[1/2] bcache: export backing_dev_name via sysfs

Commit Message

Coly Li Dec. 18, 2018, 2:32 p.m. UTC

This patch export dc->backing_dev_name to sysfs file
/sys/block/bcache<?>/bcache/backing_dev_name, then people or user space
tools may know the backing device name of this bcache device.

Of cause it can be done by parsing sysfs links, but this method can be
much simpler to find the link between bcache device and backing device.

Signed-off-by: Coly Li <[e-mail]>
---
 drivers/md/bcache/sysfs.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Patch

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 26f035a0c5b9..8f7674d199fb 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -67,6 +67,7 @@  read_attribute(written);
 read_attribute(btree_written);
 read_attribute(metadata_written);
 read_attribute(active_journal_entries);
+read_attribute(backing_dev_name);
 
 sysfs_time_stats_attribute(btree_gc,	sec, ms);
 sysfs_time_stats_attribute(btree_split, sec, us);
@@ -240,6 +241,12 @@  SHOW(__bch_cached_dev)
 		return strlen(buf);
 	}
 
+	if (attr == &sysfs_backing_dev_name) {
+		snprintf(buf, BDEVNAME_SIZE + 1, "%s", dc->backing_dev_name);
+		strcat(buf, "\n");
+		return strlen(buf);
+	}
+
 #undef var
 	return 0;
 }
@@ -431,6 +438,7 @@  static struct attribute *bch_cached_dev_files[] = {
 	&sysfs_verify,
 	&sysfs_bypass_torture_test,
 #endif
+	&sysfs_backing_dev_name,
 	NULL
 };
 KTYPE(bch_cached_dev);