UBIFS: increment commit number earlier

Increment the commit number at the beginnig of the commit, instead
of doing this after the commit. This is needed for further
optimizations.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/commit.c

@@ -74,6 +74,7 @@ static int do_commit(struct ubifs_info *c)
 			goto out_up;
 	}
 
+	c->cmt_no += 1;
 	err = ubifs_gc_start_commit(c);
 	if (err)
 		goto out_up;
@@ -115,7 +116,7 @@ static int do_commit(struct ubifs_info *c)
 		goto out;
 
 	mutex_lock(&c->mst_mutex);
-	c->mst_node->cmt_no      = cpu_to_le64(++c->cmt_no);
+	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);
 	c->mst_node->root_offs   = cpu_to_le32(zroot.offs);

fs/ubifs/log.c

@@ -412,7 +412,7 @@ int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
 		return -ENOMEM;
 
 	cs->ch.node_type = UBIFS_CS_NODE;
-	cs->cmt_no = cpu_to_le64(c->cmt_no + 1);
+	cs->cmt_no = cpu_to_le64(c->cmt_no);
 	ubifs_prepare_node(c, cs, UBIFS_CS_NODE_SZ, 0);
 
 	/*

fs/ubifs/orphan.c

@@ -310,10 +310,10 @@ static int write_orph_node(struct ubifs_info *c, int atomic)
 	c->cmt_orphans -= cnt;
 	spin_unlock(&c->orphan_lock);
 	if (c->cmt_orphans)
-		orph->cmt_no = cpu_to_le64(c->cmt_no + 1);
+		orph->cmt_no = cpu_to_le64(c->cmt_no);
 	else
 		/* Mark the last node of the commit */
-		orph->cmt_no = cpu_to_le64((c->cmt_no + 1) | (1ULL << 63));
+		orph->cmt_no = cpu_to_le64((c->cmt_no) | (1ULL << 63));
 	ubifs_assert(c->ohead_offs + len <= c->leb_size);
 	ubifs_assert(c->ohead_lnum >= c->orph_first);
 	ubifs_assert(c->ohead_lnum <= c->orph_last);

fs/ubifs/ubifs.h

@@ -865,7 +865,8 @@ struct ubifs_mount_opts {
  * @highest_inum: highest used inode number
  * @vfs_gen: VFS inode generation counter
  * @max_sqnum: current global sequence number
- * @cmt_no: commit number (last successfully completed commit)
+ * @cmt_no: commit number of the last successfully completed commit, protected
+ *          by @commit_sem
  * @cnt_lock: protects @highest_inum, @vfs_gen, and @max_sqnum counters
  * @fmt_version: UBIFS on-flash format version
  * @uuid: UUID from super block