[v3] mmc: core: Optimize the mmc erase size alignment
diff mbox

Message ID 9de99671750430d7d80a8f351c0ec7a7088c9b00.1472635587.git.baolin.wang@linaro.org
State New
Headers show

Commit Message

(Exiting) Baolin Wang Aug. 31, 2016, 9:32 a.m. UTC
Before issuing mmc_erase() function, users always have checked if it can
erase with mmc_can_erase/trim/discard() function, thus remove the redundant
erase checking in mmc_erase() function.

This patch also optimizes the erase start/end sector alignment with
round_up()/round_down() function, when erase command is MMC_ERASE_ARG.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
Changes since v2:
 - Add nr checking and other optimization in mmc_erase() function.

Changes since v1:
 - Add the alignment if card->erase_size is not power of 2.
---
 drivers/mmc/core/core.c |   82 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 53 insertions(+), 29 deletions(-)

Comments

Shawn Lin Sept. 2, 2016, 8:34 a.m. UTC | #1
Hi Baolin,

On 2016/8/31 17:32, Baolin Wang wrote:
> Before issuing mmc_erase() function, users always have checked if it can
> erase with mmc_can_erase/trim/discard() function, thus remove the redundant
> erase checking in mmc_erase() function.
>
> This patch also optimizes the erase start/end sector alignment with

It implies you could split this patch into two for dealing with diff
things. :) Otherwise, you could add my test tag,

Tested-by: Shawn Lin <shawn.lin@rock-chips.com>

> round_up()/round_down() function, when erase command is MMC_ERASE_ARG.
>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
> Changes since v2:
>  - Add nr checking and other optimization in mmc_erase() function.
>
> Changes since v1:
>  - Add the alignment if card->erase_size is not power of 2.
> ---
>  drivers/mmc/core/core.c |   82 ++++++++++++++++++++++++++++++-----------------
>  1 file changed, 53 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index e55cde6..52156d4 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2202,6 +2202,51 @@ out:
>  	return err;
>  }
>
> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
> +					 unsigned int *from,
> +					 unsigned int *to,
> +					 unsigned int nr)
> +{
> +	unsigned int from_new = *from, nr_new = nr, rem;
> +
> +	if (is_power_of_2(card->erase_size)) {
> +		unsigned int temp = from_new;
> +
> +		from_new = round_up(temp, card->erase_size);
> +		rem = from_new - temp;
> +
> +		if (nr_new > rem)
> +			nr_new -= rem;
> +		else
> +			return 0;
> +
> +		nr_new = round_down(nr_new, card->erase_size);
> +	} else {
> +		rem = from_new % card->erase_size;
> +		if (rem) {
> +			rem = card->erase_size - rem;
> +			from_new += rem;
> +			if (nr_new > rem)
> +				nr_new -= rem;
> +			else
> +				return 0;
> +		}
> +
> +		rem = nr_new % card->erase_size;
> +		if (rem)
> +			nr_new -= rem;
> +	}
> +
> +	if (nr_new == 0)
> +		return 0;
> +
> +	/* 'from' and 'to' are inclusive */
> +	*to = from_new + nr_new - 1;
> +	*from = from_new;
> +
> +	return nr_new;
> +}
> +
>  /**
>   * mmc_erase - erase sectors.
>   * @card: card to erase
> @@ -2217,13 +2262,6 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>  	unsigned int rem, to = from + nr;
>  	int err;
>
> -	if (!(card->host->caps & MMC_CAP_ERASE) ||
> -	    !(card->csd.cmdclass & CCC_ERASE))
> -		return -EOPNOTSUPP;
> -
> -	if (!card->erase_size)
> -		return -EOPNOTSUPP;
> -
>  	if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
>  		return -EOPNOTSUPP;
>
> @@ -2240,31 +2278,17 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>  			return -EINVAL;
>  	}
>
> -	if (arg == MMC_ERASE_ARG) {
> -		rem = from % card->erase_size;
> -		if (rem) {
> -			rem = card->erase_size - rem;
> -			from += rem;
> -			if (nr > rem)
> -				nr -= rem;
> -			else
> -				return 0;
> -		}
> -		rem = nr % card->erase_size;
> -		if (rem)
> -			nr -= rem;
> -	}
> -
>  	if (nr == 0)
>  		return 0;
>
> -	to = from + nr;
> -
> -	if (to <= from)
> -		return -EINVAL;
> -
> -	/* 'from' and 'to' are inclusive */
> -	to -= 1;
> +	if (arg == MMC_ERASE_ARG) {
> +		nr = mmc_align_erase_size(card, &from, &to, nr);
> +		if (nr == 0)
> +			return 0;
> +	} else {
> +		/* 'from' and 'to' are inclusive */
> +		to -= 1;
> +	}
>
>  	/*
>  	 * Special case where only one erase-group fits in the timeout budget:
>
Ulf Hansson Sept. 2, 2016, 9:43 a.m. UTC | #2
On 31 August 2016 at 11:32, Baolin Wang <baolin.wang@linaro.org> wrote:
> Before issuing mmc_erase() function, users always have checked if it can
> erase with mmc_can_erase/trim/discard() function, thus remove the redundant
> erase checking in mmc_erase() function.
>
> This patch also optimizes the erase start/end sector alignment with
> round_up()/round_down() function, when erase command is MMC_ERASE_ARG.
>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
> Changes since v2:
>  - Add nr checking and other optimization in mmc_erase() function.
>
> Changes since v1:
>  - Add the alignment if card->erase_size is not power of 2.
> ---
>  drivers/mmc/core/core.c |   82 ++++++++++++++++++++++++++++++-----------------
>  1 file changed, 53 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index e55cde6..52156d4 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2202,6 +2202,51 @@ out:
>         return err;
>  }
>
> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
> +                                        unsigned int *from,
> +                                        unsigned int *to,
> +                                        unsigned int nr)
> +{

How about make one patch that starts by moving the existing code into
a separate function, then on top as a new change, start playing with
the optimizations!?
That would be more easy to review.

> +       unsigned int from_new = *from, nr_new = nr, rem;
> +
> +       if (is_power_of_2(card->erase_size)) {

I would like some comment in the code, to understand what/why we do this.

> +               unsigned int temp = from_new;
> +
> +               from_new = round_up(temp, card->erase_size);
> +               rem = from_new - temp;
> +
> +               if (nr_new > rem)
> +                       nr_new -= rem;
> +               else
> +                       return 0;
> +
> +               nr_new = round_down(nr_new, card->erase_size);
> +       } else {

Ditto.

> +               rem = from_new % card->erase_size;
> +               if (rem) {
> +                       rem = card->erase_size - rem;
> +                       from_new += rem;
> +                       if (nr_new > rem)
> +                               nr_new -= rem;
> +                       else
> +                               return 0;
> +               }
> +
> +               rem = nr_new % card->erase_size;
> +               if (rem)
> +                       nr_new -= rem;
> +       }
> +
> +       if (nr_new == 0)
> +               return 0;
> +
> +       /* 'from' and 'to' are inclusive */
> +       *to = from_new + nr_new - 1;
> +       *from = from_new;
> +
> +       return nr_new;
> +}
> +
>  /**
>   * mmc_erase - erase sectors.
>   * @card: card to erase
> @@ -2217,13 +2262,6 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>         unsigned int rem, to = from + nr;
>         int err;
>
> -       if (!(card->host->caps & MMC_CAP_ERASE) ||
> -           !(card->csd.cmdclass & CCC_ERASE))
> -               return -EOPNOTSUPP;
> -
> -       if (!card->erase_size)
> -               return -EOPNOTSUPP;
> -

I agree with Shawn here, please try to have one patch taking care of
one thing. If we find out that things goes wrong later, then it's
easier to drop/revert a change which causes the regression.

Moreover, for the above particular change, I don't think you should
remove these validations, as this is an API being exported. You may
convert to use mmc_can_erase() though.

Regarding all the mmc erase related exported APIs, there are certainly
a need for some clean-ups. For example, I think too many APIs are
being exported and we could probably also restructure the code a bit
so it becomes more readable. Although, of course this deserves a
standalone clean-up series. :-)

>         if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
>                 return -EOPNOTSUPP;
>
> @@ -2240,31 +2278,17 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>                         return -EINVAL;
>         }
>
> -       if (arg == MMC_ERASE_ARG) {
> -               rem = from % card->erase_size;
> -               if (rem) {
> -                       rem = card->erase_size - rem;
> -                       from += rem;
> -                       if (nr > rem)
> -                               nr -= rem;
> -                       else
> -                               return 0;
> -               }
> -               rem = nr % card->erase_size;
> -               if (rem)
> -                       nr -= rem;
> -       }
> -
>         if (nr == 0)
>                 return 0;
>
> -       to = from + nr;
> -
> -       if (to <= from)
> -               return -EINVAL;
> -
> -       /* 'from' and 'to' are inclusive */
> -       to -= 1;
> +       if (arg == MMC_ERASE_ARG) {
> +               nr = mmc_align_erase_size(card, &from, &to, nr);
> +               if (nr == 0)
> +                       return 0;
> +       } else {
> +               /* 'from' and 'to' are inclusive */
> +               to -= 1;
> +       }
>
>         /*
>          * Special case where only one erase-group fits in the timeout budget:
> --
> 1.7.9.5
>

Kind regards
Uffe
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(Exiting) Baolin Wang Sept. 5, 2016, 8:17 a.m. UTC | #3
Hi Shawn,

On 2 September 2016 at 16:34, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> Hi Baolin,
>
> On 2016/8/31 17:32, Baolin Wang wrote:
>>
>> Before issuing mmc_erase() function, users always have checked if it can
>> erase with mmc_can_erase/trim/discard() function, thus remove the
>> redundant
>> erase checking in mmc_erase() function.
>>
>> This patch also optimizes the erase start/end sector alignment with
>
>
> It implies you could split this patch into two for dealing with diff
> things. :) Otherwise, you could add my test tag,

Yes, I will split it into two separate patches and thanks for your testing.

>
> Tested-by: Shawn Lin <shawn.lin@rock-chips.com>
>
>
>> round_up()/round_down() function, when erase command is MMC_ERASE_ARG.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> ---
>> Changes since v2:
>>  - Add nr checking and other optimization in mmc_erase() function.
>>
>> Changes since v1:
>>  - Add the alignment if card->erase_size is not power of 2.
>> ---
>>  drivers/mmc/core/core.c |   82
>> ++++++++++++++++++++++++++++++-----------------
>>  1 file changed, 53 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index e55cde6..52156d4 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -2202,6 +2202,51 @@ out:
>>         return err;
>>  }
>>
>> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
>> +                                        unsigned int *from,
>> +                                        unsigned int *to,
>> +                                        unsigned int nr)
>> +{
>> +       unsigned int from_new = *from, nr_new = nr, rem;
>> +
>> +       if (is_power_of_2(card->erase_size)) {
>> +               unsigned int temp = from_new;
>> +
>> +               from_new = round_up(temp, card->erase_size);
>> +               rem = from_new - temp;
>> +
>> +               if (nr_new > rem)
>> +                       nr_new -= rem;
>> +               else
>> +                       return 0;
>> +
>> +               nr_new = round_down(nr_new, card->erase_size);
>> +       } else {
>> +               rem = from_new % card->erase_size;
>> +               if (rem) {
>> +                       rem = card->erase_size - rem;
>> +                       from_new += rem;
>> +                       if (nr_new > rem)
>> +                               nr_new -= rem;
>> +                       else
>> +                               return 0;
>> +               }
>> +
>> +               rem = nr_new % card->erase_size;
>> +               if (rem)
>> +                       nr_new -= rem;
>> +       }
>> +
>> +       if (nr_new == 0)
>> +               return 0;
>> +
>> +       /* 'from' and 'to' are inclusive */
>> +       *to = from_new + nr_new - 1;
>> +       *from = from_new;
>> +
>> +       return nr_new;
>> +}
>> +
>>  /**
>>   * mmc_erase - erase sectors.
>>   * @card: card to erase
>> @@ -2217,13 +2262,6 @@ int mmc_erase(struct mmc_card *card, unsigned int
>> from, unsigned int nr,
>>         unsigned int rem, to = from + nr;
>>         int err;
>>
>> -       if (!(card->host->caps & MMC_CAP_ERASE) ||
>> -           !(card->csd.cmdclass & CCC_ERASE))
>> -               return -EOPNOTSUPP;
>> -
>> -       if (!card->erase_size)
>> -               return -EOPNOTSUPP;
>> -
>>         if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
>>                 return -EOPNOTSUPP;
>>
>> @@ -2240,31 +2278,17 @@ int mmc_erase(struct mmc_card *card, unsigned int
>> from, unsigned int nr,
>>                         return -EINVAL;
>>         }
>>
>> -       if (arg == MMC_ERASE_ARG) {
>> -               rem = from % card->erase_size;
>> -               if (rem) {
>> -                       rem = card->erase_size - rem;
>> -                       from += rem;
>> -                       if (nr > rem)
>> -                               nr -= rem;
>> -                       else
>> -                               return 0;
>> -               }
>> -               rem = nr % card->erase_size;
>> -               if (rem)
>> -                       nr -= rem;
>> -       }
>> -
>>         if (nr == 0)
>>                 return 0;
>>
>> -       to = from + nr;
>> -
>> -       if (to <= from)
>> -               return -EINVAL;
>> -
>> -       /* 'from' and 'to' are inclusive */
>> -       to -= 1;
>> +       if (arg == MMC_ERASE_ARG) {
>> +               nr = mmc_align_erase_size(card, &from, &to, nr);
>> +               if (nr == 0)
>> +                       return 0;
>> +       } else {
>> +               /* 'from' and 'to' are inclusive */
>> +               to -= 1;
>> +       }
>>
>>         /*
>>          * Special case where only one erase-group fits in the timeout
>> budget:
>>
>
>
> --
> Best Regards
> Shawn Lin
>
(Exiting) Baolin Wang Sept. 5, 2016, 8:27 a.m. UTC | #4
Hi Ulf,


On 2 September 2016 at 17:43, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 31 August 2016 at 11:32, Baolin Wang <baolin.wang@linaro.org> wrote:
>> Before issuing mmc_erase() function, users always have checked if it can
>> erase with mmc_can_erase/trim/discard() function, thus remove the redundant
>> erase checking in mmc_erase() function.
>>
>> This patch also optimizes the erase start/end sector alignment with
>> round_up()/round_down() function, when erase command is MMC_ERASE_ARG.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> ---
>> Changes since v2:
>>  - Add nr checking and other optimization in mmc_erase() function.
>>
>> Changes since v1:
>>  - Add the alignment if card->erase_size is not power of 2.
>> ---
>>  drivers/mmc/core/core.c |   82 ++++++++++++++++++++++++++++++-----------------
>>  1 file changed, 53 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index e55cde6..52156d4 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -2202,6 +2202,51 @@ out:
>>         return err;
>>  }
>>
>> +static unsigned int mmc_align_erase_size(struct mmc_card *card,
>> +                                        unsigned int *from,
>> +                                        unsigned int *to,
>> +                                        unsigned int nr)
>> +{
>
> How about make one patch that starts by moving the existing code into
> a separate function, then on top as a new change, start playing with
> the optimizations!?
> That would be more easy to review.

Make sense. I'll do what you suggested in next version.

>
>> +       unsigned int from_new = *from, nr_new = nr, rem;
>> +
>> +       if (is_power_of_2(card->erase_size)) {
>
> I would like some comment in the code, to understand what/why we do this.

I think the erase_size is power of 2 in most cases, then the
round_up/down() is more efficient than '%' operation. I'll add some
comments to explain that.

>
>> +               unsigned int temp = from_new;
>> +
>> +               from_new = round_up(temp, card->erase_size);
>> +               rem = from_new - temp;
>> +
>> +               if (nr_new > rem)
>> +                       nr_new -= rem;
>> +               else
>> +                       return 0;
>> +
>> +               nr_new = round_down(nr_new, card->erase_size);
>> +       } else {
>
> Ditto.
>
>> +               rem = from_new % card->erase_size;
>> +               if (rem) {
>> +                       rem = card->erase_size - rem;
>> +                       from_new += rem;
>> +                       if (nr_new > rem)
>> +                               nr_new -= rem;
>> +                       else
>> +                               return 0;
>> +               }
>> +
>> +               rem = nr_new % card->erase_size;
>> +               if (rem)
>> +                       nr_new -= rem;
>> +       }
>> +
>> +       if (nr_new == 0)
>> +               return 0;
>> +
>> +       /* 'from' and 'to' are inclusive */
>> +       *to = from_new + nr_new - 1;
>> +       *from = from_new;
>> +
>> +       return nr_new;
>> +}
>> +
>>  /**
>>   * mmc_erase - erase sectors.
>>   * @card: card to erase
>> @@ -2217,13 +2262,6 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>>         unsigned int rem, to = from + nr;
>>         int err;
>>
>> -       if (!(card->host->caps & MMC_CAP_ERASE) ||
>> -           !(card->csd.cmdclass & CCC_ERASE))
>> -               return -EOPNOTSUPP;
>> -
>> -       if (!card->erase_size)
>> -               return -EOPNOTSUPP;
>> -
>
> I agree with Shawn here, please try to have one patch taking care of
> one thing. If we find out that things goes wrong later, then it's
> easier to drop/revert a change which causes the regression.

OK.

>
> Moreover, for the above particular change, I don't think you should
> remove these validations, as this is an API being exported. You may
> convert to use mmc_can_erase() though.

These validations are redundant, since we always have checked if it
can erase with mmc_can_erase/trim/discard() function before issuing
mmc_erase(). Another hand these validations should be moved into
mmc_can_erase() not in mmc_erase() function.

>
> Regarding all the mmc erase related exported APIs, there are certainly
> a need for some clean-ups. For example, I think too many APIs are
> being exported and we could probably also restructure the code a bit
> so it becomes more readable. Although, of course this deserves a
> standalone clean-up series. :-)

OK. I would like to do some clean up for erase function after this
optimization. Thanks for your comments.

>
>>         if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
>>                 return -EOPNOTSUPP;
>>
>> @@ -2240,31 +2278,17 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>>                         return -EINVAL;
>>         }
>>
>> -       if (arg == MMC_ERASE_ARG) {
>> -               rem = from % card->erase_size;
>> -               if (rem) {
>> -                       rem = card->erase_size - rem;
>> -                       from += rem;
>> -                       if (nr > rem)
>> -                               nr -= rem;
>> -                       else
>> -                               return 0;
>> -               }
>> -               rem = nr % card->erase_size;
>> -               if (rem)
>> -                       nr -= rem;
>> -       }
>> -
>>         if (nr == 0)
>>                 return 0;
>>
>> -       to = from + nr;
>> -
>> -       if (to <= from)
>> -               return -EINVAL;
>> -
>> -       /* 'from' and 'to' are inclusive */
>> -       to -= 1;
>> +       if (arg == MMC_ERASE_ARG) {
>> +               nr = mmc_align_erase_size(card, &from, &to, nr);
>> +               if (nr == 0)
>> +                       return 0;
>> +       } else {
>> +               /* 'from' and 'to' are inclusive */
>> +               to -= 1;
>> +       }
>>
>>         /*
>>          * Special case where only one erase-group fits in the timeout budget:
>> --
>> 1.7.9.5
>>
>
> Kind regards
> Uffe

Patch
diff mbox

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index e55cde6..52156d4 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2202,6 +2202,51 @@  out:
 	return err;
 }
 
+static unsigned int mmc_align_erase_size(struct mmc_card *card,
+					 unsigned int *from,
+					 unsigned int *to,
+					 unsigned int nr)
+{
+	unsigned int from_new = *from, nr_new = nr, rem;
+
+	if (is_power_of_2(card->erase_size)) {
+		unsigned int temp = from_new;
+
+		from_new = round_up(temp, card->erase_size);
+		rem = from_new - temp;
+
+		if (nr_new > rem)
+			nr_new -= rem;
+		else
+			return 0;
+
+		nr_new = round_down(nr_new, card->erase_size);
+	} else {
+		rem = from_new % card->erase_size;
+		if (rem) {
+			rem = card->erase_size - rem;
+			from_new += rem;
+			if (nr_new > rem)
+				nr_new -= rem;
+			else
+				return 0;
+		}
+
+		rem = nr_new % card->erase_size;
+		if (rem)
+			nr_new -= rem;
+	}
+
+	if (nr_new == 0)
+		return 0;
+
+	/* 'from' and 'to' are inclusive */
+	*to = from_new + nr_new - 1;
+	*from = from_new;
+
+	return nr_new;
+}
+
 /**
  * mmc_erase - erase sectors.
  * @card: card to erase
@@ -2217,13 +2262,6 @@  int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
 	unsigned int rem, to = from + nr;
 	int err;
 
-	if (!(card->host->caps & MMC_CAP_ERASE) ||
-	    !(card->csd.cmdclass & CCC_ERASE))
-		return -EOPNOTSUPP;
-
-	if (!card->erase_size)
-		return -EOPNOTSUPP;
-
 	if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
 		return -EOPNOTSUPP;
 
@@ -2240,31 +2278,17 @@  int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
 			return -EINVAL;
 	}
 
-	if (arg == MMC_ERASE_ARG) {
-		rem = from % card->erase_size;
-		if (rem) {
-			rem = card->erase_size - rem;
-			from += rem;
-			if (nr > rem)
-				nr -= rem;
-			else
-				return 0;
-		}
-		rem = nr % card->erase_size;
-		if (rem)
-			nr -= rem;
-	}
-
 	if (nr == 0)
 		return 0;
 
-	to = from + nr;
-
-	if (to <= from)
-		return -EINVAL;
-
-	/* 'from' and 'to' are inclusive */
-	to -= 1;
+	if (arg == MMC_ERASE_ARG) {
+		nr = mmc_align_erase_size(card, &from, &to, nr);
+		if (nr == 0)
+			return 0;
+	} else {
+		/* 'from' and 'to' are inclusive */
+		to -= 1;
+	}
 
 	/*
 	 * Special case where only one erase-group fits in the timeout budget: