[media] vb2: Push mmap_sem down to memops

Currently vb2 core acquires mmap_sem just around call to
__qbuf_userptr(). However since commit f035eb4e97 (videobuf2: fix
lockdep warning) it isn't necessary to acquire it so early as we no
longer have to drop queue mutex before acquiring mmap_sem. So push
acquisition of mmap_sem down into .get_userptr and .put_userptr memops
so that the semaphore is acquired for a shorter time and it is clearer
what it is needed for.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/videobuf2-core.c

@@ -1657,9 +1657,7 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
 		ret = __qbuf_mmap(vb, b);
 		break;
 	case V4L2_MEMORY_USERPTR:
-		down_read(&current->mm->mmap_sem);
 		ret = __qbuf_userptr(vb, b);
-		up_read(&current->mm->mmap_sem);
 		break;
 	case V4L2_MEMORY_DMABUF:
 		ret = __qbuf_dmabuf(vb, b);

drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -532,7 +532,9 @@ static void vb2_dc_put_userptr(void *buf_priv)
 		sg_free_table(sgt);
 		kfree(sgt);
 	}
+	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
+	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }
 
@@ -616,6 +618,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		goto fail_buf;
 	}
 
+	down_read(&current->mm->mmap_sem);
 	/* current->mm->mmap_sem is taken by videobuf2 core */
 	vma = find_vma(current->mm, vaddr);
 	if (!vma) {
@@ -642,6 +645,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	if (ret) {
 		unsigned long pfn;
 		if (vb2_dc_get_user_pfn(start, n_pages, vma, &pfn) == 0) {
+			up_read(&current->mm->mmap_sem);
 			buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn);
 			buf->size = size;
 			kfree(pages);
@@ -651,6 +655,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		pr_err("failed to get user pages\n");
 		goto fail_vma;
 	}
+	up_read(&current->mm->mmap_sem);
 
 	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
 	if (!sgt) {
@@ -713,10 +718,12 @@ fail_get_user_pages:
 		while (n_pages)
 			put_page(pages[--n_pages]);
 
+	down_read(&current->mm->mmap_sem);
 fail_vma:
 	vb2_put_vma(buf->vma);
 
 fail_pages:
+	up_read(&current->mm->mmap_sem);
 	kfree(pages); /* kfree is NULL-proof */
 
 fail_buf:

drivers/media/v4l2-core/videobuf2-dma-sg.c

@@ -263,6 +263,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	if (!buf->pages)
 		goto userptr_fail_alloc_pages;
 
+	down_read(&current->mm->mmap_sem);
 	vma = find_vma(current->mm, vaddr);
 	if (!vma) {
 		dprintk(1, "no vma for address %lu\n", vaddr);
@@ -301,6 +302,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
 					     1, /* force */
 					     buf->pages,
 					     NULL);
+	up_read(&current->mm->mmap_sem);
 
 	if (num_pages_from_user != buf->num_pages)
 		goto userptr_fail_get_user_pages;
@@ -328,8 +330,10 @@ userptr_fail_get_user_pages:
 	if (!vma_is_io(buf->vma))
 		while (--num_pages_from_user >= 0)
 			put_page(buf->pages[num_pages_from_user]);
+	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
 userptr_fail_find_vma:
+	up_read(&current->mm->mmap_sem);
 	kfree(buf->pages);
 userptr_fail_alloc_pages:
 	kfree(buf);
@@ -362,7 +366,9 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
 			put_page(buf->pages[i]);
 	}
 	kfree(buf->pages);
+	down_read(&current->mm->mmap_sem);
 	vb2_put_vma(buf->vma);
+	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }
 

drivers/media/v4l2-core/videobuf2-vmalloc.c

@@ -89,7 +89,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 	offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
 
-
+	down_read(&current->mm->mmap_sem);
 	vma = find_vma(current->mm, vaddr);
 	if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
 		if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
@@ -121,6 +121,7 @@ static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 		if (!buf->vaddr)
 			goto fail_get_user_pages;
 	}
+	up_read(&current->mm->mmap_sem);
 
 	buf->vaddr += offset;
 	return buf;
@@ -133,6 +134,7 @@ fail_get_user_pages:
 	kfree(buf->pages);
 
 fail_pages_array_alloc:
+	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 
 	return NULL;
@@ -144,6 +146,7 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
 	unsigned long vaddr = (unsigned long)buf->vaddr & PAGE_MASK;
 	unsigned int i;
 
+	down_read(&current->mm->mmap_sem);
 	if (buf->pages) {
 		if (vaddr)
 			vm_unmap_ram((void *)vaddr, buf->n_pages);
@@ -157,6 +160,7 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
 		vb2_put_vma(buf->vma);
 		iounmap((__force void __iomem *)buf->vaddr);
 	}
+	up_read(&current->mm->mmap_sem);
 	kfree(buf);
 }