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: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 832cf62..4a2f23e 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -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 @@
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 @@
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 @@
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);