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 4d7cc7c504d0..52863cebd594 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);