fat: add setlease file operation

Add the setlease file_operation to fat_file_operations and
fat_dir_operations, pointing to generic_setlease.  A future patch will
change the default behavior to reject lease attempts with -EINVAL when
there is no setlease file operation defined. Add generic_setlease to
retain the ability to set leases on this filesystem.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260108-setlease-6-20-v1-9-ea4dec9b67fa@kernel.org
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/fat/dir.c

@@ -16,6 +16,7 @@
 
 #include <linux/slab.h>
 #include <linux/compat.h>
+#include <linux/filelock.h>
 #include <linux/uaccess.h>
 #include <linux/iversion.h>
 #include "fat.h"
@@ -876,6 +877,7 @@ const struct file_operations fat_dir_operations = {
 	.compat_ioctl	= fat_compat_dir_ioctl,
 #endif
 	.fsync		= fat_file_fsync,
+	.setlease	= generic_setlease,
 };
 
 static int fat_get_short_entry(struct inode *dir, loff_t *pos,

fs/fat/file.c

@@ -13,6 +13,7 @@
 #include <linux/mount.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
+#include <linux/filelock.h>
 #include <linux/fsnotify.h>
 #include <linux/security.h>
 #include <linux/falloc.h>
@@ -212,6 +213,7 @@ const struct file_operations fat_file_operations = {
 	.splice_read	= filemap_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.fallocate	= fat_fallocate,
+	.setlease	= generic_setlease,
 };
 
 static int fat_cont_expand(struct inode *inode, loff_t size)