videobuf_dma_sg: a new implementation for mmap

a mmap issue for videobuf-dma-sg: it will alloc a new page for mmaping when it encounter page fault at video_vm_ops->fault().

a new implementation for mmap, it translate the vmalloc to page at video_vm_ops->fault().

---
drivers/media/video/videobuf-dma-sg.c | 38
++++++++++++++++++++++++++++----

 1 files changed, 33 insertions(+), 5 deletions(-)

b/drivers/media/video/videobuf-dma-sg.c
index 8359e6b..c9a8817 100644

@@ -397,16 +397,44 @@ static void videobuf_vm_close(struct

vm_area_struct *vma)
*/
static int videobuf_vm_fault(struct vm_area_struct *vma, struct
vm_fault *vmf)
{
- struct page *page;
+ struct page *page = NULL;
+ struct videobuf_mapping *map = vma->vm_private_data;
+ struct videobuf_queue *q = map->q;
+ struct videobuf_dma_sg_memory *mem = NULL;
+
+ unsigned long offset;
+ unsigned long page_nr;
+ int first;

dprintk(3, "fault: fault @ %08lx [vma %08lx-%08lx]\n",
(unsigned long)vmf->virtual_address, vma->vm_start, vma->vm_end);

- page = alloc_page(GFP_USER | __GFP_DMA32);
- if (!page)
- return VM_FAULT_OOM;
- clear_user_highpage(page, (unsigned long)vmf->virtual_address);
+ mutex_lock(&q->vb_lock);
+
+ offset = (unsigned long)vmf->virtual_address - vma->vm_start;
+ page_nr = offset >> PAGE_SHIFT;
+
+ for (first = 0; first < VIDEO_MAX_FRAME; first++) {
+ if (NULL == q->bufs[first])
+ continue;
+
+ MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
+
+ if (q->bufs[first]->map == map)
+ break;
+ }
+
+ mem = q->bufs[first]->priv;
+ if (!mem)
+ return VM_FAULT_SIGBUS;
+ if (mem->dma.vmalloc)
+ page = vmalloc_to_page(mem->dma.vmalloc+
+ (offset & (~PAGE_MASK)));
+ if (mem->dma.pages)
+ page = mem->dma.pages[page_nr];
+ mutex_unlock(&q->vb_lock);
+
vmf->page = page;

return 0;

Hi,

How is that supposed to work ? mem->dma.vmalloc is NULL in the vm_fault handler for V4L2_MEMORY_MMAP buffers. Have you tested the code at all ?

Regards,

Laurent Pinchart

a mmap issue for videobuf-dma-sg: it will alloc a new page for mmaping when it encounter page fault at video_vm_ops->fault().

a new implementation for mmap, it translate the vmalloc to page at video_vm_ops->fault().

in v2, if mem->dma.vmalloc is NULL at video_vm_ops->fault(), it will alloc memory by vmalloc_32().

---
 drivers/media/video/videobuf-dma-sg.c |   51
+++++++++++++++++++++++++++------
 1 files changed, 42 insertions(+), 9 deletions(-)

b/drivers/media/video/videobuf-dma-sg.c
index 8359e6b..767483d 100644

@@ -201,10 +201,11 @@ int videobuf_dma_init_kernel(struct

videobuf_dmabuf *dma, int direction,
dprintk(1, "init kernel [%d pages]\n", nr_pages);

dma->direction = direction;
- dma->vmalloc = vmalloc_32(nr_pages << PAGE_SHIFT);
- if (NULL == dma->vmalloc) {
- dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
- return -ENOMEM;
+ if (!dma->vmalloc)
+ dma->vmalloc = vmalloc_32(nr_pages << PAGE_SHIFT);
+ if (NULL == dma->vmalloc) {
+ dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
+ return -ENOMEM;
}

dprintk(1, "vmalloc is at addr 0x%08lx, size=%d\n",
@@ -397,16 +398,48 @@ static void videobuf_vm_close(struct vm_area_struct *vma)
*/
static int videobuf_vm_fault(struct vm_area_struct *vma, struct
vm_fault *vmf)
{
- struct page *page;
+ struct page *page = NULL;
+ struct videobuf_mapping *map = vma->vm_private_data;
+ struct videobuf_queue *q = map->q;
+ struct videobuf_dma_sg_memory *mem = NULL;
+
+ unsigned long offset;
+ unsigned long page_nr;
+ int first;

dprintk(3, "fault: fault @ %08lx [vma %08lx-%08lx]\n",
(unsigned long)vmf->virtual_address, vma->vm_start, vma->vm_end);

- page = alloc_page(GFP_USER | __GFP_DMA32);
- if (!page)
- return VM_FAULT_OOM;
- clear_user_highpage(page, (unsigned long)vmf->virtual_address);
+ mutex_lock(&q->vb_lock);
+
+ offset = (unsigned long)vmf->virtual_address - vma->vm_start;
+ page_nr = offset >> PAGE_SHIFT;
+
+ for (first = 0; first < VIDEO_MAX_FRAME; first++) {
+ if (NULL == q->bufs[first])
+ continue;
+
+ MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
+
+ if (q->bufs[first]->map == map)
+ break;
+ }
+
+ mem = q->bufs[first]->priv;
+ if (!mem)
+ return VM_FAULT_SIGBUS;
+ if (!mem->dma.vmalloc) {
+ mem->dma.vmalloc = vmalloc_32(PAGE_ALIGN(q->bufs[first]->size));
+ if (NULL == mem->dma.vmalloc) {
+ dprintk(1, "%s: vmalloc_32() failed\n", __func__);
+ return VM_FAULT_OOM;
+ }
+ } else
+ page = vmalloc_to_page(mem->dma.vmalloc+
+ (offset & (~PAGE_MASK)));
+ mutex_unlock(&q->vb_lock);
+
vmf->page = page;

return 0;

a mmap issue for videobuf-dma-sg: it will alloc a new page for mmaping when it encounter page fault at video_vm_ops->fault().

a new implementation for mmap, it translate the vmalloc to page at video_vm_ops->fault().

in v2, if mem->dma.vmalloc is NULL at video_vm_ops->fault(), it will alloc memory by vmalloc_32().

---
drivers/media/video/videobuf-dma-sg.c | 51
+++++++++++++++++++++++++++------

 1 files changed, 42 insertions(+), 9 deletions(-)

b/drivers/media/video/videobuf-dma-sg.c
index 8359e6b..767483d 100644

@@ -201,10 +201,11 @@ int videobuf_dma_init_kernel(struct

videobuf_dmabuf *dma, int direction,
dprintk(1, "init kernel [%d pages]\n", nr_pages);

dma->direction = direction;
- dma->vmalloc = vmalloc_32(nr_pages << PAGE_SHIFT);
- if (NULL == dma->vmalloc) {
- dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
- return -ENOMEM;
+ if (!dma->vmalloc)
+ dma->vmalloc = vmalloc_32(nr_pages << PAGE_SHIFT);
+ if (NULL == dma->vmalloc) {
+ dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
+ return -ENOMEM;
}

dprintk(1, "vmalloc is at addr 0x%08lx, size=%d\n",
@@ -397,16 +398,48 @@ static void videobuf_vm_close(struct vm_area_struct *vma)
*/
static int videobuf_vm_fault(struct vm_area_struct *vma, struct
vm_fault *vmf)
{
- struct page *page;
+ struct page *page = NULL;
+ struct videobuf_mapping *map = vma->vm_private_data;
+ struct videobuf_queue *q = map->q;
+ struct videobuf_dma_sg_memory *mem = NULL;
+
+ unsigned long offset;
+ unsigned long page_nr;
+ int first;

dprintk(3, "fault: fault @ %08lx [vma %08lx-%08lx]\n",
(unsigned long)vmf->virtual_address, vma->vm_start, vma->vm_end);

- page = alloc_page(GFP_USER | __GFP_DMA32);
- if (!page)
- return VM_FAULT_OOM;
- clear_user_highpage(page, (unsigned long)vmf->virtual_address);
+ mutex_lock(&q->vb_lock);
+
+ offset = (unsigned long)vmf->virtual_address - vma->vm_start;
+ page_nr = offset >> PAGE_SHIFT;
+
+ for (first = 0; first < VIDEO_MAX_FRAME; first++) {
+ if (NULL == q->bufs[first])
+ continue;
+
+ MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
+
+ if (q->bufs[first]->map == map)
+ break;
+ }
+
+ mem = q->bufs[first]->priv;
+ if (!mem)
+ return VM_FAULT_SIGBUS;
+ if (!mem->dma.vmalloc) {
+ mem->dma.vmalloc = vmalloc_32(PAGE_ALIGN(q->bufs[first]->size));
+ if (NULL == mem->dma.vmalloc) {
+ dprintk(1, "%s: vmalloc_32() failed\n", __func__);
+ return VM_FAULT_OOM;
+ }
+ } else
+ page = vmalloc_to_page(mem->dma.vmalloc+
+ (offset & (~PAGE_MASK)));
+ mutex_unlock(&q->vb_lock);
+
vmf->page = page;

return 0;

hi Laurent,
would you like to test this patch?

btw, why i send the patch , patchwork websit display a part of my patch?
https://patchwork.kernel.org/patch/114760/

Best,
Figo.zhang

Em 29-07-2010 10:38, Figo.zhang escreveu:

Because your emailer broke long lines, mangling part of your patch. The way you sent, it will fail to apply.

Please, re-send it, being sure that your emailer won't break long lines.

Cheers,
Mauro.

Hi,

Can you please elaborate on what you're trying to do ? What problem is this patch supposed to fix ?

Regards,

Laurent Pinchart