ext4: hook the ext3 migration interface to the EXT4_IOC_SETFLAGS ioctl

This patch hooks the ext3 to ext4 migrate interface to
EXT4_IOC_SETFLAGS ioctl. The userspace interface is via chattr +e.  We
only allow setting extent flags.  Clearing extent flag (migrating from
ext4 to ext3) is not supported.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 16 insertions, 1 deletions

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 9f3044ac6994..3e14060b398e 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -34,7 +34,7 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 return put_user(flags, (int __user *) arg);
         case EXT4_IOC_SETFLAGS: {
                 handle_t *handle = NULL;
-                int err;
+                int err, migrate = 0;
                 struct ext4_iloc iloc;
                 unsigned int oldflags;
                 unsigned int jflag;
@@ -82,6 +82,17 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                         if (!capable(CAP_SYS_RESOURCE))
                                 goto flags_out;
                 }
+                if (oldflags & EXT4_EXTENTS_FL) {
+                        /* We don't support clearning extent flags */
+                        if (!(flags & EXT4_EXTENTS_FL)) {
+                                err = -EOPNOTSUPP;
+                                goto flags_out;
+                        }
+                } else if (flags & EXT4_EXTENTS_FL) {
+                        /* migrate the file */
+                        migrate = 1;
+                        flags &= ~EXT4_EXTENTS_FL;
+                }
 
                 handle = ext4_journal_start(inode, 1);
                 if (IS_ERR(handle)) {
@@ -109,6 +120,10 @@ flags_err:
 
                 if ((jflag ^ oldflags) & (EXT4_JOURNAL_DATA_FL))
                         err = ext4_change_inode_journal_flag(inode, jflag);
+                if (err)
+                        goto flags_out;
+                if (migrate)
+                        err = ext4_ext_migrate(inode);
 flags_out:
                 mutex_unlock(&inode->i_mutex);
                 mnt_drop_write(filp->f_path.mnt);