Btrfs: get write access for scrub

We need get write access for scrub, or we will modify the R/O fs.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ee36009..12b18c0 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3127,10 +3127,11 @@ static noinline long btrfs_ioctl_wait_sync(struct btrfs_root *root,
        return btrfs_wait_for_commit(root, transid);
 }
 
-static long btrfs_ioctl_scrub(struct btrfs_root *root, void __user *arg)
+static long btrfs_ioctl_scrub(struct file *file, void __user *arg)
 {
-       int ret;
+       struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
        struct btrfs_ioctl_scrub_args *sa;
+       int ret;
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
@@ -3139,6 +3140,12 @@ static long btrfs_ioctl_scrub(struct btrfs_root *root, void __user *arg)
        if (IS_ERR(sa))
                return PTR_ERR(sa);
 
+       if (!(sa->flags & BTRFS_SCRUB_READONLY)) {
+               ret = mnt_want_write_file(file);
+               if (ret)
+                       goto out;
+       }
+
        ret = btrfs_scrub_dev(root->fs_info, sa->devid, sa->start, sa->end,
                              &sa->progress, sa->flags & BTRFS_SCRUB_READONLY,
                              0);
@@ -3146,6 +3153,9 @@ static long btrfs_ioctl_scrub(struct btrfs_root *root, void __user *arg)
        if (copy_to_user(arg, sa, sizeof(*sa)))
                ret = -EFAULT;
 
+       if (!(sa->flags & BTRFS_SCRUB_READONLY))
+               mnt_drop_write_file(file);
+out:
        kfree(sa);
        return ret;
 }
@@ -3879,7 +3889,7 @@ long btrfs_ioctl(struct file *file, unsigned int
        case BTRFS_IOC_WAIT_SYNC:
                return btrfs_ioctl_wait_sync(root, argp);
        case BTRFS_IOC_SCRUB:
-               return btrfs_ioctl_scrub(root, argp);
+               return btrfs_ioctl_scrub(file, argp);
        case BTRFS_IOC_SCRUB_CANCEL:
                return btrfs_ioctl_scrub_cancel(root, argp);
        case BTRFS_IOC_SCRUB_PROGRESS: