49 lines
2.1 KiB
Diff
49 lines
2.1 KiB
Diff
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Chengming Zhou <chengming.zhou@linux.dev>
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Date: Tue, 4 Jun 2024 14:47:45 +0800
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Subject: [PATCH] block: fix request.queuelist usage in flush
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Friedrich Weber reported a kernel crash problem and bisected to commit
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81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine").
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The root cause is that we use "list_move_tail(&rq->queuelist, pending)"
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in the PREFLUSH/POSTFLUSH sequences. But rq->queuelist.next == xxx since
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it's popped out from plug->cached_rq in __blk_mq_alloc_requests_batch().
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We don't initialize its queuelist just for this first request, although
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the queuelist of all later popped requests will be initialized.
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Fix it by changing to use "list_add_tail(&rq->queuelist, pending)" so
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rq->queuelist doesn't need to be initialized. It should be ok since rq
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can't be on any list when PREFLUSH or POSTFLUSH, has no move actually.
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Please note the commit 81ada09cc25e ("blk-flush: reuse rq queuelist in
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flush state machine") also has another requirement that no drivers would
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touch rq->queuelist after blk_mq_end_request() since we will reuse it to
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add rq to the post-flush pending list in POSTFLUSH. If this is not true,
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we will have to revert that commit IMHO.
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Reported-by: Friedrich Weber <f.weber@proxmox.com>
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Closes: https://lore.kernel.org/lkml/14b89dfb-505c-49f7-aebb-01c54451db40@proxmox.com/
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Fixes: 81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine")
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Cc: Christoph Hellwig <hch@lst.de>
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Cc: ming.lei@redhat.com
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Cc: bvanassche@acm.org
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Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
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---
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block/blk-flush.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/block/blk-flush.c b/block/blk-flush.c
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index 3f4d41952ef2..aa5e573dd010 100644
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--- a/block/blk-flush.c
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+++ b/block/blk-flush.c
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@@ -183,7 +183,7 @@ static void blk_flush_complete_seq(struct request *rq,
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/* queue for flush */
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if (list_empty(pending))
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fq->flush_pending_since = jiffies;
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- list_move_tail(&rq->queuelist, pending);
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+ list_add_tail(&rq->queuelist, pending);
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break;
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case REQ_FSEQ_DATA:
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