From 377e208f44784174f3002d9892d553715a3ab71b Mon Sep 17 00:00:00 2001
From: Richard Weinberger <richard@nod.at>
Date: Tue, 13 Aug 2019 23:55:48 +0200
Subject: [PATCH] ubifs: Correctly initialize c->min_log_bytes
Mime-version: 1.0
Content-type: text/plain; charset=UTF-8
Content-transfer-encoding: 8bit
Git-commit: 377e208f44784174f3002d9892d553715a3ab71b
Patch-mainline: v5.3-rc6
References: bsc#1158641

Currently on a freshly mounted UBIFS, c->min_log_bytes is 0.
This can lead to a log overrun and make commits fail.

Recent kernels will report the following assert:
UBIFS assert failed: c->lhead_lnum != c->ltail_lnum, in fs/ubifs/log.c:412

c->min_log_bytes can have two states, 0 and c->leb_size.
It controls how much bytes of the log area are reserved for non-bud
nodes such as commit nodes.

After a commit it has to be set to c->leb_size such that we have always
enough space for a commit. While a commit runs it can be 0 to make the
remaining bytes of the log available to writers.

Having it set to 0 right after mount is wrong since no space for commits
is reserved.

Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Reported-and-tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/ubifs/super.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 2c0803b0ac3a..8c1d571334bc 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -609,6 +609,10 @@ static int init_constants_early(struct ubifs_info *c)
 	c->max_bu_buf_len = UBIFS_MAX_BULK_READ * UBIFS_MAX_DATA_NODE_SZ;
 	if (c->max_bu_buf_len > c->leb_size)
 		c->max_bu_buf_len = c->leb_size;
+
+	/* Log is ready, preserve one LEB for commits. */
+	c->min_log_bytes = c->leb_size;
+
 	return 0;
 }
 
-- 
2.16.4