[ 3.5.y.z extended stable ] Patch "UBIFS: fix mounting problems after power cuts" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    UBIFS: fix mounting problems after power cuts

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From b478e7e4b4e4c2af6695e60bfa5223e2108a1001 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
Date: Tue, 9 Oct 2012 16:20:15 +0300
Subject: [PATCH] UBIFS: fix mounting problems after power cuts

commit a28ad42a4a0c6f302f488f26488b8b37c9b30024 upstream.

This is a bugfix for a problem with the following symptoms:

1. A power cut happens
2. After reboot, we try to mount UBIFS
3. Mount fails with "No space left on device" error message

UBIFS complains like this:

UBIFS error (pid 28225): grab_empty_leb: could not find an empty LEB

The root cause of this problem is that when we mount, not all LEBs are
categorized. Only those which were read are. However, the
'ubifs_find_free_leb_for_idx()' function assumes that all LEBs were
categorized and 'c->freeable_cnt' is valid, which is a false assumption.

This patch fixes the problem by teaching 'ubifs_find_free_leb_for_idx()'
to always fall back to LPT scanning if no freeable LEBs were found.

This problem was reported by few people in the past, but Brent Taylor
was able to reproduce it and send me a flash image which cannot be mounted,
which made it easy to hunt the bug. Kudos to Brent.

Reported-by: Brent Taylor <motobud at gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 fs/ubifs/find.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ubifs/find.c b/fs/ubifs/find.c
index 28ec13a..2dcf3d4 100644
--- a/fs/ubifs/find.c
+++ b/fs/ubifs/find.c
@@ -681,8 +681,16 @@ int ubifs_find_free_leb_for_idx(struct ubifs_info *c)
 	if (!lprops) {
 		lprops = ubifs_fast_find_freeable(c);
 		if (!lprops) {
-			ubifs_assert(c->freeable_cnt == 0);
-			if (c->lst.empty_lebs - c->lst.taken_empty_lebs > 0) {
+			/*
+			 * The first condition means the following: go scan the
+			 * LPT if there are uncategorized lprops, which means
+			 * there may be freeable LEBs there (UBIFS does not
+			 * store the information about freeable LEBs in the
+			 * master node).
+			 */
+			if (c->in_a_category_cnt != c->main_lebs ||
+			    c->lst.empty_lebs - c->lst.taken_empty_lebs > 0) {
+				ubifs_assert(c->freeable_cnt == 0);
 				lprops = scan_for_leb_for_idx(c);
 				if (IS_ERR(lprops)) {
 					err = PTR_ERR(lprops);
--
1.7.9.5