1 files changed, 147 insertions, 25 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f8b4521de907..f878337cee6f 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -63,10 +63,10 @@ static void btrfs_put_super(struct super_block *sb)
 }
 
 enum {
-        Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
-        Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
-        Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl,
-        Opt_compress, Opt_compress_force, Opt_notreelog, Opt_ratio,
+        Opt_degraded, Opt_subvol, Opt_subvolid, Opt_device, Opt_nodatasum,
+        Opt_nodatacow, Opt_max_extent, Opt_max_inline, Opt_alloc_start,
+        Opt_nobarrier, Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool,
+        Opt_noacl, Opt_compress, Opt_compress_force, Opt_notreelog, Opt_ratio,
         Opt_flushoncommit,
         Opt_discard, Opt_err,
 };
@@ -74,6 +74,7 @@ enum {
 static match_table_t tokens = {
         {Opt_degraded, "degraded"},
         {Opt_subvol, "subvol=%s"},
+        {Opt_subvolid, "subvolid=%d"},
         {Opt_device, "device=%s"},
         {Opt_nodatasum, "nodatasum"},
         {Opt_nodatacow, "nodatacow"},
@@ -157,6 +158,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                         btrfs_set_opt(info->mount_opt, DEGRADED);
                         break;
                 case Opt_subvol:
+                case Opt_subvolid:
                 case Opt_device:
                         /*
                          * These are parsed by btrfs_parse_early_options
@@ -292,12 +294,13 @@ out:
  * only when we need to allocate a new super block.
  */
 static int btrfs_parse_early_options(const char *options, fmode_t flags,
-                void *holder, char **subvol_name,
+                void *holder, char **subvol_name, u64 *subvol_objectid,
                 struct btrfs_fs_devices **fs_devices)
 {
         substring_t args[MAX_OPT_ARGS];
         char *opts, *p;
         int error = 0;
+        int intarg;
 
         if (!options)
                 goto out;
@@ -320,6 +323,12 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
                 case Opt_subvol:
                         *subvol_name = match_strdup(&args[0]);
                         break;
+                case Opt_subvolid:
+                        intarg = 0;
+                        match_int(&args[0], &intarg);
+                        if (intarg)
+                                *subvol_objectid = intarg;
+                        break;
                 case Opt_device:
                         error = btrfs_scan_one_device(match_strdup(&args[0]),
                                         flags, holder, fs_devices);
@@ -347,6 +356,110 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
         return error;
 }
 
+static struct dentry *get_default_root(struct super_block *sb,
+                                       u64 subvol_objectid)
+{
+        struct btrfs_root *root = sb->s_fs_info;
+        struct btrfs_root *new_root;
+        struct btrfs_dir_item *di;
+        struct btrfs_path *path;
+        struct btrfs_key location;
+        struct inode *inode;
+        struct dentry *dentry;
+        u64 dir_id;
+        int new = 0;
+
+        /*
+         * We have a specific subvol we want to mount, just setup location and
+         * go look up the root.
+         */
+        if (subvol_objectid) {
+                location.objectid = subvol_objectid;
+                location.type = BTRFS_ROOT_ITEM_KEY;
+                location.offset = (u64)-1;
+                goto find_root;
+        }
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return ERR_PTR(-ENOMEM);
+        path->leave_spinning = 1;
+
+        /*
+         * Find the "default" dir item which points to the root item that we
+         * will mount by default if we haven't been given a specific subvolume
+         * to mount.
+         */
+        dir_id = btrfs_super_root_dir(&root->fs_info->super_copy);
+        di = btrfs_lookup_dir_item(NULL, root, path, dir_id, "default", 7, 0);
+        if (!di) {
+                /*
+                 * Ok the default dir item isn't there.  This is weird since
+                 * it's always been there, but don't freak out, just try and
+                 * mount to root most subvolume.
+                 */
+                btrfs_free_path(path);
+                dir_id = BTRFS_FIRST_FREE_OBJECTID;
+                new_root = root->fs_info->fs_root;
+                goto setup_root;
+        }
+
+        btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
+        btrfs_free_path(path);
+
+find_root:
+        new_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
+        if (IS_ERR(new_root))
+                return ERR_PTR(PTR_ERR(new_root));
+
+        if (btrfs_root_refs(&new_root->root_item) == 0)
+                return ERR_PTR(-ENOENT);
+
+        dir_id = btrfs_root_dirid(&new_root->root_item);
+setup_root:
+        location.objectid = dir_id;
+        location.type = BTRFS_INODE_ITEM_KEY;
+        location.offset = 0;
+
+        inode = btrfs_iget(sb, &location, new_root, &new);
+        if (!inode)
+                return ERR_PTR(-ENOMEM);
+
+        /*
+         * If we're just mounting the root most subvol put the inode and return
+         * a reference to the dentry.  We will have already gotten a reference
+         * to the inode in btrfs_fill_super so we're good to go.
+         */
+        if (!new && sb->s_root->d_inode == inode) {
+                iput(inode);
+                return dget(sb->s_root);
+        }
+
+        if (new) {
+                const struct qstr name = { .name = "/", .len = 1 };
+
+                /*
+                 * New inode, we need to make the dentry a sibling of s_root so
+                 * everything gets cleaned up properly on unmount.
+                 */
+                dentry = d_alloc(sb->s_root, &name);
+                if (!dentry) {
+                        iput(inode);
+                        return ERR_PTR(-ENOMEM);
+                }
+                d_splice_alias(inode, dentry);
+        } else {
+                /*
+                 * We found the inode in cache, just find a dentry for it and
+                 * put the reference to the inode we just got.
+                 */
+                dentry = d_find_alias(inode);
+                iput(inode);
+        }
+
+        return dentry;
+}
+
 static int btrfs_fill_super(struct super_block *sb,
                             struct btrfs_fs_devices *fs_devices,
                             void *data, int silent)
@@ -380,7 +493,7 @@ static int btrfs_fill_super(struct super_block *sb,
         key.objectid = BTRFS_FIRST_FREE_OBJECTID;
         key.type = BTRFS_INODE_ITEM_KEY;
         key.offset = 0;
-        inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root);
+        inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root, NULL);
         if (IS_ERR(inode)) {
                 err = PTR_ERR(inode);
                 goto fail_close;
@@ -392,12 +505,6 @@ static int btrfs_fill_super(struct super_block *sb,
                 err = -ENOMEM;
                 goto fail_close;
         }
-#if 0
-        /* this does the super kobj at the same time */
-        err = btrfs_sysfs_add_super(tree_root->fs_info);
-        if (err)
-                goto fail_close;
-#endif
 
         sb->s_root = root_dentry;
 
@@ -489,19 +596,22 @@ static int btrfs_test_super(struct super_block *s, void *data)
 static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
                 const char *dev_name, void *data, struct vfsmount *mnt)
 {
-        char *subvol_name = NULL;
         struct block_device *bdev = NULL;
         struct super_block *s;
         struct dentry *root;
         struct btrfs_fs_devices *fs_devices = NULL;
         fmode_t mode = FMODE_READ;
+        char *subvol_name = NULL;
+        u64 subvol_objectid = 0;
         int error = 0;
+        int found = 0;
 
         if (!(flags & MS_RDONLY))
                 mode |= FMODE_WRITE;
 
         error = btrfs_parse_early_options(data, mode, fs_type,
-                                          &subvol_name, &fs_devices);
+                                          &subvol_name, &subvol_objectid,
+                                          &fs_devices);
         if (error)
                 return error;
 
@@ -530,6 +640,7 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
                         goto error_close_devices;
                 }
 
+                found = 1;
                 btrfs_close_devices(fs_devices);
         } else {
                 char b[BDEVNAME_SIZE];
@@ -547,25 +658,35 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
                 s->s_flags |= MS_ACTIVE;
         }
 
-        if (!strcmp(subvol_name, "."))
-                root = dget(s->s_root);
-        else {
-                mutex_lock(&s->s_root->d_inode->i_mutex);
-                root = lookup_one_len(subvol_name, s->s_root,
+        root = get_default_root(s, subvol_objectid);
+        if (IS_ERR(root)) {
+                error = PTR_ERR(root);
+                deactivate_locked_super(s);
+                goto error;
+        }
+        /* if they gave us a subvolume name bind mount into that */
+        if (strcmp(subvol_name, ".")) {
+                struct dentry *new_root;
+                mutex_lock(&root->d_inode->i_mutex);
+                new_root = lookup_one_len(subvol_name, root,
                                       strlen(subvol_name));
-                mutex_unlock(&s->s_root->d_inode->i_mutex);
+                mutex_unlock(&root->d_inode->i_mutex);
 
-                if (IS_ERR(root)) {
+                if (IS_ERR(new_root)) {
                         deactivate_locked_super(s);
-                        error = PTR_ERR(root);
-                        goto error_free_subvol_name;
+                        error = PTR_ERR(new_root);
+                        dput(root);
+                        goto error_close_devices;
                 }
-                if (!root->d_inode) {
+                if (!new_root->d_inode) {
                         dput(root);
+                        dput(new_root);
                         deactivate_locked_super(s);
                         error = -ENXIO;
-                        goto error_free_subvol_name;
+                        goto error_close_devices;
                 }
+                dput(root);
+                root = new_root;
         }
 
         mnt->mnt_sb = s;
@@ -580,6 +701,7 @@ error_close_devices:
         btrfs_close_devices(fs_devices);
 error_free_subvol_name:
         kfree(subvol_name);
+error:
         return error;
 }