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mtdblock: tolerate corrected bit-flips

PATCH Superseded Bang Li 3 participants 4 messages Mar 23, 2023 – Mar 28, 2023 Memory technology devices (MTD)

v1 of 2 Superseded Latest is v2 →

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Bang Li

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#0 lore raw

PATCH 1/1 mtdblock: tolerate corrected bit-flips

mtd_read() may return -EUCLEAN in case of corrected bit-flips.This particular condition should not be treated like an error.

Signed-off-by Bang Li <[email protected]>
---
 drivers/mtd/mtdblock.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
drivers/mtd/mtdblock.c +8 -4
index 1e94e7d10b8b..a0a1194dc1d9 100644
@@ -153,7 +153,7 @@ static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 				mtdblk->cache_state = STATE_EMPTY;
 				ret = mtd_read(mtd, sect_start, sect_size,
 					       &retlen, mtdblk->cache_data);
-				if (ret)
+				if (ret && !mtd_is_bitflip(ret))
 					return ret;
 				if (retlen != sect_size)
 					return -EIO;

@@ -188,8 +188,12 @@ static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 	pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 			mtd->name, pos, len);
 
-	if (!sect_size)
-		return mtd_read(mtd, pos, len, &retlen, buf);
+	if (!sect_size) {
+		ret = mtd_read(mtd, pos, len, &retlen, buf);
+		if (ret && !mtd_is_bitflip(ret))
+			return ret;
+		return 0;
+	}
 
 	while (len > 0) {
 		unsigned long sect_start = (pos/sect_size)*sect_size;

@@ -209,7 +213,7 @@ static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 			memcpy (buf, mtdblk->cache_data + offset, size);
 		} else {
 			ret = mtd_read(mtd, pos, size, &retlen, buf);
-			if (ret)
+			if (ret && !mtd_is_bitflip(ret))
 				return ret;
 			if (retlen != size)
 				return -EIO;
Signature · 6 lines
2.25.1


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maintainer
#1 lore raw

Hello,

[email protected] wrote on Thu, 23 Mar 2023 22:03:50 +0800:

Quoted 2 lines

mtd_read() may return -EUCLEAN in case of corrected bit-flips.This particular condition should not be treated like an error.

I'm fine with the patch, Richard, are you okay as well?

Quoted 34 lines
Signed-off-by Bang Li <[email protected]>
---
 drivers/mtd/mtdblock.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
drivers/mtd/mtdblock.c +7 -3
index 1e94e7d10b8b..a0a1194dc1d9 100644
@@ -153,7 +153,7 @@ static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 				mtdblk->cache_state = STATE_EMPTY;
 				ret = mtd_read(mtd, sect_start, sect_size,
 					       &retlen, mtdblk->cache_data);
-				if (ret)
+				if (ret && !mtd_is_bitflip(ret))
 					return ret;
 				if (retlen != sect_size)
 					return -EIO;

@@ -188,8 +188,12 @@ static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 	pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 			mtd->name, pos, len);
 
-	if (!sect_size)
-		return mtd_read(mtd, pos, len, &retlen, buf);
+	if (!sect_size) {
+		ret = mtd_read(mtd, pos, len, &retlen, buf);
+		if (ret && !mtd_is_bitflip(ret))
+			return ret;
+		return 0;
+	}
 
 	while (len > 0) {
 		unsigned long sect_start = (pos/sect_size)*sect_size;

drivers/mtd/mtdblock.c static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, · line 219

Quoted 8 lines
drivers/mtd/mtdblock.c +1 -1
@@ -209,7 +213,7 @@ static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 			memcpy (buf, mtdblk->cache_data + offset, size);
 		} else {
 			ret = mtd_read(mtd, pos, size, &retlen, buf);
-			if (ret)
+			if (ret && !mtd_is_bitflip(ret))
 				return ret;
 			if (retlen != size)
 				return -EIO;

Thanks,
Miquèl

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maintainer
#2 lore raw

Hi!

----- Ursprüngliche Mail -----

Quoted 6 lines

[email protected] wrote on Thu, 23 Mar 2023 22:03:50 +0800:

Quoted 2 lines

mtd_read() may return -EUCLEAN in case of corrected bit-flips.This particular condition should not be treated like an error.

I'm fine with the patch, Richard, are you okay as well?

Hm yes. I see the bug. I think it broke about 10 years ago by e47f68587b82 ("mtd: check for max_bitflips in mtd_read_oob()").

In the early day I'd expect someone to hit this bug but I guess on the last 10 years mtdblock had no real users.

Thanks,
//richard

maintainer
#3 lore raw

Hi Richard,

[email protected] wrote on Tue, 28 Mar 2023 15:21:50 +0200 (CEST):

Quoted 8 lines

Hi!

----- Ursprüngliche Mail -----

Quoted 5 lines

[email protected] wrote on Thu, 23 Mar 2023 22:03:50 +0800:

Quoted 2 lines

mtd_read() may return -EUCLEAN in case of corrected bit-flips.This particular condition should not be treated like an error.

Quoted 7 lines
Quoted 1 line

I'm fine with the patch, Richard, are you okay as well?

Hm yes. I see the bug. I think it broke about 10 years ago by e47f68587b82 ("mtd: check for max_bitflips in mtd_read_oob()").

In the early day I'd expect someone to hit this bug but I guess on the last 10 years mtdblock had no real users.

Right.

Well, anyhow I guess this patch deserves a Fixes/Cc: stable # v3.7+

Li, can you please re-send with the proper tags? Thanks.

Thanks,
Miquèl

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