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SubjectRe: 4.13 on thinkpad x220: oops when writing to SD card
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On 06/09/17 05:44, Shawn Lin wrote:
> + Seraphime
>
> On 2017/9/6 3:47, Pavel Machek wrote:
>> Hi!
>>
>> I tried to write to the MMC card; process hung and I got this in the
>> dmesg.
>
>
> A similar report for 4.13 cycle was here:
>
> https://lkml.org/lkml/2017/8/10/824
>
> Seems 4.13-rc4 was already broken for that but unfortuantely I didn't
> reproduce that. So maybe Seraphime can do git-bisect as he said "I get
> it everytime" for which I assume it could be easy for him to find out
> the problematic commit?
>

One obvious weakness in the new mmc_init_request() is the possibility
that it might be called before card->bouncesz is set up. That could
result in bouncing being done but mq_rq->bounce_sg is null.
This might help:


diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index affa7370ba82..ad3e53e63abb 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -242,6 +242,8 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
limit = (u64)dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;

+ card->bouncesz = mmc_queue_calc_bouncesz(host);
+
mq->card = card;
mq->queue = blk_alloc_queue(GFP_KERNEL);
if (!mq->queue)
@@ -265,7 +267,6 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
if (mmc_can_erase(card))
mmc_queue_setup_discard(mq->queue, card);

- card->bouncesz = mmc_queue_calc_bouncesz(host);
if (card->bouncesz) {
blk_queue_max_hw_sectors(mq->queue, card->bouncesz / 512);
blk_queue_max_segments(mq->queue, card->bouncesz / 512);

Another unrelated issue with mmc_init_request() is that mmc_exit_request()
is not called if mmc_init_request() fails, which means mmc_init_request()
must free anything it allocates when it fails.

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