linux-kernel - [PATCH V3 19/21] famfs_fuse: Add DAX address_space_operations with noop_dirty

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Message-ID: <20260107153332.64727-20-john@groves.net>
Date: Wed,  7 Jan 2026 09:33:28 -0600
From: John Groves <John@...ves.net>
To: John Groves <John@...ves.net>,
	Miklos Szeredi <miklos@...redi.hu>,
	Dan Williams <dan.j.williams@...el.com>,
	Bernd Schubert <bschubert@....com>,
	Alison Schofield <alison.schofield@...el.com>
Cc: John Groves <jgroves@...ron.com>,
	Jonathan Corbet <corbet@....net>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Matthew Wilcox <willy@...radead.org>,
	Jan Kara <jack@...e.cz>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	David Hildenbrand <david@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Jeff Layton <jlayton@...nel.org>,
	Amir Goldstein <amir73il@...il.com>,
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	Ackerley Tng <ackerleytng@...gle.com>,
	Gregory Price <gourry@...rry.net>,
	Aravind Ramesh <arramesh@...ron.com>,
	Ajay Joshi <ajayjoshi@...ron.com>,
	venkataravis@...ron.com,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev,
	linux-cxl@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	John Groves <john@...ves.net>
Subject: [PATCH V3 19/21] famfs_fuse: Add DAX address_space_operations with noop_dirty_folio

From: John Groves <John@...ves.net>

Famfs is memory-backed; there is no place to write back to, and no
reason to mark pages dirty at all.

Signed-off-by: John Groves <john@...ves.net>
---
 fs/fuse/famfs.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/fuse/famfs.c b/fs/fuse/famfs.c
index 4eb87c5c628e..32c3d0c2ec48 100644
--- a/fs/fuse/famfs.c
+++ b/fs/fuse/famfs.c
@@ -13,6 +13,7 @@
 #include <linux/mm.h>
 #include <linux/dax.h>
 #include <linux/iomap.h>
+#include <linux/pagemap.h>
 #include <linux/path.h>
 #include <linux/namei.h>
 #include <linux/string.h>
@@ -38,6 +39,15 @@ static const struct dax_holder_operations famfs_fuse_dax_holder_ops = {
 	.notify_failure		= famfs_dax_notify_failure,
 };
 
+/*
+ * DAX address_space_operations for famfs.
+ * famfs doesn't need dirty tracking - writes go directly to
+ * memory with no writeback required.
+ */
+static const struct address_space_operations famfs_dax_aops = {
+	.dirty_folio	= noop_dirty_folio,
+};
+
 /*****************************************************************************/
 
 /*
@@ -657,6 +667,7 @@ famfs_file_init_dax(
 		}
 		i_size_write(inode, meta->file_size);
 		inode->i_flags |= S_DAX;
+		inode->i_data.a_ops = &famfs_dax_aops;
 	}
  unlock_out:
 	inode_unlock(inode);
-- 
2.49.0