Patch "mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mtd-nand-gpmi-fix-failure-when-a-erased-page-has-a-bitflip-at-bbm.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sascha Hauer <[email protected]>
Date: Tue, 5 Dec 2017 11:51:40 +0100
Subject: mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM

From: Sascha Hauer <[email protected]>

[ Upstream commit fdf2e821052958a114618a95ab18a300d0b080cb ]

When erased subpages are read then the BCH decoder returns STATUS_ERASED if they are all empty, or STATUS_UNCORRECTABLE if there are bitflips. When there are bitflips, we have to set these bits again to show the upper layers a completely erased page. When a bitflip happens in the exact byte where the bad block marker is, then this byte is swapped with another byte in block_mark_swapping(). The correction code then detects a bitflip in another subpage and no longer corrects the bitflip where it really happens.

Correct this behaviour by calling block_mark_swapping() after the bitflips have been corrected.

In our case UBIFS failed with this bug because it expects erased pages to be really empty:

UBIFS error (pid 187): ubifs_scan: corrupt empty space at LEB 36:118735 UBIFS error (pid 187): ubifs_scanned_corruption: corruption at LEB 36:118735 UBIFS error (pid 187): ubifs_scanned_corruption: first 8192 bytes from LEB 36:118735 UBIFS error (pid 187): ubifs_scan: LEB 36 scanning failed
UBIFS error (pid 187): do_commit: commit failed, error -117

---
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -1029,9 +1029,6 @@ static int gpmi_ecc_read_page(struct mtd
 		return ret;
 	}
 
-	/* handle the block mark swapping */
-	block_mark_swapping(this, payload_virt, auxiliary_virt);
-
 	/* Loop over status bytes, accumulating ECC status. */
 	status = auxiliary_virt + nfc_geo->auxiliary_status_offset;
 

@@ -1047,6 +1044,9 @@ static int gpmi_ecc_read_page(struct mtd
 		max_bitflips = max_t(unsigned int, max_bitflips, *status);
 	}
 
+	/* handle the block mark swapping */
+	block_mark_swapping(this, buf, auxiliary_virt);
+
 	if (oob_required) {
 		/*
 		 * It's time to deliver the OOB bytes. See gpmi_ecc_read_oob()

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mtd-nand-gpmi-fix-failure-when-a-erased-page-has-a-bitflip-at-bbm.patch