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btrfs: publish unknown feature bits in sysfs

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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: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Jeff Mahoney 2013-11-01 13:07:00 -04:00 committed by Chris Mason
parent 510d73600a
commit 79da4fa4d9
1 changed files with 107 additions and 1 deletions
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108
fs/btrfs/sysfs.c
View file

@ -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;
@ -146,7 +242,15 @@ 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)
btrfs_sysfs_remove_one(fs_info);
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);