From 56056c2e7d58ee705755efbe780aefff987a1dc8 Mon Sep 17 00:00:00 2001 From: Zhengyuan Liu Date: Mon, 24 Oct 2016 16:15:59 +0800 Subject: [PATCH] md/raid5: write an empty meta-block when creating log super-block If superblock points to an invalid meta block, r5l_load_log will set create_super with true and create an new superblock, this runtime path would always happen if we do no writing I/O to this array since it was created. Writing an empty meta block could avoid this unnecessary action at the first time we created log superblock. Another reason is for the corretness of log recovery. Currently we have bellow code to guarantee log revocery to be correct. if (ctx.seq > log->last_cp_seq + 1) { int ret; ret = r5l_log_write_empty_meta_block(log, ctx.pos, ctx.seq + 10); if (ret) return ret; log->seq = ctx.seq + 11; log->log_start = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS); r5l_write_super(log, ctx.pos); } else { log->log_start = ctx.pos; log->seq = ctx.seq; } If we just created a array with a journal device, log->log_start and log->last_checkpoint should all be 0, then we write three meta block which are valid except mid one and supposed crash happened. The ctx.seq would equal to log->last_cp_seq + 1 and log->log_start would be set to position of mid invalid meta block after we did a recovery, this will lead to problems which could be avoided with this patch. Signed-off-by: Zhengyuan Liu Signed-off-by: Shaohua Li --- drivers/md/raid5-cache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 998ea0025dd0..981f85515191 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -1156,6 +1156,7 @@ static int r5l_load_log(struct r5l_log *log) if (create_super) { log->last_cp_seq = prandom_u32(); cp = 0; + r5l_log_write_empty_meta_block(log, cp, log->last_cp_seq); /* * Make sure super points to correct address. Log might have * data very soon. If super hasn't correct log tail address, -- GitLab