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 drop invalid entry from
the dcache, but inode can be referenced by dentry multiple dentries.

The introduced zpl_d_drop_aliases function walks and invalidates
all aliases of an inode.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Pavel Snajdr <snajpa@snajpa.net>
Closes openzfs#9600
Closes openzfs#14070

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

@@ -93,6 +93,7 @@ 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
@@ -209,6 +210,7 @@ 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/kernel/linux/dcache_compat.h

@@ -61,4 +61,25 @@ d_clear_d_op(struct dentry *dentry)
 	    DCACHE_OP_REVALIDATE | DCACHE_OP_DELETE);
 }
 
+/*
+ * Walk and invalidate all dentry aliases of an inode
+ * unless it's a mountpoint
+ */
+static inline void
+zpl_d_drop_aliases(struct inode *inode)
+{
+	struct dentry *dentry;
+	spin_lock(&inode->i_lock);
+#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
+		if (!IS_ROOT(dentry) && !d_mountpoint(dentry) &&
+		    (dentry->d_inode == inode)) {
+			d_drop(dentry);
+		}
+	}
+	spin_unlock(&inode->i_lock);
+}
 #endif /* _ZFS_DCACHE_H */

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

@@ -62,7 +62,6 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __field(boolean_t,		z_is_sa)
 	    __field(boolean_t,		z_is_mapped)
 	    __field(boolean_t,		z_is_ctldir)
-	    __field(boolean_t,		z_is_stale)
 
 	    __field(uint32_t,		i_uid)
 	    __field(uint32_t,		i_gid)
@@ -95,7 +94,6 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __entry->z_is_sa		= zn->z_is_sa;
 	    __entry->z_is_mapped	= zn->z_is_mapped;
 	    __entry->z_is_ctldir	= zn->z_is_ctldir;
-	    __entry->z_is_stale		= zn->z_is_stale;
 
 	    __entry->i_uid		= KUID_TO_SUID(ZTOI(zn)->i_uid);
 	    __entry->i_gid		= KGID_TO_SGID(ZTOI(zn)->i_gid);
@@ -117,7 +115,7 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    "zn_prefetch %u blksz %u seq %u "
 	    "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 { "
+	    "is_mapped %d is_ctldir %d inode { "
 	    "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",
@@ -126,7 +124,7 @@ DECLARE_EVENT_CLASS(zfs_ace_class,
 	    __entry->z_seq, __entry->z_mapcnt, __entry->z_size,
 	    __entry->z_pflags, __entry->z_sync_cnt, __entry->z_mode,
 	    __entry->z_is_sa, __entry->z_is_mapped,
-	    __entry->z_is_ctldir, __entry->z_is_stale, __entry->i_uid,
+	    __entry->z_is_ctldir, __entry->i_uid,
 	    __entry->i_gid, __entry->i_ino, __entry->i_nlink,
 	    __entry->i_size, __entry->i_blkbits,
 	    __entry->i_bytes, __entry->i_mode, __entry->i_generation,

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

@@ -45,7 +45,8 @@ 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;
-extern dentry_operations_t zpl_dentry_operations;
+
+/* zpl_file.c */
 extern const struct address_space_operations zpl_address_space_operations;
 extern const struct file_operations zpl_file_operations;
 extern const struct file_operations zpl_dir_file_operations;

include/sys/zfs_znode.h

@@ -190,7 +190,6 @@ typedef struct znode {
 	boolean_t	z_is_sa;	/* are we native sa? */
 	boolean_t	z_is_mapped;	/* are we mmap'ed */
 	boolean_t	z_is_ctldir;	/* are we .zfs entry */
-	boolean_t	z_is_stale;	/* are we stale due to rollback? */
 	boolean_t	z_suspended;	/* extra ref from a suspend? */
 	uint_t		z_blksz;	/* block size in bytes */
 	uint_t		z_seq;		/* modification sequence number */

module/os/linux/zfs/zfs_ctldir.c

@@ -470,7 +470,6 @@ zfsctl_inode_alloc(zfsvfs_t *zfsvfs, uint64_t id,
 	zp->z_is_sa = B_FALSE;
 	zp->z_is_mapped = B_FALSE;
 	zp->z_is_ctldir = B_TRUE;
-	zp->z_is_stale = B_FALSE;
 	zp->z_sa_hdl = NULL;
 	zp->z_blksz = 0;
 	zp->z_seq = 0;

module/os/linux/zfs/zfs_vfsops.c

@@ -1500,7 +1500,6 @@ 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;
-	sb->s_d_op = &zpl_dentry_operations;
 
 	/* Set features for file system. */
 	zfs_set_fuid_feature(zfsvfs);
@@ -1859,8 +1858,8 @@ zfs_resume_fs(zfsvfs_t *zfsvfs, dsl_dataset_t *ds)
 	    zp = list_next(&zfsvfs->z_all_znodes, zp)) {
 		err2 = zfs_rezget(zp);
 		if (err2) {
+			zpl_d_drop_aliases(ZTOI(zp));
 			remove_inode_hash(ZTOI(zp));
-			zp->z_is_stale = B_TRUE;
 		}
 
 		/* see comment in zfs_suspend_fs() */

module/os/linux/zfs/zfs_znode.c

@@ -544,7 +544,6 @@ zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, int blksz,
 	zp->z_atime_dirty = B_FALSE;
 	zp->z_is_mapped = B_FALSE;
 	zp->z_is_ctldir = B_FALSE;
-	zp->z_is_stale = B_FALSE;
 	zp->z_suspended = B_FALSE;
 	zp->z_sa_hdl = NULL;
 	zp->z_mapcnt = 0;

module/os/linux/zfs/zpl_inode.c

@@ -698,46 +698,6 @@ zpl_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 	return (error);
 }
 
-static int
-#ifdef HAVE_D_REVALIDATE_NAMEIDATA
-zpl_revalidate(struct dentry *dentry, struct nameidata *nd)
-{
-	unsigned int flags = (nd ? nd->flags : 0);
-#else
-zpl_revalidate(struct dentry *dentry, unsigned int flags)
-{
-#endif /* HAVE_D_REVALIDATE_NAMEIDATA */
-	/* CSTYLED */
-	zfsvfs_t *zfsvfs = dentry->d_sb->s_fs_info;
-	int error;
-
-	if (flags & LOOKUP_RCU)
-		return (-ECHILD);
-
-	/*
-	 * After a rollback negative dentries created before the rollback
-	 * time must be invalidated.  Otherwise they can obscure files which
-	 * are only present in the rolled back dataset.
-	 */
-	if (dentry->d_inode == NULL) {
-		spin_lock(&dentry->d_lock);
-		error = time_before(dentry->d_time, zfsvfs->z_rollback_time);
-		spin_unlock(&dentry->d_lock);
-
-		if (error)
-			return (0);
-	}
-
-	/*
-	 * The dentry may reference a stale inode if a mounted file system
-	 * was rolled back to a point in time where the object didn't exist.
-	 */
-	if (dentry->d_inode && ITOZ(dentry->d_inode)->z_is_stale)
-		return (0);
-
-	return (1);
-}
-
 const struct inode_operations zpl_inode_operations = {
 	.setattr	= zpl_setattr,
 	.getattr	= zpl_getattr,
@@ -826,7 +786,3 @@ const struct inode_operations zpl_special_inode_operations = {
 	.get_acl	= zpl_get_acl,
 #endif /* CONFIG_FS_POSIX_ACL */
 };
-
-dentry_operations_t zpl_dentry_operations = {
-	.d_revalidate	= zpl_revalidate,
-};