Re: [f2fs-dev] [PATCH 01/14] f2fs: extend folio state for large folio write path

[Nanzhe Zhao]

On Thu, 27 Aug 2026 13:51:06 -0700, Daeho Jeong wrote:
> +		ffs->private_flags |= flags;
>
> Is this field protected by holding a lock properly?

Thanks for the review.
No, it doesn't. Thanks for pointing out.

I want to change this using per-field atomic read-modify-write ops
instead, to avoid taking state_lock, like below:

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
@@ f2fs_folio_get_private_flags()  (f2fs.h:2719)
 	if (f2fs_folio_has_ffs(folio)) {
 		struct f2fs_folio_state *ffs = folio->private;
 
-		return ffs->private_flags;
+		return READ_ONCE(ffs->private_flags);
 	}
@@ f2fs_folio_set_private_flags()  (f2fs.h:2730)
 	if (f2fs_folio_has_ffs(folio)) {
 		struct f2fs_folio_state *ffs = folio->private;
 
-		ffs->private_flags |= flags;
+		if (flags)
+			__atomic_or_fetch(&ffs->private_flags, flags,
+					  __ATOMIC_RELAXED);
 		return;
 	}
@@ f2fs_folio_clear_private_flags()  (f2fs.h:2746)
 	if (f2fs_folio_has_ffs(folio)) {
 		struct f2fs_folio_state *ffs = folio->private;
 
-		ffs->private_flags &= ~flags;
+		if (flags)
+			__atomic_and_fetch(&ffs->private_flags, ~flags,
+					   __ATOMIC_RELAXED);
 		return;
 	}

Please let me know if this lock-free approach looks acceptable.

Thanks,
Nanzhe