1 files changed, 9 insertions, 0 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ae98269a5e3af..6c18bad53cd3e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2544,6 +2544,15 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 			goto out;
 		}
 
+		/*
+		 * Don't allow defrag on pre-content watched files, as it could
+		 * populate the page cache with 0's via readahead.
+		 */
+		if (unlikely(FMODE_FSNOTIFY_HSM(file->f_mode))) {
+			ret = -EINVAL;
+			goto out;
+		}
+
 		if (argp) {
 			if (copy_from_user(&range, argp, sizeof(range))) {
 				ret = -EFAULT;