3 files changed, 163 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1aafccda05d1..498452ebfd37 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -524,7 +524,12 @@ struct btrfs_super_block {
 #define BTRFS_FEATURE_INCOMPAT_NO_HOLES         (1ULL << 9)
 
 #define BTRFS_FEATURE_COMPAT_SUPP               0ULL
+#define BTRFS_FEATURE_COMPAT_SAFE_SET           0ULL
+#define BTRFS_FEATURE_COMPAT_SAFE_CLEAR         0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP            0ULL
+#define BTRFS_FEATURE_COMPAT_RO_SAFE_SET        0ULL
+#define BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR      0ULL
+
 #define BTRFS_FEATURE_INCOMPAT_SUPP                     \
         (BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |         \
          BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |        \
@@ -536,6 +541,10 @@ struct btrfs_super_block {
          BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA |       \
          BTRFS_FEATURE_INCOMPAT_NO_HOLES)
 
+#define BTRFS_FEATURE_INCOMPAT_SAFE_SET                 \
+        (BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
+#define BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR               0ULL
+
 /*
  * A leaf is full of items. offset and size tell us where to find
  * the item in the leaf (relative to the start of the data area)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 21da5762b0b1..d4e105b54091 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4480,6 +4480,142 @@ out_unlock:
         return ret;
 }
 
+#define INIT_FEATURE_FLAGS(suffix) \
+        { .compat_flags = BTRFS_FEATURE_COMPAT_##suffix, \
+          .compat_ro_flags = BTRFS_FEATURE_COMPAT_RO_##suffix, \
+          .incompat_flags = BTRFS_FEATURE_INCOMPAT_##suffix }
+
+static int btrfs_ioctl_get_supported_features(struct file *file,
+                                              void __user *arg)
+{
+        static struct btrfs_ioctl_feature_flags features[3] = {
+                INIT_FEATURE_FLAGS(SUPP),
+                INIT_FEATURE_FLAGS(SAFE_SET),
+                INIT_FEATURE_FLAGS(SAFE_CLEAR)
+        };
+
+        if (copy_to_user(arg, &features, sizeof(features)))
+                return -EFAULT;
+
+        return 0;
+}
+
+static int btrfs_ioctl_get_features(struct file *file, void __user *arg)
+{
+        struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
+        struct btrfs_super_block *super_block = root->fs_info->super_copy;
+        struct btrfs_ioctl_feature_flags features;
+
+        features.compat_flags = btrfs_super_compat_flags(super_block);
+        features.compat_ro_flags = btrfs_super_compat_ro_flags(super_block);
+        features.incompat_flags = btrfs_super_incompat_flags(super_block);
+
+        if (copy_to_user(arg, &features, sizeof(features)))
+                return -EFAULT;
+
+        return 0;
+}
+
+static int check_feature_bits(struct btrfs_root *root, const char *type,
+                              u64 change_mask, u64 flags, u64 supported_flags,
+                              u64 safe_set, u64 safe_clear)
+{
+        u64 disallowed, unsupported;
+        u64 set_mask = flags & change_mask;
+        u64 clear_mask = ~flags & change_mask;
+
+        unsupported = set_mask & ~supported_flags;
+        if (unsupported) {
+                btrfs_warn(root->fs_info,
+                           "this kernel does not support %s bits 0x%llx",
+                           type, unsupported);
+                return -EOPNOTSUPP;
+        }
+
+        disallowed = set_mask & ~safe_set;
+        if (disallowed) {
+                btrfs_warn(root->fs_info,
+                           "can't set %s bits 0x%llx while mounted",
+                           type, disallowed);
+                return -EPERM;
+        }
+
+        disallowed = clear_mask & ~safe_clear;
+        if (disallowed) {
+                btrfs_warn(root->fs_info,
+                           "can't clear %s bits 0x%llx while mounted",
+                           type, disallowed);
+                return -EPERM;
+        }
+
+        return 0;
+}
+
+#define check_feature(root, change_mask, flags, mask_base)      \
+check_feature_bits(root, # mask_base, change_mask, flags,       \
+                   BTRFS_FEATURE_ ## mask_base ## _SUPP,        \
+                   BTRFS_FEATURE_ ## mask_base ## _SAFE_SET,    \
+                   BTRFS_FEATURE_ ## mask_base ## _SAFE_CLEAR)
+
+static int btrfs_ioctl_set_features(struct file *file, void __user *arg)
+{
+        struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
+        struct btrfs_super_block *super_block = root->fs_info->super_copy;
+        struct btrfs_ioctl_feature_flags flags[2];
+        struct btrfs_trans_handle *trans;
+        u64 newflags;
+        int ret;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (copy_from_user(flags, arg, sizeof(flags)))
+                return -EFAULT;
+
+        /* Nothing to do */
+        if (!flags[0].compat_flags && !flags[0].compat_ro_flags &&
+            !flags[0].incompat_flags)
+                return 0;
+
+        ret = check_feature(root, flags[0].compat_flags,
+                            flags[1].compat_flags, COMPAT);
+        if (ret)
+                return ret;
+
+        ret = check_feature(root, flags[0].compat_ro_flags,
+                            flags[1].compat_ro_flags, COMPAT_RO);
+        if (ret)
+                return ret;
+
+        ret = check_feature(root, flags[0].incompat_flags,
+                            flags[1].incompat_flags, INCOMPAT);
+        if (ret)
+                return ret;
+
+        trans = btrfs_start_transaction(root, 1);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
+
+        spin_lock(&root->fs_info->super_lock);
+        newflags = btrfs_super_compat_flags(super_block);
+        newflags |= flags[0].compat_flags & flags[1].compat_flags;
+        newflags &= ~(flags[0].compat_flags & ~flags[1].compat_flags);
+        btrfs_set_super_compat_flags(super_block, newflags);
+
+        newflags = btrfs_super_compat_ro_flags(super_block);
+        newflags |= flags[0].compat_ro_flags & flags[1].compat_ro_flags;
+        newflags &= ~(flags[0].compat_ro_flags & ~flags[1].compat_ro_flags);
+        btrfs_set_super_compat_ro_flags(super_block, newflags);
+
+        newflags = btrfs_super_incompat_flags(super_block);
+        newflags |= flags[0].incompat_flags & flags[1].incompat_flags;
+        newflags &= ~(flags[0].incompat_flags & ~flags[1].incompat_flags);
+        btrfs_set_super_incompat_flags(super_block, newflags);
+        spin_unlock(&root->fs_info->super_lock);
+
+        return btrfs_end_transaction(trans, root);
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
                 cmd, unsigned long arg)
 {
@@ -4598,6 +4734,12 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_set_fslabel(file, argp);
         case BTRFS_IOC_FILE_EXTENT_SAME:
                 return btrfs_ioctl_file_extent_same(file, argp);
+        case BTRFS_IOC_GET_SUPPORTED_FEATURES:
+                return btrfs_ioctl_get_supported_features(file, argp);
+        case BTRFS_IOC_GET_FEATURES:
+                return btrfs_ioctl_get_features(file, argp);
+        case BTRFS_IOC_SET_FEATURES:
+                return btrfs_ioctl_set_features(file, argp);
         }
 
         return -ENOTTY;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 45e618921c61..b4d69092fbdb 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -184,6 +184,12 @@ struct btrfs_ioctl_fs_info_args {
         __u64 reserved[124];                    /* pad to 1k */
 };
 
+struct btrfs_ioctl_feature_flags {
+        __u64 compat_flags;
+        __u64 compat_ro_flags;
+        __u64 incompat_flags;
+};
+
 /* balance control ioctl modes */
 #define BTRFS_BALANCE_CTL_PAUSE         1
 #define BTRFS_BALANCE_CTL_CANCEL        2
@@ -606,5 +612,11 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
                                     struct btrfs_ioctl_dev_replace_args)
 #define BTRFS_IOC_FILE_EXTENT_SAME _IOWR(BTRFS_IOCTL_MAGIC, 54, \
                                          struct btrfs_ioctl_same_args)
+#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 57, \
+                                   struct btrfs_ioctl_feature_flags)
+#define BTRFS_IOC_SET_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 57, \
+                                   struct btrfs_ioctl_feature_flags[2])
+#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 57, \
+                                   struct btrfs_ioctl_feature_flags[3])
 
 #endif /* _UAPI_LINUX_BTRFS_H */