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SubjectRe: 4.13 on thinkpad x220: oops when writing to SD card
From
Date
On 07/09/17 10:18, Ulf Hansson wrote:
> + Linus
>
> On 6 September 2017 at 08:03, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> 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);
>>
>
> Even if this fixes the problem it seems like we are papering over the
> real issue, which earlier fixes also did during the release cycle for
> v4.13.

blk_init_allocated_queue() allocates 1 request for flush and 4 requests
for a memory pool. The memory pool requests only get used under memory
pressure. That is why the error doesn't come up straight away.

>
> Anyway I am happy to apply this as fix for 4.14, if Seraphime/Pavel
> can report it solved the problem. Could you send a proper patch with
> some changlog please?
>
> I would also appreciate if can add you a small comment in the code,
> why moving this line is needed.

From: Adrian Hunter <adrian.hunter@intel.com>
Date: Thu, 7 Sep 2017 10:40:35 +0300
Subject: [PATCH] mmc: block: Fix incorrectly initialized requests

mmc_init_request() depends on card->bouncesz so it must be calculated
before blk_init_allocated_queue() starts allocating requests.

Reported-by: Seraphime Kirkovski <kirkseraph@gmail.com>
Fixes: 304419d8a7e92 ("mmc: core: Allocate per-request data using the block layer core")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
drivers/mmc/core/queue.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index affa7370ba82..74c663b1c0a7 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -242,6 +242,12 @@ 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;

+ /*
+ * mmc_init_request() depends on card->bouncesz so it must be calculated
+ * before blk_init_allocated_queue() starts allocating requests.
+ */
+ card->bouncesz = mmc_queue_calc_bouncesz(host);
+
mq->card = card;
mq->queue = blk_alloc_queue(GFP_KERNEL);
if (!mq->queue)
@@ -265,7 +271,6 @@ 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);
--
1.9.1
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