Partially revert 5a6ac4c

Reinstate the zpl_revalidate() functionality to resolve a regression
where dentries for open files during a rollback are not invalidated.

The unrelated functionality for automatically unmounting .zfs/snapshots
was not reverted.  Nor was the addition of shrink_dcache_sb() to the
zfs_resume_fs() function.

This issue was not immediately caught by the CI because the test case
intended to catch it was included in the list of ZTS tests which may
occasionally fail for unrelated reasons.  Remove all of the rollback
tests from this list to help identify the frequency of any spurious
failures.

The rollback_003_pos.ksh test case exposes a real issue with the
long standing code which needs to be investigated.  Regardless,
it has been enable with a small workaround in the test case itself.

Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Pavel Snajdr <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #9587
Closes #9592 

2 files changed, 45 insertions, 0 deletions

diff --git a/module/os/linux/zfs/zfs_vfsops.c b/module/os/linux/zfs/zfs_vfsops.c
index c0acaab0b..154933a4c 100644
--- a/module/os/linux/zfs/zfs_vfsops.c
+++ b/module/os/linux/zfs/zfs_vfsops.c
@@ -1926,6 +1926,7 @@ 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);
diff --git a/module/os/linux/zfs/zpl_inode.c b/module/os/linux/zfs/zpl_inode.c
index 7912a5b3d..124021166 100644
--- a/module/os/linux/zfs/zpl_inode.c
+++ b/module/os/linux/zfs/zpl_inode.c
@@ -602,6 +602,46 @@ out:
 	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,
@@ -690,3 +730,7 @@ 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,
+};