-			list_for_each_entry_safe(mmap_vma, tmp,
-						 &vdev->vma_list, vma_next) {
-				struct vm_area_struct *vma = mmap_vma->vma;
+		} else {
+			mutex_lock(&vdev->vma_lock);
+		}
+		list_for_each_entry_safe(mmap_vma, tmp,
+					 &vdev->vma_list, vma_next) {
+			struct vm_area_struct *vma = mmap_vma->vma;
 
-				if (vma->vm_mm != mm)
-					continue;
+			if (vma->vm_mm != mm)
+				continue;
 
-				list_del(&mmap_vma->vma_next);
-				kfree(mmap_vma);
+			list_del(&mmap_vma->vma_next);
+			kfree(mmap_vma);
 
-				zap_vma_ptes(vma, vma->vm_start,
-					     vma->vm_end - vma->vm_start);
-			}
-			mutex_unlock(&vdev->vma_lock);
+			zap_vma_ptes(vma, vma->vm_start,
+				     vma->vm_end - vma->vm_start);
 		}
+		mutex_unlock(&vdev->vma_lock);
 		mmap_read_unlock(mm);
 		mmput(mm);
 	}
-- 
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