[PATCH 1/2] UBIFS: add debugfs knob to switch to R/O mode

[PATCH 1/2] UBIFS: add debugfs knob to switch to R/O mode

[Artem Bityutskiy]

From: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>

This patch adds another debugfs knob which switches UBIFS to R/O mode.
I needed it while trying to reproduce the 'first log node is not CS node'
bug. Without this debugfs knob you have to perform a power cut to repruduce
the bug. The knob is named 'ro_error' and all it does is it sets the
'ro_error' UBIFS flag which makes UBIFS disallow any further writes - even
write-back will fail with -EROFS. Useful for debugging.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
---
 fs/ubifs/debug.c |   11 +++++++++++
 fs/ubifs/debug.h |    5 +++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 92df3b0..bb31672 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -2802,6 +2802,8 @@ static ssize_t dfs_file_read(struct file *file, char __user *u, size_t count,
 		val = d->chk_fs;
 	else if (dent == d->dfs_tst_rcvry)
 		val = d->tst_rcvry;
+	else if (dent == d->dfs_ro_error)
+		val = c->ro_error;
 	else
 		return -EINVAL;
 
@@ -2885,6 +2887,8 @@ static ssize_t dfs_file_write(struct file *file, const char __user *u,
 		d->chk_fs = val;
 	else if (dent == d->dfs_tst_rcvry)
 		d->tst_rcvry = val;
+	else if (dent == d->dfs_ro_error)
+		c->ro_error = !!val;
 	else
 		return -EINVAL;
 
@@ -2996,6 +3000,13 @@ int dbg_debugfs_init_fs(struct ubifs_info *c)
 		goto out_remove;
 	d->dfs_tst_rcvry = dent;
 
+	fname = "ro_error";
+	dent = debugfs_create_file(fname, S_IRUSR | S_IWUSR, d->dfs_dir, c,
+				   &dfs_fops);
+	if (IS_ERR_OR_NULL(dent))
+		goto out_remove;
+	d->dfs_ro_error = dent;
+
 	return 0;
 
 out_remove:
diff --git a/fs/ubifs/debug.h b/fs/ubifs/debug.h
index 486a8e0..8b8cc4e 100644
--- a/fs/ubifs/debug.h
+++ b/fs/ubifs/debug.h
@@ -79,6 +79,10 @@ typedef int (*dbg_znode_callback)(struct ubifs_info *c,
  * @dfs_chk_lprops: debugfs knob to enable UBIFS LEP properties extra checks
  * @dfs_chk_fs: debugfs knob to enable UBIFS contents extra checks
  * @dfs_tst_rcvry: debugfs knob to enable UBIFS recovery testing
+ * @dfs_ro_error: debugfs knob to switch UBIFS to R/O mode (different to
+ *                re-mounting to R/O mode because it does not flush any buffers
+ *                and UBIFS just starts returning -EROFS on all write
+ *               operations)
  */
 struct ubifs_debug_info {
 	struct ubifs_zbranch old_zroot;
@@ -122,6 +126,7 @@ struct ubifs_debug_info {
 	struct dentry *dfs_chk_lprops;
 	struct dentry *dfs_chk_fs;
 	struct dentry *dfs_tst_rcvry;
+	struct dentry *dfs_ro_error;
 };
 
 /**
-- 
1.7.7.6

[PATCH 2/2] UBIFS: simplify reply code a bit

[Artem Bityutskiy]

From: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>

In the log reply code we assume that 'c->lhead_offs' is known and may be
non-zero, which is not the case because we do not store it in the master
node and have to find out by scanning on every mount. Knowing this fact
allows us to simplify the log scanning loop a bit and remove a couple
of unneeded local variables.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
---
 fs/ubifs/replay.c |   20 ++++++--------------
 1 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/fs/ubifs/replay.c b/fs/ubifs/replay.c
index 3a2da7e..eba46d4 100644
--- a/fs/ubifs/replay.c
+++ b/fs/ubifs/replay.c
@@ -1007,7 +1007,7 @@ out:
  */
 int ubifs_replay_journal(struct ubifs_info *c)
 {
-	int err, i, lnum, offs, free;
+	int err, lnum, free;
 
 	BUILD_BUG_ON(UBIFS_TRUN_KEY > 5);
 
@@ -1025,25 +1025,17 @@ int ubifs_replay_journal(struct ubifs_info *c)
 	dbg_mnt("start replaying the journal");
 	c->replaying = 1;
 	lnum = c->ltail_lnum = c->lhead_lnum;
-	offs = c->lhead_offs;
 
-	for (i = 0; i < c->log_lebs; i++, lnum++) {
-		if (lnum >= UBIFS_LOG_LNUM + c->log_lebs) {
-			/*
-			 * The log is logically circular, we reached the last
-			 * LEB, switch to the first one.
-			 */
-			lnum = UBIFS_LOG_LNUM;
-			offs = 0;
-		}
-		err = replay_log_leb(c, lnum, offs, c->sbuf);
+	lnum = UBIFS_LOG_LNUM;
+	do {
+		err = replay_log_leb(c, lnum, 0, c->sbuf);
 		if (err == 1)
 			/* We hit the end of the log */
 			break;
 		if (err)
 			goto out;
-		offs = 0;
-	}
+		lnum = ubifs_next_log_lnum(c, lnum);
+	} while (lnum != UBIFS_LOG_LNUM);
 
 	err = replay_buds(c);
 	if (err)
-- 
1.7.7.6