[PATCH AUTOSEL 5.4 094/108] scsi: ufs: Fix ufshcd_hold() caused scheduling while atomic

[Sasha Levin]

From: Can Guo <cang@xxxxxxxxxxxxxx>

[ Upstream commit c63d6099a7959ecc919b2549dc6b71f53521f819 ]

The async version of ufshcd_hold(async == true), which is only called in
queuecommand path as for now, is expected to work in atomic context, thus
it should not sleep or schedule out. When it runs into the condition that
clocks are ON but link is still in hibern8 state, it should bail out
without flushing the clock ungate work.

Fixes: f2a785ac2312 ("scsi: ufshcd: Fix race between clk scaling and ungate work")
Link: https://lore.kernel.org/r/1581392451-28743-6-git-send-email-cang@xxxxxxxxxxxxxx
Reviewed-by: Hongwu Su <hongwus@xxxxxxxxxxxxxx>
Reviewed-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>
Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/scsi/ufs/ufshcd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index d9ea0ae4f374f..5582fbcfd7395 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1539,6 +1539,11 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
 		 */
 		if (ufshcd_can_hibern8_during_gating(hba) &&
 		    ufshcd_is_link_hibern8(hba)) {
+			if (async) {
+				rc = -EAGAIN;
+				hba->clk_gating.active_reqs--;
+				break;
+			}
 			spin_unlock_irqrestore(hba->host->host_lock, flags);
 			flush_work(&hba->clk_gating.ungate_work);
 			spin_lock_irqsave(hba->host->host_lock, flags);
-- 
2.20.1