On 07/20/2010 12:53 PM, Karel Zak wrote:
>
> My suggestion is to use /sys as alternative to useless
> LOOP_GET_STATUS ioctl, something like:
>
> /sys/block/<devname>/loop/backing_file
> /sys/block/<devname>/loop/offset
> /sys/block/<devname>/loop/sizelimit
> /sys/block/<devname>/loop/autoclear
Maybe naive, but quick implementation of this idea...
Milan
From: Milan Broz <mbroz@xxxxxxxxxx>
Subject: [PATCH] loop: add some basic read-only sysfs attributes
Create /sys/block/loopX/loop directory and provide these attributes:
- backing_device
- readonly
- autoclear
- offset
Signed-off-by: Milan Broz <mbroz@xxxxxxxxxx>
---
drivers/block/loop.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++-
include/linux/loop.h | 2 +
2 files changed, 113 insertions(+), 1 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 6120922..453c6d7 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -73,6 +73,7 @@
#include <linux/highmem.h>
#include <linux/kthread.h>
#include <linux/splice.h>
+#include <linux/sysfs.h>
#include <asm/uaccess.h>
@@ -1542,8 +1543,114 @@ out:
return NULL;
}
+/* loop sysfs attributes */
+
+struct loop_sysfs_attr {
+ struct attribute attr;
+ ssize_t (*show)(struct loop_device *, char *);
+ ssize_t (*store)(struct loop_device *, char *);
+};
+
+#define LOOP_ATTR_RO(_name) \
+struct loop_sysfs_attr loop_attr_##_name = \
+ __ATTR(_name, S_IRUGO, loop_attr_##_name##_show, NULL)
+
+static ssize_t loop_attr_show(struct kobject *kobj,
+ struct attribute *attr,
+ char *page)
+{
+ struct loop_device *lo;
+ struct loop_sysfs_attr *loop_attr;
+
+ lo = container_of(kobj, struct loop_device, lo_kobj);
+ loop_attr = container_of(attr, struct loop_sysfs_attr, attr);
+
+ if (!loop_attr->show)
+ return -EIO;
+
+ return loop_attr->show(lo, page);
+}
+
+static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
+{
+ ssize_t ret;
+ char *p;
+
+ if (lo->lo_state != Lo_bound)
+ return 0;
+
+ mutex_lock(&lo->lo_ctl_mutex);
+ p = d_path(&lo->lo_backing_file->f_path, buf, PAGE_SIZE - 1);
+ mutex_unlock(&lo->lo_ctl_mutex);
+
+ if (IS_ERR(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_readonly_show(struct loop_device *lo, char *buf)
+{
+ int read_only = (lo->lo_flags & LO_FLAGS_READ_ONLY);
+
+ return sprintf(buf, "%s\n", read_only ? "1" : "0");
+}
+
+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");
+}
+
+static LOOP_ATTR_RO(backing_file);
+static LOOP_ATTR_RO(offset);
+static LOOP_ATTR_RO(readonly);
+static LOOP_ATTR_RO(autoclear);
+
+static struct attribute *loop_attrs[] = {
+ &loop_attr_backing_file.attr,
+ &loop_attr_offset.attr,
+ &loop_attr_readonly.attr,
+ &loop_attr_autoclear.attr,
+ NULL,
+};
+
+static const struct sysfs_ops loop_sysfs_ops = {
+ .show = loop_attr_show,
+};
+
+static struct kobj_type loop_ktype = {
+ .sysfs_ops = &loop_sysfs_ops,
+ .default_attrs = loop_attrs,
+};
+
+static int loop_sysfs_init(struct loop_device *lo)
+{
+ return kobject_init_and_add(&lo->lo_kobj, &loop_ktype,
+ &disk_to_dev(lo->lo_disk)->kobj,
+ "%s", "loop");
+}
+
+static void loop_sysfs_exit(struct loop_device *lo)
+{
+ kobject_put(&lo->lo_kobj);
+}
+
static void loop_free(struct loop_device *lo)
{
+ loop_sysfs_exit(lo);
blk_cleanup_queue(lo->lo_queue);
put_disk(lo->lo_disk);
list_del(&lo->lo_list);
@@ -1562,6 +1669,7 @@ static struct loop_device *loop_init_one(int i)
lo = loop_alloc(i);
if (lo) {
add_disk(lo->lo_disk);
+ loop_sysfs_init(lo);
list_add_tail(&lo->lo_list, &loop_devices);
}
return lo;
@@ -1635,8 +1743,10 @@ static int __init loop_init(void)
/* point of no return */
- list_for_each_entry(lo, &loop_devices, lo_list)
+ list_for_each_entry(lo, &loop_devices, lo_list) {
add_disk(lo->lo_disk);
+ loop_sysfs_init(lo);
+ }
blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
THIS_MODULE, loop_probe, NULL, NULL);
diff --git a/include/linux/loop.h b/include/linux/loop.h
index 66c194e..0b26385 100644
--- a/include/linux/loop.h
+++ b/include/linux/loop.h
@@ -65,6 +65,8 @@ struct loop_device {
struct request_queue *lo_queue;
struct gendisk *lo_disk;
struct list_head lo_list;
+
+ struct kobject lo_kobj;
};
#endif /* __KERNEL__ */
--
1.7.1
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