linux-kernel - [PATCH 05/13] sysfs: support get_unmapped

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Message-Id: <20251220040446.274991-6-houtao@huaweicloud.com>
Date: Sat, 20 Dec 2025 12:04:38 +0800
From: Hou Tao <houtao@...weicloud.com>
To: linux-kernel@...r.kernel.org
Cc: linux-pci@...r.kernel.org,
	linux-mm@...ck.org,
	linux-nvme@...ts.infradead.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>,
	Alistair Popple <apopple@...dia.com>,
	Leon Romanovsky <leonro@...dia.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Keith Busch <kbusch@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>,
	houtao1@...wei.com
Subject: [PATCH 05/13] sysfs: support get_unmapped_area callback for binary file

From: Hou Tao <houtao1@...wei.com>

Add support for ->get_unmapped_area callback for binary sysfs file. The
following patch will use it to support compound page for p2pdma device
memory when the device memory is mapped into userspace.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 fs/sysfs/file.c       | 15 +++++++++++++++
 include/linux/sysfs.h |  4 ++++
 2 files changed, 19 insertions(+)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 3825e780cc58..e843795ebdc2 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -164,6 +164,20 @@ static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 	return battr->write(of->file, kobj, battr, buf, pos, count);
 }
 
+static unsigned long sysfs_kf_bin_get_unmapped_area(struct kernfs_open_file *of,
+						    unsigned long uaddr, unsigned long len,
+						    unsigned long pgoff, unsigned long flags)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj;
+
+	if (!battr->get_unmapped_area)
+		return -EOPNOTSUPP;
+
+	kobj = sysfs_file_kobj(of->kn);
+	return battr->get_unmapped_area(of->file, kobj, battr, uaddr, len, pgoff, flags);
+}
+
 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
 			     struct vm_area_struct *vma)
 {
@@ -268,6 +282,7 @@ static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 	.mmap		= sysfs_kf_bin_mmap,
 	.open		= sysfs_kf_bin_open,
 	.llseek		= sysfs_kf_bin_llseek,
+	.get_unmapped_area = sysfs_kf_bin_get_unmapped_area,
 };
 
 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index c33a96b7391a..f4a50f244f4d 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -321,6 +321,10 @@ struct bin_attribute {
 			 loff_t, int);
 	int (*mmap)(struct file *, struct kobject *, const struct bin_attribute *attr,
 		    struct vm_area_struct *vma);
+	unsigned long (*get_unmapped_area)(struct file *, struct kobject *,
+					   const struct bin_attribute *attr,
+					   unsigned long uaddr, unsigned long len,
+					   unsigned long pgoff, unsigned long flags);
 };
 
 /**
-- 
2.29.2