[PATCH 2/6] sysfs: add mmap_allocates parameter to struct bin_attribute

[Martin Oliveira]

Now that a struct kernfs_ops can have an "mmap_allocates" parameter to
avoid the page_mkwrite() operator, the struct bin_attribute needs a way
to choose the appropriate kernfs_ops.

Introduce a "mmap_allocates" boolean on struct bin_attribute to achieve
that.

Co-developed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Martin Oliveira <martin.oliveira@xxxxxxxxxxxxx>
---
 fs/sysfs/file.c       | 25 +++++++++++++++++++------
 include/linux/sysfs.h |  1 +
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index d1995e2d6c94..77c21009ceee 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -264,6 +264,15 @@ static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 	.llseek		= sysfs_kf_bin_llseek,
 };
 
+static const struct kernfs_ops sysfs_bin_kfops_mmap_allocates = {
+	.read		= sysfs_kf_bin_read,
+	.write		= sysfs_kf_bin_write,
+	.mmap		= sysfs_kf_bin_mmap,
+	.open		= sysfs_kf_bin_open,
+	.llseek		= sysfs_kf_bin_llseek,
+	.mmap_allocates = true,
+};
+
 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 		const struct attribute *attr, umode_t mode, kuid_t uid,
 		kgid_t gid, const void *ns)
@@ -323,16 +332,20 @@ int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
 	const struct kernfs_ops *ops;
 	struct kernfs_node *kn;
 
-	if (battr->mmap)
-		ops = &sysfs_bin_kfops_mmap;
-	else if (battr->read && battr->write)
+	if (battr->mmap) {
+		if (battr->mmap_allocates)
+			ops = &sysfs_bin_kfops_mmap_allocates;
+		else
+			ops = &sysfs_bin_kfops_mmap;
+	} else if (battr->read && battr->write) {
 		ops = &sysfs_bin_kfops_rw;
-	else if (battr->read)
+	} else if (battr->read) {
 		ops = &sysfs_bin_kfops_ro;
-	else if (battr->write)
+	} else if (battr->write) {
 		ops = &sysfs_bin_kfops_wo;
-	else
+	} else {
 		ops = &sysfs_file_kfops_empty;
+	}
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	if (!attr->ignore_lockdep)
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index a7d725fbf739..190b4b9355df 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -294,6 +294,7 @@ struct bin_attribute {
 	struct attribute	attr;
 	size_t			size;
 	void			*private;
+	bool			mmap_allocates;
 	struct address_space *(*f_mapping)(void);
 	ssize_t (*read)(struct file *, struct kobject *, struct bin_attribute *,
 			char *, loff_t, size_t);
-- 
2.34.1