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Commit 79da4fa4 authored by Jeff Mahoney's avatar Jeff Mahoney Committed by Chris Mason
Browse files

btrfs: publish unknown feature bits in sysfs 



With the compat and compat-ro bits, it's possible for file systems to
exist that have features that aren't supported by the kernel's file system
implementation yet still be mountable.

This patch publishes read-only info on those features using a prefix:number
format, where the number is the bit number rather than the shifted value.
e.g. "compat:12"

Signed-off-by: default avatarJeff Mahoney <jeffm@suse.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 510d7360

fs/btrfs/sysfs.c

+107 −1
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/completion.h>

#include <linux/buffer_head.h>

#include <linux/kobject.h>

#include <linux/bug.h>



#include "ctree.h"

#include "disk-io.h"
@@ -131,6 +132,101 @@ void btrfs_sysfs_remove_one(struct btrfs_fs_info *fs_info) 
	wait_for_completion(&fs_info->kobj_unregister);

}



const char * const btrfs_feature_set_names[3] = {

	[FEAT_COMPAT]	 = "compat",

	[FEAT_COMPAT_RO] = "compat_ro",

	[FEAT_INCOMPAT]	 = "incompat",

};



#define NUM_FEATURE_BITS 64

static char btrfs_unknown_feature_names[3][NUM_FEATURE_BITS][13];

static struct btrfs_feature_attr btrfs_feature_attrs[3][NUM_FEATURE_BITS];



static void init_feature_attrs(void)

{

	struct btrfs_feature_attr *fa;

	int set, i;



	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names) !=

		     ARRAY_SIZE(btrfs_feature_attrs));

	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names[0]) !=

		     ARRAY_SIZE(btrfs_feature_attrs[0]));



	for (i = 0; btrfs_supported_feature_attrs[i]; i++) {

		struct btrfs_feature_attr *sfa;

		struct attribute *a = btrfs_supported_feature_attrs[i];

		sfa = attr_to_btrfs_feature_attr(a);

		fa = &btrfs_feature_attrs[sfa->feature_set][sfa->feature_bit];



		fa->kobj_attr.attr.name = sfa->kobj_attr.attr.name;

	}



	for (set = 0; set < FEAT_MAX; set++) {

		for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[set]); i++) {

			char *name = btrfs_unknown_feature_names[set][i];

			fa = &btrfs_feature_attrs[set][i];



			if (fa->kobj_attr.attr.name)

				continue;



			snprintf(name, 13, "%s:%u",

				 btrfs_feature_set_names[set], i);



			fa->kobj_attr.attr.name = name;

			fa->kobj_attr.attr.mode = S_IRUGO;

			fa->feature_set = set;

			fa->feature_bit = 1ULL << i;

		}

	}

}



static u64 supported_feature_masks[3] = {

	[FEAT_COMPAT]    = BTRFS_FEATURE_COMPAT_SUPP,

	[FEAT_COMPAT_RO] = BTRFS_FEATURE_COMPAT_RO_SUPP,

	[FEAT_INCOMPAT]  = BTRFS_FEATURE_INCOMPAT_SUPP,

};



static int add_unknown_feature_attrs(struct btrfs_fs_info *fs_info)

{

	int set;



	for (set = 0; set < FEAT_MAX; set++) {

		int i, count, ret, index = 0;

		struct attribute **attrs;

		struct attribute_group agroup = {

			.name = "features",

		};

		u64 features = get_features(fs_info, set);

		features &= ~supported_feature_masks[set];



		count = hweight64(features);



		if (!count)

			continue;



		attrs = kcalloc(count + 1, sizeof(void *), GFP_KERNEL);



		for (i = 0; i < NUM_FEATURE_BITS; i++) {

			struct btrfs_feature_attr *fa;



			if (!(features & (1ULL << i)))

				continue;



			fa = &btrfs_feature_attrs[set][i];

			attrs[index++] = &fa->kobj_attr.attr;

		}



		attrs[index] = NULL;

		agroup.attrs = attrs;



		ret = sysfs_merge_group(&fs_info->super_kobj, &agroup);

		kfree(attrs);

		if (ret)

			return ret;

	}

	return 0;

}



/* /sys/fs/btrfs/ entry */

static struct kset *btrfs_kset;
@@ -146,6 +242,14 @@ int btrfs_sysfs_add_one(struct btrfs_fs_info *fs_info) 
	error = sysfs_create_group(&fs_info->super_kobj,

				   &btrfs_feature_attr_group);

	if (error)

		goto failure;



	error = add_unknown_feature_attrs(fs_info);

	if (error)

		goto failure;



	return 0;

failure:

	btrfs_sysfs_remove_one(fs_info);

	return error;

}
@@ -157,6 +261,8 @@ int btrfs_init_sysfs(void) 
	if (!btrfs_kset)

		return -ENOMEM;



	init_feature_attrs();



	ret = sysfs_create_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);

	if (ret) {

		kset_unregister(btrfs_kset);