[PATCH] f2fs: remove folio_detach_private() in .invalidate_folio and .release_folio

[Chao Yu]

We have maintain PagePrivate and page_private and page reference
w/ {set,clear}_page_private_*, it doesn't need to call
folio_detach_private() in the end of .invalidate_folio and
.release_folio, remove it and use f2fs_bug_on instead.

Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
[Jaegeuk Kim: cover f2fs_delete_entry case]
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
 fs/f2fs/data.c |  4 ++--
 fs/f2fs/dir.c  |  5 ++---
 fs/f2fs/f2fs.h | 32 ++++++++------------------------
 3 files changed, 12 insertions(+), 29 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5a3636b70f48..8870ff630409 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3734,7 +3734,7 @@ void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 			inode->i_ino == F2FS_COMPRESS_INO(sbi))
 		clear_page_private_data(&folio->page);
 
-	folio_detach_private(folio);
+	f2fs_bug_on(sbi, page_private(&folio->page));
 }
 
 bool f2fs_release_folio(struct folio *folio, gfp_t wait)
@@ -3756,7 +3756,7 @@ bool f2fs_release_folio(struct folio *folio, gfp_t wait)
 	clear_page_private_reference(&folio->page);
 	clear_page_private_gcing(&folio->page);
 
-	folio_detach_private(folio);
+	f2fs_bug_on(sbi, page_private(&folio->page));
 	return true;
 }
 
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index d6dd8327e82d..cea179dec3b6 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -906,13 +906,12 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
 		clear_page_dirty_for_io(page);
 		ClearPageUptodate(page);
 
+		clear_page_private_reference(page);
 		clear_page_private_gcing(page);
+		f2fs_bug_on(F2FS_I_SB(dir), page_private(page));
 
 		inode_dec_dirty_pages(dir);
 		f2fs_remove_dirty_inode(dir);
-
-		detach_page_private(page);
-		set_page_private(page, 0);
 	}
 	f2fs_put_page(page, 1);
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 68eadc1ac130..1b1df9e33028 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1408,11 +1408,8 @@ static inline bool page_private_##name(struct page *page) \
 #define PAGE_PRIVATE_SET_FUNC(name, flagname) \
 static inline void set_page_private_##name(struct page *page) \
 { \
-	if (!PagePrivate(page)) { \
-		get_page(page); \
-		SetPagePrivate(page); \
-		set_page_private(page, 0); \
-	} \
+	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)); \
 }
@@ -1421,13 +1418,8 @@ static inline void set_page_private_##name(struct page *page) \
 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)) { \
-		set_page_private(page, 0); \
-		if (PagePrivate(page)) { \
-			ClearPagePrivate(page); \
-			put_page(page); \
-		}\
-	} \
+	if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) \
+		detach_page_private(page); \
 }
 
 PAGE_PRIVATE_GET_FUNC(nonpointer, NOT_POINTER);
@@ -1456,11 +1448,8 @@ static inline unsigned long get_page_private_data(struct page *page)
 
 static inline void set_page_private_data(struct page *page, unsigned long data)
 {
-	if (!PagePrivate(page)) {
-		get_page(page);
-		SetPagePrivate(page);
-		set_page_private(page, 0);
-	}
+	if (!PagePrivate(page))
+		attach_page_private(page, (void *)0);
 	set_bit(PAGE_PRIVATE_NOT_POINTER, &page_private(page));
 	page_private(page) |= data << PAGE_PRIVATE_MAX;
 }
@@ -1468,13 +1457,8 @@ static inline void set_page_private_data(struct page *page, unsigned long data)
 static inline void clear_page_private_data(struct page *page)
 {
 	page_private(page) &= GENMASK(PAGE_PRIVATE_MAX - 1, 0);
-	if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER)) {
-		set_page_private(page, 0);
-		if (PagePrivate(page)) {
-			ClearPagePrivate(page);
-			put_page(page);
-		}
-	}
+	if (page_private(page) == BIT(PAGE_PRIVATE_NOT_POINTER))
+		detach_page_private(page);
 }
 
 /* For compression */
-- 
2.40.0.577.gac1e443424-goog


> 
> With above two patches, I didn't hit any panic or use-after-free issue when testing
> xfstest until now.
> 
> Thanks,
> 
> 
> > I feel attach/detach_page_private would look better?
> > 
> > > 
> > > Thanks,
> > > 
> > > > 1429                         put_page(page); \
> > > > 1430                 }\
> > > > 1431         } \
> > > > 1432 }
> > > > 
> > > > > page is now free, gets reallocated into a THP
> > > > > lookup from the f2fs file finds the new THP
> > > > > things explode messily
> > > > > 
> > > > > Checking page->mapping is going to avoid the messy explosion, but
> > > > > you'll still have a page in the page cache which doesn't actually
> > > > > belong to you, and that's going to lead to subtle data corruption.
> > > > > 
> > > > > This should be caught by page_expected_state(), called from
> > > > > free_page_is_bad(), called from free_pages_prepare().  Do your testers
> > > > > have CONFIG_DEBUG_VM enabled?  That might give you a fighting chance at
> > > > > finding the last place which called put_page().  It won't necessarily be
> > > > > the _wrong_ place to call put_page() (that may have happened earlier),
> > > > > but it may give you a clue.
> > > > > 
> > > > > > > 
> > > > > > > struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> > > > > > > 		int fgp_flags, gfp_t gfp)
> > > > > > > {
> > > > > > > 	struct folio *folio;
> > > > > > > 
> > > > > > > 	folio = __filemap_get_folio(mapping, index, fgp_flags, gfp);
> > > > > > > 	if (IS_ERR(folio))
> > > > > > > 		return NULL;
> > > > > > > 	return folio_file_page(folio, index);
> > > > > > > }
> > > > > > > 
> > > > > > > Thanks,
> > > > > > > 
> > > > > > > > -		f2fs_put_page(page, 1);
> > > > > > > > -		goto repeat;
> > > > > > > > -	}
> > > > > > > > -	if (unlikely(!PageUptodate(page))) {
> > > > > > > > +	if (unlikely(page->mapping != mapping || !PageUptodate(page))) {
> > > > > > > >     		f2fs_put_page(page, 1);
> > > > > > > >     		return ERR_PTR(-EIO);
> > > > > > > >     	}