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

Martin Oliveira
2024-06-05T19:30:19Z

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@deltatee.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Martin Oliveira <martin.oliveira@eideticom.com>
---
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