USB: gadget: f_mass_storage: use static attribute groups for sysfs entries

Instead of manual device_create_file() and device_remove_file() calls,
assign the static attribute groups to the lun device to register.
The RO or RW permissions for some entries are decided in is_visible
callback.  This simplifies the code (also the logic) and avoids the
possible races, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
index 811929cd4c9e21b7c59061375e4ad9de335e0c03..49a2f19c2b87c68c26bbc1981bef25134e8f2376 100644 (file)
--- a/drivers/usb/gadget/function/f_mass_storage.c
+++ b/drivers/usb/gadget/function/f_mass_storage.c
@@ -2624,13 +2624,10 @@ static ssize_t file_store(struct device *dev, struct device_attribute *attr,
        return fsg_store_file(curlun, filesem, buf, count);
 }
 
-static DEVICE_ATTR_RW(ro);
 static DEVICE_ATTR_RW(nofua);
-static DEVICE_ATTR_RW(file);
-
-static struct device_attribute dev_attr_ro_cdrom = __ATTR_RO(ro);
-static struct device_attribute dev_attr_file_nonremovable = __ATTR_RO(file);
-
+/* mode wil be set in fsg_lun_attr_is_visible() */
+static DEVICE_ATTR(ro, 0, ro_show, ro_store);
+static DEVICE_ATTR(file, 0, file_show, file_store);
 
 /****************************** FSG COMMON ******************************/
 
@@ -2745,40 +2742,10 @@ error_release:
 }
 EXPORT_SYMBOL_GPL(fsg_common_set_num_buffers);
 
-static inline void fsg_common_remove_sysfs(struct fsg_lun *lun)
-{
-       device_remove_file(&lun->dev, &dev_attr_nofua);
-       /*
-        * device_remove_file() =>
-        *
-        * here the attr (e.g. dev_attr_ro) is only used to be passed to:
-        *
-        *      sysfs_remove_file() =>
-        *
-        *      here e.g. both dev_attr_ro_cdrom and dev_attr_ro are in
-        *      the same namespace and
-        *      from here only attr->name is passed to:
-        *
-        *              sysfs_hash_and_remove()
-        *
-        *              attr->name is the same for dev_attr_ro_cdrom and
-        *              dev_attr_ro
-        *              attr->name is the same for dev_attr_file and
-        *              dev_attr_file_nonremovable
-        *
-        * so we don't differentiate between removing e.g. dev_attr_ro_cdrom
-        * and dev_attr_ro
-        */
-       device_remove_file(&lun->dev, &dev_attr_ro);
-       device_remove_file(&lun->dev, &dev_attr_file);
-}
-
 void fsg_common_remove_lun(struct fsg_lun *lun, bool sysfs)
 {
-       if (sysfs) {
-               fsg_common_remove_sysfs(lun);
+       if (sysfs)
                device_unregister(&lun->dev);
-       }
        fsg_lun_close(lun);
        kfree(lun);
 }
@@ -2877,41 +2844,35 @@ int fsg_common_set_cdev(struct fsg_common *common,
 }
 EXPORT_SYMBOL_GPL(fsg_common_set_cdev);
 
-static inline int fsg_common_add_sysfs(struct fsg_common *common,
-                                      struct fsg_lun *lun)
-{
-       int rc;
+static struct attribute *fsg_lun_dev_attrs[] = {
+       &dev_attr_ro.attr,
+       &dev_attr_file.attr,
+       &dev_attr_nofua.attr,
+       NULL
+};
 
-       rc = device_register(&lun->dev);
-       if (rc) {
-               put_device(&lun->dev);
-               return rc;
-       }
+static umode_t fsg_lun_dev_is_visible(struct kobject *kobj,
+                                     struct attribute *attr, int idx)
+{
+       struct device *dev = kobj_to_dev(kobj);
+       struct fsg_lun *lun = fsg_lun_from_dev(dev);
 
-       rc = device_create_file(&lun->dev,
-                               lun->cdrom
-                             ? &dev_attr_ro_cdrom
-                             : &dev_attr_ro);
-       if (rc)
-               goto error;
-       rc = device_create_file(&lun->dev,
-                               lun->removable
-                             ? &dev_attr_file
-                             : &dev_attr_file_nonremovable);
-       if (rc)
-               goto error;
-       rc = device_create_file(&lun->dev, &dev_attr_nofua);
-       if (rc)
-               goto error;
+       if (attr == &dev_attr_ro.attr)
+               return lun->cdrom ? S_IRUGO : (S_IWUSR | S_IRUGO);
+       if (attr == &dev_attr_file.attr)
+               return lun->removable ? (S_IWUSR | S_IRUGO) : S_IRUGO;
+       return attr->mode;
+}
 
-       return 0;
+static const struct attribute_group fsg_lun_dev_group = {
+       .attrs = fsg_lun_dev_attrs,
+       .is_visible = fsg_lun_dev_is_visible,
+};
 
-error:
-       /* removing nonexistent files is a no-op */
-       fsg_common_remove_sysfs(lun);
-       device_unregister(&lun->dev);
-       return rc;
-}
+static const struct attribute_group *fsg_lun_dev_groups[] = {
+       &fsg_lun_dev_group,
+       NULL
+};
 
 int fsg_common_create_lun(struct fsg_common *common, struct fsg_lun_config *cfg,
                          unsigned int id, const char *name,
@@ -2949,13 +2910,15 @@ int fsg_common_create_lun(struct fsg_common *common, struct fsg_lun_config *cfg,
        } else {
                lun->dev.release = fsg_lun_release;
                lun->dev.parent = &common->gadget->dev;
+               lun->dev.groups = fsg_lun_dev_groups;
                dev_set_drvdata(&lun->dev, &common->filesem);
                dev_set_name(&lun->dev, "%s", name);
                lun->name = dev_name(&lun->dev);
 
-               rc = fsg_common_add_sysfs(common, lun);
+               rc = device_register(&lun->dev);
                if (rc) {
                        pr_info("failed to register LUN%d: %d\n", id, rc);
+                       put_device(&lun->dev);
                        goto error_sysfs;
                }
        }
@@ -2988,10 +2951,8 @@ int fsg_common_create_lun(struct fsg_common *common, struct fsg_lun_config *cfg,
        return 0;
 
 error_lun:
-       if (common->sysfs) {
-               fsg_common_remove_sysfs(lun);
+       if (common->sysfs)
                device_unregister(&lun->dev);
-       }
        fsg_lun_close(lun);
        common->luns[id] = NULL;
 error_sysfs:
@@ -3077,8 +3038,6 @@ static void fsg_common_release(struct kref *ref)
                        struct fsg_lun *lun = *lun_it;
                        if (!lun)
                                continue;
-                       if (common->sysfs)
-                               fsg_common_remove_sysfs(lun);
                        fsg_lun_close(lun);
                        if (common->sysfs)
                                device_unregister(&lun->dev);