[RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[Guoqing Jiang]

Since the new pair function is introduced, we can call them to clean the
code in btrfs.

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
---
 fs/btrfs/disk-io.c   |  4 +---
 fs/btrfs/extent_io.c | 21 ++++++---------------
 fs/btrfs/inode.c     | 17 ++++-------------
 3 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a6cb5cbbdb9f..1230863e80f9 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -980,9 +980,7 @@ static void btree_invalidatepage(struct page *page, unsigned int offset,
 		btrfs_warn(BTRFS_I(page->mapping->host)->root->fs_info,
 			   "page private not zero on page %llu",
 			   (unsigned long long)page_offset(page));
-		ClearPagePrivate(page);
-		set_page_private(page, 0);
-		put_page(page);
+		clear_fs_page_private(page);
 	}
 }
 
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 39e45b8a5031..de8c2d5a99db 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3076,22 +3076,16 @@ static int submit_extent_page(unsigned int opf,
 static void attach_extent_buffer_page(struct extent_buffer *eb,
 				      struct page *page)
 {
-	if (!PagePrivate(page)) {
-		SetPagePrivate(page);
-		get_page(page);
-		set_page_private(page, (unsigned long)eb);
-	} else {
+	if (!PagePrivate(page))
+		set_fs_page_private(page, eb);
+	else
 		WARN_ON(page->private != (unsigned long)eb);
-	}
 }
 
 void set_page_extent_mapped(struct page *page)
 {
-	if (!PagePrivate(page)) {
-		SetPagePrivate(page);
-		get_page(page);
-		set_page_private(page, EXTENT_PAGE_PRIVATE);
-	}
+	if (!PagePrivate(page))
+		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);
 }
 
 static struct extent_map *
@@ -4929,10 +4923,7 @@ static void btrfs_release_extent_buffer_pages(struct extent_buffer *eb)
 			 * We need to make sure we haven't be attached
 			 * to a new eb.
 			 */
-			ClearPagePrivate(page);
-			set_page_private(page, 0);
-			/* One for the page private */
-			put_page(page);
+			clear_fs_page_private(page);
 		}
 
 		if (mapped)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 320d1062068d..07871c57ba96 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8303,11 +8303,8 @@ btrfs_readpages(struct file *file, struct address_space *mapping,
 static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
 {
 	int ret = try_release_extent_mapping(page, gfp_flags);
-	if (ret == 1) {
-		ClearPagePrivate(page);
-		set_page_private(page, 0);
-		put_page(page);
-	}
+	if (ret == 1)
+		clear_fs_page_private(page);
 	return ret;
 }
 
@@ -8331,11 +8328,9 @@ static int btrfs_migratepage(struct address_space *mapping,
 
 	if (page_has_private(page)) {
 		ClearPagePrivate(page);
-		get_page(newpage);
-		set_page_private(newpage, page_private(page));
+		set_fs_page_private(newpage, (void *)page_private(page));
 		set_page_private(page, 0);
 		put_page(page);
-		SetPagePrivate(newpage);
 	}
 
 	if (PagePrivate2(page)) {
@@ -8458,11 +8453,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset,
 	}
 
 	ClearPageChecked(page);
-	if (PagePrivate(page)) {
-		ClearPagePrivate(page);
-		set_page_private(page, 0);
-		put_page(page);
-	}
+	clear_fs_page_private(page);
 }
 
 /*
-- 
2.17.1

Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[Dave Chinner]

On Sun, Apr 26, 2020 at 11:49:19PM +0200, Guoqing Jiang wrote:
> Since the new pair function is introduced, we can call them to clean the
> code in btrfs.
> 
> Cc: Chris Mason <clm@fb.com>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: linux-btrfs@vger.kernel.org
> Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>

....

>  void set_page_extent_mapped(struct page *page)
>  {
> -	if (!PagePrivate(page)) {
> -		SetPagePrivate(page);
> -		get_page(page);
> -		set_page_private(page, EXTENT_PAGE_PRIVATE);
> -	}
> +	if (!PagePrivate(page))
> +		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);

Change the definition of EXTENT_PAGE_PRIVATE so the cast is not
needed? Nothing ever reads EXTENT_PAGE_PRIVATE; it's only there to
set the private flag for other code to check and release the extent
mapping reference to the page...

> @@ -8331,11 +8328,9 @@ static int btrfs_migratepage(struct address_space *mapping,
>  
>  	if (page_has_private(page)) {
>  		ClearPagePrivate(page);
> -		get_page(newpage);
> -		set_page_private(newpage, page_private(page));
> +		set_fs_page_private(newpage, (void *)page_private(page));
>  		set_page_private(page, 0);
>  		put_page(page);
> -		SetPagePrivate(newpage);
>  	}

This is just:
		set_fs_page_private(newpage, clear_fs_page_private(page));

Cheers,

Dave.

-- 
Dave Chinner
david@fromorbit.com

Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[Christoph Hellwig]

On Mon, Apr 27, 2020 at 08:20:54AM +1000, Dave Chinner wrote:
> >  void set_page_extent_mapped(struct page *page)
> >  {
> > -	if (!PagePrivate(page)) {
> > -		SetPagePrivate(page);
> > -		get_page(page);
> > -		set_page_private(page, EXTENT_PAGE_PRIVATE);
> > -	}
> > +	if (!PagePrivate(page))
> > +		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);
> 
> Change the definition of EXTENT_PAGE_PRIVATE so the cast is not
> needed? Nothing ever reads EXTENT_PAGE_PRIVATE; it's only there to
> set the private flag for other code to check and release the extent
> mapping reference to the page...

IIRC there as a patch on the btrfs list to remove EXTENT_PAGE_PRIVATE,
it might be better to not bother changing it.  Maybe the btrfs
maintainers remember this better.

Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[David Sterba]

On Sun, Apr 26, 2020 at 10:54:28PM -0700, Christoph Hellwig wrote:
> On Mon, Apr 27, 2020 at 08:20:54AM +1000, Dave Chinner wrote:
> > >  void set_page_extent_mapped(struct page *page)
> > >  {
> > > -	if (!PagePrivate(page)) {
> > > -		SetPagePrivate(page);
> > > -		get_page(page);
> > > -		set_page_private(page, EXTENT_PAGE_PRIVATE);
> > > -	}
> > > +	if (!PagePrivate(page))
> > > +		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);
> > 
> > Change the definition of EXTENT_PAGE_PRIVATE so the cast is not
> > needed? Nothing ever reads EXTENT_PAGE_PRIVATE; it's only there to
> > set the private flag for other code to check and release the extent
> > mapping reference to the page...
> 
> IIRC there as a patch on the btrfs list to remove EXTENT_PAGE_PRIVATE,
> it might be better to not bother changing it.  Maybe the btrfs
> maintainers remember this better.

The patch removing it is part of patchset adding full iomap support to
btrfs,
(https://lore.kernel.org/linux-btrfs/20190905150650.21089-4-rgoldwyn@suse.de/)
but it'll still take some time so I'm OK with using the
set_fs_page_private helper and adding the cast to EXTENT_PAGE_PRIVATE
definition.

Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[Guoqing Jiang]

On 4/27/20 12:20 AM, Dave Chinner wrote:
> On Sun, Apr 26, 2020 at 11:49:19PM +0200, Guoqing Jiang wrote:
>> Since the new pair function is introduced, we can call them to clean the
>> code in btrfs.
>>
>> Cc: Chris Mason <clm@fb.com>
>> Cc: Josef Bacik <josef@toxicpanda.com>
>> Cc: David Sterba <dsterba@suse.com>
>> Cc: linux-btrfs@vger.kernel.org
>> Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
> ....
>
>>   void set_page_extent_mapped(struct page *page)
>>   {
>> -	if (!PagePrivate(page)) {
>> -		SetPagePrivate(page);
>> -		get_page(page);
>> -		set_page_private(page, EXTENT_PAGE_PRIVATE);
>> -	}
>> +	if (!PagePrivate(page))
>> +		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);
> Change the definition of EXTENT_PAGE_PRIVATE so the cast is not
> needed? Nothing ever reads EXTENT_PAGE_PRIVATE; it's only there to
> set the private flag for other code to check and release the extent
> mapping reference to the page...

Not know the code well, so I just make the cast ...

>> @@ -8331,11 +8328,9 @@ static int btrfs_migratepage(struct address_space *mapping,
>>   
>>   	if (page_has_private(page)) {
>>   		ClearPagePrivate(page);
>> -		get_page(newpage);
>> -		set_page_private(newpage, page_private(page));
>> +		set_fs_page_private(newpage, (void *)page_private(page));
>>   		set_page_private(page, 0);
>>   		put_page(page);
>> -		SetPagePrivate(newpage);
>>   	}
> This is just:
> 		set_fs_page_private(newpage, clear_fs_page_private(page));
>

Thanks a lot! It is more better.

Thanks,
Guoqing