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 <je...@suse.com> --- fs/btrfs/sysfs.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 72 insertions(+), 4 deletions(-) --- a/fs/btrfs/sysfs.c 2013-09-10 00:10:02.549453084 -0400 +++ b/fs/btrfs/sysfs.c 2013-09-10 00:17:01.813242796 -0400 @@ -56,6 +56,58 @@ static struct attribute *btrfs_supp_feat NULL }; +const char * const btrfs_feature_set_names[FEAT_MAX] = { + [FEAT_COMPAT] = "compat", + [FEAT_COMPAT_RO] = "compat_ro", + [FEAT_INCOMPAT] = "incompat", +}; + +static char btrfs_feature_names[FEAT_MAX][64][13]; +static struct btrfs_feature_attr btrfs_feature_attrs[FEAT_MAX][64]; + +static void init_feature_set_attrs(enum btrfs_feature_set set) +{ + int i; + int len = strlen(btrfs_feature_set_names[set]) + 4; + + for (i = 0; i < 64; i++) { + char *name = btrfs_feature_names[set][i]; + struct btrfs_feature_attr *fa; + + snprintf(name, len, "%s:%u", btrfs_feature_set_names[set], i); + + fa = &btrfs_feature_attrs[set][i]; + fa->attr.name = name; + fa->attr.mode = S_IRUGO; + fa->feature_set = set; + fa->feature_bit = (1ULL << i); + } +} + +static void init_feature_attrs(void) +{ + int i; + + init_feature_set_attrs(FEAT_COMPAT); + init_feature_set_attrs(FEAT_COMPAT_RO); + init_feature_set_attrs(FEAT_INCOMPAT); + + /* Copy the names over for supported features */ + for (i = 0; btrfs_supp_feature_attrs[i]; i++) { + struct btrfs_feature_attr *fa; + struct attribute *attr; + int n; + + fa = to_btrfs_feature_attr(btrfs_supp_feature_attrs[i]); + n = ilog2(fa->feature_bit); + + attr = &btrfs_feature_attrs[fa->feature_set][n].attr; + attr->name = fa->attr.name; + + btrfs_feature_names[fa->feature_set][n][0] = '\0'; + } +} + static void btrfs_feature_release(struct kobject *kobj) { struct btrfs_features *feat; @@ -148,12 +200,12 @@ static u64 get_features(struct btrfs_fs_ return btrfs_super_incompat_flags(disk_super); } -static int add_per_fs_features(struct btrfs_fs_info *fs_info) +static int add_per_fs_feature_set(struct btrfs_fs_info *fs_info, + enum btrfs_feature_set set) { int i; - for (i = 0; btrfs_supp_feature_attrs[i]; i++) { - struct attribute *attr = btrfs_supp_feature_attrs[i]; - struct btrfs_feature_attr *fa = to_btrfs_feature_attr(attr); + for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[0]); i++) { + struct btrfs_feature_attr *fa = &btrfs_feature_attrs[set][i]; u64 features = get_features(fs_info, fa->feature_set); int error; @@ -167,6 +219,21 @@ static int add_per_fs_features(struct bt return 0; } +static int add_per_fs_features(struct btrfs_fs_info *fs_info) +{ + enum btrfs_feature_set set; + int error; + + for (set = FEAT_COMPAT; set < FEAT_MAX; set++) { + error = add_per_fs_feature_set(fs_info, set); + if (error) + return error; + } + + return 0; +} + + int btrfs_sysfs_add_one(struct btrfs_fs_info *fs_info) { int error; @@ -276,6 +343,7 @@ int btrfs_init_sysfs(void) if (!btrfs_kset) return -ENOMEM; + init_feature_attrs(); ret = btrfs_init_feat_adverts(); if (ret) { kset_unregister(btrfs_kset); -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html