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

- ioctl: device replace - disallow

- mount: raid56 - remount RO

- mount: seeding device - deny mount

- balance: use of raid56 taints kernel

Signed-off-by: David Sterba <dsterba@suse.cz>

---

 fs/btrfs/ctree.h   |    7 +++++++

 fs/btrfs/disk-io.c |   15 +++++++++++++++

 fs/btrfs/ioctl.c   |    8 +++++++-

 fs/btrfs/super.c   |   20 ++++++++++++++++++++

 4 files changed, 49 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ctree.h

+++ b/fs/btrfs/ctree.h

@@ -37,6 +37,7 @@

 #include <linux/sizes.h>

 #include <linux/dynamic_debug.h>

 #include <linux/refcount.h>

+#include <linux/unsupported-feature.h>

 #include "extent_io.h"

 #include "extent_map.h"

 #include "async-thread.h"

@@ -3555,4 +3556,11 @@ static inline int btrfs_test_is_dummy_ro

 #endif

 	return 0;

 }

+

+/*

+ * Module parameter

+ */

+DECLARE_SUSE_UNSUPPORTED_FEATURE(btrfs)

+#define btrfs_allow_unsupported btrfs_allow_unsupported()

+

 #endif

--- a/fs/btrfs/disk-io.c

+++ b/fs/btrfs/disk-io.c

@@ -2797,6 +2797,14 @@ int open_ctree(struct super_block *sb,

 	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)

 		set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);

+	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;

+		}

+	}

+

 	/*

 	 * run through our array of backup supers and setup

 	 * our ring pointer to the oldest one

@@ -2863,6 +2871,13 @@ int 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 |= MS_RDONLY;

+		}

+	}

+

 	/*

 	 * Needn't use the lock because there is no other task which will

 	 * update the flag.

--- a/fs/btrfs/ioctl.c

+++ b/fs/btrfs/ioctl.c

@@ -5617,6 +5617,7 @@ long btrfs_ioctl(struct file *file, unsi

 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

 	struct btrfs_root *root = BTRFS_I(inode)->root;

 	void __user *argp = (void __user *)arg;

+	int ret = -ENOTTY;

 	switch (cmd) {

 	case FS_IOC_GETFLAGS:

@@ -5737,6 +5738,11 @@ long btrfs_ioctl(struct file *file, unsi

 	case BTRFS_IOC_QUOTA_RESCAN_WAIT:

 		return btrfs_ioctl_quota_rescan_wait(file, argp);

 	case BTRFS_IOC_DEV_REPLACE:

+		if (!btrfs_allow_unsupported) {

+			printk(KERN_WARNING "btrfs: IOC_DEV_REPLACE is not supported, load module with allow_unsupported=1\n");

+			ret = -EOPNOTSUPP;

+			break;

+		}

 		return btrfs_ioctl_dev_replace(fs_info, argp);

 	case BTRFS_IOC_GET_FSLABEL:

 		return btrfs_ioctl_get_fslabel(file, argp);

@@ -5752,7 +5758,7 @@ long btrfs_ioctl(struct file *file, unsi

 		return btrfs_ioctl_set_features(file, argp);

 	}

-	return -ENOTTY;

+	return ret;

 }

 #ifdef CONFIG_COMPAT

--- a/fs/btrfs/super.c

+++ b/fs/btrfs/super.c

@@ -18,6 +18,7 @@

 #include <linux/blkdev.h>

 #include <linux/module.h>

+#include <linux/moduleparam.h>

 #include <linux/buffer_head.h>

 #include <linux/fs.h>

 #include <linux/pagemap.h>

@@ -64,6 +65,8 @@

 #define CREATE_TRACE_POINTS

 #include <trace/events/btrfs.h>

+DEFINE_SUSE_UNSUPPORTED_FEATURE(btrfs)

+

 static const struct super_operations btrfs_super_ops;

 static struct file_system_type btrfs_fs_type;

@@ -663,6 +666,11 @@ int btrfs_parse_options(struct btrfs_roo

 			}

 			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;

@@ -684,6 +692,11 @@ int btrfs_parse_options(struct btrfs_roo

 			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;

@@ -1758,6 +1771,13 @@ static int btrfs_remount(struct super_bl

 			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;