linux-kernel - Re: [GIT PULL] JFFS2, UBI and UBIFS updates for v6.3-rc1

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Date:   Fri, 10 Mar 2023 18:32:17 +0100 (CET)
From:   Richard Weinberger <richard@....at>
To:     torvalds <torvalds@...ux-foundation.org>
Cc:     Daniel Palmer <daniel@...f.com>, hch <hch@....de>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] JFFS2, UBI and UBIFS updates for v6.3-rc1

----- Ursprüngliche Mail -----
>> This seems to be causing one of my machines to lock up during boot.
>> It's using a squashfs root that is on a ubiblock that is located on an SPI NAND.
> 
> Hmm. That commit 91cc8fbcc8c7 ("ubi: block: set BLK_MQ_F_BLOCKING") is odd.
> 
> Christoph - you removed the
> 
>        blk_mq_start_request(req);
>        ...
>        blk_mq_end_request(req, errno_to_blk_status(ret));
> 
> from the workqueue function, but while you added the
> blk_mq_start_request() into ubiblock_read(), the 'end_request()' is
> missing.
> 
> So I suspect the IO has completed, but the change means that nobody
> was informed about said completion, so now trying to mount an ext4
> filesystem on it hangs on the read.
> 
> But I don't actually know this code, that was just from looking at the
> commit that breaks.
> 
> Christoph? Daniel used your infradead address, I don't know if it all
> goes into the same pile, but let's use your regular one. And I can't
> see Daniel's message on lore.kernel.org at all, for whatever reason,
> 

Indeed, I'm able to reproduce the problem and adding blk_mq_end_request()
back fixes it.

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 1de87062c67b..3711d7f74600 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -221,7 +221,10 @@ static blk_status_t ubiblock_read(struct request *req)
 
 	rq_for_each_segment(bvec, req, iter)
 		flush_dcache_page(bvec.bv_page);
-	return errno_to_blk_status(ret);
+
+	blk_mq_end_request(req, errno_to_blk_status(ret));
+
+	return BLK_STS_OK;
 }
 
 static int ubiblock_open(struct block_device *bdev, fmode_t mode)

Thanks,
//richard