md: support updating bitmap parameters via sysfs.

A new attribute directory 'bitmap' in 'md' is created which
contains files for configuring the bitmap.
'location' identifies where the bitmap is, either 'none',
or 'file' or 'sector offset from metadata'.
Writing 'location' can create or remove a bitmap.
Adding a 'file' bitmap this way is not yet supported.
'chunksize' and 'time_base' must be set before 'location'
can be set.

'chunksize' can be set before creating a bitmap, but is
currently always over-ridden by the bitmap superblock.

'time_base' and 'backlog' can be updated at any time.


Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Andre Noll <maan@systemlinux.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 93287f88f1f4..859edbf8c9b0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4018,6 +4018,7 @@ static void mddev_delayed_delete(struct work_struct *ws)
                 mddev->sysfs_action = NULL;
                 mddev->private = NULL;
         }
+        sysfs_remove_group(&mddev->kobj, &md_bitmap_group);
         kobject_del(&mddev->kobj);
         kobject_put(&mddev->kobj);
 }
@@ -4109,6 +4110,8 @@ static int md_alloc(dev_t dev, char *name)
                        disk->disk_name);
                 error = 0;
         }
+        if (sysfs_create_group(&mddev->kobj, &md_bitmap_group))
+                printk(KERN_DEBUG "pointless warning\n");
  abort:
         mutex_unlock(&disks_mutex);
         if (!error) {
@@ -4434,7 +4437,7 @@ static int deny_bitmap_write_access(struct file * file)
         return 0;
 }
 
-static void restore_bitmap_write_access(struct file *file)
+void restore_bitmap_write_access(struct file *file)
 {
         struct inode *inode = file->f_mapping->host;