raid5-cache: add journal hot add/remove support
Add support for journal disk hot add/remove. Mostly trival checks in md
part. The raid5 part is a little tricky. For hot-remove, we can't wait
pending write as it's called from raid5d. The wait will cause deadlock.
We simplily fail the hot-remove. A hot-remove retry can success
eventually since if journal disk is faulty all pending write will be
failed and finish. For hot-add, since an array supporting journal but
without journal disk will be marked read-only, we are safe to hot add
journal without stopping IO (should be read IO, while journal only
handles write IO).
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 2236250..a086014 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7139,14 +7139,19 @@
struct disk_info *p = conf->disks + number;
print_raid5_conf(conf);
- if (test_bit(Journal, &rdev->flags)) {
+ if (test_bit(Journal, &rdev->flags) && conf->log) {
+ struct r5l_log *log;
/*
- * journal disk is not removable, but we need give a chance to
- * update superblock of other disks. Otherwise journal disk
- * will be considered as 'fresh'
+ * we can't wait pending write here, as this is called in
+ * raid5d, wait will deadlock.
*/
- set_bit(MD_CHANGE_DEVS, &mddev->flags);
- return -EINVAL;
+ if (atomic_read(&mddev->writes_pending))
+ return -EBUSY;
+ log = conf->log;
+ conf->log = NULL;
+ synchronize_rcu();
+ r5l_exit_log(log);
+ return 0;
}
if (rdev == p->rdev)
rdevp = &p->rdev;
@@ -7210,8 +7215,21 @@
int first = 0;
int last = conf->raid_disks - 1;
- if (test_bit(Journal, &rdev->flags))
- return -EINVAL;
+ if (test_bit(Journal, &rdev->flags)) {
+ char b[BDEVNAME_SIZE];
+ if (conf->log)
+ return -EBUSY;
+
+ rdev->raid_disk = 0;
+ /*
+ * The array is in readonly mode if journal is missing, so no
+ * write requests running. We should be safe
+ */
+ r5l_init_log(conf, rdev);
+ printk(KERN_INFO"md/raid:%s: using device %s as journal\n",
+ mdname(mddev), bdevname(rdev->bdev, b));
+ return 0;
+ }
if (mddev->recovery_disabled == conf->recovery_disabled)
return -EBUSY;