Remove zpl_revalidate: fix snapshot rollback

Open files, which aren't present in the snapshot, which is being
roll-backed to, need to disappear from the visible VFS image of
the dataset.

Kernel provides __d_drop function to locklessly drop invalid entry
from the dcache, but inode can be referenced by multiple dentries.

The introduced spl_d_drop_aliases function locklessly walks and
invalidates all aliases of an inode; the lockless approach assumes
the function is only called when z_teardown_lock is active or the
inode in question is locked.

Signed-off-by: Pavel Snajdr <[email protected]>

config/kernel-dentry-alias.m4

@@ -0,0 +1,30 @@
+dnl #
+dnl # 3.18 API change
+dnl # Dentry aliases are in d_u struct dentry member
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_DENTRY_ALIAS_D_U], [
+	ZFS_LINUX_TEST_SRC([dentry_alias_d_u], [
+		#include <linux/fs.h>
+		#include <linux/dcache.h>
+		#include <linux/list.h>
+	], [
+		struct inode *inode __attribute__ ((unused)) = NULL;
+		struct dentry *dentry __attribute__ ((unused)) = NULL;
+		hlist_for_each_entry(dentry, &inode->i_dentry,
+		    d_u.d_alias) {
+			__d_drop(dentry);
+		}
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_DENTRY_ALIAS_D_U], [
+	AC_MSG_CHECKING([whether dentry aliases are in d_u member])
+	ZFS_LINUX_TEST_RESULT([dentry_alias_d_u], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_DENTRY_D_U_ALIASES, 1,
+		    [dentry aliases are in d_u member])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+

config/kernel.m4

@@ -87,6 +87,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_SETATTR_PREPARE
 	ZFS_AC_KERNEL_SRC_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_SRC_DENTRY
+	ZFS_AC_KERNEL_SRC_DENTRY_ALIAS_D_U
 	ZFS_AC_KERNEL_SRC_TRUNCATE_SETSIZE
 	ZFS_AC_KERNEL_SRC_SECURITY_INODE
 	ZFS_AC_KERNEL_SRC_FST_MOUNT
@@ -181,6 +182,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_SETATTR_PREPARE
 	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_DENTRY
+	ZFS_AC_KERNEL_DENTRY_ALIAS_D_U
 	ZFS_AC_KERNEL_TRUNCATE_SETSIZE
 	ZFS_AC_KERNEL_SECURITY_INODE
 	ZFS_AC_KERNEL_FST_MOUNT

include/os/linux/spl/sys/Makefile.am

@@ -9,6 +9,7 @@ KERNEL_H = \
 	$(top_srcdir)/include/os/linux/spl/sys/console.h \
 	$(top_srcdir)/include/os/linux/spl/sys/cred.h \
 	$(top_srcdir)/include/os/linux/spl/sys/ctype.h \
+	$(top_srcdir)/include/os/linux/spl/sys/dcache.h \
 	$(top_srcdir)/include/os/linux/spl/sys/debug.h \
 	$(top_srcdir)/include/os/linux/spl/sys/disp.h \
 	$(top_srcdir)/include/os/linux/spl/sys/dkio.h \

include/os/linux/spl/sys/dcache.h

@@ -0,0 +1,30 @@
+/*
+ *  Copyright (C) 2019 OpenZFS Project
+ *  Written by Pavel Snajdr <[email protected]>
+ *
+ *  This file is part of the SPL, Solaris Porting Layer.
+ *  For details, see <http://zfsonlinux.org/>.
+ *
+ *  The SPL is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License as published by the
+ *  Free Software Foundation; either version 2 of the License, or (at your
+ *  option) any later version.
+ *
+ *  The SPL is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _SPL_DCACHE_H
+#define	_SPL_DCACHE_H
+
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/fs_struct.h>
+
+extern void spl_d_drop_aliases(struct inode *inode);
+#endif /* SPL_DCACHE_H */

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

@@ -45,7 +45,9 @@ extern const struct inode_operations zpl_inode_operations;
 extern const struct inode_operations zpl_dir_inode_operations;
 extern const struct inode_operations zpl_symlink_inode_operations;
 extern const struct inode_operations zpl_special_inode_operations;
+#if 0
 extern dentry_operations_t zpl_dentry_operations;
+#endif
 
 /* zpl_file.c */
 extern ssize_t zpl_read_common(struct inode *ip, const char *buf,

module/os/linux/spl/Makefile.in

@@ -1,6 +1,7 @@
 $(MODULE)-objs += ../os/linux/spl/spl-atomic.o
 $(MODULE)-objs += ../os/linux/spl/spl-condvar.o
 $(MODULE)-objs += ../os/linux/spl/spl-cred.o
+$(MODULE)-objs += ../os/linux/spl/spl-dcache.o
 $(MODULE)-objs += ../os/linux/spl/spl-err.o
 $(MODULE)-objs += ../os/linux/spl/spl-generic.o
 $(MODULE)-objs += ../os/linux/spl/spl-kmem.o

module/os/linux/spl/spl-dcache.c

@@ -0,0 +1,48 @@
+/*
+ *  Copyright (C) 2019 OpenZFS Project
+ *  Written by Pavel Snajdr <[email protected]>
+ *
+ *  This file is part of the SPL, Solaris Porting Layer.
+ *  For details, see <http://zfsonlinux.org/>.
+ *
+ *  The SPL is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License as published by the
+ *  Free Software Foundation; either version 2 of the License, or (at your
+ *  option) any later version.
+ *
+ *  The SPL is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sys/debug.h>
+#include <sys/dcache.h>
+#include <sys/sysmacros.h>
+#include <sys/kmem.h>
+#include <sys/vmem.h>
+#include <linux/mm.h>
+#include <linux/dcache.h>
+#include <linux/list.h>
+
+/*
+ * Locklessly walk and invalidate all aliases of an inode; the lockless
+ * approach assumes the function is only called when z_teardown_lock is
+ * active or the inode in question is locked.
+ */
+void
+spl_d_drop_aliases(struct inode *inode)
+{
+	struct dentry *dentry;
+#ifdef HAVE_DENTRY_D_U_ALIASES
+	hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
+#else
+	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+#endif
+		__d_drop(dentry);
+	}
+}
+EXPORT_SYMBOL(spl_d_drop_aliases);

module/os/linux/zfs/zfs_vfsops.c

@@ -54,6 +54,7 @@
 #include <sys/zfs_fuid.h>
 #include <sys/sunddi.h>
 #include <sys/dmu_objset.h>
+#include <sys/dcache.h>
 #include <sys/spa_boot.h>
 #include <sys/objlist.h>
 #include <sys/zpl.h>
@@ -1926,7 +1927,9 @@ zfs_domount(struct super_block *sb, zfs_mnt_t *zm, int silent)
 	sb->s_op = &zpl_super_operations;
 	sb->s_xattr = zpl_xattr_handlers;
 	sb->s_export_op = &zpl_export_operations;
+#if 0
 	sb->s_d_op = &zpl_dentry_operations;
+#endif
 
 	/* Set features for file system. */
 	zfs_set_fuid_feature(zfsvfs);
@@ -2275,6 +2278,7 @@ zfs_resume_fs(zfsvfs_t *zfsvfs, dsl_dataset_t *ds)
 	    zp = list_next(&zfsvfs->z_all_znodes, zp)) {
 		err2 = zfs_rezget(zp);
 		if (err2) {
+			spl_d_drop_aliases(ZTOI(zp));
 			remove_inode_hash(ZTOI(zp));
 			zp->z_is_stale = B_TRUE;
 		}

module/os/linux/zfs/zpl_inode.c

@@ -602,6 +602,7 @@ zpl_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 	return (error);
 }
 
+#if 0
 static int
 #ifdef HAVE_D_REVALIDATE_NAMEIDATA
 zpl_revalidate(struct dentry *dentry, struct nameidata *nd)
@@ -641,6 +642,7 @@ zpl_revalidate(struct dentry *dentry, unsigned int flags)
 
 	return (1);
 }
+#endif
 
 const struct inode_operations zpl_inode_operations = {
 	.setattr	= zpl_setattr,
@@ -731,6 +733,8 @@ const struct inode_operations zpl_special_inode_operations = {
 #endif /* CONFIG_FS_POSIX_ACL */
 };
 
+#if 0
 dentry_operations_t zpl_dentry_operations = {
 	.d_revalidate	= zpl_revalidate,
 };
+#endif