linux-kernel - [PATCH] mmc: inline the first mmc_scan() on mmc_start

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Date:   Wed, 29 Mar 2023 13:21:48 -0700
From:   Dennis Zhou <dennis@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dennis Zhou <dennis@...nel.org>
Subject: [PATCH] mmc: inline the first mmc_scan() on mmc_start_host()

When using dm-verity with a data partition on an emmc device, dm-verity
races with the discovery of attached emmc devices. This is because mmc's
probing code sets up the host data structure then a work item is
scheduled to do discovery afterwards. To prevent this race on init,
let's inline the first call to detection, __mm_scan(), and let
subsequent detect calls be handled via the workqueue.

Signed-off-by: Dennis Zhou <dennis@...nel.org>
---
 drivers/mmc/core/core.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 368f10405e13..c0fdc438c882 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2185,10 +2185,8 @@ int mmc_card_alternative_gpt_sector(struct mmc_card *card, sector_t *gpt_sector)
 }
 EXPORT_SYMBOL(mmc_card_alternative_gpt_sector);
 
-void mmc_rescan(struct work_struct *work)
+void __mmc_rescan(struct mmc_host *host)
 {
-	struct mmc_host *host =
-		container_of(work, struct mmc_host, detect.work);
 	int i;
 
 	if (host->rescan_disable)
@@ -2249,6 +2247,14 @@ void mmc_rescan(struct work_struct *work)
 		mmc_schedule_delayed_work(&host->detect, HZ);
 }
 
+void mmc_rescan(struct work_struct *work)
+{
+	struct mmc_host *host =
+		container_of(work, struct mmc_host, detect.work);
+
+	__mmc_rescan(host);
+}
+
 void mmc_start_host(struct mmc_host *host)
 {
 	host->f_init = max(min(freqs[0], host->f_max), host->f_min);
@@ -2261,7 +2267,8 @@ void mmc_start_host(struct mmc_host *host)
 	}
 
 	mmc_gpiod_request_cd_irq(host);
-	_mmc_detect_change(host, 0, false);
+	host->detect_change = 1;
+	__mmc_rescan(host);
 }
 
 void __mmc_stop_host(struct mmc_host *host)
-- 
2.40.0