[PATCH 1/9] [media] vb2: Push mmap_sem down to memops

Jan Kara
2015-05-06T07:28:08Z

Currently vb2 core acquires mmap_sem just around call to
__qbuf_userptr(). However since commit f035eb4e976ef5 (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>
---
drivers/media/v4l2-core/videobuf2-core.c | 2 --
drivers/media/v4l2-core/videobuf2-dma-contig.c | 7 +++++++
drivers/media/v4l2-core/videobuf2-dma-sg.c | 6 ++++++
drivers/media/v4l2-core/videobuf2-vmalloc.c | 6 +++++-
4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 66ada01c796c..20cdbc0900ea 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/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);
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 644dec73d220..620c4aa78881 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ 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:
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 45c708e463b9..afd4b514affc 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/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);
}

diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index 657ab302a5cf..0ba40be21ebd 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/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);
}

--
2.1.4

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