[PATCH RFC v2 04/14] md: add a new sysfs api bitmap_version

[Yu Kuai]

From: Yu Kuai <yuku...@huawei.com>

The api will be used by mdadm to set bitmap version while creating new
array or assemble array, prepare to add a new bitmap.

Currently available options are:

cat /sys/block/md0/md/bitmap_version
none [bitmap]

Signed-off-by: Yu Kuai <yuku...@huawei.com>
---
 drivers/md/md.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++---
 drivers/md/md.h |  2 ++
 2 files changed, 84 insertions(+), 5 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c4fbd4d6a9f1..6ec8b5311a0a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -649,13 +649,13 @@ static void active_io_release(struct percpu_ref *ref)
 
 static void no_op(struct percpu_ref *r) {}
 
-static void mddev_set_bitmap_ops(struct mddev *mddev, enum md_submodule_id id)
+static void mddev_set_bitmap_ops(struct mddev *mddev)
 {
        xa_lock(&md_submodule);
-       mddev->bitmap_ops = xa_load(&md_submodule, id);
+       mddev->bitmap_ops = xa_load(&md_submodule, mddev->bitmap_id);
        xa_unlock(&md_submodule);
        if (!mddev->bitmap_ops)
-               pr_warn_once("md: can't find bitmap id %d\n", id);
+               pr_warn_once("md: can't find bitmap id %d\n", mddev->bitmap_id);
 }
 
 static void mddev_clear_bitmap_ops(struct mddev *mddev)
@@ -665,8 +665,8 @@ static void mddev_clear_bitmap_ops(struct mddev *mddev)
 
 int mddev_init(struct mddev *mddev)
 {
-       /* TODO: support more versions */
-       mddev_set_bitmap_ops(mddev, ID_BITMAP);
+       mddev->bitmap_id = ID_BITMAP;
+       mddev_set_bitmap_ops(mddev);
 
        if (percpu_ref_init(&mddev->active_io, active_io_release,
                            PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
@@ -4145,6 +4145,82 @@ new_level_store(struct mddev *mddev, const char *buf, 
size_t len)
 static struct md_sysfs_entry md_new_level =
 __ATTR(new_level, 0664, new_level_show, new_level_store);
 
+static ssize_t
+bitmap_version_show(struct mddev *mddev, char *page)
+{
+       struct md_submodule_head *head;
+       unsigned long i;
+       ssize_t len = 0;
+
+       if (mddev->bitmap_id == ID_BITMAP_NONE)
+               len += sprintf(page + len, "[none] ");
+       else
+               len += sprintf(page + len, "none ");
+
+       xa_lock(&md_submodule);
+       xa_for_each(&md_submodule, i, head) {
+               if (head->type != MD_BITMAP)
+                       continue;
+
+               if (mddev->bitmap_id == head->id)
+                       len += sprintf(page + len, "[%s] ", head->name);
+               else
+                       len += sprintf(page + len, "%s ", head->name);
+       }
+       xa_unlock(&md_submodule);
+
+       len += sprintf(page + len, "\n");
+       return len;
+}
+
+static ssize_t
+bitmap_version_store(struct mddev *mddev, const char *buf, size_t len)
+{
+       struct md_submodule_head *head;
+       enum md_submodule_id id;
+       unsigned long i;
+       int err;
+
+       if (mddev->bitmap_ops)
+               return -EBUSY;
+
+       err = kstrtoint(buf, 10, &id);
+       if (!err) {
+               if (id == ID_BITMAP_NONE) {
+                       mddev->bitmap_id = id;
+                       return len;
+               }
+
+               xa_lock(&md_submodule);
+               head = xa_load(&md_submodule, id);
+               xa_unlock(&md_submodule);
+
+               if (head && head->type == MD_BITMAP) {
+                       mddev->bitmap_id = id;
+                       return len;
+               }
+       }
+
+       if (cmd_match(buf, "none")) {
+               mddev->bitmap_id = ID_BITMAP_NONE;
+               return len;
+       }
+
+       xa_lock(&md_submodule);
+       xa_for_each(&md_submodule, i, head) {
+               if (head->type == MD_BITMAP && cmd_match(buf, head->name)) {
+                       mddev->bitmap_id = head->id;
+                       xa_unlock(&md_submodule);
+                       return len;
+               }
+       }
+       xa_unlock(&md_submodule);
+       return -ENOENT;
+}
+
+static struct md_sysfs_entry md_bitmap_version =
+__ATTR(bitmap_version, 0664, bitmap_version_show, bitmap_version_store);
+
 static ssize_t
 layout_show(struct mddev *mddev, char *page)
 {
@@ -5680,6 +5756,7 @@ __ATTR(serialize_policy, S_IRUGO | S_IWUSR, 
serialize_policy_show,
 static struct attribute *md_default_attrs[] = {
        &md_level.attr,
        &md_new_level.attr,
+       &md_bitmap_version.attr,
        &md_layout.attr,
        &md_raid_disks.attr,
        &md_uuid.attr,
diff --git a/drivers/md/md.h b/drivers/md/md.h
index ad18ef9b5061..3bc367f6bd62 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -40,6 +40,7 @@ enum md_submodule_id {
        ID_CLUSTER,
        ID_BITMAP,
        ID_LLBITMAP,    /* TODO */
+       ID_BITMAP_NONE,
 };
 
 struct md_submodule_head {
@@ -562,6 +563,7 @@ struct mddev {
        struct percpu_ref               writes_pending;
        int                             sync_checkers;  /* # of threads 
checking writes_pending */
 
+       enum md_submodule_id            bitmap_id;
        void                            *bitmap; /* the bitmap for the device */
        struct bitmap_operations        *bitmap_ops;
        struct {
-- 
2.39.2