If that's the problem, I think there is another problem about next_checkpoint initialization.
No initial operation was done to this field when we loaded/recovery the log , it got
assignment only when IO to raid disk was finished. So r5l_quiesce may use wrong
next_checkpoint to reclaim log space, that would confuse log recovery. Bellow patch
may help the expression.
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 1b1ab4a..998ea00 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1096,6 +1096,8 @@ static int r5l_recovery_log(struct r5l_log *log)
log->seq = ctx.seq + 11;
log->log_start = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
r5l_write_super(log, ctx.pos);
+ log->last_checkpoint = ctx.pos;
+ log->next_checkpoint = ctx.pos;
} else {
log->log_start = ctx.pos;
log->seq = ctx.seq;@@ -1168,6 +1170,7 @@ create:
if (log->max_free_space > RECLAIM_MAX_FREE_SPACE)
log->max_free_space = RECLAIM_MAX_FREE_SPACE;
log->last_checkpoint = cp;
+ log->next_checkpoint = cp;
__free_page(page);
Thanks,
--Zhengyuan
------------------ Original ------------------
From: "Shaohua Li"<shli@kernel.org>;
Date: Tue, Oct 18, 2016 08:28 AM
To: "Zhengyuan Liu"<redacted>;
Cc: "shli"<redacted>; "Song Liu"<redacted>; "linux-raid"<redacted>;
Subject: Re: Superblock of raid5 log can't be updated when array stoped
On Sat, Oct 15, 2016 at 10:19:36AM +0800, liuzhengyuan wrote:
Hi, Shaohua.
when we stop raid5 array with "mdadm -S" or reboot the system, md module will
call raid5_quiesce and r5l_quiesce to do some clean work. Some code of r5l_quiesce
was pasted bellow.
/* make sure r5l_write_super_and_discard_space exits */
mddev = log->rdev->mddev;
wake_up(&mddev->sb_wait);
r5l_wake_reclaim(log, -1L);
md_unregister_thread(&log->reclaim_thread);
r5l_do_reclaim(log);
+ md_update_sb(mddev, 1);
It will reclaim all used space of log and call r5l_write_super to reset rdev->journal_tail
to log->next_checkpoint . However, new rdev->journal_tail would not be written to
journal device for persistent because journal device may not support discard operation
or due to mddev_trylock fail (this trylock should always get failed since raid5_quiesce
was called with reconfig_mutex hold, isn't it?). As a result, it will take a long time to
recovery the log when the arrary was restarted. Should r5l_quiesce call md_update_sb
directly to guarantee superblock update?
Yep, that's problem here. Unfortunately we can't call md_update_sb here,
because we might not hold the mddev lock. I think we should call it at do_md_stop.
Thanks,
Shaohua