mmc: block: Remove error check of hw_reset on reset

PATCH Superseded Christian Löhle 3 participants 5 messages Oct 7, 2022 – Oct 10, 2022 MMC, SD and SDIO

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Christian Löhle

author

2022-10-07 15:42 UTC #0 lore raw

PATCH v2 1/2 mmc: block: Remove error check of hw_reset on reset

Before switching back to the right partition in mmc_blk_reset there used to be a check if hw_reset was even supported. This return value was removed, so there is no reason to check.

Fixes fefdd3c91e0a ("mmc: core: Drop superfluous validations in mmc_hw|sw_reset()")

Cc [email protected]

Signed-off-by Christian Loehle <[email protected]>

---
-v2: Do not attempt to switch partitions if reset failed

 drivers/mmc/core/block.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

drivers/mmc/core/block.c +13 ~~-15~~

index ce89611a136e..8db72cba2bbe 100644
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
 			 int type)
 {
 	int err;
+	struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+	int part_err;
 
 	if (md->reset_done & type)
 		return -EEXIST;
 
 	md->reset_done |= type;
 	err = mmc_hw_reset(host->card);
+	if (err)
+		return err;
 	/* Ensure we switch back to the correct partition */
-	if (err) {
-		struct mmc_blk_data *main_md =
-			dev_get_drvdata(&host->card->dev);
-		int part_err;
-
-		main_md->part_curr = main_md->part_type;
-		part_err = mmc_blk_part_switch(host->card, md->part_type);
-		if (part_err) {
-			/*
-			 * We have failed to get back into the correct
-			 * partition, so we need to abort the whole request.
-			 */
-			return -ENODEV;
-		}
+	main_md->part_curr = main_md->part_type;
+	part_err = mmc_blk_part_switch(host->card, md->part_type);
+	if (part_err) {
+		/*
+		 * We have failed to get back into the correct
+		 * partition, so we need to abort the whole request.
+		 */
+		return -ENODEV;
 	}
-	return err;
+	return 0;
 }
 
 static inline void mmc_blk_reset_success(struct mmc_blk_data *md, int type)

Signature · 5 lines

2.37.3

Hyperstone GmbH | Reichenaustr. 39a  | 78467 Konstanz
Managing Director: Dr. Jan Peter Berns.
Commercial register of local courts: Freiburg HRB381782

Adrian Hunter

2022-10-08 08:38 UTC #1 lore raw

Quoted 22 lines · Christian Löhle

Before switching back to the right partition in mmc_blk_reset there used to be a check if hw_reset was even supported. This return value was removed, so there is no reason to check.
Fixes fefdd3c91e0a ("mmc: core: Drop superfluous validations in mmc_hw|sw_reset()")
Cc [email protected]
Signed-off-by Christian Loehle <[email protected]>
---
(quoted diff) +0 -1
-v2: Do not attempt to switch partitions if reset failed
 
 drivers/mmc/core/block.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)
drivers/mmc/core/block.c +0 -0
index ce89611a136e..8db72cba2bbe 100644
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
 			 int type)
 {
 	int err;

drivers/mmc/core/block.c static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host, · line 1003

Quoted 10 lines

drivers/mmc/core/block.c +4 -0

+	struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+	int part_err;
 
 	if (md->reset_done & type)
 		return -EEXIST;
 
 	md->reset_done |= type;
 	err = mmc_hw_reset(host->card);
+	if (err)
+		return err;

This could be a potential source of data corruption.

There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.

I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.

Quoted 29 lines

drivers/mmc/core/block.c +9 ~~-15~~

 	/* Ensure we switch back to the correct partition */
-	if (err) {
-		struct mmc_blk_data *main_md =
-			dev_get_drvdata(&host->card->dev);
-		int part_err;
-
-		main_md->part_curr = main_md->part_type;
-		part_err = mmc_blk_part_switch(host->card, md->part_type);
-		if (part_err) {
-			/*
-			 * We have failed to get back into the correct
-			 * partition, so we need to abort the whole request.
-			 */
-			return -ENODEV;
-		}
+	main_md->part_curr = main_md->part_type;
+	part_err = mmc_blk_part_switch(host->card, md->part_type);
+	if (part_err) {
+		/*
+		 * We have failed to get back into the correct
+		 * partition, so we need to abort the whole request.
+		 */
+		return -ENODEV;
 	}
-	return err;
+	return 0;
 }
 
 static inline void mmc_blk_reset_success(struct mmc_blk_data *md, int type)

Christian Löhle

author

2022-10-10 08:08 UTC #2 lore raw

Quoted 45 lines

-----Original Message-----
From: Adrian Hunter <[email protected]>
Sent: Samstag, 8. Oktober 2022 10:38
To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
Quoted 23 lines · Christian Löhle
Before switching back to the right partition in mmc_blk_reset there used to be a check if hw_reset was even supported.
This return value was removed, so there is no reason to check.
Fixes fefdd3c91e0a ("mmc: core: Drop superfluous validations in
mmc_hw|sw_reset()")
Cc: [email protected]
Signed-off-by Christian Loehle <[email protected]>
---
(quoted diff) +0 -1
-v2: Do not attempt to switch partitions if reset failed
 
 drivers/mmc/core/block.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)
drivers/mmc/core/block.c index renamed from drivers/mmc/core/block.c +0 -0
ce89611a136e..8db72cba2bbe 100644
drivers/mmc/core/block.c +0 -0
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
 			 int type)
 {
 	int err;
drivers/mmc/core/block.c static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host, · line 1003
Quoted 10 lines
drivers/mmc/core/block.c +4 -0
+	struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+	int part_err;
 
 	if (md->reset_done & type)
 		return -EEXIST;
 
 	md->reset_done |= type;
 	err = mmc_hw_reset(host->card);
+	if (err)
+		return err;
This could be a potential source of data corruption.

Quoted 3 lines

There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.
I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.

I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch. Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch) Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
Or what do you suggest?

Regards,
Christian

Hyperstone GmbH | Reichenaustr. 39a | 78467 Konstanz Managing Director: Dr. Jan Peter Berns. Commercial register of local courts: Freiburg HRB381782

Adrian Hunter

2022-10-10 12:36 UTC #3 lore raw

Quoted 45 lines · Christian Löhle

Quoted 45 lines
-----Original Message-----
From: Adrian Hunter <[email protected]>
Sent: Samstag, 8. Oktober 2022 10:38
To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
Quoted 23 lines · Christian Löhle
Before switching back to the right partition in mmc_blk_reset there used to be a check if hw_reset was even supported.
This return value was removed, so there is no reason to check.
Fixes fefdd3c91e0a ("mmc: core: Drop superfluous validations in
mmc_hw|sw_reset()")
Cc: [email protected]
Signed-off-by Christian Loehle <[email protected]>
---
(quoted diff) +0 -1
-v2: Do not attempt to switch partitions if reset failed
 
 drivers/mmc/core/block.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)
drivers/mmc/core/block.c index renamed from drivers/mmc/core/block.c +0 -0
ce89611a136e..8db72cba2bbe 100644
drivers/mmc/core/block.c +0 -0
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
 			 int type)
 {
 	int err;
drivers/mmc/core/block.c static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host, · line 1003
Quoted 10 lines
drivers/mmc/core/block.c +4 -0
+	struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+	int part_err;
 
 	if (md->reset_done & type)
 		return -EEXIST;
 
 	md->reset_done |= type;
 	err = mmc_hw_reset(host->card);
+	if (err)
+		return err;
This could be a potential source of data corruption.

Quoted 6 lines

Quoted 3 lines
There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.
I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.
I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch.

I wasn't clear sorry. I meant setting main_md->part_curr to a value that doesn't match any partition, thereby forcing the next I/O to switch partition first.

Quoted 3 lines

Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch) Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
Or what do you suggest?

What about what I just described above.

Ulf Hansson

2022-10-10 14:02 UTC #4 lore raw

Quoted 49 lines · Adrian Hunter

Quoted 47 lines · Christian Löhle
Quoted 47 lines
-----Original Message-----
From: Adrian Hunter <[email protected]>
Sent: Samstag, 8. Oktober 2022 10:38
To: Christian Löhle <[email protected]>; Ulf Hansson <[email protected]>; Linux MMC List <[email protected]>; [email protected]
Subject: Re: [PATCHv2 1/2] mmc: block: Remove error check of hw_reset on reset
Quoted 23 lines · Christian Löhle
Before switching back to the right partition in mmc_blk_reset there used to be a check if hw_reset was even supported.
This return value was removed, so there is no reason to check.
Fixes fefdd3c91e0a ("mmc: core: Drop superfluous validations in
mmc_hw|sw_reset()")
Cc: [email protected]
Signed-off-by Christian Loehle <[email protected]>
---
(quoted diff) +0 -1
-v2: Do not attempt to switch partitions if reset failed
 
 drivers/mmc/core/block.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)
drivers/mmc/core/block.c index renamed from drivers/mmc/core/block.c +0 -0
ce89611a136e..8db72cba2bbe 100644
drivers/mmc/core/block.c +0 -0
@@ -991,29 +991,27 @@ static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host,
                     int type)
 {
    int err;
drivers/mmc/core/block.c static int mmc_blk_reset(struct mmc_blk_data *md, struct mmc_host *host, · line 1003
Quoted 10 lines
drivers/mmc/core/block.c +4 -0
+   struct mmc_blk_data *main_md = dev_get_drvdata(&host->card->dev);
+   int part_err;
 
    if (md->reset_done & type)
            return -EEXIST;
 
    md->reset_done |= type;
    err = mmc_hw_reset(host->card);
+   if (err)
+           return err;
This could be a potential source of data corruption.
There is no guarantee that a subsequent I/O will fail just because the reset failed. Reading / writing the wrong partition would be disastrous, so we should always try to get back to the correct partition.

Quoted 8 lines

Quoted 4 lines
Quoted 1 line
I haven't looked at the possibility of just flagging the partition as invalid - need to be sure any subsequent I/O attempts still go through a path that switches the partition.
I can see where youre coming from, but similarly a failing mmc_blk_part_switch doesn't imply all subsequent IO will fail.
Flagging the partition as invalid can be seen as rendering the system to a potentially useless state, which is a bit overboard for e.g. one CRC7 failure on the switch.
I wasn't clear sorry. I meant setting main_md->part_curr to a value that doesn't match any partition, thereby forcing the next I/O to switch partition first.

If I understand correctly, you are suggesting to ignore the return code from mmc_hw_reset() and then always try to switch to the correct partition. If we end up failing to switch the partition, then we should set an invalid value in main_md->part_curr and return an error code?

Quoted 7 lines

Quoted 4 lines
Not sure yet what the ideal behavior is, but either way I would go with v1 1/2 and v2 2/2 for now? That already fixes imo the most relevant potential data corruptions. (successful reset -> no switch) Then we can come up with a a good handling for mmc_blk_reset or even around mmc_blk_part_switch.
Or what do you suggest?
What about what I just described above.

It seems reasonable to me (assuming I have understood correctly).

One additional thing though. I would appreciate some comments in the code, so it becomes clear of what goes on.

Kind regards
Uffe