[PATCH v8 01/11] VFS: move cross device copy_file_range() check into filesystems

[Olga Kornievskaia <olga.kornievskaia@gmail.com>]

From: Olga Kornievskaia <kolga@netapp.com>

This patch makes it the responsibility of individual filesystems to
allow or deny cross device copies.  Both NFS and CIFS have operations
for cross-server copies, and later patches will implement this feature.

Note that as of this patch, the copy_file_range() function might be passed
superblocks from different filesystem types. -EXDEV should be returned
if cross device copies aren't supported.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
---
 Documentation/filesystems/porting |  7 +++++++
 fs/cifs/cifsfs.c                  |  3 +++
 fs/nfs/nfs4file.c                 |  3 +++
 fs/overlayfs/file.c               |  3 +++
 fs/read_write.c                   | 13 ++++++++-----
 5 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 7b7b845..897e1e7 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -622,3 +622,10 @@ in your dentry operations instead.
 	alloc_file_clone(file, flags, ops) does not affect any caller's references.
 	On success you get a new struct file sharing the mount/dentry with the
 	original, on failure - ERR_PTR().
+--
+[mandatory]
+	->copy_file_range() may now be passed files which belong to two
+	different superblocks of the same file system type or which belong
+	to two different filesystems types all together. As before, the
+	destination's copy_file_range() is the function which is called.
+	If it cannot copy ranges from the source, it should return -EXDEV.
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 7065426..ca8fc87 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1114,6 +1114,9 @@ static ssize_t cifs_copy_file_range(struct file *src_file, loff_t off,
 	unsigned int xid = get_xid();
 	ssize_t rc;
 
+	if (file_inode(src_file)->i_sb != file_inode(dst_file)->i_sb)
+		return -EXDEV;
+
 	rc = cifs_file_copychunk_range(xid, src_file, off, dst_file, destoff,
 					len, flags);
 	free_xid(xid);
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 4288a6e..5a73c90 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -135,6 +135,9 @@ static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 {
 	ssize_t ret;
 
+	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
+		return -EXDEV;
+
 	if (file_inode(file_in) == file_inode(file_out))
 		return -EINVAL;
 retry:
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index aeaefd2..0331e33 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -483,6 +483,9 @@ static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
 				   struct file *file_out, loff_t pos_out,
 				   size_t len, unsigned int flags)
 {
+	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
+		return -EXDEV;
+
 	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
 			    OVL_COPY);
 }
diff --git a/fs/read_write.c b/fs/read_write.c
index 39b4a21..cfb1d10 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1575,10 +1575,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	    (file_out->f_flags & O_APPEND))
 		return -EBADF;
 
-	/* this could be relaxed once a method supports cross-fs copies */
-	if (inode_in->i_sb != inode_out->i_sb)
-		return -EXDEV;
-
 	if (len == 0)
 		return 0;
 
@@ -1588,7 +1584,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	 * Try cloning first, this is supported by more file systems, and
 	 * more efficient if both clone and copy are supported (e.g. NFS).
 	 */
-	if (file_in->f_op->clone_file_range) {
+	if (inode_in->i_sb == inode_out->i_sb &&
+	    file_in->f_op->clone_file_range) {
 		ret = file_in->f_op->clone_file_range(file_in, pos_in,
 				file_out, pos_out, len);
 		if (ret == 0) {
@@ -1604,6 +1601,12 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 			goto done;
 	}
 
+	/* this could be relaxed once generic cross fs support is added */
+	if (inode_in->i_sb != inode_out->i_sb) {
+		ret = -EXDEV;
+		goto done;
+	}
+
 	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
 			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
 
-- 
1.8.3.1