Re: [PATCH] add label interface for cache device in sysfs

[Coly Li]

On 9/14/18 5:51 PM, Dongbo Cao wrote:
label interface will be called by bcache tools in user space.

Signed-off-by: Dongbo Cao <cdb...@163.com>

Hi Dongbo,


In your change I see you set superblock label to cache set. What is the 
use case for doing this ?

Thanks.


Coly Li


---
  drivers/md/bcache/sysfs.c | 19 +++++++++++++++++++
  1 file changed, 19 insertions(+)

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 225b15aa..e64c718f 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -950,6 +950,13 @@ SHOW(__bch_cache)
                return ret;
        }
  
+	if (attr == &sysfs_label) {
+               memcpy(buf, ca->sb.label, SB_LABEL_SIZE);
+               buf[SB_LABEL_SIZE + 1] = '\0';
+               strcat(buf, "\n");
+               return strlen(buf);
+       }
+
        return 0;
  }
  SHOW_LOCKED(bch_cache)
@@ -993,6 +1000,17 @@ STORE(__bch_cache)
                atomic_set(&ca->io_errors, 0);
        }
  
+	if (attr == &sysfs_label) {
+               if (size > SB_LABEL_SIZE)
+                       return -EINVAL;
+               memcpy(ca->sb.label, buf, size);
+               if (size < SB_LABEL_SIZE)
+                       ca->sb.label[size] = '\0';
+               if (size && ca->sb.label[size - 1] == '\n')
+                       ca->sb.label[size - 1] = '\0';
+               bcache_write_super(ca->set);
+       }
+
        return size;
  }
  STORE_LOCKED(bch_cache)
@@ -1009,6 +1027,7 @@ static struct attribute *bch_cache_files[] = {
        &sysfs_io_errors,
        &sysfs_clear_stats,
        &sysfs_cache_replacement_policy,
+       &sysfs_label,
        NULL
  };
  KTYPE(bch_cache);