nfs42: add NFS_IOC_CLONE ioctl

It can be called by user space to CLONE two files.
Follow btrfs lead and define NFS_IOC_CLONE same as BTRFS_IOC_CLONE.
Thus we don't mess up userspace with too many ioctls.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

2 files changed, 106 insertions, 0 deletions

diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index b0dbe0abed53..fc68ba5f030c 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -4,6 +4,7 @@
  *  Copyright (C) 1992  Rick Sladkey
  */
 #include <linux/fs.h>
+#include <linux/file.h>
 #include <linux/falloc.h>
 #include <linux/nfs_fs.h>
 #include "delegation.h"
@@ -192,8 +193,104 @@ static long nfs42_fallocate(struct file *filep, int mode, loff_t offset, loff_t
                 return nfs42_proc_deallocate(filep, offset, len);
         return nfs42_proc_allocate(filep, offset, len);
 }
+
+static noinline long
+nfs42_ioctl_clone(struct file *dst_file, unsigned long srcfd,
+                  u64 src_off, u64 dst_off, u64 count)
+{
+        struct inode *dst_inode = file_inode(dst_file);
+        struct fd src_file;
+        struct inode *src_inode;
+        int ret;
+
+        /* dst file must be opened for writing */
+        if (!(dst_file->f_mode & FMODE_WRITE))
+                return -EINVAL;
+
+        ret = mnt_want_write_file(dst_file);
+        if (ret)
+                return ret;
+
+        src_file = fdget(srcfd);
+        if (!src_file.file) {
+                ret = -EBADF;
+                goto out_drop_write;
+        }
+
+        src_inode = file_inode(src_file.file);
+
+        /* src and dst must be different files */
+        ret = -EINVAL;
+        if (src_inode == dst_inode)
+                goto out_fput;
+
+        /* src file must be opened for reading */
+        if (!(src_file.file->f_mode & FMODE_READ))
+                goto out_fput;
+
+        /* src and dst must be regular files */
+        ret = -EISDIR;
+        if (!S_ISREG(src_inode->i_mode) || !S_ISREG(dst_inode->i_mode))
+                goto out_fput;
+
+        ret = -EXDEV;
+        if (src_file.file->f_path.mnt != dst_file->f_path.mnt ||
+            src_inode->i_sb != dst_inode->i_sb)
+                goto out_fput;
+
+        /* XXX: do we lock at all? what if server needs CB_RECALL_LAYOUT? */
+        if (dst_inode < src_inode) {
+                mutex_lock_nested(&dst_inode->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_CHILD);
+        } else {
+                mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&dst_inode->i_mutex, I_MUTEX_CHILD);
+        }
+
+        /* flush all pending writes on both src and dst so that server
+         * has the latest data */
+        ret = nfs_sync_inode(src_inode);
+        if (ret)
+                goto out_unlock;
+        ret = nfs_sync_inode(dst_inode);
+        if (ret)
+                goto out_unlock;
+
+        ret = nfs42_proc_clone(src_file.file, dst_file, src_off, dst_off, count);
+
+        /* truncate inode page cache of the dst range so that future reads can fetch
+         * new data from server */
+        if (!ret)
+                truncate_inode_pages_range(&dst_inode->i_data, dst_off, dst_off + count - 1);
+
+out_unlock:
+        if (dst_inode < src_inode) {
+                mutex_unlock(&src_inode->i_mutex);
+                mutex_unlock(&dst_inode->i_mutex);
+        } else {
+                mutex_unlock(&dst_inode->i_mutex);
+                mutex_unlock(&src_inode->i_mutex);
+        }
+out_fput:
+        fdput(src_file);
+out_drop_write:
+        mnt_drop_write_file(dst_file);
+        return ret;
+}
 #endif /* CONFIG_NFS_V4_2 */
 
+long nfs4_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        switch (cmd) {
+#ifdef CONFIG_NFS_V4_2
+        case NFS_IOC_CLONE:
+                return nfs42_ioctl_clone(file, arg, 0, 0, 0);
+#endif
+        }
+
+        return -ENOTTY;
+}
+
 const struct file_operations nfs4_file_operations = {
 #ifdef CONFIG_NFS_V4_2
         .llseek         = nfs4_file_llseek,
@@ -216,4 +313,9 @@ const struct file_operations nfs4_file_operations = {
 #endif /* CONFIG_NFS_V4_2 */
         .check_flags    = nfs_check_flags,
         .setlease       = simple_nosetlease,
+#ifdef CONFIG_COMPAT
+        .unlocked_ioctl = nfs4_ioctl,
+#else
+        .compat_ioctl   = nfs4_ioctl,
+#endif /* CONFIG_COMPAT */
 };
diff --git a/include/uapi/linux/nfs.h b/include/uapi/linux/nfs.h
index 5199a36dd574..d85748d3564d 100644
--- a/include/uapi/linux/nfs.h
+++ b/include/uapi/linux/nfs.h
@@ -31,6 +31,10 @@
 
 #define NFS_PIPE_DIRNAME "nfs"
 
+/* NFS ioctls */
+/* Let's follow btrfs lead on CLONE to avoid messing userspace */
+#define NFS_IOC_CLONE   _IOW(0x94, 9, int)
+
 /*
  * NFS stats. The good thing with these values is that NFSv3 errors are
  * a superset of NFSv2 errors (with the exception of NFSERR_WFLUSH which