thr3ads.net - Btrfs devel - [PATCH] btrfs: add ability to query/change feature bits online [Aug 2013]

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Jeff Mahoney

2013-Aug-27 19:17 UTC

[PATCH] btrfs: add ability to query/change feature bits online

There are some feature bits that require no offline setup and can
be enabled online. I''ve only reviewed extended irefs, but there will
probably be more.

We introduce three new ioctls:
- BTRFS_IOC_GET_SUPPORTED_FEATURES: query the kernel for supported features
- BTRFS_IOC_GET_FEATURES: query the kernel for enabled features on a per-fs
  basis.
- BTRFS_IOC_ADD_FEATURES: enable new features on a per-fs basis.

We introduce a new mask _SAFE_ONLINE that allows us to define which
features are safe to enable at runtime.

The failure modes for BTRFS_IOC_ADD_FEATURES are as follows:
- Enabling a completely unsupported feature: warns and returns -ENOTSUPP
- Enabling a feature that can only be done offline: warns and returns -EPERM

The structure passed in is not modified on return since it is possible
to isolate which features would bounce a -EPERM by subtracting the features
provided by a GET_SUPPORTED_FEATURES call.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 fs/btrfs/ctree.h           |    6 ++
 fs/btrfs/ioctl.c           |  127 +++++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/btrfs.h |   12 ++++
 3 files changed, 145 insertions(+)

--- a/fs/btrfs/ctree.h	2013-08-27 11:02:35.062626912 -0400
+++ b/fs/btrfs/ctree.h	2013-08-27 11:03:32.002352821 -0400
@@ -512,7 +512,10 @@ struct btrfs_super_block {
 #define BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA	(1ULL << 8)
 
 #define BTRFS_FEATURE_COMPAT_SUPP		0ULL
+#define BTRFS_FEATURE_COMPAT_ONLINE_SAFE	0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP		0ULL
+#define BTRFS_FEATURE_COMPAT_RO_ONLINE_SAFE	0ULL
+
 #define BTRFS_FEATURE_INCOMPAT_SUPP			\
 	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |		\
 	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |	\
@@ -523,6 +526,9 @@ struct btrfs_super_block {
 	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF |		\
 	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA)
 
+#define BTRFS_FEATURE_INCOMPAT_ONLINE_SAFE	\
+	(BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
+
 /*
  * 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)
--- a/fs/btrfs/ioctl.c	2013-08-27 11:02:35.062626912 -0400
+++ b/fs/btrfs/ioctl.c	2013-08-27 15:08:06.900740843 -0400
@@ -4098,6 +4098,127 @@ out_unlock:
 	return ret;
 }
 
+static int btrfs_ioctl_get_supported_features(struct file *file,
+					      void __user *arg)
+{
+	struct btrfs_ioctl_feature_flags features[2];
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	features[0].compat_flags = BTRFS_FEATURE_COMPAT_SUPP;
+	features[0].compat_ro_flags = BTRFS_FEATURE_COMPAT_RO_SUPP;
+	features[0].incompat_flags = BTRFS_FEATURE_INCOMPAT_SUPP;
+
+	features[1].compat_flags = BTRFS_FEATURE_COMPAT_ONLINE_SAFE;
+	features[1].compat_ro_flags = BTRFS_FEATURE_COMPAT_RO_ONLINE_SAFE;
+	features[1].incompat_flags = BTRFS_FEATURE_INCOMPAT_ONLINE_SAFE;
+
+	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;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	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 flags, u64 supported_flags,
+			      u64 allowed_flags)
+{
+	u64 disallowed, unsupported;
+
+	unsupported = flags & ~supported_flags;
+	if (unsupported) {
+		btrfs_warn(root->fs_info,
+			   "this kernel does not support %s bits %llx", type,
+			   unsupported);
+		return -EOPNOTSUPP;
+	}
+
+	disallowed = flags & ~allowed_flags;
+	if (disallowed) {
+		btrfs_warn(root->fs_info,
+			   "can''t enable %s bits %llx while mounted", type,
+			   disallowed);
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+#define check_feature(root, flags, mask_base)			\
+check_feature_bits(root, # mask_base, flags,			\
+		BTRFS_FEATURE_ ## mask_base ## _SUPP,		\
+		BTRFS_FEATURE_ ## mask_base ## _ONLINE_SAFE)
+
+static int btrfs_ioctl_add_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;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (copy_from_user(&features, arg, sizeof(features)))
+		return -EFAULT;
+
+	ret = check_feature(root, features.compat_flags, COMPAT);
+	if (ret)
+		return ret;
+
+	ret = check_feature(root, features.compat_ro_flags, COMPAT_RO);
+	if (ret)
+		return ret;
+
+	ret = check_feature(root, features.incompat_flags, INCOMPAT);
+	if (ret)
+		return ret;
+
+	if (features.compat_flags || features.compat_ro_flags ||
+	    features.incompat_flags) {
+		u64 flags;
+		struct btrfs_trans_handle *trans;
+		trans = btrfs_start_transaction(root, 1);
+		if (IS_ERR(trans))
+			return PTR_ERR(trans);
+
+		flags = btrfs_super_compat_flags(super_block);
+		flags |= features.compat_flags;
+		btrfs_set_super_compat_flags(super_block, flags);
+
+		flags = btrfs_super_compat_ro_flags(super_block);
+		flags |= features.compat_ro_flags;
+		btrfs_set_super_compat_ro_flags(super_block, flags);
+
+		flags = btrfs_super_incompat_flags(super_block);
+		flags |= features.incompat_flags;
+		btrfs_set_super_incompat_flags(super_block, flags);
+		return btrfs_end_transaction(trans, root);
+	}
+
+	return 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -4208,6 +4329,12 @@ long btrfs_ioctl(struct file *file, unsi
 		return btrfs_ioctl_get_fslabel(file, argp);
 	case BTRFS_IOC_SET_FSLABEL:
 		return btrfs_ioctl_set_fslabel(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_ADD_FEATURES:
+		return btrfs_ioctl_add_features(file, argp);
 	}
 
 	return -ENOTTY;
--- a/include/uapi/linux/btrfs.h	2013-08-27 11:02:35.062626912 -0400
+++ b/include/uapi/linux/btrfs.h	2013-08-27 11:03:32.006352802 -0400
@@ -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
@@ -579,4 +585,10 @@ static inline char *btrfs_err_str(enum b
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
 				    struct btrfs_ioctl_dev_replace_args)
+#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 54, \
+				   struct btrfs_ioctl_feature_flags)
+#define BTRFS_IOC_ADD_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 55, \
+				   struct btrfs_ioctl_feature_flags)
+#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 56, \
+				   struct btrfs_ioctl_feature_flags[2])
 #endif /* _UAPI_LINUX_BTRFS_H */

-- 
Jeff Mahoney
SUSE Labs
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Stefan Behrens

2013-Sep-03 09:25 UTC

head link

Re: [PATCH] btrfs: add ability to query/change feature bits online

On Tue, 27 Aug 2013 15:17:54 -0400, Jeff Mahoney wrote:> There are some feature bits that require no offline setup and can
> be enabled online. I''ve only reviewed extended irefs, but there
will
> probably be more.
> 
> We introduce three new ioctls:
> - BTRFS_IOC_GET_SUPPORTED_FEATURES: query the kernel for supported features
> - BTRFS_IOC_GET_FEATURES: query the kernel for enabled features on a per-fs
>   basis.
> - BTRFS_IOC_ADD_FEATURES: enable new features on a per-fs basis.
> 
> We introduce a new mask _SAFE_ONLINE that allows us to define which
> features are safe to enable at runtime.
> 
> The failure modes for BTRFS_IOC_ADD_FEATURES are as follows:
> - Enabling a completely unsupported feature: warns and returns -ENOTSUPP
> - Enabling a feature that can only be done offline: warns and returns
-EPERM
> 
> The structure passed in is not modified on return since it is possible
> to isolate which features would bounce a -EPERM by subtracting the features
> provided by a GET_SUPPORTED_FEATURES call.
> 
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
[...]> --- a/include/uapi/linux/btrfs.h	2013-08-27 11:02:35.062626912 -0400
> +++ b/include/uapi/linux/btrfs.h	2013-08-27 11:03:32.006352802 -0400
> @@ -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
> @@ -579,4 +585,10 @@ static inline char *btrfs_err_str(enum b
>  				      struct btrfs_ioctl_get_dev_stats)
>  #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
>  				    struct btrfs_ioctl_dev_replace_args)
> +#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 54, \
> +				   struct btrfs_ioctl_feature_flags)
> +#define BTRFS_IOC_ADD_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 55, \
> +				   struct btrfs_ioctl_feature_flags)
#define BTRFS_IOC_ADD_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 54, \
				   struct btrfs_ioctl_feature_flags)

Using 54 for both would also be possible since the directions are
different. _IOR(54) for the get ioctl and _IOW(54) for the set/add ioctl.

> +#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 56, \
> +				   struct btrfs_ioctl_feature_flags[2])
This could share the type value 54 too, since the parameter size is
different. There are only 8 bits for the type field.

And in order to support clearing feature bits you could replace the add
ioctl with a set ioctl and use a mask + value scheme.
#define BTRFS_IOC_SET_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 54, \
				   struct btrfs_ioctl_feature_flags[2])
btrfs_ioctl_feature_flags[0] is the mask and
btrfs_ioctl_feature_flags[1] is the value. Only bits that are set to one
in the mask are taken from the value and modified in the filesystem flags.


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Jeff Mahoney

2013-Sep-04 00:32 UTC

head link

Re: [PATCH] btrfs: add ability to query/change feature bits online

On 9/3/13 5:25 AM, Stefan Behrens wrote:> On Tue, 27 Aug 2013 15:17:54 -0400, Jeff Mahoney wrote:
>> There are some feature bits that require no offline setup and can
>> be enabled online. I''ve only reviewed extended irefs, but
there will
>> probably be more.
>>
>> We introduce three new ioctls:
>> - BTRFS_IOC_GET_SUPPORTED_FEATURES: query the kernel for supported
features
>> - BTRFS_IOC_GET_FEATURES: query the kernel for enabled features on a
per-fs
>>   basis.
>> - BTRFS_IOC_ADD_FEATURES: enable new features on a per-fs basis.
>>
>> We introduce a new mask _SAFE_ONLINE that allows us to define which
>> features are safe to enable at runtime.
>>
>> The failure modes for BTRFS_IOC_ADD_FEATURES are as follows:
>> - Enabling a completely unsupported feature: warns and returns
-ENOTSUPP
>> - Enabling a feature that can only be done offline: warns and returns
-EPERM
>>
>> The structure passed in is not modified on return since it is possible
>> to isolate which features would bounce a -EPERM by subtracting the
features
>> provided by a GET_SUPPORTED_FEATURES call.
>>
>> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> [...]
>> --- a/include/uapi/linux/btrfs.h	2013-08-27 11:02:35.062626912 -0400
>> +++ b/include/uapi/linux/btrfs.h	2013-08-27 11:03:32.006352802 -0400
>> @@ -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
>> @@ -579,4 +585,10 @@ static inline char *btrfs_err_str(enum b
>>  				      struct btrfs_ioctl_get_dev_stats)
>>  #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
>>  				    struct btrfs_ioctl_dev_replace_args)
>> +#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 54, \
>> +				   struct btrfs_ioctl_feature_flags)
>> +#define BTRFS_IOC_ADD_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 55, \
>> +				   struct btrfs_ioctl_feature_flags)
> 
> #define BTRFS_IOC_ADD_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 54, \
> 				   struct btrfs_ioctl_feature_flags)
> 
> Using 54 for both would also be possible since the directions are
> different. _IOR(54) for the get ioctl and _IOW(54) for the set/add ioctl.
> 
> 
>> +#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 56, \
>> +				   struct btrfs_ioctl_feature_flags[2])
> 
> This could share the type value 54 too, since the parameter size is
> different. There are only 8 bits for the type field.
Ah, yep. You''re right.
> And in order to support clearing feature bits you could replace the add
> ioctl with a set ioctl and use a mask + value scheme.
> #define BTRFS_IOC_SET_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 54, \
> 				   struct btrfs_ioctl_feature_flags[2])
> btrfs_ioctl_feature_flags[0] is the mask and
> btrfs_ioctl_feature_flags[1] is the value. Only bits that are set to one
> in the mask are taken from the value and modified in the filesystem flags.
Yep. Though for now I think I''d implement the clear as an EOPNOTSUPP.

-Jeff

-- 
Jeff Mahoney
SUSE Labs

David Sterba

2013-Sep-09 16:56 UTC

head link

Re: [PATCH] btrfs: add ability to query/change feature bits online

On Tue, Aug 27, 2013 at 03:17:54PM -0400, Jeff Mahoney
wrote:> +static int btrfs_ioctl_add_features(struct file *file, void __user *arg)
> +{...

		spin_lock(&fs_info->super_lock);
> +		flags = btrfs_super_compat_flags(super_block);
> +		flags |= features.compat_flags;
> +		btrfs_set_super_compat_flags(super_block, flags);
> +
> +		flags = btrfs_super_compat_ro_flags(super_block);
> +		flags |= features.compat_ro_flags;
> +		btrfs_set_super_compat_ro_flags(super_block, flags);
> +
> +		flags = btrfs_super_incompat_flags(super_block);
> +		flags |= features.incompat_flags;
> +		btrfs_set_super_incompat_flags(super_block, flags);
		spin_unlock(&fs_info->super_lock);
> +		return btrfs_end_transaction(trans, root);
> +	}
> +
> +	return 0;
> +}--
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Btrfs devel - Aug 2013 - [PATCH] btrfs: add ability to query/change feature bits online

[PATCH] btrfs: add ability to query/change feature bits online

Re: [PATCH] btrfs: add ability to query/change feature bits online

Re: [PATCH] btrfs: add ability to query/change feature bits online

Re: [PATCH] btrfs: add ability to query/change feature bits online