ceph: new mount option that specifies fscache uniquifier

Current ceph uses FSID as primary index key of fscache data. This
allows ceph to retain cached data across remount. But this causes
problem (kernel opps, fscache does not support sharing data) when
a filesystem get mounted several times (with fscache enabled, with
different mount options).

The fix is adding a new mount option, which specifies uniquifier
for fscache.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 29 insertions, 12 deletions

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 14e78dd52ef9..aa06a8c24792 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -121,6 +121,7 @@ enum {
 	/* int args above */
 	Opt_snapdirname,
 	Opt_mds_namespace,
+	Opt_fscache_uniq,
 	Opt_last_string,
 	/* string args above */
 	Opt_dirstat,
@@ -158,6 +159,7 @@ static match_table_t fsopt_tokens = {
 	/* int args above */
 	{Opt_snapdirname, "snapdirname=%s"},
 	{Opt_mds_namespace, "mds_namespace=%s"},
+	{Opt_fscache_uniq, "fsc=%s"},
 	/* string args above */
 	{Opt_dirstat, "dirstat"},
 	{Opt_nodirstat, "nodirstat"},
@@ -223,6 +225,14 @@ static int parse_fsopt_token(char *c, void *private)
 		if (!fsopt->mds_namespace)
 			return -ENOMEM;
 		break;
+	case Opt_fscache_uniq:
+		fsopt->fscache_uniq = kstrndup(argstr[0].from,
+					       argstr[0].to-argstr[0].from,
+					       GFP_KERNEL);
+		if (!fsopt->fscache_uniq)
+			return -ENOMEM;
+		fsopt->flags |= CEPH_MOUNT_OPT_FSCACHE;
+		break;
 		/* misc */
 	case Opt_wsize:
 		fsopt->wsize = intval;
@@ -317,6 +327,7 @@ static void destroy_mount_options(struct ceph_mount_options *args)
 	kfree(args->snapdir_name);
 	kfree(args->mds_namespace);
 	kfree(args->server_path);
+	kfree(args->fscache_uniq);
 	kfree(args);
 }
 
@@ -350,10 +361,12 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
 	ret = strcmp_null(fsopt1->mds_namespace, fsopt2->mds_namespace);
 	if (ret)
 		return ret;
-
 	ret = strcmp_null(fsopt1->server_path, fsopt2->server_path);
 	if (ret)
 		return ret;
+	ret = strcmp_null(fsopt1->fscache_uniq, fsopt2->fscache_uniq);
+	if (ret)
+		return ret;
 
 	return ceph_compare_options(new_opt, fsc->client);
 }
@@ -475,8 +488,12 @@ static int ceph_show_options(struct seq_file *m, struct dentry *root)
 		seq_puts(m, ",noasyncreaddir");
 	if ((fsopt->flags & CEPH_MOUNT_OPT_DCACHE) == 0)
 		seq_puts(m, ",nodcache");
-	if (fsopt->flags & CEPH_MOUNT_OPT_FSCACHE)
-		seq_puts(m, ",fsc");
+	if (fsopt->flags & CEPH_MOUNT_OPT_FSCACHE) {
+		if (fsopt->fscache_uniq)
+			seq_printf(m, ",fsc=%s", fsopt->fscache_uniq);
+		else
+			seq_puts(m, ",fsc");
+	}
 	if (fsopt->flags & CEPH_MOUNT_OPT_NOPOOLPERM)
 		seq_puts(m, ",nopoolperm");
 
@@ -597,18 +614,11 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
 	if (!fsc->wb_pagevec_pool)
 		goto fail_trunc_wq;
 
-	/* setup fscache */
-	if ((fsopt->flags & CEPH_MOUNT_OPT_FSCACHE) &&
-	    (ceph_fscache_register_fs(fsc) != 0))
-		goto fail_fscache;
-
 	/* caps */
 	fsc->min_caps = fsopt->max_readdir;
 
 	return fsc;
 
-fail_fscache:
-	ceph_fscache_unregister_fs(fsc);
 fail_trunc_wq:
 	destroy_workqueue(fsc->trunc_wq);
 fail_pg_inv_wq:
@@ -626,8 +636,6 @@ static void destroy_fs_client(struct ceph_fs_client *fsc)
 {
 	dout("destroy_fs_client %p\n", fsc);
 
-	ceph_fscache_unregister_fs(fsc);
-
 	destroy_workqueue(fsc->wb_wq);
 	destroy_workqueue(fsc->pg_inv_wq);
 	destroy_workqueue(fsc->trunc_wq);
@@ -820,6 +828,13 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 		if (err < 0)
 			goto out;
 
+		/* setup fscache */
+		if (fsc->mount_options->flags & CEPH_MOUNT_OPT_FSCACHE) {
+			err = ceph_fscache_register_fs(fsc);
+			if (err < 0)
+				goto out;
+		}
+
 		if (!fsc->mount_options->server_path) {
 			path = "";
 			dout("mount opening path \\t\n");
@@ -1042,6 +1057,8 @@ static void ceph_kill_sb(struct super_block *s)
 	fsc->client->extra_mon_dispatch = NULL;
 	ceph_fs_debugfs_cleanup(fsc);
 
+	ceph_fscache_unregister_fs(fsc);
+
 	ceph_mdsc_destroy(fsc);
 
 	destroy_fs_client(fsc);