UBIFS: allow sync option in rootflags

When passing UBIFS parameters via kernel command line, the
sync option will be passed to UBIFS as a string, not as an
MS_SYNCHRONOUS flag. Teach UBIFS interpreting this flag.

Reported-by: Aurélien GÉRÔME <ag@debian.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 35 insertions, 5 deletions

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 42b818daa162..d10fc88c7bbd 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -940,6 +940,27 @@ static const match_table_t tokens = {
 };
 
 /**
+ * parse_standard_option - parse a standard mount option.
+ * @option: the option to parse
+ *
+ * Normally, standard mount options like "sync" are passed to file-systems as
+ * flags. However, when a "rootflags=" kernel boot parameter is used, they may
+ * be present in the options string. This function tries to deal with this
+ * situation and parse standard options. Returns 0 if the option was not
+ * recognized, and the corresponding integer flag if it was.
+ *
+ * UBIFS is only interested in the "sync" option, so do not check for anything
+ * else.
+ */
+static int parse_standard_option(const char *option)
+{
+        ubifs_msg("parse %s", option);
+        if (!strcmp(option, "sync"))
+                return MS_SYNCHRONOUS;
+        return 0;
+}
+
+/**
  * ubifs_parse_options - parse mount parameters.
  * @c: UBIFS file-system description object
  * @options: parameters to parse
@@ -1015,9 +1036,19 @@ static int ubifs_parse_options(struct ubifs_info *c, char *options,
                         break;
                 }
                 default:
-                        ubifs_err("unrecognized mount option \"%s\" "
-                                  "or missing value", p);
-                        return -EINVAL;
+                {
+                        unsigned long flag;
+                        struct super_block *sb = c->vfs_sb;
+
+                        flag = parse_standard_option(p);
+                        if (!flag) {
+                                ubifs_err("unrecognized mount option \"%s\" "
+                                          "or missing value", p);
+                                return -EINVAL;
+                        }
+                        sb->s_flags |= flag;
+                        break;
+                }
                 }
         }
 
@@ -1908,6 +1939,7 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
         INIT_LIST_HEAD(&c->orph_list);
         INIT_LIST_HEAD(&c->orph_new);
 
+        c->vfs_sb = sb;
         c->highest_inum = UBIFS_FIRST_INO;
         c->lhead_lnum = c->ltail_lnum = UBIFS_LOG_LNUM;
 
@@ -1939,8 +1971,6 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
         if (err)
                 goto out_bdi;
 
-        c->vfs_sb = sb;
-
         sb->s_fs_info = c;
         sb->s_magic = UBIFS_SUPER_MAGIC;
         sb->s_blocksize = UBIFS_BLOCK_SIZE;