Currently, we increase journal entry seq by 10 after recovery.
However, this is not sufficient in the following case.
After crash the journal looks like
| seq+0 | +1 | +2 | +3 | +4 | +5 | +6 | +7 | ... | +11 | +12 |
If +1 is not valid, we dropped all entries from +1 to +12; and
write seq+10:
| seq+0 | +10 | +2 | +3 | +4 | +5 | +6 | +7 | ... | +11 | +12 |
However, if we write a big journal entry with seq+11, it will
connect with some stale journal entry:
| seq+0 | +10 | +11 | +12 |
To reduce the risk of this issue, we increase seq by 1000 instead.
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
drivers/md/raid5-cache.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 875f963..5301081 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -2003,8 +2003,8 @@ static int r5c_recovery_flush_log(struct r5l_log *log,
* happens again, new recovery will start from meta 1. Since meta 2n is
* valid now, recovery will think meta 3 is valid, which is wrong.
* The solution is we create a new meta in meta2 with its seq == meta
- * 1's seq + 10 and let superblock points to meta2. The same recovery will
- * not think meta 3 is a valid meta, because its seq doesn't match
+ * 1's seq + 1000 and let superblock points to meta2. The same recovery
+ * will not think meta 3 is a valid meta, because its seq doesn't match
*/
/*
@@ -2034,7 +2034,7 @@ static int r5c_recovery_flush_log(struct r5l_log *log,
* ---------------------------------------------
* ^ ^
* |- log->last_checkpoint |- ctx->pos+1
- * |- log->last_cp_seq |- ctx->seq+11
+ * |- log->last_cp_seq |- ctx->seq+1001
*
* However, it is not safe to start the state machine yet, because data only
* parities are not yet secured in RAID. To save these data only parities, we
@@ -2045,7 +2045,7 @@ static int r5c_recovery_flush_log(struct r5l_log *log,
* -----------------------------------------------------------------
* ^ ^
* |- log->last_checkpoint |- ctx->pos+n
- * |- log->last_cp_seq |- ctx->seq+10+n
+ * |- log->last_cp_seq |- ctx->seq+1000+n
*
* If failure happens again during this process, the recovery can safe start
* again from log->last_checkpoint.
@@ -2057,7 +2057,7 @@ static int r5c_recovery_flush_log(struct r5l_log *log,
* -----------------------------------------------------------------
* ^ ^
* |- log->last_checkpoint |- ctx->pos+n
- * |- log->last_cp_seq |- ctx->seq+10+n
+ * |- log->last_cp_seq |- ctx->seq+1000+n
*
* Then we can safely start the state machine. If failure happens from this
* point on, the recovery will start from new log->last_checkpoint.
@@ -2157,8 +2157,8 @@ static int r5l_recovery_log(struct r5l_log *log)
if (ret)
return ret;
- pos = ctx.pos;
- ctx.seq += 10;
+ pos = ctx.pos;
+ ctx.seq += 1000;
if (ctx.data_only_stripes == 0) {
log->next_checkpoint = ctx.pos;
--
2.9.3
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