diff mbox series

mmc: core: don't set limits.discard_granularity as 0

Message ID 20200930160854.65710-1-colyli@suse.de
State New
Headers show
Series mmc: core: don't set limits.discard_granularity as 0 | expand

Commit Message

Coly Li Sept. 30, 2020, 4:08 p.m. UTC
In mmc_queue_setup_discard() the mmc driver queue's discard_granularity
might be set as 0 (when card->pref_erase > max_discard) while the mmc
device still declares to support discard operation. This is buggy and
triggered the following kernel warning message,

WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294
CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1
Hardware name: Google Kevin (DT)
pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
pc : __blkdev_issue_discard+0x200/0x294
lr : __blkdev_issue_discard+0x54/0x294
sp : ffff800011dd3b10
x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:
__blkdev_issue_discard+0x200/0x294
__submit_discard_cmd+0x128/0x374
__issue_discard_cmd_orderly+0x188/0x244
__issue_discard_cmd+0x2e8/0x33c
issue_discard_thread+0xe8/0x2f0
kthread+0x11c/0x120
ret_from_fork+0x10/0x1c
---[ end trace e4c8023d33dfe77a ]---

This patch fixes the issue by setting discard_granularity as SECTOR_SIZE
instead of 0 when (card->pref_erase > max_discard) is true. Now no more
complain from __blkdev_issue_discard() for the improper value of discard
granularity.

Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")
Reported-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/mmc/core/queue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Adrian Hunter Sept. 30, 2020, 5:23 p.m. UTC | #1
On 30/09/20 7:08 pm, Coly Li wrote:
> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity

> might be set as 0 (when card->pref_erase > max_discard) while the mmc

> device still declares to support discard operation. This is buggy and

> triggered the following kernel warning message,

> 

> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294

> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1

> Hardware name: Google Kevin (DT)

> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)

> pc : __blkdev_issue_discard+0x200/0x294

> lr : __blkdev_issue_discard+0x54/0x294

> sp : ffff800011dd3b10

> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:

> __blkdev_issue_discard+0x200/0x294

> __submit_discard_cmd+0x128/0x374

> __issue_discard_cmd_orderly+0x188/0x244

> __issue_discard_cmd+0x2e8/0x33c

> issue_discard_thread+0xe8/0x2f0

> kthread+0x11c/0x120

> ret_from_fork+0x10/0x1c

> ---[ end trace e4c8023d33dfe77a ]---

> 

> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE

> instead of 0 when (card->pref_erase > max_discard) is true. Now no more

> complain from __blkdev_issue_discard() for the improper value of discard

> granularity.

> 

> Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")


That "Fixes" tag is a bit misleading.  For some time, the block layer had
no problem with discard_granularity of zero, and blk_bio_discard_split()
still doesn't (see below).

static struct bio *blk_bio_discard_split(struct request_queue *q,
					 struct bio *bio,
					 struct bio_set *bs,
					 unsigned *nsegs)
{
	unsigned int max_discard_sectors, granularity;
	int alignment;
	sector_t tmp;
	unsigned split_sectors;

	*nsegs = 1;

	/* Zero-sector (unknown) and one-sector granularities are the same.  */
	granularity = max(q->limits.discard_granularity >> 9, 1U);


> Reported-by: Vicente Bergas <vicencb@gmail.com>

> Signed-off-by: Coly Li <colyli@suse.de>

> Cc: Adrian Hunter <adrian.hunter@intel.com>

> Cc: Ulf Hansson <ulf.hansson@linaro.org>

> ---

>  drivers/mmc/core/queue.c | 2 +-

>  1 file changed, 1 insertion(+), 1 deletion(-)

> 

> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c

> index 6c022ef0f84d..350d0cc4ee62 100644

> --- a/drivers/mmc/core/queue.c

> +++ b/drivers/mmc/core/queue.c

> @@ -190,7 +190,7 @@ static void mmc_queue_setup_discard(struct request_queue *q,

>  	q->limits.discard_granularity = card->pref_erase << 9;

>  	/* granularity must not be greater than max. discard */

>  	if (card->pref_erase > max_discard)

> -		q->limits.discard_granularity = 0;

> +		q->limits.discard_granularity = SECTOR_SIZE;

>  	if (mmc_can_secure_erase_trim(card))

>  		blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);

>  }

>
Coly Li Oct. 1, 2020, 4:36 a.m. UTC | #2
On 2020/10/1 01:23, Adrian Hunter wrote:
> On 30/09/20 7:08 pm, Coly Li wrote:
>> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity
>> might be set as 0 (when card->pref_erase > max_discard) while the mmc
>> device still declares to support discard operation. This is buggy and
>> triggered the following kernel warning message,
>>
>> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294
>> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1
>> Hardware name: Google Kevin (DT)
>> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
>> pc : __blkdev_issue_discard+0x200/0x294
>> lr : __blkdev_issue_discard+0x54/0x294
>> sp : ffff800011dd3b10
>> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:
>> __blkdev_issue_discard+0x200/0x294
>> __submit_discard_cmd+0x128/0x374
>> __issue_discard_cmd_orderly+0x188/0x244
>> __issue_discard_cmd+0x2e8/0x33c
>> issue_discard_thread+0xe8/0x2f0
>> kthread+0x11c/0x120
>> ret_from_fork+0x10/0x1c
>> ---[ end trace e4c8023d33dfe77a ]---
>>
>> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE
>> instead of 0 when (card->pref_erase > max_discard) is true. Now no more
>> complain from __blkdev_issue_discard() for the improper value of discard
>> granularity.
>>
>> Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")
> 
> That "Fixes" tag is a bit misleading.  For some time, the block layer had
> no problem with discard_granularity of zero, and blk_bio_discard_split()
> still doesn't (see below).
> 
> static struct bio *blk_bio_discard_split(struct request_queue *q,
> 					 struct bio *bio,
> 					 struct bio_set *bs,
> 					 unsigned *nsegs)
> {
> 	unsigned int max_discard_sectors, granularity;
> 	int alignment;
> 	sector_t tmp;
> 	unsigned split_sectors;
> 
> 	*nsegs = 1;
> 
> 	/* Zero-sector (unknown) and one-sector granularities are the same.  */
> 	granularity = max(q->limits.discard_granularity >> 9, 1U);
>
Adrian Hunter Oct. 1, 2020, 6:14 a.m. UTC | #3
On 1/10/20 7:36 am, Coly Li wrote:
> On 2020/10/1 01:23, Adrian Hunter wrote:
>> On 30/09/20 7:08 pm, Coly Li wrote:
>>> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity
>>> might be set as 0 (when card->pref_erase > max_discard) while the mmc
>>> device still declares to support discard operation. This is buggy and
>>> triggered the following kernel warning message,
>>>
>>> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294
>>> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1
>>> Hardware name: Google Kevin (DT)
>>> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
>>> pc : __blkdev_issue_discard+0x200/0x294
>>> lr : __blkdev_issue_discard+0x54/0x294
>>> sp : ffff800011dd3b10
>>> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:
>>> __blkdev_issue_discard+0x200/0x294
>>> __submit_discard_cmd+0x128/0x374
>>> __issue_discard_cmd_orderly+0x188/0x244
>>> __issue_discard_cmd+0x2e8/0x33c
>>> issue_discard_thread+0xe8/0x2f0
>>> kthread+0x11c/0x120
>>> ret_from_fork+0x10/0x1c
>>> ---[ end trace e4c8023d33dfe77a ]---
>>>
>>> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE
>>> instead of 0 when (card->pref_erase > max_discard) is true. Now no more
>>> complain from __blkdev_issue_discard() for the improper value of discard
>>> granularity.
>>>
>>> Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")
>>
>> That "Fixes" tag is a bit misleading.  For some time, the block layer had
>> no problem with discard_granularity of zero, and blk_bio_discard_split()
>> still doesn't (see below).
>>
>> static struct bio *blk_bio_discard_split(struct request_queue *q,
>> 					 struct bio *bio,
>> 					 struct bio_set *bs,
>> 					 unsigned *nsegs)
>> {
>> 	unsigned int max_discard_sectors, granularity;
>> 	int alignment;
>> 	sector_t tmp;
>> 	unsigned split_sectors;
>>
>> 	*nsegs = 1;
>>
>> 	/* Zero-sector (unknown) and one-sector granularities are the same.  */
>> 	granularity = max(q->limits.discard_granularity >> 9, 1U);
>>
> 
>>From Documentation/block/queue-sysfs.rst, the discard_granularity is
> described as,
> 
> discard_granularity (RO)
> ------------------------
> This shows the size of internal allocation of the device in bytes, if
> reported by the device. A value of '0' means device does not support
> the discard functionality.
> 
> 
> And from Documentation/ABI/testing/sysfs-block, the discard_granularity
> is described as,
> 
> What:           /sys/block/<disk>/queue/discard_granularity
> Date:           May 2011
> Contact:        Martin K. Petersen <martin.petersen@oracle.com>
> Description:
>                 Devices that support discard functionality may
>                 internally allocate space using units that are bigger
>                 than the logical block size. The discard_granularity
>                 parameter indicates the size of the internal allocation
>                 unit in bytes if reported by the device. Otherwise the
>                 discard_granularity will be set to match the device's
>                 physical block size. A discard_granularity of 0 means
>                 that the device does not support discard functionality.
> 
> 
> Therefore I took it as a bug when a driver sets its queue
> discard_granularity as 0 but still announces to support discard operation.
> 
> But if you don't like the Fixes: tag, it is OK for me to remove it in
> next version.

Not at all.  I just wrote "a bit misleading" because people might also want
to know from what patch things stopped working.

> 
> (CC Martin because he is the origin of the above information)
> 
> Thanks.
> 
> Coly Li
>
Coly Li Oct. 1, 2020, 6:29 a.m. UTC | #4
On 2020/10/1 14:14, Adrian Hunter wrote:
> On 1/10/20 7:36 am, Coly Li wrote:

>> On 2020/10/1 01:23, Adrian Hunter wrote:

>>> On 30/09/20 7:08 pm, Coly Li wrote:

>>>> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity

>>>> might be set as 0 (when card->pref_erase > max_discard) while the mmc

>>>> device still declares to support discard operation. This is buggy and

>>>> triggered the following kernel warning message,

>>>>

>>>> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294

>>>> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1

>>>> Hardware name: Google Kevin (DT)

>>>> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)

>>>> pc : __blkdev_issue_discard+0x200/0x294

>>>> lr : __blkdev_issue_discard+0x54/0x294

>>>> sp : ffff800011dd3b10

>>>> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:

>>>> __blkdev_issue_discard+0x200/0x294

>>>> __submit_discard_cmd+0x128/0x374

>>>> __issue_discard_cmd_orderly+0x188/0x244

>>>> __issue_discard_cmd+0x2e8/0x33c

>>>> issue_discard_thread+0xe8/0x2f0

>>>> kthread+0x11c/0x120

>>>> ret_from_fork+0x10/0x1c

>>>> ---[ end trace e4c8023d33dfe77a ]---

>>>>

>>>> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE

>>>> instead of 0 when (card->pref_erase > max_discard) is true. Now no more

>>>> complain from __blkdev_issue_discard() for the improper value of discard

>>>> granularity.

>>>>

>>>> Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")

>>>

>>> That "Fixes" tag is a bit misleading.  For some time, the block layer had

>>> no problem with discard_granularity of zero, and blk_bio_discard_split()

>>> still doesn't (see below).

>>>

>>> static struct bio *blk_bio_discard_split(struct request_queue *q,

>>> 					 struct bio *bio,

>>> 					 struct bio_set *bs,

>>> 					 unsigned *nsegs)

>>> {

>>> 	unsigned int max_discard_sectors, granularity;

>>> 	int alignment;

>>> 	sector_t tmp;

>>> 	unsigned split_sectors;

>>>

>>> 	*nsegs = 1;

>>>

>>> 	/* Zero-sector (unknown) and one-sector granularities are the same.  */

>>> 	granularity = max(q->limits.discard_granularity >> 9, 1U);

>>>

>>

>> >From Documentation/block/queue-sysfs.rst, the discard_granularity is

>> described as,

>>

>> discard_granularity (RO)

>> ------------------------

>> This shows the size of internal allocation of the device in bytes, if

>> reported by the device. A value of '0' means device does not support

>> the discard functionality.

>>

>>

>> And from Documentation/ABI/testing/sysfs-block, the discard_granularity

>> is described as,

>>

>> What:           /sys/block/<disk>/queue/discard_granularity

>> Date:           May 2011

>> Contact:        Martin K. Petersen <martin.petersen@oracle.com>

>> Description:

>>                 Devices that support discard functionality may

>>                 internally allocate space using units that are bigger

>>                 than the logical block size. The discard_granularity

>>                 parameter indicates the size of the internal allocation

>>                 unit in bytes if reported by the device. Otherwise the

>>                 discard_granularity will be set to match the device's

>>                 physical block size. A discard_granularity of 0 means

>>                 that the device does not support discard functionality.

>>

>>

>> Therefore I took it as a bug when a driver sets its queue

>> discard_granularity as 0 but still announces to support discard operation.

>>

>> But if you don't like the Fixes: tag, it is OK for me to remove it in

>> next version.

> 

> Not at all.  I just wrote "a bit misleading" because people might also want

> to know from what patch things stopped working.


Oh maybe I understand you. Yes, although this fixed patch was bug, but
the warning was triggered since the new discard alignment changes got
merged.

Hmm, maybe I should add the Fixes tag to commit b35fd7422c2f ("block:
check queue's limits.discard_granularity in __blkdev_issue_discard()").

How do you think of this commit id ?

Thanks.

Coly Li
Adrian Hunter Oct. 1, 2020, 7:02 a.m. UTC | #5
On 1/10/20 9:29 am, Coly Li wrote:
> On 2020/10/1 14:14, Adrian Hunter wrote:

>> On 1/10/20 7:36 am, Coly Li wrote:

>>> On 2020/10/1 01:23, Adrian Hunter wrote:

>>>> On 30/09/20 7:08 pm, Coly Li wrote:

>>>>> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity

>>>>> might be set as 0 (when card->pref_erase > max_discard) while the mmc

>>>>> device still declares to support discard operation. This is buggy and

>>>>> triggered the following kernel warning message,

>>>>>

>>>>> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294

>>>>> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1

>>>>> Hardware name: Google Kevin (DT)

>>>>> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)

>>>>> pc : __blkdev_issue_discard+0x200/0x294

>>>>> lr : __blkdev_issue_discard+0x54/0x294

>>>>> sp : ffff800011dd3b10

>>>>> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:

>>>>> __blkdev_issue_discard+0x200/0x294

>>>>> __submit_discard_cmd+0x128/0x374

>>>>> __issue_discard_cmd_orderly+0x188/0x244

>>>>> __issue_discard_cmd+0x2e8/0x33c

>>>>> issue_discard_thread+0xe8/0x2f0

>>>>> kthread+0x11c/0x120

>>>>> ret_from_fork+0x10/0x1c

>>>>> ---[ end trace e4c8023d33dfe77a ]---

>>>>>

>>>>> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE

>>>>> instead of 0 when (card->pref_erase > max_discard) is true. Now no more

>>>>> complain from __blkdev_issue_discard() for the improper value of discard

>>>>> granularity.

>>>>>

>>>>> Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")

>>>>

>>>> That "Fixes" tag is a bit misleading.  For some time, the block layer had

>>>> no problem with discard_granularity of zero, and blk_bio_discard_split()

>>>> still doesn't (see below).

>>>>

>>>> static struct bio *blk_bio_discard_split(struct request_queue *q,

>>>> 					 struct bio *bio,

>>>> 					 struct bio_set *bs,

>>>> 					 unsigned *nsegs)

>>>> {

>>>> 	unsigned int max_discard_sectors, granularity;

>>>> 	int alignment;

>>>> 	sector_t tmp;

>>>> 	unsigned split_sectors;

>>>>

>>>> 	*nsegs = 1;

>>>>

>>>> 	/* Zero-sector (unknown) and one-sector granularities are the same.  */

>>>> 	granularity = max(q->limits.discard_granularity >> 9, 1U);

>>>>

>>>

>>> >From Documentation/block/queue-sysfs.rst, the discard_granularity is

>>> described as,

>>>

>>> discard_granularity (RO)

>>> ------------------------

>>> This shows the size of internal allocation of the device in bytes, if

>>> reported by the device. A value of '0' means device does not support

>>> the discard functionality.

>>>

>>>

>>> And from Documentation/ABI/testing/sysfs-block, the discard_granularity

>>> is described as,

>>>

>>> What:           /sys/block/<disk>/queue/discard_granularity

>>> Date:           May 2011

>>> Contact:        Martin K. Petersen <martin.petersen@oracle.com>

>>> Description:

>>>                 Devices that support discard functionality may

>>>                 internally allocate space using units that are bigger

>>>                 than the logical block size. The discard_granularity

>>>                 parameter indicates the size of the internal allocation

>>>                 unit in bytes if reported by the device. Otherwise the

>>>                 discard_granularity will be set to match the device's

>>>                 physical block size. A discard_granularity of 0 means

>>>                 that the device does not support discard functionality.

>>>

>>>

>>> Therefore I took it as a bug when a driver sets its queue

>>> discard_granularity as 0 but still announces to support discard operation.

>>>

>>> But if you don't like the Fixes: tag, it is OK for me to remove it in

>>> next version.

>>

>> Not at all.  I just wrote "a bit misleading" because people might also want

>> to know from what patch things stopped working.

> 

> Oh maybe I understand you. Yes, although this fixed patch was bug, but

> the warning was triggered since the new discard alignment changes got

> merged.

> 

> Hmm, maybe I should add the Fixes tag to commit b35fd7422c2f ("block:

> check queue's limits.discard_granularity in __blkdev_issue_discard()").

> 

> How do you think of this commit id ?


Yes that could be mentioned in the commit message or Fixes or both.
With that:

Acked-by: Adrian Hunter <adrian.hunter@intel.com>
diff mbox series

Patch

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 6c022ef0f84d..350d0cc4ee62 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -190,7 +190,7 @@  static void mmc_queue_setup_discard(struct request_queue *q,
 	q->limits.discard_granularity = card->pref_erase << 9;
 	/* granularity must not be greater than max. discard */
 	if (card->pref_erase > max_discard)
-		q->limits.discard_granularity = 0;
+		q->limits.discard_granularity = SECTOR_SIZE;
 	if (mmc_can_secure_erase_trim(card))
 		blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
 }