From 79da4fa4d9dcf8c948ef8b5848f747ef08f6e732 Mon Sep 17 00:00:00 2001 From: Jeff Mahoney Date: Fri, 1 Nov 2013 13:07:00 -0400 Subject: [PATCH] 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 Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/sysfs.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 107 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 832cf62151ff..4a2f23ee163f 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -22,6 +22,7 @@ #include #include #include +#include #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); -- 2.20.1