[v8,20/26] powerpc: book3s64: convert to pin_user_pages() and put_user_page()
diff mbox series

Message ID 20191209225344.99740-21-jhubbard@nvidia.com
State New
Headers show
Series
  • mm/gup: track dma-pinned pages: FOLL_PIN
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Commit Message

John Hubbard Dec. 9, 2019, 10:53 p.m. UTC
1. Convert from get_user_pages() to pin_user_pages().

2. As required by pin_user_pages(), release these pages via
put_user_page(). In this case, do so via put_user_pages_dirty_lock().

That has the side effect of calling set_page_dirty_lock(), instead
of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Cc: Jan Kara <jack@suse.cz>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 arch/powerpc/mm/book3s64/iommu_api.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

Comments

John Hubbard Dec. 9, 2019, 11:46 p.m. UTC | #1
On 12/9/19 2:53 PM, John Hubbard wrote:
...
> @@ -212,10 +211,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>  		if (!page)
>  			continue;
>  
> -		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
> -			SetPageDirty(page);
> +		put_user_pages_dirty_lock(&page, 1,
> +				mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY);
>  
> -		put_page(page);


Correction: this is somehow missing the fixes that resulted from Jan Kara's review (he
noted that we can't take a page lock in this context). I must have picked up the 
wrong version of it, when I rebased for -rc1.

Will fix in the next version (including the commit description). Here's what the
corrected hunk will look like:

@@ -215,7 +214,8 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
                if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
                        SetPageDirty(page);
 
-               put_page(page);
+               put_user_page(page);
+
                mem->hpas[i] = 0;
        }
 }


thanks,
John Hubbard Dec. 10, 2019, 5:53 a.m. UTC | #2
On 12/9/19 3:46 PM, John Hubbard wrote:
> On 12/9/19 2:53 PM, John Hubbard wrote:
> ...
>> @@ -212,10 +211,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>>   		if (!page)
>>   			continue;
>>   
>> -		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
>> -			SetPageDirty(page);
>> +		put_user_pages_dirty_lock(&page, 1,
>> +				mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY);
>>   
>> -		put_page(page);
> 
> 
> Correction: this is somehow missing the fixes that resulted from Jan Kara's review (he
> noted that we can't take a page lock in this context). I must have picked up the
> wrong version of it, when I rebased for -rc1.
> 

Andrew, given that the series is now in -mm, what's the preferred way for me to fix this?
Send a v9 version of the whole series? Or something else?

I'm still learning the ropes...

thanks,
Andrew Morton Dec. 11, 2019, 12:49 a.m. UTC | #3
On Mon, 9 Dec 2019 21:53:00 -0800 John Hubbard <jhubbard@nvidia.com> wrote:

> > Correction: this is somehow missing the fixes that resulted from Jan Kara's review (he
> > noted that we can't take a page lock in this context). I must have picked up the
> > wrong version of it, when I rebased for -rc1.
> > 
> 
> Andrew, given that the series is now in -mm, what's the preferred way for me to fix this?
> Send a v9 version of the whole series? Or something else?

I think a full resend is warranted at this time - it's only been in
there a day and there seem to be quite a number of changes to be made.

Patch
diff mbox series

diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
index 56cc84520577..fc1670a6fc3c 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -103,7 +103,7 @@  static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
 	for (entry = 0; entry < entries; entry += chunk) {
 		unsigned long n = min(entries - entry, chunk);
 
-		ret = get_user_pages(ua + (entry << PAGE_SHIFT), n,
+		ret = pin_user_pages(ua + (entry << PAGE_SHIFT), n,
 				FOLL_WRITE | FOLL_LONGTERM,
 				mem->hpages + entry, NULL);
 		if (ret == n) {
@@ -167,9 +167,8 @@  static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
 	return 0;
 
 free_exit:
-	/* free the reference taken */
-	for (i = 0; i < pinned; i++)
-		put_page(mem->hpages[i]);
+	/* free the references taken */
+	put_user_pages(mem->hpages, pinned);
 
 	vfree(mem->hpas);
 	kfree(mem);
@@ -212,10 +211,9 @@  static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
 		if (!page)
 			continue;
 
-		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
-			SetPageDirty(page);
+		put_user_pages_dirty_lock(&page, 1,
+				mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY);
 
-		put_page(page);
 		mem->hpas[i] = 0;
 	}
 }