Before switching back to the right partition in mmc_blk_reset
there used to be a check if hw_reset was even supported.
This return value was removed, so there is no reason to check.
Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in mmc_hw|sw_reset()")
Cc: [email protected]
Signed-off-by: Christian Loehle <[email protected]>
---
-v2: Do not attempt to switch partitions if reset failed
drivers/mmc/core/block.c | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)
diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index ce89611a136e..8db72cba2bbe 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
int type)
{
int err;
+ struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+ int part_err;
if (md->reset_done & type)
return -EEXIST;
md->reset_done |= type;
err = mmc_hw_reset(host->card);
+ if (err)
+ return err;
/* Ensure we switch back to the correct partition */
- if (err) {
- struct mmc_blk_data *main_md =
- dev_get_drvdata(&host->card->dev);
- int part_err;
-
- main_md->part_curr = main_md->part_type;
- part_err = mmc_blk_part_switch(host->card, md->part_type);
- if (part_err) {
- /*
- * We have failed to get back into the correct
- * partition, so we need to abort the whole request.
- */
- return -ENODEV;
- }
+ main_md->part_curr = main_md->part_type;
+ part_err = mmc_blk_part_switch(host->card, md->part_type);
+ if (part_err) {
+ /*
+ * We have failed to get back into the correct
+ * partition, so we need to abort the whole request.
+ */
+ return -ENODEV;
}
- return err;
+ return 0;
}
static inline void mmc_blk_reset_success(struct mmc_blk_data *md, int type)
--
2.37.3
Hyperstone GmbH | Reichenaustr. 39a | 78467 Konstanz
Managing Director: Dr. Jan Peter Berns.
Commercial register of local courts: Freiburg HRB381782
On 7/10/22 18:42, Christian Löhle wrote:
> Before switching back to the right partition in mmc_blk_reset
> there used to be a check if hw_reset was even supported.
> This return value was removed, so there is no reason to check.
>
> Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in mmc_hw|sw_reset()")
> Cc: [email protected]
>
> Signed-off-by: Christian Loehle <[email protected]>
> ---
> -v2: Do not attempt to switch partitions if reset failed
>
> drivers/mmc/core/block.c | 28 +++++++++++++---------------
> 1 file changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index ce89611a136e..8db72cba2bbe 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
> int type)
> {
> int err;
> + struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
> + int part_err;
>
> if (md->reset_done & type)
> return -EEXIST;
>
> md->reset_done |= type;
> err = mmc_hw_reset(host->card);
> + if (err)
> + return err;
This could be a potential source of data corruption.
There is no guarantee that a subsequent I/O will fail just because
the reset failed. Reading / writing the wrong partition would be
disastrous, so we should always try to get back to the correct
partition.
I haven't looked at the possibility of just flagging the partition
as invalid - need to be sure any subsequent I/O attempts still go
through a path that switches the partition.
> /* Ensure we switch back to the correct partition */
> - if (err) {
> - struct mmc_blk_data *main_md =
> - dev_get_drvdata(&host->card->dev);
> - int part_err;
> -
> - main_md->part_curr = main_md->part_type;
> - part_err = mmc_blk_part_switch(host->card, md->part_type);
> - if (part_err) {
> - /*
> - * We have failed to get back into the correct
> - * partition, so we need to abort the whole request.
> - */
> - return -ENODEV;
> - }
> + main_md->part_curr = main_md->part_type;
> + part_err = mmc_blk_part_switch(host->card, md->part_type);
> + if (part_err) {
> + /*
> + * We have failed to get back into the correct
> + * partition, so we need to abort the whole request.
> + */
> + return -ENODEV;
> }
> - return err;
> + return 0;
> }
>
> static inline void mmc_blk_reset_success(struct mmc_blk_data *md, int type)
>
>-----Original Message-----
>From: Adrian Hunter <[email protected]>
>Sent: Samstag, 8. Oktober 2022 10:38
>To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
>Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
>
>On 7/10/22 18:42, Christian Löhle wrote:
>> Before switching back to the right partition in mmc_blk_reset there
>> used to be a check if hw_reset was even supported.
>> This return value was removed, so there is no reason to check.
>>
>> Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in
>> mmc_hw|sw_reset()")
>> Cc: [email protected]
>>
>> Signed-off-by: Christian Loehle <[email protected]>
>> ---
>> -v2: Do not attempt to switch partitions if reset failed
>>
>> drivers/mmc/core/block.c | 28 +++++++++++++---------------
>> 1 file changed, 13 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
>> ce89611a136e..8db72cba2bbe 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
>> int type)
>> {
>> int err;
>> + struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
>> + int part_err;
>>
>> if (md->reset_done & type)
>> return -EEXIST;
>>
>> md->reset_done |= type;
>> err = mmc_hw_reset(host->card);
>> + if (err)
>> + return err;
>
> This could be a potential source of data corruption.
>
> There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.
>
> I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.
I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch.
Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch)
Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
Or what do you suggest?
Regards,
Christian
Hyperstone GmbH | Reichenaustr. 39a | 78467 Konstanz
Managing Director: Dr. Jan Peter Berns.
Commercial register of local courts: Freiburg HRB381782
On 10/10/22 11:08, Christian Löhle wrote:
>
>>
>> -----Original Message-----
>> From: Adrian Hunter <[email protected]>
>> Sent: Samstag, 8. Oktober 2022 10:38
>> To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
>> Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
>>
>> On 7/10/22 18:42, Christian Löhle wrote:
>>> Before switching back to the right partition in mmc_blk_reset there
>>> used to be a check if hw_reset was even supported.
>>> This return value was removed, so there is no reason to check.
>>>
>>> Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in
>>> mmc_hw|sw_reset()")
>>> Cc: [email protected]
>>>
>>> Signed-off-by: Christian Loehle <[email protected]>
>>> ---
>>> -v2: Do not attempt to switch partitions if reset failed
>>>
>>> drivers/mmc/core/block.c | 28 +++++++++++++---------------
>>> 1 file changed, 13 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
>>> ce89611a136e..8db72cba2bbe 100644
>>> --- a/drivers/mmc/core/block.c
>>> +++ b/drivers/mmc/core/block.c
>>> @@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
>>> int type)
>>> {
>>> int err;
>>> + struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
>>> + int part_err;
>>>
>>> if (md->reset_done & type)
>>> return -EEXIST;
>>>
>>> md->reset_done |= type;
>>> err = mmc_hw_reset(host->card);
>>> + if (err)
>>> + return err;
>>
>> This could be a potential source of data corruption.
>>
>> There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.
>>
>> I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.
>
> I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
> Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch.
I wasn't clear sorry. I meant setting main_md->part_curr to a value
that doesn't match any partition, thereby forcing the next I/O to
switch partition first.
> Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch)
> Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
> Or what do you suggest?
What about what I just described above.
On Mon, 10 Oct 2022 at 14:36, Adrian Hunter <[email protected]> wrote:
>
> On 10/10/22 11:08, Christian Löhle wrote:
> >
> >>
> >> -----Original Message-----
> >> From: Adrian Hunter <[email protected]>
> >> Sent: Samstag, 8. Oktober 2022 10:38
> >> To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
> >> Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
> >>
> >> On 7/10/22 18:42, Christian Löhle wrote:
> >>> Before switching back to the right partition in mmc_blk_reset there
> >>> used to be a check if hw_reset was even supported.
> >>> This return value was removed, so there is no reason to check.
> >>>
> >>> Fixes: fefdd3c91e0a ("mmc: core: Drop superfluous validations in
> >>> mmc_hw|sw_reset()")
> >>> Cc: [email protected]
> >>>
> >>> Signed-off-by: Christian Loehle <[email protected]>
> >>> ---
> >>> -v2: Do not attempt to switch partitions if reset failed
> >>>
> >>> drivers/mmc/core/block.c | 28 +++++++++++++---------------
> >>> 1 file changed, 13 insertions(+), 15 deletions(-)
> >>>
> >>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
> >>> ce89611a136e..8db72cba2bbe 100644
> >>> --- a/drivers/mmc/core/block.c
> >>> +++ b/drivers/mmc/core/block.c
> >>> @@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
> >>> int type)
> >>> {
> >>> int err;
> >>> + struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
> >>> + int part_err;
> >>>
> >>> if (md->reset_done & type)
> >>> return -EEXIST;
> >>>
> >>> md->reset_done |= type;
> >>> err = mmc_hw_reset(host->card);
> >>> + if (err)
> >>> + return err;
> >>
> >> This could be a potential source of data corruption.
> >>
> >> There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.
> >>
> >> I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.
> >
> > I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
> > Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch.
>
> I wasn't clear sorry. I meant setting main_md->part_curr to a value
> that doesn't match any partition, thereby forcing the next I/O to
> switch partition first.
If I understand correctly, you are suggesting to ignore the return
code from mmc_hw_reset() and then always try to switch to the correct
partition. If we end up failing to switch the partition, then we
should set an invalid value in main_md->part_curr and return an error
code?
>
> > Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch)
> > Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
> > Or what do you suggest?
>
> What about what I just described above.
>
It seems reasonable to me (assuming I have understood correctly).
One additional thing though. I would appreciate some comments in the
code, so it becomes clear of what goes on.
Kind regards
Uffe