Linux 4.16 compat: inode_set_iversion()

A new interface was added to manipulate the version field of an
inode.  Add a inode_set_iversion() wrapper for older kernels and
use the new interface when available.

The i_version field was dropped from the trace point due to the
switch to an atomic64_t i_version type.

Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@nutanix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7148

config/kernel-inode-set-iversion.m4

@@ -0,0 +1,19 @@
+dnl #
+dnl # 4.16 API change
+dnl # inode_set_iversion introduced to set i_version
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_INODE_SET_IVERSION], [
+	AC_MSG_CHECKING([whether inode_set_iversion() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/iversion.h>
+	],[
+		struct inode inode;
+		inode_set_iversion(&inode, 1);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_INODE_SET_IVERSION, 1,
+		    [inode_set_iversion() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -65,6 +65,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_INODE_OPERATIONS_SET_ACL
 	ZFS_AC_KERNEL_INODE_OPERATIONS_GETATTR
 	ZFS_AC_KERNEL_INODE_SET_FLAGS
+	ZFS_AC_KERNEL_INODE_SET_IVERSION
 	ZFS_AC_KERNEL_GET_ACL_HANDLE_CACHE
 	ZFS_AC_KERNEL_SHOW_OPTIONS
 	ZFS_AC_KERNEL_FILE_INODE

include/linux/vfs_compat.h

@@ -578,4 +578,18 @@ current_time(struct inode *ip)
 }
 #endif
 
+/*
+ * 4.16 API change
+ * Added iversion interface for managing inode version field.
+ */
+#ifdef HAVE_INODE_SET_IVERSION
+#include <linux/iversion.h>
+#else
+static inline void
+inode_set_iversion(struct inode *ip, u64 val)
+{
+	ip->i_version = val;
+}
+#endif
+
 #endif /* _ZFS_VFS_H */

include/sys/trace_acl.h

@@ -68,7 +68,6 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __field(uint32_t,		i_gid)
 	    __field(unsigned long,	i_ino)
 	    __field(unsigned int,	i_nlink)
-	    __field(u64,		i_version)
 	    __field(loff_t,		i_size)
 	    __field(unsigned int,	i_blkbits)
 	    __field(unsigned short,	i_bytes)
@@ -103,7 +102,6 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __entry->i_gid		= KGID_TO_SGID(ZTOI(zn)->i_gid);
 	    __entry->i_ino		= zn->z_inode.i_ino;
 	    __entry->i_nlink		= zn->z_inode.i_nlink;
-	    __entry->i_version		= zn->z_inode.i_version;
 	    __entry->i_size		= zn->z_inode.i_size;
 	    __entry->i_blkbits		= zn->z_inode.i_blkbits;
 	    __entry->i_bytes		= zn->z_inode.i_bytes;
@@ -121,7 +119,7 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    "mapcnt %llu size %llu pflags %llu "
 	    "sync_cnt %u mode 0x%x is_sa %d "
 	    "is_mapped %d is_ctldir %d is_stale %d inode { "
-	    "uid %u gid %u ino %lu nlink %u version %llu size %lli "
+	    "uid %u gid %u ino %lu nlink %u size %lli "
 	    "blkbits %u bytes %u mode 0x%x generation %x } } "
 	    "ace { type %u flags %u access_mask %u } mask_matched %u",
 	    __entry->z_id, __entry->z_unlinked, __entry->z_atime_dirty,
@@ -131,7 +129,7 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __entry->z_is_sa, __entry->z_is_mapped,
 	    __entry->z_is_ctldir, __entry->z_is_stale, __entry->i_uid,
 	    __entry->i_gid, __entry->i_ino, __entry->i_nlink,
-	    __entry->i_version, __entry->i_size, __entry->i_blkbits,
+	    __entry->i_size, __entry->i_blkbits,
 	    __entry->i_bytes, __entry->i_mode, __entry->i_generation,
 	    __entry->z_type, __entry->z_flags, __entry->z_access_mask,
 	    __entry->mask_matched)

module/zfs/zpl_super.c

@@ -36,7 +36,7 @@ zpl_inode_alloc(struct super_block *sb)
 	struct inode *ip;
 
 	VERIFY3S(zfs_inode_alloc(sb, &ip), ==, 0);
-	ip->i_version = 1;
+	inode_set_iversion(ip, 1);
 
 	return (ip);
 }