[PATCH] mmc: core: don't initialize block size from ext_csd if not present

[Peter Collingbourne <pcc@google.com>]

If extended CSD was not available, the eMMC driver would incorrectly
set the block size to 0, as the data_sector_size field of ext_csd
was never initialized. This issue was exposed by commit 817046ecddbc
("block: Align max_hw_sectors to logical blocksize") which caused
max_sectors and max_hw_sectors to be set to 0 after setting the block
size to 0, resulting in a kernel panic in bio_split when attempting
to read from the device. Fix it by only reading the block size from
ext_csd if it is available.

Fixes: 817046ecddbc ("block: Align max_hw_sectors to logical blocksize")
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/If244d178da4d86b52034459438fec295b02d6e60
---
 drivers/mmc/core/queue.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index de7cb0369c30..735cdbf1145c 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -20,6 +20,7 @@
 #include "core.h"
 #include "card.h"
 #include "host.h"
+#include "mmc_ops.h"
 
 #define MMC_DMA_MAP_MERGE_SEGMENTS	512
 
@@ -384,7 +385,7 @@ static void mmc_setup_queue(struct mmc_queue *mq, struct mmc_card *card)
 		     "merging was advertised but not possible");
 	blk_queue_max_segments(mq->queue, mmc_get_max_segments(host));
 
-	if (mmc_card_mmc(card))
+	if (mmc_card_mmc(card) && mmc_can_ext_csd(card))
 		block_size = card->ext_csd.data_sector_size;
 
 	blk_queue_logical_block_size(mq->queue, block_size);
-- 
2.30.0.284.gd98b1dd5eaa7-goog