* [PATCH 2/2] raid5-cache: add journal hot add/remove support
2015-12-16 21:13 [PATCH 1/2] MD: change journal disk role to disk 0 Shaohua Li
@ 2015-12-16 21:13 ` Shaohua Li
2015-12-16 22:50 ` NeilBrown
0 siblings, 1 reply; 3+ messages in thread
From: Shaohua Li @ 2015-12-16 21:13 UTC (permalink / raw)
To: linux-raid; +Cc: Kernel-team, songliubraving, hch, neilb
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>
---
drivers/md/md.c | 42 ++++++++++++++++++++++++++++++------------
drivers/md/raid5-cache.c | 16 ++++++++++++----
drivers/md/raid5.c | 34 ++++++++++++++++++++++++++--------
3 files changed, 68 insertions(+), 24 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 874c843..7e0a7c6 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2052,8 +2052,9 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
return -EEXIST;
/* make sure rdev->sectors exceeds mddev->dev_sectors */
- if (rdev->sectors && (mddev->dev_sectors == 0 ||
- rdev->sectors < mddev->dev_sectors)) {
+ if (!test_bit(Journal, &rdev->flags) &&
+ rdev->sectors &&
+ (mddev->dev_sectors == 0 || rdev->sectors < mddev->dev_sectors)) {
if (mddev->pers) {
/* Cannot change size, so fail
* If mddev->level <= 0, then we don't care
@@ -2084,7 +2085,8 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
}
}
rcu_read_unlock();
- if (mddev->max_disks && rdev->desc_nr >= mddev->max_disks) {
+ if (!test_bit(Journal, &rdev->flags) &&
+ mddev->max_disks && rdev->desc_nr >= mddev->max_disks) {
printk(KERN_WARNING "md: %s: array is limited to %d devices\n",
mdname(mddev), mddev->max_disks);
return -EBUSY;
@@ -6031,8 +6033,23 @@ static int add_new_disk(struct mddev *mddev, mdu_disk_info_t *info)
else
clear_bit(WriteMostly, &rdev->flags);
- if (info->state & (1<<MD_DISK_JOURNAL))
+ if (info->state & (1<<MD_DISK_JOURNAL)) {
+ struct md_rdev *rdev2;
+ bool has_journal = false;
+
+ /* make sure no existing journal disk */
+ rdev_for_each(rdev2, mddev) {
+ if (test_bit(Journal, &rdev2->flags)) {
+ has_journal = true;
+ break;
+ }
+ }
+ if (has_journal) {
+ export_rdev(rdev);
+ return -EBUSY;
+ }
set_bit(Journal, &rdev->flags);
+ }
/*
* check whether the device shows up in other nodes
*/
@@ -8162,19 +8179,20 @@ static int remove_and_add_spares(struct mddev *mddev,
continue;
if (test_bit(Faulty, &rdev->flags))
continue;
- if (test_bit(Journal, &rdev->flags))
- continue;
- if (mddev->ro &&
- ! (rdev->saved_raid_disk >= 0 &&
- !test_bit(Bitmap_sync, &rdev->flags)))
- continue;
+ if (!test_bit(Journal, &rdev->flags)) {
+ if (mddev->ro &&
+ ! (rdev->saved_raid_disk >= 0 &&
+ !test_bit(Bitmap_sync, &rdev->flags)))
+ continue;
- rdev->recovery_offset = 0;
+ rdev->recovery_offset = 0;
+ }
if (mddev->pers->
hot_add_disk(mddev, rdev) == 0) {
if (sysfs_link_rdev(mddev, rdev))
/* failure here is OK */;
- spares++;
+ if (!test_bit(Journal, &rdev->flags))
+ spares++;
md_new_event(mddev);
set_bit(MD_CHANGE_DEVS, &mddev->flags);
}
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index b887e04..9cd32c2 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -806,10 +806,18 @@ void r5l_quiesce(struct r5l_log *log, int state)
bool r5l_log_disk_error(struct r5conf *conf)
{
+ struct r5l_log *log;
+ bool ret;
/* don't allow write if journal disk is missing */
- if (!conf->log)
- return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
- return test_bit(Faulty, &conf->log->rdev->flags);
+ rcu_read_lock();
+ log = rcu_dereference(conf->log);
+
+ if (!log)
+ ret = test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
+ else
+ ret = test_bit(Faulty, &log->rdev->flags);
+ rcu_read_unlock();
+ return ret;
}
struct r5l_recovery_ctx {
@@ -1172,7 +1180,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
if (r5l_load_log(log))
goto error;
- conf->log = log;
+ rcu_assign_pointer(conf->log, log);
return 0;
error:
md_unregister_thread(&log->reclaim_thread);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 704ef7f..783376b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7141,14 +7141,19 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
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;
@@ -7212,8 +7217,21 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
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;
--
2.4.6
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