From: David Sterba <dsterba@suse.cz>
Date: Fri, 18 Jan 2013 00:28:40 +0100
Patch-mainline: Never, SLES-specific
References: fate#314697
Subject: [PATCH] btrfs: add allow_unsupported module parameter

Disallow access to filesystem with unsupported features by default but
leave a chance to access the filesystem via module parameter override
(taints kernel).

The status can be toggled during runtime by changing the exported module
parameter in /sys/module/btrfs/parameters/allow_unsupported.

Current:
- mount: inode_cache - deny mount
- mount: autodefrag - deny mount
- mount: raid56 - remount RO
- mount: seeding device - deny mount
- balance: use of raid56 taints kernel

fate#325563 - allow device replace

Signed-off-by: David Sterba <dsterba@suse.cz>
---
 fs/btrfs/ctree.h   |  7 +++++++
 fs/btrfs/disk-io.c | 15 +++++++++++++++
 fs/btrfs/super.c   | 20 ++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f73b17694..0a852b5bc 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -29,6 +29,7 @@
 #include <linux/dynamic_debug.h>
 #include <linux/refcount.h>
 #include <linux/crc32c.h>
+#include <linux/unsupported-feature.h>
 #include "extent-io-tree.h"
 #include "extent_io.h"
 #include "extent_map.h"
@@ -3531,6 +3532,12 @@ static inline int btrfs_is_testing(struct btrfs_fs_info *fs_info)
 }
 #endif
 
+/*
+ * Module parameter
+ */
+DECLARE_SUSE_UNSUPPORTED_FEATURE(btrfs)
+#define btrfs_allow_unsupported btrfs_allow_unsupported()
+
 static inline void cond_wake_up(struct wait_queue_head *wq)
 {
 	/*
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c97a20783..7a1eca676 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2945,6 +2945,14 @@ int __cold open_ctree(struct super_block *sb,
 
 	disk_super = fs_info->super_copy;
 
+	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
+		if (!btrfs_allow_unsupported) {
+			printk(KERN_WARNING "btrfs: seeding mode is not supported, load module with allow_unsupported=1\n");
+			ret = -EOPNOTSUPP;
+			goto fail_alloc;
+		}
+	}
+
 	ASSERT(!memcmp(fs_info->fs_devices->fsid, fs_info->super_copy->fsid,
 		       BTRFS_FSID_SIZE));
 
@@ -3045,6 +3053,13 @@ int __cold open_ctree(struct super_block *sb,
 		goto fail_alloc;
 	}
 
+	if (features & BTRFS_FEATURE_INCOMPAT_RAID56) {
+		if (!btrfs_allow_unsupported) {
+			printk(KERN_WARNING "btrfs: RAID56 is supported read-only, load module with allow_unsupported=1\n");
+			sb->s_flags |= SB_RDONLY;
+		}
+	}
+
 	/*
 	 * Needn't use the lock because there is no other task which will
 	 * update the flag.
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 831956f9f..ea57682f7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -27,6 +27,7 @@
 #include <linux/ratelimit.h>
 #include <linux/crc32c.h>
 #include <linux/btrfs.h>
+#include <linux/moduleparam.h>
 #include "delayed-inode.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -50,6 +51,8 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/btrfs.h>
 
+DEFINE_SUSE_UNSUPPORTED_FEATURE(btrfs)
+
 static const struct super_operations btrfs_super_ops;
 
 /*
@@ -733,6 +736,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			}
 			break;
 		case Opt_inode_cache:
+			if (!btrfs_allow_unsupported) {
+				printk(KERN_WARNING "btrfs: inode_cache is not supported, load module with allow_unsupported=1\n");
+				ret = -EOPNOTSUPP;
+				break;
+			}
 			btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
 					   "enabling inode map caching");
 			break;
@@ -754,6 +762,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			btrfs_clear_opt(info->mount_opt, ENOSPC_DEBUG);
 			break;
 		case Opt_defrag:
+			if (!btrfs_allow_unsupported) {
+				printk(KERN_WARNING "btrfs: autodefrag is not supported, load module with allow_unsupported=1\n");
+				ret = -EOPNOTSUPP;
+				break;
+			}
 			btrfs_set_and_info(info, AUTO_DEFRAG,
 					   "enabling auto defrag");
 			break;
@@ -1828,6 +1841,13 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 			ret = -EACCES;
 			goto restore;
 		}
+		if ((btrfs_super_incompat_flags(fs_info->super_copy)
+					& BTRFS_FEATURE_INCOMPAT_RAID56)
+				&& !btrfs_allow_unsupported) {
+			printk(KERN_WARNING "btrfs: cannot remount RW, RAID56 is supported read-only, load module with allow_unsupported=1\n");
+			ret = -EINVAL;
+			goto restore;
+		}
 
 		if (btrfs_super_log_root(fs_info->super_copy) != 0) {
 			ret = -EINVAL;
-- 
2.26.2