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, 22 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4d7cc7c504d..52863cebd59 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -378,6 +378,9 @@ static int btrfs_ioctl_resize(struct btrfs_root *root, void __user *arg)
 	int namelen;
 	int mod = 0;
 
+	if (root->fs_info->sb->s_flags & MS_RDONLY)
+		return -EROFS;
+
 	vol_args = kmalloc(sizeof(*vol_args), GFP_NOFS);
 
 	if (!vol_args)
@@ -478,6 +481,9 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
 	int namelen;
 	int ret;
 
+	if (root->fs_info->sb->s_flags & MS_RDONLY)
+		return -EROFS;
+
 	vol_args = kmalloc(sizeof(*vol_args), GFP_NOFS);
 
 	if (!vol_args)
@@ -534,6 +540,11 @@ static int btrfs_ioctl_defrag(struct file *file)
 {
 	struct inode *inode = fdentry(file)->d_inode;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+
+	ret = mnt_want_write(file->f_path.mnt);
+	if (ret)
+		return ret;
 
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFDIR:
@@ -575,6 +586,9 @@ long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)
 	struct btrfs_ioctl_vol_args *vol_args;
 	int ret;
 
+	if (root->fs_info->sb->s_flags & MS_RDONLY)
+		return -EROFS;
+
 	vol_args = kmalloc(sizeof(*vol_args), GFP_NOFS);
 
 	if (!vol_args)
@@ -621,6 +635,10 @@ long btrfs_ioctl_clone(struct file *file, unsigned long srcfd, u64 off,
 	 *   they don't overlap)?
 	 */
 
+	ret = mnt_want_write(file->f_path.mnt);
+	if (ret)
+		return ret;
+
 	src_file = fget(srcfd);
 	if (!src_file)
 		return -EBADF;
@@ -958,6 +976,10 @@ long btrfs_ioctl_trans_start(struct file *file)
 		goto out;
 	}
 
+	ret = mnt_want_write(file->f_path.mnt);
+	if (ret)
+		goto out;
+
 	mutex_lock(&root->fs_info->trans_mutex);
 	root->fs_info->open_ioctl_trans++;
 	mutex_unlock(&root->fs_info->trans_mutex);