Btrfs: Use mount -o subvol to select the subvol directory instead of dev:

Signed-off-by: Chris Mason <chris.mason@oracle.com>

2 files changed, 45 insertions, 10 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ffeee546a0d7..cd75c906048f 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1064,6 +1064,12 @@ static inline int btrfs_set_root_name(struct btrfs_root *root,
         ((type *)(btrfs_leaf_data(leaf) + \
         btrfs_item_offset((leaf)->items + (slot))))
 
+/* mount option defines and helpers */
+#define BTRFS_MOUNT_SUBVOL              0x000001
+#define btrfs_clear_opt(o, opt)         o &= ~BTRFS_MOUNT_##opt
+#define btrfs_set_opt(o, opt)           o |= BTRFS_MOUNT_##opt
+#define btrfs_test_opt(sb, opt)         (BTRFS_SB(sb)->s_mount_opt & \
+                                         BTRFS_MOUNT_##opt)
 /* extent-tree.c */
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8a94be1a773b..66a01cbbbea1 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -33,6 +33,7 @@
 #include <linux/writeback.h>
 #include <linux/statfs.h>
 #include <linux/compat.h>
+#include <linux/parser.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -58,6 +59,41 @@ static void btrfs_put_super (struct super_block * sb)
         sb->s_fs_info = NULL;
 }
 
+enum {
+        Opt_subvol, Opt_err,
+};
+
+static match_table_t tokens = {
+        {Opt_subvol, "subvol=%s"},
+        {Opt_err, NULL}
+};
+
+static int parse_options (char * options,
+                          struct btrfs_root *root,
+                          char **subvol_name)
+{
+        char * p;
+        substring_t args[MAX_OPT_ARGS];
+        if (!options)
+                return 1;
+
+        while ((p = strsep (&options, ",")) != NULL) {
+                int token;
+                if (!*p)
+                        continue;
+
+                token = match_token(p, tokens, args);
+                switch (token) {
+                case Opt_subvol:
+                        *subvol_name = match_strdup(&args[0]);
+                        break;
+                default:
+                        return 0;
+                }
+        }
+        return 1;
+}
+
 static int btrfs_fill_super(struct super_block * sb, void * data, int silent)
 {
         struct inode * inode;
@@ -250,22 +286,15 @@ error:
 /* end copy & paste */
 
 static int btrfs_get_sb(struct file_system_type *fs_type,
-        int flags, const char *identifier, void *data, struct vfsmount *mnt)
+        int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
         int ret;
-        char *_identifier = kstrdup(identifier, GFP_KERNEL);
-        char *subvol_name;
-        const char *dev_name;
-
-        subvol_name = _identifier;
-        dev_name = strsep(&subvol_name, ":");
-        if (!dev_name)
-                return -ENOMEM;
+        char *subvol_name = NULL;
 
+        parse_options((char *)data, NULL, &subvol_name);
         ret = btrfs_get_sb_bdev(fs_type, flags, dev_name, data,
                         btrfs_fill_super, mnt,
                         subvol_name ? subvol_name : "default");
-        kfree(_identifier);
         return ret;
 }