Btrfs: mount ro and remount support

This patch adds mount ro and remount support. The main
changes in patch are: adding btrfs_remount and related
helper function; splitting the transaction related code
out of close_ctree into btrfs_commit_super; updating
allocator to properly handle read only block group.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 35 insertions, 2 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ab9d5e89ed13..04a3bf816509 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -370,6 +370,9 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
         int ret;
         root = btrfs_sb(sb);
 
+        if (sb->s_flags & MS_RDONLY)
+                return 0;
+
         sb->s_dirt = 0;
         if (!wait) {
                 filemap_flush(root->fs_info->btree_inode->i_mapping);
@@ -438,7 +441,7 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
                         up_write(&s->s_umount);
                         deactivate_super(s);
                         error = -EBUSY;
-                        goto error_bdev;
+                        goto error_close_devices;
                 }
 
         } else {
@@ -487,7 +490,7 @@ static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
 
 error_s:
         error = PTR_ERR(s);
-error_bdev:
+error_close_devices:
         btrfs_close_devices(fs_devices);
 error_free_subvol_name:
         kfree(subvol_name);
@@ -495,6 +498,35 @@ error:
         return error;
 }
 
+static int btrfs_remount(struct super_block *sb, int *flags, char *data)
+{
+        struct btrfs_root *root = btrfs_sb(sb);
+        int ret;
+
+        if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
+                return 0;
+
+        if (*flags & MS_RDONLY) {
+                sb->s_flags |= MS_RDONLY;
+
+                ret =  btrfs_commit_super(root);
+                WARN_ON(ret);
+        } else {
+                if (btrfs_super_log_root(&root->fs_info->super_copy) != 0)
+                        return -EINVAL;
+
+                ret = btrfs_cleanup_reloc_trees(root);
+                WARN_ON(ret);
+
+                ret = btrfs_cleanup_fs_roots(root->fs_info);
+                WARN_ON(ret);
+
+                sb->s_flags &= ~MS_RDONLY;
+        }
+
+        return 0;
+}
+
 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
         struct btrfs_root *root = btrfs_sb(dentry->d_sb);
@@ -582,6 +614,7 @@ static struct super_operations btrfs_super_ops = {
         .alloc_inode    = btrfs_alloc_inode,
         .destroy_inode  = btrfs_destroy_inode,
         .statfs         = btrfs_statfs,
+        .remount_fs     = btrfs_remount,
         .write_super_lockfs = btrfs_write_super_lockfs,
         .unlockfs       = btrfs_unlockfs,
 };