[added to the 4.1 stable tree] drivers/scsi/sg.c: mark VMA as VM_IO to prevent migration

From: "Kirill A. Shutemov" <redacted>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 461c7fa126794157484dca48e88effa4963e3af3 ]

Reduced testcase:

    #include <fcntl.h>
    #include <unistd.h>
    #include <sys/mman.h>
    #include <numaif.h>

    #define SIZE 0x2000

    int main()
    {
        int fd;
        void *p;

        fd = open("/dev/sg0", O_RDWR);
        p = mmap(NULL, SIZE, PROT_EXEC, MAP_PRIVATE | MAP_LOCKED, fd, 0);
        mbind(p, SIZE, 0, NULL, 0, MPOL_MF_MOVE);
        return 0;
    }

We shouldn't try to migrate pages in sg VMA as we don't have a way to
update Sg_scatter_hold::pages accordingly from mm core.

Let's mark the VMA as VM_IO to indicate to mm core that the VMA is not
migratable.

Signed-off-by: Kirill A. Shutemov <redacted>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Vlastimil Babka <redacted>
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Naoya Horiguchi <redacted>
Cc: "Kirill A. Shutemov" <redacted>
Cc: Shiraz Hashim <redacted>
Cc: Hugh Dickins <hughd@google.com>
Cc: Sasha Levin <redacted>
Cc: syzkaller <redacted>
Cc: Kostya Serebryany <redacted>
Cc: Alexander Potapenko <glider@google.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <redacted>
---
 drivers/scsi/sg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 9d7b7db..3bbf485 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c

@@ -1255,7 +1255,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
 	}
 
 	sfp->mmap_called = 1;
-	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_private_data = sfp;
 	vma->vm_ops = &sg_mmap_vm_ops;
 	return 0;

-- 
2.5.0