1 files changed, 27 insertions, 4 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 38e3d6ab89d3..4d7f4bbf4c96 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -181,6 +181,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
         int ret;
         u64 ip_oldflags;
         unsigned int i_oldflags;
+        umode_t mode;
 
         if (btrfs_root_readonly(root))
                 return -EROFS;
@@ -203,6 +204,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 
         ip_oldflags = ip->flags;
         i_oldflags = inode->i_flags;
+        mode = inode->i_mode;
 
         flags = btrfs_mask_flags(inode->i_mode, flags);
         oldflags = btrfs_flags_to_ioctl(ip->flags);
@@ -237,10 +239,31 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
                 ip->flags |= BTRFS_INODE_DIRSYNC;
         else
                 ip->flags &= ~BTRFS_INODE_DIRSYNC;
-        if (flags & FS_NOCOW_FL)
-                ip->flags |= BTRFS_INODE_NODATACOW;
-        else
-                ip->flags &= ~BTRFS_INODE_NODATACOW;
+        if (flags & FS_NOCOW_FL) {
+                if (S_ISREG(mode)) {
+                        /*
+                         * It's safe to turn csums off here, no extents exist.
+                         * Otherwise we want the flag to reflect the real COW
+                         * status of the file and will not set it.
+                         */
+                        if (inode->i_size == 0)
+                                ip->flags |= BTRFS_INODE_NODATACOW
+                                           | BTRFS_INODE_NODATASUM;
+                } else {
+                        ip->flags |= BTRFS_INODE_NODATACOW;
+                }
+        } else {
+                /*
+                 * Revert back under same assuptions as above
+                 */
+                if (S_ISREG(mode)) {
+                        if (inode->i_size == 0)
+                                ip->flags &= ~(BTRFS_INODE_NODATACOW
+                                             | BTRFS_INODE_NODATASUM);
+                } else {
+                        ip->flags &= ~BTRFS_INODE_NODATACOW;
+                }
+        }
 
         /*
          * The COMPRESS flag can only be changed by users, while the NOCOMPRESS