[2/7] btrfs-progs: cmds: add "btrfs tune set" subcommand group

Commit Message

Qu Wenruo Sept. 5, 2023, 7:51 a.m. UTC

As the first step to convert btrfstune into "btrfs tune" subcommand
group, this patch would add the following subcommand group:

 btrfs tune set <feature> [<device>]

For now the following features are supported:

- extref
- skinny-metadata
- no-holes
  All those are simple super block flags toggle.

- list-all
  This acts the same way as "mkfs.btrfs -O list-all", the difference is
  it would only list the supported features.
  (In the future, there will be "btrfs tune clear" subcommand, which
   would support a different set of features).

Signed-off-by: Qu Wenruo <[e-mail]>
---
 Documentation/btrfs-tune.rst |  40 ++++++
 Documentation/btrfs.rst      |   5 +
 Documentation/conf.py        |   1 +
 Documentation/man-index.rst  |   1 +
 Makefile                     |   2 +-
 btrfs.c                      |   1 +
 cmds/commands.h              |   1 +
 cmds/tune.c                  | 227 +++++++++++++++++++++++++++++++++++
 8 files changed, 277 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/btrfs-tune.rst
 create mode 100644 cmds/tune.c

Comments

Anand Jain Sept. 21, 2023, 12:53 a.m. UTC | #1

On 05/09/2023 15:51, Qu Wenruo wrote:
> As the first step to convert btrfstune into "btrfs tune" subcommand
> group, this patch would add the following subcommand group:
> 
>   btrfs tune set <feature> [<device>]
> 
> For now the following features are supported:
> 
> - extref
> - skinny-metadata
> - no-holes
>    All those are simple super block flags toggle.
> 
> - list-all
>    This acts the same way as "mkfs.btrfs -O list-all", the difference is
>    it would only list the supported features.
>    (In the future, there will be "btrfs tune clear" subcommand, which
>     would support a different set of features).
> 

With this patchset, the syntax is structured as follows:


    $ btrfs tune --help
    usage: btrfs tune <command> <args>

       btrfs tune set <feature> [<device>]
           Set/enable specified feature for the unmounted filesystem
       btrfs tune clear <feature> [<device>]
           Clear/disable specified feature for the unmounted filesystem

    change various btrfs features



However, for consistency, I suggest the following syntax:

   set:
    $ btrfs tune <feature> /dev/sda

   clear:
    $ btrfs tune <feature> --clear /dev/sda

   list:
    $ btrfs tune --list-all

This syntax aligns with the:

    $ btrfs device scan --forget


Thanks, Anand


> Signed-off-by: Qu Wenruo <[e-mail]>
> ---
>   Documentation/btrfs-tune.rst |  40 ++++++
>   Documentation/btrfs.rst      |   5 +
>   Documentation/conf.py        |   1 +
>   Documentation/man-index.rst  |   1 +
>   Makefile                     |   2 +-
>   btrfs.c                      |   1 +
>   cmds/commands.h              |   1 +
>   cmds/tune.c                  | 227 +++++++++++++++++++++++++++++++++++
>   8 files changed, 277 insertions(+), 1 deletion(-)
>   create mode 100644 Documentation/btrfs-tune.rst
>   create mode 100644 cmds/tune.c
> 
> diff --git a/Documentation/btrfs-tune.rst b/Documentation/btrfs-tune.rst
> new file mode 100644
> index 000000000000..827c92eadb72
> --- /dev/null
> +++ b/Documentation/btrfs-tune.rst
> @@ -0,0 +1,40 @@
> +btrfs-tune(8)
> +==================
> +
> +SYNOPSIS
> +--------
> +
> +**btrfs tune** <subcommand> [<args>]
> +
> +DESCRIPTION
> +-----------
> +
> +:command:`btrfs tune` is used to tweak various btrfs features on a
> +unmounted filesystem.
> +
> +SUBCOMMAND
> +-----------
> +
> +set <feature> [<device>]
> +        Set/enable a feature.
> +
> +        If *feature* is `list-all`, all supported features would be listed, and
> +	no *device* parameter is needed.
> +
> +EXIT STATUS
> +-----------
> +
> +**btrfs tune** returns a zero exit status if it succeeds. A non-zero value is
> +returned in case of failure.
> +
> +AVAILABILITY
> +------------
> +
> +**btrfs** is part of btrfs-progs.  Please refer to the documentation at
> +`https://btrfs.readthedocs.io <https://btrfs.readthedocs.io>`_.
> +
> +SEE ALSO
> +--------
> +
> +:doc:`mkfs.btrfs`,
> +``mount(8)``
> diff --git a/Documentation/btrfs.rst b/Documentation/btrfs.rst
> index e878f158aaa1..5aea0d1a208c 100644
> --- a/Documentation/btrfs.rst
> +++ b/Documentation/btrfs.rst
> @@ -134,6 +134,10 @@ subvolume
>   	Create/delete/list/manage btrfs subvolume.
>   	See :doc:`btrfs-subvolume` for details.
>   
> +tune
> +	Change various btrfs features.
> +	See :doc:`btrfs-tune` for details.
> +
>   .. _man-btrfs8-standalone-tools:
>   
>   STANDALONE TOOLS
> @@ -150,6 +154,7 @@ btrfs-convert
>           in-place conversion from ext2/3/4 filesystems to btrfs
>   btrfstune
>           tweak some filesystem properties on a unmounted filesystem
> +	(will be replaced by `btrfs-tune`)
>   btrfs-select-super
>           rescue tool to overwrite primary superblock from a spare copy
>   btrfs-find-root
> diff --git a/Documentation/conf.py b/Documentation/conf.py
> index 1025e10d7206..e0801bca4686 100644
> --- a/Documentation/conf.py
> +++ b/Documentation/conf.py
> @@ -66,6 +66,7 @@ man_pages = [
>       ('btrfs-check', 'btrfs-check', 'check or repair a btrfs filesystem', '', 8),
>       ('btrfs-balance', 'btrfs-balance', 'balance block groups on a btrfs filesystem', '', 8),
>       ('btrfs-subvolume', 'btrfs-subvolume', 'manage btrfs subvolumes', '', 8),
> +    ('btrfs-tune', 'btrfs-tune', 'tweak btrfs features', '', 8),
>       ('btrfs-map-logical', 'btrfs-map-logical', 'map btrfs logical extent to physical extent', '', 8),
>       ('btrfs', 'btrfs', 'a toolbox to manage btrfs filesystems', '', 8),
>       ('mkfs.btrfs', 'mkfs.btrfs', 'create a btrfs filesystem', '', 8),
> diff --git a/Documentation/man-index.rst b/Documentation/man-index.rst
> index 36d45d2903ea..5fcd4cbc4bee 100644
> --- a/Documentation/man-index.rst
> +++ b/Documentation/man-index.rst
> @@ -28,6 +28,7 @@ Manual pages
>      btrfs-select-super
>      btrfs-send
>      btrfs-subvolume
> +   btrfs-tune
>      btrfstune
>      fsck.btrfs
>      mkfs.btrfs
> diff --git a/Makefile b/Makefile
> index f4feb1fff8e1..9857daaa42ac 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -239,7 +239,7 @@ cmds_objects = cmds/subvolume.o cmds/subvolume-list.o \
>   	       cmds/rescue-super-recover.o \
>   	       cmds/property.o cmds/filesystem-usage.o cmds/inspect-dump-tree.o \
>   	       cmds/inspect-dump-super.o cmds/inspect-tree-stats.o cmds/filesystem-du.o \
> -	       cmds/reflink.o \
> +	       cmds/reflink.o cmds/tune.o \
>   	       mkfs/common.o check/mode-common.o check/mode-lowmem.o \
>   	       check/clear-cache.o
>   
> diff --git a/btrfs.c b/btrfs.c
> index 751f193ee2e0..c2dae0303ffe 100644
> --- a/btrfs.c
> +++ b/btrfs.c
> @@ -389,6 +389,7 @@ static const struct cmd_group btrfs_cmd_group = {
>   		&cmd_struct_scrub,
>   		&cmd_struct_send,
>   		&cmd_struct_subvolume,
> +		&cmd_struct_tune,
>   
>   		/* Help and version stay last */
>   		&cmd_struct_help,
> diff --git a/cmds/commands.h b/cmds/commands.h
> index 5ab7c881f634..aebacd718a7b 100644
> --- a/cmds/commands.h
> +++ b/cmds/commands.h
> @@ -151,5 +151,6 @@ DECLARE_COMMAND(qgroup);
>   DECLARE_COMMAND(replace);
>   DECLARE_COMMAND(restore);
>   DECLARE_COMMAND(rescue);
> +DECLARE_COMMAND(tune);
>   
>   #endif
> diff --git a/cmds/tune.c b/cmds/tune.c
> new file mode 100644
> index 000000000000..92c7b9f1502c
> --- /dev/null
> +++ b/cmds/tune.c
> @@ -0,0 +1,227 @@
> +/*
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public
> + * License v2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public
> + * License along with this program; if not, write to the
> + * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
> + * Boston, MA 021110-1307, USA.
> + */
> +
> +#include <unistd.h>
> +#include "kerncompat.h"
> +#include "cmds/commands.h"
> +#include "common/help.h"
> +#include "common/fsfeatures.h"
> +#include "kernel-shared/messages.h"
> +#include "kernel-shared/disk-io.h"
> +#include "kernel-shared/transaction.h"
> +
> +static const char * const cmd_tune_set_usage[] = {
> +	"btrfs tune set <feature> [<device>]",
> +	"Set/enable specified feature for the unmounted filesystem",
> +	"",
> +	HELPINFO_INSERT_GLOBALS,
> +	HELPINFO_INSERT_VERBOSE,
> +	NULL,
> +};
> +
> +static const struct btrfs_feature set_features[] = {
> +	{
> +		.name		= "extref",
> +		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF,
> +		.sysfs_name	= "extended_iref",
> +		VERSION_TO_STRING2(compat, 3,7),
> +		VERSION_TO_STRING2(safe, 3,12),
> +		VERSION_TO_STRING2(default, 3,12),
> +		.desc		= "increased hardlink limit per file to 65536"
> +	}, {
> +		.name		= "skinny-metadata",
> +		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA,
> +		.sysfs_name	= "skinny_metadata",
> +		VERSION_TO_STRING2(compat, 3,10),
> +		VERSION_TO_STRING2(safe, 3,18),
> +		VERSION_TO_STRING2(default, 3,18),
> +		.desc		= "reduced-size metadata extent refs"
> +	}, {
> +		.name		= "no-holes",
> +		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_NO_HOLES,
> +		.sysfs_name	= "no_holes",
> +		VERSION_TO_STRING2(compat, 3,14),
> +		VERSION_TO_STRING2(safe, 4,0),
> +		VERSION_TO_STRING2(default, 5,15),
> +		.desc		= "no explicit hole extents for files"
> +	},
> +	/* Keep this one last */
> +	{
> +		.name		= "list-all",
> +		.runtime_flag	= BTRFS_FEATURE_RUNTIME_LIST_ALL,
> +		.sysfs_name	= NULL,
> +		VERSION_NULL(compat),
> +		VERSION_NULL(safe),
> +		VERSION_NULL(default),
> +		.desc		= NULL
> +	}
> +};
> +
> +static void list_all_features(const char *prefix,
> +			      const struct btrfs_feature *features,
> +			      int nr_features)
> +{
> +	/* We should have at least one empty feature. */
> +	ASSERT(nr_features > 1);
> +
> +	printf("features available to %s:\n", prefix);
> +	for (int i = 0; i < nr_features - 1; i++) {
> +		const struct btrfs_feature *feat = features + i;
> +		const char *sep = "";
> +
> +		fprintf(stderr, "%-20s- %s (", feat->name, feat->desc);
> +		if (feat->compat_ver) {
> +			fprintf(stderr, "compat=%s", feat->compat_str);
> +			sep = ", ";
> +		}
> +		if (feat->safe_ver) {
> +			fprintf(stderr, "%ssafe=%s", sep, feat->safe_str);
> +			sep = ", ";
> +		}
> +		if (feat->default_ver)
> +			fprintf(stderr, "%sdefault=%s", sep, feat->default_str);
> +		fprintf(stderr, ")\n");
> +	}
> +}
> +
> +static int check_features(const char *name, const struct btrfs_feature *features,
> +			  int nr_features)
> +{
> +	bool found = false;
> +
> +	for (int i = 0; i < nr_features; i++) {
> +		const struct btrfs_feature *feat = features + i;
> +
> +		if (!strcmp(feat->name, name)) {
> +			found = true;
> +			break;
> +		}
> +	}
> +	if (found)
> +		return 0;
> +	return -EINVAL;
> +}
> +
> +static int set_super_incompat_flags(struct btrfs_fs_info *fs_info, u64 flags)
> +{
> +	struct btrfs_root *root = fs_info->tree_root;
> +	struct btrfs_trans_handle *trans;
> +	struct btrfs_super_block *disk_super;
> +	u64 super_flags;
> +	int ret;
> +
> +	disk_super = fs_info->super_copy;
> +	super_flags = btrfs_super_incompat_flags(disk_super);
> +	super_flags |= flags;
> +	trans = btrfs_start_transaction(root, 1);
> +	BUG_ON(IS_ERR(trans));
> +	btrfs_set_super_incompat_flags(disk_super, super_flags);
> +	ret = btrfs_commit_transaction(trans, root);
> +
> +	return ret;
> +}
> +
> +static int cmd_tune_set(const struct cmd_struct *cmd, int argc, char **argv)
> +{
> +	struct btrfs_fs_info *fs_info;
> +	struct open_ctree_args oca = { 0 };
> +	char *feature;
> +	char *path;
> +	int ret = 0;
> +
> +	optind = 0;
> +	while (1) {
> +		int c = getopt(argc, argv, "");
> +		if (c < 0)
> +			break;
> +
> +		switch (c) {
> +		default:
> +			usage_unknown_option(cmd, argv);
> +		}
> +	}
> +
> +	if (check_argc_min(argc - optind, 1))
> +		return 1;
> +
> +	feature = argv[optind];
> +
> +	if (check_features(feature, set_features, ARRAY_SIZE(set_features))) {
> +		error("Unknown feature to set: %s", feature);
> +		return 1;
> +	}
> +	if (!strcmp(feature, "list-all")) {
> +		list_all_features("set", set_features, ARRAY_SIZE(set_features));
> +		return 0;
> +	}
> +
> +	if (check_argc_exact(argc - optind, 2))
> +		return 1;
> +
> +	path = argv[optind + 1];
> +	oca.flags = OPEN_CTREE_WRITES;
> +	oca.filename = path;
> +	fs_info = open_ctree_fs_info(&oca);
> +	if (!fs_info) {
> +		error("failed to open btrfs");
> +		ret = -EIO;
> +		goto out;
> +	}
> +	/*
> +	 * For those 3 features, we only need to update the superblock to add
> +	 * the new feature flags.
> +	 */
> +	if (!strcmp(feature, "extref") ||
> +	    !strcmp(feature, "skinny-metadata") ||
> +	    !strcmp(feature, "no-holes")) {
> +		u64 incompat_flags = 0;
> +
> +		if (!strcmp(feature, "extref"))
> +			incompat_flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
> +		if (!strcmp(feature, "skinny-metadata"))
> +			incompat_flags |= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA;
> +		if (!strcmp(feature, "no-holes"))
> +			incompat_flags |= BTRFS_FEATURE_INCOMPAT_NO_HOLES;
> +		ret = set_super_incompat_flags(fs_info, incompat_flags);
> +		if (ret < 0) {
> +			errno = -ret;
> +			error("failed to set feature '%s': %m", feature);
> +		}
> +		goto out;
> +	}
> +
> +out:
> +	if (fs_info)
> +		close_ctree_fs_info(fs_info);
> +	return !!ret;
> +}
> +
> +static DEFINE_SIMPLE_COMMAND(tune_set, "set");
> +
> +static const char * const tune_cmd_group_usage[] = {
> +	"btrfs tune <command> <args>",
> +	NULL,
> +};
> +
> +static const char tune_cmd_group_info[] = "change various btrfs features";
> +
> +static const struct cmd_group tune_cmd_group = {
> +	tune_cmd_group_usage, tune_cmd_group_info, {
> +		&cmd_struct_tune_set,
> +		NULL
> +	}
> +};
> +DEFINE_GROUP_COMMAND_TOKEN(tune);

Qu Wenruo Sept. 21, 2023, 2:13 a.m. UTC | #2

On 2023/9/21 10:23, Anand Jain wrote:
> On 05/09/2023 15:51, Qu Wenruo wrote:
>> As the first step to convert btrfstune into "btrfs tune" subcommand
>> group, this patch would add the following subcommand group:
>>
>>   btrfs tune set <feature> [<device>]
>>
>> For now the following features are supported:
>>
>> - extref
>> - skinny-metadata
>> - no-holes
>>    All those are simple super block flags toggle.
>>
>> - list-all
>>    This acts the same way as "mkfs.btrfs -O list-all", the difference is
>>    it would only list the supported features.
>>    (In the future, there will be "btrfs tune clear" subcommand, which
>>     would support a different set of features).
>>
> 
> With this patchset, the syntax is structured as follows:
> 
> 
>     $ btrfs tune --help
>     usage: btrfs tune <command> <args>
> 
>        btrfs tune set <feature> [<device>]
>            Set/enable specified feature for the unmounted filesystem
>        btrfs tune clear <feature> [<device>]
>            Clear/disable specified feature for the unmounted filesystem
> 
>     change various btrfs features
> 
> 
> 
> However, for consistency, I suggest the following syntax:
> 
>    set:
>     $ btrfs tune <feature> /dev/sda
> 
>    clear:
>     $ btrfs tune <feature> --clear /dev/sda
> 
>    list:
>     $ btrfs tune --list-all

This can be confusing instead.

Remember set and clear have different supported feature set.
E.g. we can not disable no-holes/extref features.

Thus here we want set/clear as subcommands, not the features name itself.

Furthermore, using <feature> as the subcommand wil later conflicts with 
other subcommand like "change-csum" and "change-fsid".

> 
> This syntax aligns with the:
> 
>     $ btrfs device scan --forget

In fact, the current "set/clear" follows the existing behavior, it's 
more clear if you scan a single device:

   btrfs device scan <device_name>

As for btrfs tune it goes:

   btrfs tune set <feature_name> <mnt>

We should put the variable parameter last, not between some fixed 
subcommand.

Thanks,
Qu

> 
> 
> Thanks, Anand
> 
> 
>> Signed-off-by: Qu Wenruo <[e-mail]>
>> ---
>>   Documentation/btrfs-tune.rst |  40 ++++++
>>   Documentation/btrfs.rst      |   5 +
>>   Documentation/conf.py        |   1 +
>>   Documentation/man-index.rst  |   1 +
>>   Makefile                     |   2 +-
>>   btrfs.c                      |   1 +
>>   cmds/commands.h              |   1 +
>>   cmds/tune.c                  | 227 +++++++++++++++++++++++++++++++++++
>>   8 files changed, 277 insertions(+), 1 deletion(-)
>>   create mode 100644 Documentation/btrfs-tune.rst
>>   create mode 100644 cmds/tune.c
>>
>> diff --git a/Documentation/btrfs-tune.rst b/Documentation/btrfs-tune.rst
>> new file mode 100644
>> index 000000000000..827c92eadb72
>> --- /dev/null
>> +++ b/Documentation/btrfs-tune.rst
>> @@ -0,0 +1,40 @@
>> +btrfs-tune(8)
>> +==================
>> +
>> +SYNOPSIS
>> +--------
>> +
>> +**btrfs tune** <subcommand> [<args>]
>> +
>> +DESCRIPTION
>> +-----------
>> +
>> +:command:`btrfs tune` is used to tweak various btrfs features on a
>> +unmounted filesystem.
>> +
>> +SUBCOMMAND
>> +-----------
>> +
>> +set <feature> [<device>]
>> +        Set/enable a feature.
>> +
>> +        If *feature* is `list-all`, all supported features would be 
>> listed, and
>> +    no *device* parameter is needed.
>> +
>> +EXIT STATUS
>> +-----------
>> +
>> +**btrfs tune** returns a zero exit status if it succeeds. A non-zero 
>> value is
>> +returned in case of failure.
>> +
>> +AVAILABILITY
>> +------------
>> +
>> +**btrfs** is part of btrfs-progs.  Please refer to the documentation at
>> +`https://btrfs.readthedocs.io <https://btrfs.readthedocs.io>`_.
>> +
>> +SEE ALSO
>> +--------
>> +
>> +:doc:`mkfs.btrfs`,
>> +``mount(8)``
>> diff --git a/Documentation/btrfs.rst b/Documentation/btrfs.rst
>> index e878f158aaa1..5aea0d1a208c 100644
>> --- a/Documentation/btrfs.rst
>> +++ b/Documentation/btrfs.rst
>> @@ -134,6 +134,10 @@ subvolume
>>       Create/delete/list/manage btrfs subvolume.
>>       See :doc:`btrfs-subvolume` for details.
>> +tune
>> +    Change various btrfs features.
>> +    See :doc:`btrfs-tune` for details.
>> +
>>   .. _man-btrfs8-standalone-tools:
>>   STANDALONE TOOLS
>> @@ -150,6 +154,7 @@ btrfs-convert
>>           in-place conversion from ext2/3/4 filesystems to btrfs
>>   btrfstune
>>           tweak some filesystem properties on a unmounted filesystem
>> +    (will be replaced by `btrfs-tune`)
>>   btrfs-select-super
>>           rescue tool to overwrite primary superblock from a spare copy
>>   btrfs-find-root
>> diff --git a/Documentation/conf.py b/Documentation/conf.py
>> index 1025e10d7206..e0801bca4686 100644
>> --- a/Documentation/conf.py
>> +++ b/Documentation/conf.py
>> @@ -66,6 +66,7 @@ man_pages = [
>>       ('btrfs-check', 'btrfs-check', 'check or repair a btrfs 
>> filesystem', '', 8),
>>       ('btrfs-balance', 'btrfs-balance', 'balance block groups on a 
>> btrfs filesystem', '', 8),
>>       ('btrfs-subvolume', 'btrfs-subvolume', 'manage btrfs 
>> subvolumes', '', 8),
>> +    ('btrfs-tune', 'btrfs-tune', 'tweak btrfs features', '', 8),
>>       ('btrfs-map-logical', 'btrfs-map-logical', 'map btrfs logical 
>> extent to physical extent', '', 8),
>>       ('btrfs', 'btrfs', 'a toolbox to manage btrfs filesystems', '', 8),
>>       ('mkfs.btrfs', 'mkfs.btrfs', 'create a btrfs filesystem', '', 8),
>> diff --git a/Documentation/man-index.rst b/Documentation/man-index.rst
>> index 36d45d2903ea..5fcd4cbc4bee 100644
>> --- a/Documentation/man-index.rst
>> +++ b/Documentation/man-index.rst
>> @@ -28,6 +28,7 @@ Manual pages
>>      btrfs-select-super
>>      btrfs-send
>>      btrfs-subvolume
>> +   btrfs-tune
>>      btrfstune
>>      fsck.btrfs
>>      mkfs.btrfs
>> diff --git a/Makefile b/Makefile
>> index f4feb1fff8e1..9857daaa42ac 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -239,7 +239,7 @@ cmds_objects = cmds/subvolume.o 
>> cmds/subvolume-list.o \
>>              cmds/rescue-super-recover.o \
>>              cmds/property.o cmds/filesystem-usage.o 
>> cmds/inspect-dump-tree.o \
>>              cmds/inspect-dump-super.o cmds/inspect-tree-stats.o 
>> cmds/filesystem-du.o \
>> -           cmds/reflink.o \
>> +           cmds/reflink.o cmds/tune.o \
>>              mkfs/common.o check/mode-common.o check/mode-lowmem.o \
>>              check/clear-cache.o
>> diff --git a/btrfs.c b/btrfs.c
>> index 751f193ee2e0..c2dae0303ffe 100644
>> --- a/btrfs.c
>> +++ b/btrfs.c
>> @@ -389,6 +389,7 @@ static const struct cmd_group btrfs_cmd_group = {
>>           &cmd_struct_scrub,
>>           &cmd_struct_send,
>>           &cmd_struct_subvolume,
>> +        &cmd_struct_tune,
>>           /* Help and version stay last */
>>           &cmd_struct_help,
>> diff --git a/cmds/commands.h b/cmds/commands.h
>> index 5ab7c881f634..aebacd718a7b 100644
>> --- a/cmds/commands.h
>> +++ b/cmds/commands.h
>> @@ -151,5 +151,6 @@ DECLARE_COMMAND(qgroup);
>>   DECLARE_COMMAND(replace);
>>   DECLARE_COMMAND(restore);
>>   DECLARE_COMMAND(rescue);
>> +DECLARE_COMMAND(tune);
>>   #endif
>> diff --git a/cmds/tune.c b/cmds/tune.c
>> new file mode 100644
>> index 000000000000..92c7b9f1502c
>> --- /dev/null
>> +++ b/cmds/tune.c
>> @@ -0,0 +1,227 @@
>> +/*
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public
>> + * License v2 as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public
>> + * License along with this program; if not, write to the
>> + * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
>> + * Boston, MA 021110-1307, USA.
>> + */
>> +
>> +#include <unistd.h>
>> +#include "kerncompat.h"
>> +#include "cmds/commands.h"
>> +#include "common/help.h"
>> +#include "common/fsfeatures.h"
>> +#include "kernel-shared/messages.h"
>> +#include "kernel-shared/disk-io.h"
>> +#include "kernel-shared/transaction.h"
>> +
>> +static const char * const cmd_tune_set_usage[] = {
>> +    "btrfs tune set <feature> [<device>]",
>> +    "Set/enable specified feature for the unmounted filesystem",
>> +    "",
>> +    HELPINFO_INSERT_GLOBALS,
>> +    HELPINFO_INSERT_VERBOSE,
>> +    NULL,
>> +};
>> +
>> +static const struct btrfs_feature set_features[] = {
>> +    {
>> +        .name        = "extref",
>> +        .incompat_flag    = BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF,
>> +        .sysfs_name    = "extended_iref",
>> +        VERSION_TO_STRING2(compat, 3,7),
>> +        VERSION_TO_STRING2(safe, 3,12),
>> +        VERSION_TO_STRING2(default, 3,12),
>> +        .desc        = "increased hardlink limit per file to 65536"
>> +    }, {
>> +        .name        = "skinny-metadata",
>> +        .incompat_flag    = BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA,
>> +        .sysfs_name    = "skinny_metadata",
>> +        VERSION_TO_STRING2(compat, 3,10),
>> +        VERSION_TO_STRING2(safe, 3,18),
>> +        VERSION_TO_STRING2(default, 3,18),
>> +        .desc        = "reduced-size metadata extent refs"
>> +    }, {
>> +        .name        = "no-holes",
>> +        .incompat_flag    = BTRFS_FEATURE_INCOMPAT_NO_HOLES,
>> +        .sysfs_name    = "no_holes",
>> +        VERSION_TO_STRING2(compat, 3,14),
>> +        VERSION_TO_STRING2(safe, 4,0),
>> +        VERSION_TO_STRING2(default, 5,15),
>> +        .desc        = "no explicit hole extents for files"
>> +    },
>> +    /* Keep this one last */
>> +    {
>> +        .name        = "list-all",
>> +        .runtime_flag    = BTRFS_FEATURE_RUNTIME_LIST_ALL,
>> +        .sysfs_name    = NULL,
>> +        VERSION_NULL(compat),
>> +        VERSION_NULL(safe),
>> +        VERSION_NULL(default),
>> +        .desc        = NULL
>> +    }
>> +};
>> +
>> +static void list_all_features(const char *prefix,
>> +                  const struct btrfs_feature *features,
>> +                  int nr_features)
>> +{
>> +    /* We should have at least one empty feature. */
>> +    ASSERT(nr_features > 1);
>> +
>> +    printf("features available to %s:\n", prefix);
>> +    for (int i = 0; i < nr_features - 1; i++) {
>> +        const struct btrfs_feature *feat = features + i;
>> +        const char *sep = "";
>> +
>> +        fprintf(stderr, "%-20s- %s (", feat->name, feat->desc);
>> +        if (feat->compat_ver) {
>> +            fprintf(stderr, "compat=%s", feat->compat_str);
>> +            sep = ", ";
>> +        }
>> +        if (feat->safe_ver) {
>> +            fprintf(stderr, "%ssafe=%s", sep, feat->safe_str);
>> +            sep = ", ";
>> +        }
>> +        if (feat->default_ver)
>> +            fprintf(stderr, "%sdefault=%s", sep, feat->default_str);
>> +        fprintf(stderr, ")\n");
>> +    }
>> +}
>> +
>> +static int check_features(const char *name, const struct 
>> btrfs_feature *features,
>> +              int nr_features)
>> +{
>> +    bool found = false;
>> +
>> +    for (int i = 0; i < nr_features; i++) {
>> +        const struct btrfs_feature *feat = features + i;
>> +
>> +        if (!strcmp(feat->name, name)) {
>> +            found = true;
>> +            break;
>> +        }
>> +    }
>> +    if (found)
>> +        return 0;
>> +    return -EINVAL;
>> +}
>> +
>> +static int set_super_incompat_flags(struct btrfs_fs_info *fs_info, 
>> u64 flags)
>> +{
>> +    struct btrfs_root *root = fs_info->tree_root;
>> +    struct btrfs_trans_handle *trans;
>> +    struct btrfs_super_block *disk_super;
>> +    u64 super_flags;
>> +    int ret;
>> +
>> +    disk_super = fs_info->super_copy;
>> +    super_flags = btrfs_super_incompat_flags(disk_super);
>> +    super_flags |= flags;
>> +    trans = btrfs_start_transaction(root, 1);
>> +    BUG_ON(IS_ERR(trans));
>> +    btrfs_set_super_incompat_flags(disk_super, super_flags);
>> +    ret = btrfs_commit_transaction(trans, root);
>> +
>> +    return ret;
>> +}
>> +
>> +static int cmd_tune_set(const struct cmd_struct *cmd, int argc, char 
>> **argv)
>> +{
>> +    struct btrfs_fs_info *fs_info;
>> +    struct open_ctree_args oca = { 0 };
>> +    char *feature;
>> +    char *path;
>> +    int ret = 0;
>> +
>> +    optind = 0;
>> +    while (1) {
>> +        int c = getopt(argc, argv, "");
>> +        if (c < 0)
>> +            break;
>> +
>> +        switch (c) {
>> +        default:
>> +            usage_unknown_option(cmd, argv);
>> +        }
>> +    }
>> +
>> +    if (check_argc_min(argc - optind, 1))
>> +        return 1;
>> +
>> +    feature = argv[optind];
>> +
>> +    if (check_features(feature, set_features, 
>> ARRAY_SIZE(set_features))) {
>> +        error("Unknown feature to set: %s", feature);
>> +        return 1;
>> +    }
>> +    if (!strcmp(feature, "list-all")) {
>> +        list_all_features("set", set_features, 
>> ARRAY_SIZE(set_features));
>> +        return 0;
>> +    }
>> +
>> +    if (check_argc_exact(argc - optind, 2))
>> +        return 1;
>> +
>> +    path = argv[optind + 1];
>> +    oca.flags = OPEN_CTREE_WRITES;
>> +    oca.filename = path;
>> +    fs_info = open_ctree_fs_info(&oca);
>> +    if (!fs_info) {
>> +        error("failed to open btrfs");
>> +        ret = -EIO;
>> +        goto out;
>> +    }
>> +    /*
>> +     * For those 3 features, we only need to update the superblock to 
>> add
>> +     * the new feature flags.
>> +     */
>> +    if (!strcmp(feature, "extref") ||
>> +        !strcmp(feature, "skinny-metadata") ||
>> +        !strcmp(feature, "no-holes")) {
>> +        u64 incompat_flags = 0;
>> +
>> +        if (!strcmp(feature, "extref"))
>> +            incompat_flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
>> +        if (!strcmp(feature, "skinny-metadata"))
>> +            incompat_flags |= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA;
>> +        if (!strcmp(feature, "no-holes"))
>> +            incompat_flags |= BTRFS_FEATURE_INCOMPAT_NO_HOLES;
>> +        ret = set_super_incompat_flags(fs_info, incompat_flags);
>> +        if (ret < 0) {
>> +            errno = -ret;
>> +            error("failed to set feature '%s': %m", feature);
>> +        }
>> +        goto out;
>> +    }
>> +
>> +out:
>> +    if (fs_info)
>> +        close_ctree_fs_info(fs_info);
>> +    return !!ret;
>> +}
>> +
>> +static DEFINE_SIMPLE_COMMAND(tune_set, "set");
>> +
>> +static const char * const tune_cmd_group_usage[] = {
>> +    "btrfs tune <command> <args>",
>> +    NULL,
>> +};
>> +
>> +static const char tune_cmd_group_info[] = "change various btrfs 
>> features";
>> +
>> +static const struct cmd_group tune_cmd_group = {
>> +    tune_cmd_group_usage, tune_cmd_group_info, {
>> +        &cmd_struct_tune_set,
>> +        NULL
>> +    }
>> +};
>> +DEFINE_GROUP_COMMAND_TOKEN(tune);
>

David Sterba Oct. 13, 2023, 5:47 p.m. UTC | #3

On Thu, Sep 21, 2023 at 08:53:11AM +0800, Anand Jain wrote:
> On 05/09/2023 15:51, Qu Wenruo wrote:
> > As the first step to convert btrfstune into "btrfs tune" subcommand
> > group, this patch would add the following subcommand group:
> > 
> >   btrfs tune set <feature> [<device>]
> > 
> > For now the following features are supported:
> > 
> > - extref
> > - skinny-metadata
> > - no-holes
> >    All those are simple super block flags toggle.
> > 
> > - list-all
> >    This acts the same way as "mkfs.btrfs -O list-all", the difference is
> >    it would only list the supported features.
> >    (In the future, there will be "btrfs tune clear" subcommand, which
> >     would support a different set of features).
> > 
> 
> With this patchset, the syntax is structured as follows:
> 
> 
>     $ btrfs tune --help
>     usage: btrfs tune <command> <args>
> 
>        btrfs tune set <feature> [<device>]
>            Set/enable specified feature for the unmounted filesystem
>        btrfs tune clear <feature> [<device>]
>            Clear/disable specified feature for the unmounted filesystem
> 
>     change various btrfs features
> 
> 
> 
> However, for consistency, I suggest the following syntax:

Consistency with what? If it's with btrfstune then no, the reason why
the command is split into subcommands is because the command line
parameters became unwieldy and what you suggest below copies that.

> 
>    set:
>     $ btrfs tune <feature> /dev/sda
> 
>    clear:
>     $ btrfs tune <feature> --clear /dev/sda
> 
>    list:
>     $ btrfs tune --list-all
> 
> This syntax aligns with the:
> 
>     $ btrfs device scan --forget

The difference is that scan won't be extended much if ever. The 'tune'
interface grows over time so we need properly structure that so we don't
end in command line option mess.

As an anti-pattern I can mention the 'mdadm' utility, that comes from
times when the commands were not without the initial "--" like we know
from git etc, so the main commands like assemble are specified by -A or
--assemble. What I find confusing is that it's just another option but
means a main action. The command groups logically and visually
encapsulate one action and can be possibly fine tuned by parameters
without affecting other commands.

Anand Jain Oct. 30, 2023, 8:26 a.m. UTC | #4

On 10/14/23 01:47, David Sterba wrote:
> On Thu, Sep 21, 2023 at 08:53:11AM +0800, Anand Jain wrote:
>> On 05/09/2023 15:51, Qu Wenruo wrote:
>>> As the first step to convert btrfstune into "btrfs tune" subcommand
>>> group, this patch would add the following subcommand group:
>>>
>>>    btrfs tune set <feature> [<device>]
>>>
>>> For now the following features are supported:
>>>
>>> - extref
>>> - skinny-metadata
>>> - no-holes
>>>     All those are simple super block flags toggle.
>>>
>>> - list-all
>>>     This acts the same way as "mkfs.btrfs -O list-all", the difference is
>>>     it would only list the supported features.
>>>     (In the future, there will be "btrfs tune clear" subcommand, which
>>>      would support a different set of features).
>>>
>>
>> With this patchset, the syntax is structured as follows:
>>
>>
>>      $ btrfs tune --help
>>      usage: btrfs tune <command> <args>
>>
>>         btrfs tune set <feature> [<device>]
>>             Set/enable specified feature for the unmounted filesystem
>>         btrfs tune clear <feature> [<device>]
>>             Clear/disable specified feature for the unmounted filesystem
>>
>>      change various btrfs features
>>
>>
>>
>> However, for consistency, I suggest the following syntax:
> 
> Consistency with what? If it's with btrfstune then no, the reason why
> the command is split into subcommands is because the command line
> parameters became unwieldy and what you suggest below copies that.
> 
>>
>>     set:
>>      $ btrfs tune <feature> /dev/sda
>>
>>     clear:
>>      $ btrfs tune <feature> --clear /dev/sda
>>
>>     list:
>>      $ btrfs tune --list-all
>>
>> This syntax aligns with the:
>>
>>      $ btrfs device scan --forget
> 
> The difference is that scan won't be extended much if ever. The 'tune'
> interface grows over time so we need properly structure that so we don't
> end in command line option mess.


My apologies for not responding earlier. When designing the 'btrfs tune' 
command, pls consider we may need '--noscan' and '--device' options at 
some point. For example:

$ btrfs tune metadata --device=/dev/sda --noscan /dev/sdb

This idea is inspired by the following command:

$ btrfs inspect-internal dump-tree --noscan /dev/sda1

OR

Since some of the commands perform a user-space system-wide scan for
btrfs-block-devices, so global options like is also not a bad idea.

    '--devices' (specify btrfs image files and continue scanning for 
block devices across the system)

and

    '--noscan' (to avoid a system-wide block device scan when needed).


Thx, Anand


> 
> As an anti-pattern I can mention the 'mdadm' utility, that comes from
> times when the commands were not without the initial "--" like we know
> from git etc, so the main commands like assemble are specified by -A or
> --assemble. What I find confusing is that it's just another option but
> means a main action. The command groups logically and visually
> encapsulate one action and can be possibly fine tuned by parameters
> without affecting other commands.

Patch

diff --git a/Documentation/btrfs-tune.rst b/Documentation/btrfs-tune.rst
new file mode 100644
index 000000000000..827c92eadb72
--- /dev/null
+++ b/Documentation/btrfs-tune.rst
@@ -0,0 +1,40 @@ 
+btrfs-tune(8)
+==================
+
+SYNOPSIS
+--------
+
+**btrfs tune** <subcommand> [<args>]
+
+DESCRIPTION
+-----------
+
+:command:`btrfs tune` is used to tweak various btrfs features on a
+unmounted filesystem.
+
+SUBCOMMAND
+-----------
+
+set <feature> [<device>]
+        Set/enable a feature.
+
+        If *feature* is `list-all`, all supported features would be listed, and
+	no *device* parameter is needed.
+
+EXIT STATUS
+-----------
+
+**btrfs tune** returns a zero exit status if it succeeds. A non-zero value is
+returned in case of failure.
+
+AVAILABILITY
+------------
+
+**btrfs** is part of btrfs-progs.  Please refer to the documentation at
+`https://btrfs.readthedocs.io <https://btrfs.readthedocs.io>`_.
+
+SEE ALSO
+--------
+
+:doc:`mkfs.btrfs`,
+``mount(8)``
diff --git a/Documentation/btrfs.rst b/Documentation/btrfs.rst
index e878f158aaa1..5aea0d1a208c 100644
--- a/Documentation/btrfs.rst
+++ b/Documentation/btrfs.rst
@@ -134,6 +134,10 @@  subvolume
 	Create/delete/list/manage btrfs subvolume.
 	See :doc:`btrfs-subvolume` for details.
 
+tune
+	Change various btrfs features.
+	See :doc:`btrfs-tune` for details.
+
 .. _man-btrfs8-standalone-tools:
 
 STANDALONE TOOLS
@@ -150,6 +154,7 @@  btrfs-convert
         in-place conversion from ext2/3/4 filesystems to btrfs
 btrfstune
         tweak some filesystem properties on a unmounted filesystem
+	(will be replaced by `btrfs-tune`)
 btrfs-select-super
         rescue tool to overwrite primary superblock from a spare copy
 btrfs-find-root
diff --git a/Documentation/conf.py b/Documentation/conf.py
index 1025e10d7206..e0801bca4686 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -66,6 +66,7 @@  man_pages = [
     ('btrfs-check', 'btrfs-check', 'check or repair a btrfs filesystem', '', 8),
     ('btrfs-balance', 'btrfs-balance', 'balance block groups on a btrfs filesystem', '', 8),
     ('btrfs-subvolume', 'btrfs-subvolume', 'manage btrfs subvolumes', '', 8),
+    ('btrfs-tune', 'btrfs-tune', 'tweak btrfs features', '', 8),
     ('btrfs-map-logical', 'btrfs-map-logical', 'map btrfs logical extent to physical extent', '', 8),
     ('btrfs', 'btrfs', 'a toolbox to manage btrfs filesystems', '', 8),
     ('mkfs.btrfs', 'mkfs.btrfs', 'create a btrfs filesystem', '', 8),
diff --git a/Documentation/man-index.rst b/Documentation/man-index.rst
index 36d45d2903ea..5fcd4cbc4bee 100644
--- a/Documentation/man-index.rst
+++ b/Documentation/man-index.rst
@@ -28,6 +28,7 @@  Manual pages
    btrfs-select-super
    btrfs-send
    btrfs-subvolume
+   btrfs-tune
    btrfstune
    fsck.btrfs
    mkfs.btrfs
diff --git a/Makefile b/Makefile
index f4feb1fff8e1..9857daaa42ac 100644
--- a/Makefile
+++ b/Makefile
@@ -239,7 +239,7 @@  cmds_objects = cmds/subvolume.o cmds/subvolume-list.o \
 	       cmds/rescue-super-recover.o \
 	       cmds/property.o cmds/filesystem-usage.o cmds/inspect-dump-tree.o \
 	       cmds/inspect-dump-super.o cmds/inspect-tree-stats.o cmds/filesystem-du.o \
-	       cmds/reflink.o \
+	       cmds/reflink.o cmds/tune.o \
 	       mkfs/common.o check/mode-common.o check/mode-lowmem.o \
 	       check/clear-cache.o
 
diff --git a/btrfs.c b/btrfs.c
index 751f193ee2e0..c2dae0303ffe 100644
--- a/btrfs.c
+++ b/btrfs.c
@@ -389,6 +389,7 @@  static const struct cmd_group btrfs_cmd_group = {
 		&cmd_struct_scrub,
 		&cmd_struct_send,
 		&cmd_struct_subvolume,
+		&cmd_struct_tune,
 
 		/* Help and version stay last */
 		&cmd_struct_help,
diff --git a/cmds/commands.h b/cmds/commands.h
index 5ab7c881f634..aebacd718a7b 100644
--- a/cmds/commands.h
+++ b/cmds/commands.h
@@ -151,5 +151,6 @@  DECLARE_COMMAND(qgroup);
 DECLARE_COMMAND(replace);
 DECLARE_COMMAND(restore);
 DECLARE_COMMAND(rescue);
+DECLARE_COMMAND(tune);
 
 #endif
diff --git a/cmds/tune.c b/cmds/tune.c
new file mode 100644
index 000000000000..92c7b9f1502c
--- /dev/null
+++ b/cmds/tune.c
@@ -0,0 +1,227 @@ 
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <unistd.h>
+#include "kerncompat.h"
+#include "cmds/commands.h"
+#include "common/help.h"
+#include "common/fsfeatures.h"
+#include "kernel-shared/messages.h"
+#include "kernel-shared/disk-io.h"
+#include "kernel-shared/transaction.h"
+
+static const char * const cmd_tune_set_usage[] = {
+	"btrfs tune set <feature> [<device>]",
+	"Set/enable specified feature for the unmounted filesystem",
+	"",
+	HELPINFO_INSERT_GLOBALS,
+	HELPINFO_INSERT_VERBOSE,
+	NULL,
+};
+
+static const struct btrfs_feature set_features[] = {
+	{
+		.name		= "extref",
+		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF,
+		.sysfs_name	= "extended_iref",
+		VERSION_TO_STRING2(compat, 3,7),
+		VERSION_TO_STRING2(safe, 3,12),
+		VERSION_TO_STRING2(default, 3,12),
+		.desc		= "increased hardlink limit per file to 65536"
+	}, {
+		.name		= "skinny-metadata",
+		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA,
+		.sysfs_name	= "skinny_metadata",
+		VERSION_TO_STRING2(compat, 3,10),
+		VERSION_TO_STRING2(safe, 3,18),
+		VERSION_TO_STRING2(default, 3,18),
+		.desc		= "reduced-size metadata extent refs"
+	}, {
+		.name		= "no-holes",
+		.incompat_flag	= BTRFS_FEATURE_INCOMPAT_NO_HOLES,
+		.sysfs_name	= "no_holes",
+		VERSION_TO_STRING2(compat, 3,14),
+		VERSION_TO_STRING2(safe, 4,0),
+		VERSION_TO_STRING2(default, 5,15),
+		.desc		= "no explicit hole extents for files"
+	},
+	/* Keep this one last */
+	{
+		.name		= "list-all",
+		.runtime_flag	= BTRFS_FEATURE_RUNTIME_LIST_ALL,
+		.sysfs_name	= NULL,
+		VERSION_NULL(compat),
+		VERSION_NULL(safe),
+		VERSION_NULL(default),
+		.desc		= NULL
+	}
+};
+
+static void list_all_features(const char *prefix,
+			      const struct btrfs_feature *features,
+			      int nr_features)
+{
+	/* We should have at least one empty feature. */
+	ASSERT(nr_features > 1);
+
+	printf("features available to %s:\n", prefix);
+	for (int i = 0; i < nr_features - 1; i++) {
+		const struct btrfs_feature *feat = features + i;
+		const char *sep = "";
+
+		fprintf(stderr, "%-20s- %s (", feat->name, feat->desc);
+		if (feat->compat_ver) {
+			fprintf(stderr, "compat=%s", feat->compat_str);
+			sep = ", ";
+		}
+		if (feat->safe_ver) {
+			fprintf(stderr, "%ssafe=%s", sep, feat->safe_str);
+			sep = ", ";
+		}
+		if (feat->default_ver)
+			fprintf(stderr, "%sdefault=%s", sep, feat->default_str);
+		fprintf(stderr, ")\n");
+	}
+}
+
+static int check_features(const char *name, const struct btrfs_feature *features,
+			  int nr_features)
+{
+	bool found = false;
+
+	for (int i = 0; i < nr_features; i++) {
+		const struct btrfs_feature *feat = features + i;
+
+		if (!strcmp(feat->name, name)) {
+			found = true;
+			break;
+		}
+	}
+	if (found)
+		return 0;
+	return -EINVAL;
+}
+
+static int set_super_incompat_flags(struct btrfs_fs_info *fs_info, u64 flags)
+{
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_super_block *disk_super;
+	u64 super_flags;
+	int ret;
+
+	disk_super = fs_info->super_copy;
+	super_flags = btrfs_super_incompat_flags(disk_super);
+	super_flags |= flags;
+	trans = btrfs_start_transaction(root, 1);
+	BUG_ON(IS_ERR(trans));
+	btrfs_set_super_incompat_flags(disk_super, super_flags);
+	ret = btrfs_commit_transaction(trans, root);
+
+	return ret;
+}
+
+static int cmd_tune_set(const struct cmd_struct *cmd, int argc, char **argv)
+{
+	struct btrfs_fs_info *fs_info;
+	struct open_ctree_args oca = { 0 };
+	char *feature;
+	char *path;
+	int ret = 0;
+
+	optind = 0;
+	while (1) {
+		int c = getopt(argc, argv, "");
+		if (c < 0)
+			break;
+
+		switch (c) {
+		default:
+			usage_unknown_option(cmd, argv);
+		}
+	}
+
+	if (check_argc_min(argc - optind, 1))
+		return 1;
+
+	feature = argv[optind];
+
+	if (check_features(feature, set_features, ARRAY_SIZE(set_features))) {
+		error("Unknown feature to set: %s", feature);
+		return 1;
+	}
+	if (!strcmp(feature, "list-all")) {
+		list_all_features("set", set_features, ARRAY_SIZE(set_features));
+		return 0;
+	}
+
+	if (check_argc_exact(argc - optind, 2))
+		return 1;
+
+	path = argv[optind + 1];
+	oca.flags = OPEN_CTREE_WRITES;
+	oca.filename = path;
+	fs_info = open_ctree_fs_info(&oca);
+	if (!fs_info) {
+		error("failed to open btrfs");
+		ret = -EIO;
+		goto out;
+	}
+	/*
+	 * For those 3 features, we only need to update the superblock to add
+	 * the new feature flags.
+	 */
+	if (!strcmp(feature, "extref") ||
+	    !strcmp(feature, "skinny-metadata") ||
+	    !strcmp(feature, "no-holes")) {
+		u64 incompat_flags = 0;
+
+		if (!strcmp(feature, "extref"))
+			incompat_flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
+		if (!strcmp(feature, "skinny-metadata"))
+			incompat_flags |= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA;
+		if (!strcmp(feature, "no-holes"))
+			incompat_flags |= BTRFS_FEATURE_INCOMPAT_NO_HOLES;
+		ret = set_super_incompat_flags(fs_info, incompat_flags);
+		if (ret < 0) {
+			errno = -ret;
+			error("failed to set feature '%s': %m", feature);
+		}
+		goto out;
+	}
+
+out:
+	if (fs_info)
+		close_ctree_fs_info(fs_info);
+	return !!ret;
+}
+
+static DEFINE_SIMPLE_COMMAND(tune_set, "set");
+
+static const char * const tune_cmd_group_usage[] = {
+	"btrfs tune <command> <args>",
+	NULL,
+};
+
+static const char tune_cmd_group_info[] = "change various btrfs features";
+
+static const struct cmd_group tune_cmd_group = {
+	tune_cmd_group_usage, tune_cmd_group_info, {
+		&cmd_struct_tune_set,
+		NULL
+	}
+};
+DEFINE_GROUP_COMMAND_TOKEN(tune);