[PATCH] sg: mark VMA as VM_IO to prevent migration

[Kirill A. Shutemov]

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
migratable.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
---
 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 503ab8b46c0b..5e820674432c 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1261,7 +1261,7 @@ 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;
-- 
 Kirill A. Shutemov