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>

1 files changed, 13 insertions, 3 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ee36009f8aa1..12b18c01b911 100644
--- 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: