[PATCH 6.1 221/481] mmc: core: Avoid bitfield RMW for claim/retune flags

Greg Kroah-Hartman
2026-03-23T16:16:55Z

6.1-stable review patch. If anyone has any objections, please let me know.

------------------

From: Penghe Geng <pgeng@nvidia.com>

commit 901084c51a0a8fb42a3f37d2e9c62083c495f824 upstream.

Move claimed and retune control flags out of the bitfield word to
avoid unrelated RMW side effects in asynchronous contexts.

The host->claimed bit shared a word with retune flags. Writes to claimed
in __mmc_claim_host() or retune_now in mmc_mq_queue_rq() can overwrite
other bits when concurrent updates happen in other contexts, triggering
spurious WARN_ON(!host->claimed). Convert claimed, can_retune,
retune_now and retune_paused to bool to remove shared-word coupling.

Fixes: 6c0cedd1ef952 ("mmc: core: Introduce host claiming by context")
Fixes: 1e8e55b67030c ("mmc: block: Add CQE support")
Cc: stable@vger.kernel.org
Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Penghe Geng <pgeng@nvidia.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/mmc/host.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -440,14 +440,12 @@ struct mmc_host {

struct mmc_ios ios; /* current io bus settings */

+ bool claimed; /* host exclusively claimed */
+
/* group bitfields together to minimize padding */
unsigned int use_spi_crc:1;
- unsigned int claimed:1; /* host exclusively claimed */
unsigned int doing_init_tune:1; /* initial tuning in progress */
- unsigned int can_retune:1; /* re-tuning can be used */
unsigned int doing_retune:1; /* re-tuning in progress */
- unsigned int retune_now:1; /* do re-tuning at next req */
- unsigned int retune_paused:1; /* re-tuning is temporarily disabled */
unsigned int retune_crc_disable:1; /* don't trigger retune upon crc */
unsigned int can_dma_map_merge:1; /* merging can be used */
unsigned int vqmmc_enabled:1; /* vqmmc regulator is enabled */
@@ -455,6 +453,9 @@ struct mmc_host {
int rescan_disable; /* disable card detection */
int rescan_entered; /* used with nonremovable devices */

+ bool can_retune; /* re-tuning can be used */
+ bool retune_now; /* do re-tuning at next req */
+ bool retune_paused; /* re-tuning is temporarily disabled */
int need_retune; /* re-tuning is needed */
int hold_retune; /* hold off re-tuning */
unsigned int retune_period; /* re-tuning period in secs */