In the (not so unlikely) case that the mmc controller timeout budget is
enough for exactly one erase-group, the simplification of allowing one
sector has an enormous performance penalty. We optimize this special case
by introducing a flag that prohibits erase-group boundary crossing, so
that we can allow trimming more than one sector at a time.
Signed-off-by: David Jander <da...@protonic.nl>
---
Changes since v1:
- Added more comment
drivers/mmc/core/core.c | 38 ++++++++++++++++++++++++++++++++++----
include/linux/mmc/card.h | 1 +
2 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 92e7671..2771391 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2089,6 +2089,7 @@ int mmc_erase(struct mmc_card *card, unsigned int from,
unsigned int nr,
unsigned int arg)
{
unsigned int rem, to = from + nr;
+ int err;
if (!(card->host->caps & MMC_CAP_ERASE) ||
!(card->csd.cmdclass & CCC_ERASE))
@@ -2139,6 +2140,23 @@ int mmc_erase(struct mmc_card *card, unsigned int from,
unsigned int nr,
/* 'from' and 'to' are inclusive */
to -= 1;
+ /*
+ * Special case where only one erase-group fits in the timeout budget:
+ * If the region crosses an erase-group boundary on this particular
+ * case, we will be trimming more than one erase-group which, does not
+ * fit in the timeout budget of the controller, so we need to split it
+ * and call mmc_do_erase() twice if necessary. This special case is
+ * identified by the card->eg_boundary flag.
+ */
+ if ((arg & MMC_TRIM_ARGS) && (card->eg_boundary) &&
+ (from % card->erase_size)) {
+ rem = card->erase_size - (from % card->erase_size);
+ err = mmc_do_erase(card, from, from + rem - 1, arg);
+ from += rem;
+ if ((err) || (to <= from))
+ return err;
+ }
+
return mmc_do_erase(card, from, to, arg);
}
EXPORT_SYMBOL(mmc_erase);
@@ -2234,16 +2252,28 @@ static unsigned int mmc_do_calc_max_discard(struct
mmc_card *card,
if (!qty)
return 0;
+ /*
+ * When specifying a sector range to trim, chances are we might cross
+ * an erase-group boundary even if the amount of sectors is less than
+ * one erase-group.
+ * If we can only fit one erase-group in the controller timeout budget,
+ * we have to care that erase-group boundaries are not crossed by a
+ * single trim operation. We flag that special case with "eg_boundary".
+ * In all other cases we can just decrement qty and pretend that we
+ * always touch (qty + 1) erase-groups as a simple optimization.
+ */
if (qty == 1)
- return 1;
+ card->eg_boundary = 1;
+ else
+ qty--;
/* Convert qty to sectors */
if (card->erase_shift)
- max_discard = --qty << card->erase_shift;
+ max_discard = qty << card->erase_shift;
else if (mmc_card_sd(card))
- max_discard = qty;
+ max_discard = qty + 1;
else
- max_discard = --qty * card->erase_size;
+ max_discard = qty * card->erase_size;
return max_discard;
}
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 19f0175..704b60d 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -282,6 +282,7 @@ struct mmc_card {
unsigned int erase_size; /* erase size in sectors */
unsigned int erase_shift; /* if erase unit is power 2 */
unsigned int pref_erase; /* in sectors */
+ unsigned int eg_boundary; /* don't cross erase-group
boundaries */
u8 erased_byte; /* value of erased bytes */
u32 raw_cid[4]; /* raw card CID */
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
