linux-kernel - Re: [PATCH 4/5] mm: gup: use get_user_pages

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Date:	Thu, 30 Oct 2014 14:28:53 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michel Lespinasse <walken@...gle.com>,
	Andrew Jones <drjones@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"\\\"Dr. David Alan Gilbert\\\"" <dgilbert@...hat.com>,
	Peter Feiner <pfeiner@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	David Miller <davem@...emloft.net>,
	Steve Capper <steve.capper@...aro.org>,
	Johannes Weiner <jweiner@...hat.com>
Subject: Re: [PATCH 4/5] mm: gup: use get_user_pages_unlocked

On Wed, Oct 29, 2014 at 05:35:19PM +0100, Andrea Arcangeli wrote:
> This allows those get_user_pages calls to pass FAULT_FLAG_ALLOW_RETRY
> to the page fault in order to release the mmap_sem during the I/O.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
> ---
>  drivers/iommu/amd_iommu_v2.c       | 6 ++----
>  drivers/media/pci/ivtv/ivtv-udma.c | 6 ++----
>  drivers/scsi/st.c                  | 7 ++-----
>  drivers/video/fbdev/pvr2fb.c       | 6 ++----
>  mm/process_vm_access.c             | 7 ++-----
>  net/ceph/pagevec.c                 | 6 ++----
>  6 files changed, 12 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
> index 90d734b..4cd8a87 100644
> --- a/drivers/iommu/amd_iommu_v2.c
> +++ b/drivers/iommu/amd_iommu_v2.c
> @@ -521,10 +521,8 @@ static void do_fault(struct work_struct *work)
>  
>  	write = !!(fault->flags & PPR_FAULT_WRITE);
>  
> -	down_read(&fault->state->mm->mmap_sem);
> -	npages = get_user_pages(NULL, fault->state->mm,
> -				fault->address, 1, write, 0, &page, NULL);
> -	up_read(&fault->state->mm->mmap_sem);
> +	npages = get_user_pages_unlocked(NULL, fault->state->mm,
> +					 fault->address, 1, write, 0, &page);
>  
>  	if (npages == 1) {
>  		put_page(page);
> diff --git a/drivers/media/pci/ivtv/ivtv-udma.c b/drivers/media/pci/ivtv/ivtv-udma.c
> index 7338cb2..96d866b 100644
> --- a/drivers/media/pci/ivtv/ivtv-udma.c
> +++ b/drivers/media/pci/ivtv/ivtv-udma.c
> @@ -124,10 +124,8 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
>  	}
>  
>  	/* Get user pages for DMA Xfer */
> -	down_read(&current->mm->mmap_sem);
> -	err = get_user_pages(current, current->mm,
> -			user_dma.uaddr, user_dma.page_count, 0, 1, dma->map, NULL);
> -	up_read(&current->mm->mmap_sem);
> +	err = get_user_pages_unlocked(current, current->mm,
> +			user_dma.uaddr, user_dma.page_count, 0, 1, dma->map);
>  
>  	if (user_dma.page_count != err) {
>  		IVTV_DEBUG_WARN("failed to map user pages, returned %d instead of %d\n",
> diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
> index 4daa372..a98e00b 100644
> --- a/drivers/scsi/st.c
> +++ b/drivers/scsi/st.c
> @@ -4538,18 +4538,15 @@ static int sgl_map_user_pages(struct st_buffer *STbp,
>  		return -ENOMEM;
>  
>          /* Try to fault in all of the necessary pages */
> -	down_read(&current->mm->mmap_sem);
>          /* rw==READ means read from drive, write into memory area */

Consolidate two one-line configs into a one?


Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov
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