linux: implement filesystem-side copy/clone functions for EL7

Redhat have backported copy_file_range and clone_file_range to the EL7
kernel using an "extended file operations" wrapper structure. This
connects all that up to let cloning work there too.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Kay Pedersen <mail@mkwg.de>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Sponsored-By: OpenDrives Inc.
Sponsored-By: Klara Inc.
Closes #15050

config/kernel-vfs-extended-file_range.m4

@@ -0,0 +1,50 @@
+dnl #
+dnl # EL7 have backported copy_file_range and clone_file_range and
+dnl # added them to an "extended" file_operations struct.
+dnl #
+dnl # We're testing for both functions in one here, because they will only
+dnl # ever appear together and we don't want to match a similar method in
+dnl # some future vendor kernel.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_VFS_FILE_OPERATIONS_EXTEND], [
+	ZFS_LINUX_TEST_SRC([vfs_file_operations_extend], [
+		#include <linux/fs.h>
+
+		static ssize_t test_copy_file_range(struct file *src_file,
+		    loff_t src_off, struct file *dst_file, loff_t dst_off,
+		    size_t len, unsigned int flags) {
+			(void) src_file; (void) src_off;
+			(void) dst_file; (void) dst_off;
+			(void) len; (void) flags;
+			return (0);
+		}
+
+		static int test_clone_file_range(struct file *src_file,
+		    loff_t src_off, struct file *dst_file, loff_t dst_off,
+		    u64 len) {
+			(void) src_file; (void) src_off;
+			(void) dst_file; (void) dst_off;
+			(void) len;
+			return (0);
+		}
+
+		static const struct file_operations_extend
+		    fops __attribute__ ((unused)) = {
+			.kabi_fops = {},
+			.copy_file_range = test_copy_file_range,
+			.clone_file_range = test_clone_file_range,
+		};
+	],[])
+])
+AC_DEFUN([ZFS_AC_KERNEL_VFS_FILE_OPERATIONS_EXTEND], [
+	AC_MSG_CHECKING([whether file_operations_extend takes \
+.copy_file_range() and .clone_file_range()])
+	ZFS_LINUX_TEST_RESULT([vfs_file_operations_extend], [
+		AC_MSG_RESULT([yes])
+		AC_DEFINE(HAVE_VFS_FILE_OPERATIONS_EXTEND, 1,
+		    [file_operations_extend takes .copy_file_range()
+		    and .clone_file_range()])
+	],[
+		AC_MSG_RESULT([no])
+	])
+])

config/kernel.m4

@@ -121,6 +121,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_VFS_REMAP_FILE_RANGE
 	ZFS_AC_KERNEL_SRC_VFS_CLONE_FILE_RANGE
 	ZFS_AC_KERNEL_SRC_VFS_DEDUPE_FILE_RANGE
+	ZFS_AC_KERNEL_SRC_VFS_FILE_OPERATIONS_EXTEND
 	ZFS_AC_KERNEL_SRC_KMAP_ATOMIC_ARGS
 	ZFS_AC_KERNEL_SRC_FOLLOW_DOWN_ONE
 	ZFS_AC_KERNEL_SRC_MAKE_REQUEST_FN
@@ -259,6 +260,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_VFS_REMAP_FILE_RANGE
 	ZFS_AC_KERNEL_VFS_CLONE_FILE_RANGE
 	ZFS_AC_KERNEL_VFS_DEDUPE_FILE_RANGE
+	ZFS_AC_KERNEL_VFS_FILE_OPERATIONS_EXTEND
 	ZFS_AC_KERNEL_KMAP_ATOMIC_ARGS
 	ZFS_AC_KERNEL_FOLLOW_DOWN_ONE
 	ZFS_AC_KERNEL_MAKE_REQUEST_FN

include/os/linux/zfs/sys/zpl.h

@@ -52,7 +52,11 @@ extern const struct inode_operations zpl_special_inode_operations;
 
 /* zpl_file.c */
 extern const struct address_space_operations zpl_address_space_operations;
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+extern const struct file_operations_extend zpl_file_operations;
+#else
 extern const struct file_operations zpl_file_operations;
+#endif
 extern const struct file_operations zpl_dir_file_operations;
 
 /* zpl_super.c */

module/os/linux/zfs/zfs_vfsops.c

@@ -2092,6 +2092,9 @@ zfs_init(void)
 	zfs_znode_init();
 	dmu_objset_register_type(DMU_OST_ZFS, zpl_get_file_info);
 	register_filesystem(&zpl_fs_type);
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+	register_fo_extend(&zpl_file_operations);
+#endif
 }
 
 void
@@ -2102,6 +2105,9 @@ zfs_fini(void)
 	 */
 	taskq_wait(system_delay_taskq);
 	taskq_wait(system_taskq);
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+	unregister_fo_extend(&zpl_file_operations);
+#endif
 	unregister_filesystem(&zpl_fs_type);
 	zfs_znode_fini();
 	zfsctl_fini();

module/os/linux/zfs/zfs_znode.c

@@ -415,7 +415,11 @@ zfs_inode_set_ops(zfsvfs_t *zfsvfs, struct inode *ip)
 	switch (ip->i_mode & S_IFMT) {
 	case S_IFREG:
 		ip->i_op = &zpl_inode_operations;
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+		ip->i_fop = &zpl_file_operations.kabi_fops;
+#else
 		ip->i_fop = &zpl_file_operations;
+#endif
 		ip->i_mapping->a_ops = &zpl_address_space_operations;
 		break;
 
@@ -455,7 +459,11 @@ zfs_inode_set_ops(zfsvfs_t *zfsvfs, struct inode *ip)
 		/* Assume the inode is a file and attempt to continue */
 		ip->i_mode = S_IFREG | 0644;
 		ip->i_op = &zpl_inode_operations;
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+		ip->i_fop = &zpl_file_operations.kabi_fops;
+#else
 		ip->i_fop = &zpl_file_operations;
+#endif
 		ip->i_mapping->a_ops = &zpl_address_space_operations;
 		break;
 	}

module/os/linux/zfs/zpl_file.c

@@ -1311,7 +1311,12 @@ const struct address_space_operations zpl_address_space_operations = {
 #endif
 };
 
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+const struct file_operations_extend zpl_file_operations = {
+	.kabi_fops = {
+#else
 const struct file_operations zpl_file_operations = {
+#endif
 	.open		= zpl_open,
 	.release	= zpl_release,
 	.llseek		= zpl_llseek,
@@ -1341,12 +1346,12 @@ const struct file_operations zpl_file_operations = {
 #ifdef HAVE_VFS_COPY_FILE_RANGE
 	.copy_file_range	= zpl_copy_file_range,
 #endif
-#ifdef HAVE_VFS_REMAP_FILE_RANGE
-	.remap_file_range	= zpl_remap_file_range,
-#endif
 #ifdef HAVE_VFS_CLONE_FILE_RANGE
 	.clone_file_range	= zpl_clone_file_range,
 #endif
+#ifdef HAVE_VFS_REMAP_FILE_RANGE
+	.remap_file_range	= zpl_remap_file_range,
+#endif
 #ifdef HAVE_VFS_DEDUPE_FILE_RANGE
 	.dedupe_file_range	= zpl_dedupe_file_range,
 #endif
@@ -1357,6 +1362,11 @@ const struct file_operations zpl_file_operations = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= zpl_compat_ioctl,
 #endif
+#ifdef HAVE_VFS_FILE_OPERATIONS_EXTEND
+	}, /* kabi_fops */
+	.copy_file_range	= zpl_copy_file_range,
+	.clone_file_range	= zpl_clone_file_range,
+#endif
 };
 
 const struct file_operations zpl_dir_file_operations = {

module/os/linux/zfs/zpl_file_range.c

@@ -77,7 +77,8 @@ __zpl_clone_file_range(struct file *src_file, loff_t src_off,
 	return ((ssize_t)len_o);
 }
 
-#ifdef HAVE_VFS_COPY_FILE_RANGE
+#if defined(HAVE_VFS_COPY_FILE_RANGE) || \
+    defined(HAVE_VFS_FILE_OPERATIONS_EXTEND)
 /*
  * Entry point for copy_file_range(). Copy len bytes from src_off in src_file
  * to dst_off in dst_file. We are permitted to do this however we like, so we
@@ -109,7 +110,7 @@ zpl_copy_file_range(struct file *src_file, loff_t src_off,
 
 	return (ret);
 }
-#endif /* HAVE_VFS_COPY_FILE_RANGE */
+#endif /* HAVE_VFS_COPY_FILE_RANGE || HAVE_VFS_FILE_OPERATIONS_EXTEND */
 
 #ifdef HAVE_VFS_REMAP_FILE_RANGE
 /*
@@ -152,7 +153,8 @@ zpl_remap_file_range(struct file *src_file, loff_t src_off,
 }
 #endif /* HAVE_VFS_REMAP_FILE_RANGE */
 
-#ifdef HAVE_VFS_CLONE_FILE_RANGE
+#if defined(HAVE_VFS_CLONE_FILE_RANGE) || \
+    defined(HAVE_VFS_FILE_OPERATIONS_EXTEND)
 /*
  * Entry point for FICLONE and FICLONERANGE, before Linux 4.20.
  */
@@ -167,7 +169,7 @@ zpl_clone_file_range(struct file *src_file, loff_t src_off,
 	return (__zpl_clone_file_range(src_file, src_off,
 	    dst_file, dst_off, len));
 }
-#endif /* HAVE_VFS_CLONE_FILE_RANGE */
+#endif /* HAVE_VFS_CLONE_FILE_RANGE || HAVE_VFS_FILE_OPERATIONS_EXTEND */
 
 #ifdef HAVE_VFS_DEDUPE_FILE_RANGE
 /*