loop: add some basic read-only sysfs attributes (ee862730) · Commits · 戴 / test

drivers/block/loop.c

+101 −0

Original line number	Diff line number	Diff line
		@@ -74,6 +74,7 @@
		#include <linux/highmem.h>
		#include <linux/kthread.h>
		#include <linux/splice.h>
		#include <linux/sysfs.h>

		#include <asm/uaccess.h>

		@@ -737,6 +738,103 @@ static inline int is_loop_device(struct file *file)
		return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
		}

		/* loop sysfs attributes */

		static ssize_t loop_attr_show(struct device dev, char page,
		ssize_t (callback)(struct loop_device , char *))
		{
		struct loop_device l, lo = NULL;

		mutex_lock(&loop_devices_mutex);
		list_for_each_entry(l, &loop_devices, lo_list)
		if (disk_to_dev(l->lo_disk) == dev) {
		lo = l;
		break;
		}
		mutex_unlock(&loop_devices_mutex);

		return lo ? callback(lo, page) : -EIO;
		}

		#define LOOP_ATTR_RO(_name) \
		static ssize_t loop_attr_##_name##_show(struct loop_device , char ); \
		static ssize_t loop_attr_do_show_##_name(struct device *d, \
		struct device_attribute attr, char b) \
		{ \
		return loop_attr_show(d, b, loop_attr_##_name##_show); \
		} \
		static struct device_attribute loop_attr_##_name = \
		__ATTR(_name, S_IRUGO, loop_attr_do_show_##_name, NULL);

		static ssize_t loop_attr_backing_file_show(struct loop_device lo, char buf)
		{
		ssize_t ret;
		char *p = NULL;

		mutex_lock(&lo->lo_ctl_mutex);
		if (lo->lo_backing_file)
		p = d_path(&lo->lo_backing_file->f_path, buf, PAGE_SIZE - 1);
		mutex_unlock(&lo->lo_ctl_mutex);

		if (IS_ERR_OR_NULL(p))
		ret = PTR_ERR(p);
		else {
		ret = strlen(p);
		memmove(buf, p, ret);
		buf[ret++] = '\n';
		buf[ret] = 0;
		}

		return ret;
		}

		static ssize_t loop_attr_offset_show(struct loop_device lo, char buf)
		{
		return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
		}

		static ssize_t loop_attr_sizelimit_show(struct loop_device lo, char buf)
		{
		return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
		}

		static ssize_t loop_attr_autoclear_show(struct loop_device lo, char buf)
		{
		int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);

		return sprintf(buf, "%s\n", autoclear ? "1" : "0");
		}

		LOOP_ATTR_RO(backing_file);
		LOOP_ATTR_RO(offset);
		LOOP_ATTR_RO(sizelimit);
		LOOP_ATTR_RO(autoclear);

		static struct attribute *loop_attrs[] = {
		&loop_attr_backing_file.attr,
		&loop_attr_offset.attr,
		&loop_attr_sizelimit.attr,
		&loop_attr_autoclear.attr,
		NULL,
		};

		static struct attribute_group loop_attribute_group = {
		.name = "loop",
		.attrs= loop_attrs,
		};

		static int loop_sysfs_init(struct loop_device *lo)
		{
		return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
		&loop_attribute_group);
		}

		static void loop_sysfs_exit(struct loop_device *lo)
		{
		sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
		&loop_attribute_group);
		}

		static int loop_set_fd(struct loop_device *lo, fmode_t mode,
		struct block_device *bdev, unsigned int arg)
		{
		@@ -836,6 +934,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,

		set_capacity(lo->lo_disk, size);
		bd_set_size(bdev, size << 9);
		loop_sysfs_init(lo);
		/* let user-space know about the new size */
		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);

		@@ -854,6 +953,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
		return 0;

		out_clr:
		loop_sysfs_exit(lo);
		lo->lo_thread = NULL;
		lo->lo_device = NULL;
		lo->lo_backing_file = NULL;
		@@ -950,6 +1050,7 @@ static int loop_clr_fd(struct loop_device lo, struct block_device bdev)
		set_capacity(lo->lo_disk, 0);
		if (bdev) {
		bd_set_size(bdev, 0);
		loop_sysfs_exit(lo);
		/* let user-space know about this change */
		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
		}

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