[3.16.y-ckt stable] Patch "UBIFS: remove mst_mutex" has been added to staging queue

[Luis Henriques]

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

    UBIFS: remove mst_mutex

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a342c13312f529d625ea038bf6db1bb098b0b743 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
Date: Sun, 29 Jun 2014 16:55:02 +0300
Subject: UBIFS: remove mst_mutex

commit 07e19dff63e3d5d6500d831e36554ac9b1b0560e upstream.

The 'mst_mutex' is not needed since because 'ubifs_write_master()' is only
called on the mount path and commit path. The mount path is sequential and
there is no parallelism, and the commit path is also serialized - there is only
one commit going on at a time.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ubifs/commit.c | 2 --
 fs/ubifs/master.c | 7 +++----
 fs/ubifs/super.c  | 1 -
 fs/ubifs/ubifs.h  | 2 --
 4 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/fs/ubifs/commit.c b/fs/ubifs/commit.c
index ff8229340cd5..aa13ad053b14 100644
--- a/fs/ubifs/commit.c
+++ b/fs/ubifs/commit.c
@@ -174,7 +174,6 @@ static int do_commit(struct ubifs_info *c)
 	if (err)
 		goto out;

-	mutex_lock(&c->mst_mutex);
 	c->mst_node->cmt_no      = cpu_to_le64(c->cmt_no);
 	c->mst_node->log_lnum    = cpu_to_le32(new_ltail_lnum);
 	c->mst_node->root_lnum   = cpu_to_le32(zroot.lnum);
@@ -204,7 +203,6 @@ static int do_commit(struct ubifs_info *c)
 	else
 		c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_NO_ORPHS);
 	err = ubifs_write_master(c);
-	mutex_unlock(&c->mst_mutex);
 	if (err)
 		goto out;

diff --git a/fs/ubifs/master.c b/fs/ubifs/master.c
index ab83ace9910a..1a4bb9e8b3b8 100644
--- a/fs/ubifs/master.c
+++ b/fs/ubifs/master.c
@@ -352,10 +352,9 @@ int ubifs_read_master(struct ubifs_info *c)
  * ubifs_write_master - write master node.
  * @c: UBIFS file-system description object
  *
- * This function writes the master node. The caller has to take the
- * @c->mst_mutex lock before calling this function. Returns zero in case of
- * success and a negative error code in case of failure. The master node is
- * written twice to enable recovery.
+ * This function writes the master node. Returns zero in case of success and a
+ * negative error code in case of failure. The master node is written twice to
+ * enable recovery.
  */
 int ubifs_write_master(struct ubifs_info *c)
 {
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 3904c8574ef9..eb25aa9d7710 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1963,7 +1963,6 @@ static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi)
 		mutex_init(&c->lp_mutex);
 		mutex_init(&c->tnc_mutex);
 		mutex_init(&c->log_mutex);
-		mutex_init(&c->mst_mutex);
 		mutex_init(&c->umount_mutex);
 		mutex_init(&c->bu_mutex);
 		mutex_init(&c->write_reserve_mutex);
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index c1f71fe17cc0..2a18270b02c0 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1051,7 +1051,6 @@ struct ubifs_debug_info;
  *
  * @mst_node: master node
  * @mst_offs: offset of valid master node
- * @mst_mutex: protects the master node area, @mst_node, and @mst_offs
  *
  * @max_bu_buf_len: maximum bulk-read buffer length
  * @bu_mutex: protects the pre-allocated bulk-read buffer and @c->bu
@@ -1292,7 +1291,6 @@ struct ubifs_info {

 	struct ubifs_mst_node *mst_node;
 	int mst_offs;
-	struct mutex mst_mutex;

 	int max_bu_buf_len;
 	struct mutex bu_mutex;
--
2.1.0