[PATCH] UBIFS: don't fail on -EBADMSG when fixing free space

[Ben Gardiner]

The free space fixup was introduced so that UBIFS on NAND flashes where the
empty pages at the end need to be dropped when flashing or else -74
(aka -EBADMSG) failures will occur -- but due to the limited functionality of
flash-programming facilities the emtpy pages cannot be dropped.

In fixup_leb, which is called during free space fixup, the now-expected return
code of -EBADMSG is treated as a failure.

Don't fail when -EBADMSG is encountered during ubi_read.

Signed-off-by: Ben Gardiner <bengardiner@xxxxxxxxxxxxxx>
CC: Matthew L. Creech <mlcreech@xxxxxxxxx>

---
I tested this patch on-top-of l2 head : 'bbf2b37 UBIFS: fix extremely rare
mount failure' using Matthew's 'mkfs.ubifs: add "-F" option for "free-space
fixup"' patch to create the UBIFS image with the flag set.

The test system was a da850evm, the image was flashed with U-boot's plain-old
'nand write' and the rootfs is mounted with 'ubi.mtd=X,2048 root=ubi0:rootfs
rootfstype=ubifs' bootargs.

Without this patch the first attemp to start fixing free space fails
with -EBADMSG:

UBIFS: start fixing up free space
UBI error: ubi_io_read: error -74 (ECC error) while reading 4096 bytes from PEB 18:4096, read 4096 bytes
VFS: Cannot open root device "ubi0:rootfs" or unknown-block(0,0)
[...]

---
 fs/ubifs/sb.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index c606f01..6e7da54 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -1,3 +1,4 @@
+#define DEBUG
 /*
  * This file is part of UBIFS.
  *
@@ -679,7 +680,12 @@ static int fixup_leb(struct ubifs_info *c, int lnum, int len)
 
 	dbg_mnt("fixup LEB %d, data len %d", lnum, len);
 	err = ubi_read(c->ubi, lnum, c->sbuf, 0, len);
-	if (err)
+	/*
+	 * Don't fail on -EBADMSG since these are precisely the error codes that
+	 * are returned by ubi_red in the cases where free-space fix-ups are
+	 * required.
+	 */
+	if (err && err != -EBADMSG)
 		return err;
 
 	return ubi_leb_change(c->ubi, lnum, c->sbuf, len, UBI_UNKNOWN);
-- 
1.7.4.1

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