[RFC PATCH 4/4] btrfs: sysfs: export supported checksums

[Johannes Thumshirn]

From: David Sterba <dste...@suse.com>

Export supported checksum algorithms via sysfs.

Signed-off-by: David Sterba <dste...@suse.com>
Signed-off-by: Johannes Thumshirn <jthumsh...@suse.de>
---
 fs/btrfs/sysfs.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 9539f8143b7a..920282a3452b 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -182,6 +182,30 @@ static umode_t btrfs_feature_visible(struct kobject *kobj,
        return mode;
 }
 
+static ssize_t btrfs_checksums_show(struct kobject *kobj,
+                                      struct kobj_attribute *a, char *buf)
+{
+       ssize_t ret = 0;
+       int i;
+
+       for (i = 0; i < ARRAY_SIZE(btrfs_csums); i++) {
+               ret += snprintf(buf + ret, PAGE_SIZE, "%s%s",
+                               (i == 0 ? "" : ", "),
+                               btrfs_csums[i].name);
+
+       }
+
+       ret += snprintf(buf + ret, PAGE_SIZE, "\n");
+       return ret;
+}
+
+static ssize_t btrfs_checksums_store(struct kobject *kobj,
+                                       struct kobj_attribute *a,
+                                       const char *buf, size_t count)
+{
+       return -EPERM;
+}
+
 BTRFS_FEAT_ATTR_INCOMPAT(mixed_backref, MIXED_BACKREF);
 BTRFS_FEAT_ATTR_INCOMPAT(default_subvol, DEFAULT_SUBVOL);
 BTRFS_FEAT_ATTR_INCOMPAT(mixed_groups, MIXED_GROUPS);
@@ -195,6 +219,14 @@ BTRFS_FEAT_ATTR_INCOMPAT(no_holes, NO_HOLES);
 BTRFS_FEAT_ATTR_INCOMPAT(metadata_uuid, METADATA_UUID);
 BTRFS_FEAT_ATTR_COMPAT_RO(free_space_tree, FREE_SPACE_TREE);
 
+static struct btrfs_feature_attr btrfs_attr_features_checksums_name = {
+       .kobj_attr = __INIT_KOBJ_ATTR(checksums, S_IRUGO,
+                                     btrfs_checksums_show,
+                                     btrfs_checksums_store),
+       .feature_set    = FEAT_INCOMPAT,
+       .feature_bit    = 0,
+};
+
 static struct attribute *btrfs_supported_feature_attrs[] = {
        BTRFS_FEAT_ATTR_PTR(mixed_backref),
        BTRFS_FEAT_ATTR_PTR(default_subvol),
@@ -208,6 +240,9 @@ static struct attribute *btrfs_supported_feature_attrs[] = {
        BTRFS_FEAT_ATTR_PTR(no_holes),
        BTRFS_FEAT_ATTR_PTR(metadata_uuid),
        BTRFS_FEAT_ATTR_PTR(free_space_tree),
+
+       &btrfs_attr_features_checksums_name.kobj_attr.attr,
+
        NULL
 };
 
-- 
2.16.4