[PATCH] mtd: rawnand: serialize lock/unlock against other NAND operations

[Kamal Dasu]

nand_lock() and nand_unlock() call into chip->ops.lock_area/unlock_area
without holding the NAND device lock. On controllers that implement
SET_FEATURES via multiple low-level PIO commands, these can race with
concurrent UBI/UBIFS background erase/write operations that hold the
device lock, resulting in cmd_pending conflicts on the NAND controller.

Add nand_get_device()/nand_release_device() around the lock/unlock
operations to serialize them against all other NAND controller access.

Fixes: 92270086b7e5 ("mtd: rawnand: Add support for manufacturer specific lock/unlock operation")
Signed-off-by: Kamal Dasu <kamal.dasu@xxxxxxxxxxxx>
---
 drivers/mtd/nand/raw/nand_base.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 38429363251c..dfd8361bdd36 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -4737,11 +4737,16 @@ static void nand_shutdown(struct mtd_info *mtd)
 static int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
+	int ret;
 
 	if (!chip->ops.lock_area)
 		return -ENOTSUPP;
 
-	return chip->ops.lock_area(chip, ofs, len);
+	nand_get_device(chip);
+	ret = chip->ops.lock_area(chip, ofs, len);
+	nand_release_device(chip);
+
+	return ret;
 }
 
 /**
@@ -4753,11 +4758,16 @@ static int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 static int nand_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
+	int ret;
 
 	if (!chip->ops.unlock_area)
 		return -ENOTSUPP;
 
-	return chip->ops.unlock_area(chip, ofs, len);
+	nand_get_device(chip);
+	ret = chip->ops.unlock_area(chip, ofs, len);
+	nand_release_device(chip);
+
+	return ret;
 }
 
 /* Set default functions */
-- 
2.34.1