card->erased_byte read from SCR(for SD cards) or EXT_CSD[181](for eMMC) indicates whether the TRIM or ERASE make the erased data content zeros, but DISCARD doesn't. Use the fact to implement REQ_OP_WRITE_ZEROES. Cc: Faiz Abbas <faiz_abbas@xxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> --- Hi Faiz, Would you like to test this patch to see if it could solve your performance drop on the first write after filesystem creation? drivers/mmc/core/block.c | 10 +++++++++- drivers/mmc/core/queue.c | 3 +++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index a0b9102..7d59887 100644 --- a/drivers/mmc/core/block.c +++ b/drivers/mmc/core/block.c @@ -1132,7 +1132,14 @@ static void mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req) from = blk_rq_pos(req); nr = blk_rq_sectors(req); - if (mmc_can_discard(card)) + /* + * DISCARD says the contents of a write block where the discard + * function has been applied shold be 'don't care'. But TRIM and + * ERASE should have explicit '1' or '0' indicated by + * card->erased_byte. So REQ_OP_WRITE_ZEROES should use TRIM/ERASE + * instead. + */ + if (mmc_can_discard(card) && req_op(req) != REQ_OP_WRITE_ZEROES) arg = MMC_DISCARD_ARG; else if (mmc_can_trim(card)) arg = MMC_TRIM_ARG; @@ -2228,6 +2235,7 @@ enum mmc_issued mmc_blk_mq_issue_rq(struct mmc_queue *mq, struct request *req) mmc_blk_issue_drv_op(mq, req); break; case REQ_OP_DISCARD: + case REQ_OP_WRITE_ZEROES: mmc_blk_issue_discard_rq(mq, req); break; case REQ_OP_SECURE_ERASE: diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index 56e9a80..2657a46 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -51,6 +51,7 @@ static enum mmc_issue_type mmc_cqe_issue_type(struct mmc_host *host, case REQ_OP_DRV_OUT: case REQ_OP_DISCARD: case REQ_OP_SECURE_ERASE: + case REQ_OP_WRITE_ZEROES: return MMC_ISSUE_SYNC; case REQ_OP_FLUSH: return mmc_cqe_can_dcmd(host) ? MMC_ISSUE_DCMD : MMC_ISSUE_SYNC; @@ -193,6 +194,8 @@ static void mmc_queue_setup_discard(struct request_queue *q, q->limits.discard_granularity = 0; if (mmc_can_secure_erase_trim(card)) blk_queue_flag_set(QUEUE_FLAG_SECERASE, q); + if (!card->erased_byte) + q->limits.max_write_zeroes_sectors = max_discard; } /** -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
