Re: [PATCH v3 06/14] f2fs: stop using PG_private

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/8/26 04:56, Zi Yan wrote:
> f2fs sets its PAGE_PRIVATE_* flags in page->private and checking
> page->private != NULL is equivalent to checking PG_private. Change
> PagePrivate() to page_private(). Meanwhile, in set_page_private_##name(),
> page->private is first set to 0/NULL before an PAGE_PRIVATE_* flag is set,
> but it can cause confusion when PG_private is removed and
> page->private != NULL is used instead. Change it to initialize
> page->private to PAGE_PRIVATE_NOT_POINTER instead and retain the original
> semantics.
> 
> It prepares for a future commit that removes PG_private.
> 
> No functional change intended.
> 
> Assisted-by: Claude:claude-opus-4-8
> Assisted-by: Codex:gpt-5
> To: Jaegeuk Kim <jaegeuk@kernel.org>
> To: Chao Yu <chao@kernel.org>
> Cc: linux-f2fs-devel@lists.sourceforge.net
> Cc: linux-kernel@vger.kernel.org
> Acked-by: Usama Arif <usama.arif@linux.dev>
> Acked-by: Chao Yu <chao@kernel.org>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  fs/f2fs/f2fs.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9940a6cecf1a2..2f7ab5888b078 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2691,7 +2691,7 @@ static inline bool folio_test_f2fs_##name(const struct folio *folio)	\
>  }									\
>  static inline bool page_private_##name(struct page *page) \
>  { \
> -	return PagePrivate(page) && \
> +	return page_private(page) && \
>  		test_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)) && \
>  		test_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
>  }
> @@ -2710,9 +2710,9 @@ static inline void folio_set_f2fs_##name(struct folio *folio)		\
>  }									\
>  static inline void set_page_private_##name(struct page *page) \
>  { \
> -	if (!PagePrivate(page)) \
> -		attach_page_private(page, (void *)0); \
> -	set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); \
> +	if (!page_private(page)) \
> +		attach_page_private(page, \
> +				(void *)BIT(PAGE_PRIVATE_NOT_POINTER)); \
>  	set_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
>  }

Very weird interface. Why do we even need the page-based interface still?

$ git grep -E "(set|clear)_page_private"
compress.c:             clear_page_private_gcing(cc->rpages[i]);
compress.c:                     set_page_private_gcing(cc->rpages[i]);
compress.c:             clear_page_private_gcing(cic->rpages[i]);
f2fs.h:static inline void set_page_private_##name(struct page *page) \
f2fs.h:static inline void clear_page_private_##name(struct page *page) \

Seeing code like:

clear_page_private_gcing(cc->rpages[i]);
if (folio_test_writeback(page_folio(cc->rpages[i])))
	end_page_writeback(cc->rpages[i]);

Makes me wonder whether we can just use the folio helper instead?

In f2fs_iget(), we enable large folios only when !f2fs_compressed_file(inode).

So naive me would assume that we can just get rid of the
set_page_private_/clear_page_private_ stuff entirely.

IOW something like:


From efcde918178604de11d16c6dc5485542ab4dcdaf Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Tue, 8 Sep 2026 17:46:06 +0200
Subject: [PATCH] tmp

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 fs/f2fs/compress.c | 29 ++++++++++++++++++-----------
 fs/f2fs/f2fs.h     | 13 -------------
 2 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index ce88092d9ce26..0e9cc0fa297a4 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1064,13 +1064,15 @@ static void cancel_cluster_writeback(struct compress_ctx *cc,
 
 	/* Cancel writeback and stay locked. */
 	for (i = 0; i < cc->cluster_size; i++) {
+		struct folio *folio = page_folio(cc->rpages[i]);
+
 		if (i < submitted) {
 			inode_inc_dirty_pages(cc->inode);
-			lock_page(cc->rpages[i]);
+			folio_lock(folio);
 		}
-		clear_page_private_gcing(cc->rpages[i]);
-		if (folio_test_writeback(page_folio(cc->rpages[i])))
-			end_page_writeback(cc->rpages[i]);
+		folio_clear_f2fs_gcing(folio);
+		if (folio_test_writeback(folio))
+			folio_end_writeback(folio);
 	}
 }
 
@@ -1078,11 +1080,15 @@ static void set_cluster_dirty(struct compress_ctx *cc)
 {
 	int i;
 
-	for (i = 0; i < cc->cluster_size; i++)
-		if (cc->rpages[i]) {
-			set_page_dirty(cc->rpages[i]);
-			set_page_private_gcing(cc->rpages[i]);
-		}
+	for (i = 0; i < cc->cluster_size; i++) {
+		struct folio *folio;
+
+		if (!cc->rpages[i])
+			continue;
+		folio = page_folio(cc->rpages[i]);
+		folio_mark_dirty(folio);
+		folio_set_f2fs_gcing(folio);
+	}
 }
 
 static int prepare_compress_overwrite(struct compress_ctx *cc,
@@ -1477,8 +1483,9 @@ void f2fs_compress_write_end_io(struct bio *bio, struct folio *folio)
 
 	for (i = 0; i < cic->nr_rpages; i++) {
 		WARN_ON(!cic->rpages[i]);
-		clear_page_private_gcing(cic->rpages[i]);
-		end_page_writeback(cic->rpages[i]);
+		folio = page_folio(cic->rpages[i]);
+		folio_clear_f2fs_gcing(folio);
+		folio_end_writeback(folio);
 	}
 
 	page_array_free(sbi, cic->rpages, cic->nr_rpages);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9940a6cecf1a2..0cfba8742d4b4 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2707,13 +2707,6 @@ static inline void folio_set_f2fs_##name(struct folio *folio)		\
 		v |= (unsigned long)folio->private;			\
 		folio->private = (void *)v;				\
 	}								\
-}									\
-static inline void set_page_private_##name(struct page *page) \
-{ \
-	if (!PagePrivate(page)) \
-		attach_page_private(page, (void *)0); \
-	set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page)); \
-	set_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
 }
 
 #define PAGE_PRIVATE_CLEAR_FUNC(name, flagname) \
@@ -2726,12 +2719,6 @@ static inline void folio_clear_f2fs_##name(struct folio *folio)		\
 		folio_detach_private(folio);				\
 	else								\
 		folio->private = (void *)v;				\
-}									\
-static inline void clear_page_private_##name(struct page *page) \
-{ \
-	clear_bit(PAGE_PRIVATE_##flagname, &page_private(page)); \
-	if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) \
-		detach_page_private(page); \
 }
 
 PAGE_PRIVATE_GET_FUNC(nonpointer, NOT_POINTER);
-- 
2.43.0


-- 
Cheers,

David