From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: [PATCH 1/10] [media] vb2: Push mmap_sem down to memops Date: Thu, 18 Jun 2015 16:08:31 +0200 Message-ID: <1434636520-25116-2-git-send-email-jack@suse.cz> References: <1434636520-25116-1-git-send-email-jack@suse.cz> Return-path: In-Reply-To: <1434636520-25116-1-git-send-email-jack@suse.cz> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Hans Verkuil , linux-media@vger.kernel.org, Mauro Carvalho Chehab , linux-samsung-soc@vger.kernel.org, linux-mm@kvack.org, Jan Kara List-Id: linux-samsung-soc@vger.kernel.org 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 memop so that the semaphore is acquired for a shorter time and it is clearer what it is needed for. Note that we also need mmap_sem in .put_userptr memop since that ends up calling vb2_put_vma() which calls vma->vm_ops->close() which should be called with mmap_sem held. However we didn't hold mmap_sem in some code paths anyway (e.g. when called via vb2_ioctl_reqbufs() -> __vb2_queue_free() -> vb2_dma_sg_put_userptr()) and getting mmap_sem in put_userptr() introduces a lock inversion with queue->mmap_lock in the above mentioned call path. Luckily this whole locking mess will get resolved once we convert videobuf2 core to the new mm helper which avoids the need for mmap_sem in .put_userptr memop altogether. Signed-off-by: Jan Kara --- drivers/media/v4l2-core/videobuf2-core.c | 2 -- drivers/media/v4l2-core/videobuf2-dma-contig.c | 5 +++++ drivers/media/v4l2-core/videobuf2-dma-sg.c | 4 ++++ drivers/media/v4l2-core/videobuf2-vmalloc.c | 4 +++- 4 files changed, 12 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(¤t->mm->mmap_sem); ret = __qbuf_userptr(vb, b); - up_read(¤t->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..8e660f033d3c 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c @@ -616,6 +616,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, goto fail_buf; } + down_read(¤t->mm->mmap_sem); /* current->mm->mmap_sem is taken by videobuf2 core */ vma = find_vma(current->mm, vaddr); if (!vma) { @@ -642,6 +643,7 @@ 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(¤t->mm->mmap_sem); buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn); buf->size = size; kfree(pages); @@ -651,6 +653,7 @@ 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(¤t->mm->mmap_sem); sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); if (!sgt) { @@ -713,10 +716,12 @@ fail_get_user_pages: while (n_pages) put_page(pages[--n_pages]); + down_read(¤t->mm->mmap_sem); fail_vma: vb2_put_vma(buf->vma); fail_pages: + up_read(¤t->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..cdcf5ad79012 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(¤t->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(¤t->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(¤t->mm->mmap_sem); vb2_put_vma(buf->vma); userptr_fail_find_vma: + up_read(¤t->mm->mmap_sem); kfree(buf->pages); userptr_fail_alloc_pages: kfree(buf); diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c index 657ab302a5cf..3199c379cd47 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(¤t->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(¤t->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(¤t->mm->mmap_sem); kfree(buf); return NULL; -- 2.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from cantor2.suse.de ([195.135.220.15]:46758 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753982AbbFROIv (ORCPT ); Thu, 18 Jun 2015 10:08:51 -0400 From: Jan Kara To: Andrew Morton Cc: Hans Verkuil , linux-media@vger.kernel.org, Mauro Carvalho Chehab , linux-samsung-soc@vger.kernel.org, linux-mm@kvack.org, Jan Kara Subject: [PATCH 1/10] [media] vb2: Push mmap_sem down to memops Date: Thu, 18 Jun 2015 16:08:31 +0200 Message-Id: <1434636520-25116-2-git-send-email-jack@suse.cz> In-Reply-To: <1434636520-25116-1-git-send-email-jack@suse.cz> References: <1434636520-25116-1-git-send-email-jack@suse.cz> Sender: linux-media-owner@vger.kernel.org List-ID: 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 memop so that the semaphore is acquired for a shorter time and it is clearer what it is needed for. Note that we also need mmap_sem in .put_userptr memop since that ends up calling vb2_put_vma() which calls vma->vm_ops->close() which should be called with mmap_sem held. However we didn't hold mmap_sem in some code paths anyway (e.g. when called via vb2_ioctl_reqbufs() -> __vb2_queue_free() -> vb2_dma_sg_put_userptr()) and getting mmap_sem in put_userptr() introduces a lock inversion with queue->mmap_lock in the above mentioned call path. Luckily this whole locking mess will get resolved once we convert videobuf2 core to the new mm helper which avoids the need for mmap_sem in .put_userptr memop altogether. Signed-off-by: Jan Kara --- drivers/media/v4l2-core/videobuf2-core.c | 2 -- drivers/media/v4l2-core/videobuf2-dma-contig.c | 5 +++++ drivers/media/v4l2-core/videobuf2-dma-sg.c | 4 ++++ drivers/media/v4l2-core/videobuf2-vmalloc.c | 4 +++- 4 files changed, 12 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(¤t->mm->mmap_sem); ret = __qbuf_userptr(vb, b); - up_read(¤t->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..8e660f033d3c 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c @@ -616,6 +616,7 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, goto fail_buf; } + down_read(¤t->mm->mmap_sem); /* current->mm->mmap_sem is taken by videobuf2 core */ vma = find_vma(current->mm, vaddr); if (!vma) { @@ -642,6 +643,7 @@ 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(¤t->mm->mmap_sem); buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, pfn); buf->size = size; kfree(pages); @@ -651,6 +653,7 @@ 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(¤t->mm->mmap_sem); sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); if (!sgt) { @@ -713,10 +716,12 @@ fail_get_user_pages: while (n_pages) put_page(pages[--n_pages]); + down_read(¤t->mm->mmap_sem); fail_vma: vb2_put_vma(buf->vma); fail_pages: + up_read(¤t->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..cdcf5ad79012 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(¤t->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(¤t->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(¤t->mm->mmap_sem); vb2_put_vma(buf->vma); userptr_fail_find_vma: + up_read(¤t->mm->mmap_sem); kfree(buf->pages); userptr_fail_alloc_pages: kfree(buf); diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c index 657ab302a5cf..3199c379cd47 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(¤t->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(¤t->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(¤t->mm->mmap_sem); kfree(buf); return NULL; -- 2.1.4