btrfs: allow scanning multiple devices during mount

Allows to specify one or multiple device=/dev/foo options during mount
so that ioctls on the control device can be avoided.  Especially useful
when trying to mount a multi-device setup as root.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 16 insertions, 5 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 288300fa5848..346932e546ba 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -65,7 +65,7 @@ static void btrfs_put_super (struct super_block * sb)
 }
 
 enum {
-        Opt_degraded, Opt_subvol, Opt_nodatasum, Opt_nodatacow,
+        Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
         Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
         Opt_ssd, Opt_err,
 };
@@ -73,6 +73,7 @@ enum {
 static match_table_t tokens = {
         {Opt_degraded, "degraded"},
         {Opt_subvol, "subvol=%s"},
+        {Opt_device, "device=%s"},
         {Opt_nodatasum, "nodatasum"},
         {Opt_nodatacow, "nodatacow"},
         {Opt_nobarrier, "nobarrier"},
@@ -142,8 +143,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                         btrfs_set_opt(info->mount_opt, DEGRADED);
                         break;
                 case Opt_subvol:
+                case Opt_device:
                         /*
-                         * This one is parsed by btrfs_parse_early_options
+                         * These are parsed by btrfs_parse_early_options
                          * and can be happily ignored here.
                          */
                         break;
@@ -212,8 +214,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
  * All other options will be parsed on much later in the mount process and
  * only when we need to allocate a new super block.
  */
-static int btrfs_parse_early_options(const char *options,
-                        char **subvol_name)
+static int btrfs_parse_early_options(const char *options, int flags,
+                void *holder, char **subvol_name,
+                struct btrfs_fs_devices **fs_devices)
 {
         substring_t args[MAX_OPT_ARGS];
         char *opts, *p;
@@ -240,11 +243,18 @@ static int btrfs_parse_early_options(const char *options,
                 case Opt_subvol:
                         *subvol_name = match_strdup(&args[0]);
                         break;
+                case Opt_device:
+                        error = btrfs_scan_one_device(match_strdup(&args[0]),
+                                        flags, holder, fs_devices);
+                        if (error)
+                                goto out_free_opts;
+                        break;
                 default:
                         break;
                 }
         }
 
+ out_free_opts:
         kfree(opts);
  out:
         /*
@@ -380,7 +390,8 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
         struct btrfs_fs_devices *fs_devices = NULL;
         int error = 0;
 
-        error = btrfs_parse_early_options(data, &subvol_name);
+        error = btrfs_parse_early_options(data, flags, fs_type,
+                                          &subvol_name, &fs_devices);
         if (error)
                 goto error;