From b70da899940777d92338d8f83f7a6236818ad08a Mon Sep 17 00:00:00 2001 From: Jonathan Bell Date: Mon, 16 May 2022 10:28:27 +0100 Subject: [PATCH] mmc: block: Don't do single-sector reads during recovery See https://github.com/raspberrypi/linux/issues/5019 If an SD card has degraded performance such that IO operations time out then the MMC block layer will leak SG DMA mappings in the swiotlb during recovery. It retries the same SG and this causes the leak, as it is mapped twice - once in sdhci_pre_req() and again during single-block reads in sdhci_prepare_data(). Resetting the card (including power-cycling if a regulator for vmmc is present) ought to be enough to recover a stuck state, so for now don't try single-block reads in the recovery path. Signed-off-by: Jonathan Bell --- drivers/mmc/core/block.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/mmc/core/block.c +++ b/drivers/mmc/core/block.c @@ -1886,7 +1886,11 @@ static void mmc_blk_mq_rw_recovery(struc return; } - if (rq_data_dir(req) == READ && brq->data.blocks > + /* + * XXX: don't do single-sector reads, as it leaks a SG DMA + * mapping when reusing the still-pending req. + */ + if (0 && rq_data_dir(req) == READ && brq->data.blocks > queue_physical_block_size(mq->queue) >> 9) { /* Read one (native) sector at a time */ mmc_blk_read_single(mq, req);