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

Currently bitmap_ops is registered while allocating mddev, this is fine
when there is only one bitmap_ops, however, after introduing a new
bitmap_ops, user space need a time window to choose which bitmap_ops to
use while creating new array.

Signed-off-by: Yu Kuai <yuku...@huawei.com>
---
 drivers/md/md.c | 84 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 55 insertions(+), 29 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6ec8b5311a0a..c1f13288069a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -651,32 +651,47 @@ static void no_op(struct percpu_ref *r) {}
 
 static void mddev_set_bitmap_ops(struct mddev *mddev)
 {
+       struct bitmap_operations *old = mddev->bitmap_ops;
+       struct md_submodule_head *head;
+
+       if (mddev->bitmap_id == ID_BITMAP_NONE ||
+           (old && old->head.id == mddev->bitmap_id))
+               return;
+
        xa_lock(&md_submodule);
-       mddev->bitmap_ops = xa_load(&md_submodule, mddev->bitmap_id);
+       head = 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", mddev->bitmap_id);
+
+       if (WARN_ON_ONCE(!head || head->type != MD_BITMAP)) {
+               pr_err("md: can't find bitmap id %d\n", mddev->bitmap_id);
+               return;
+       }
+
+       if (old && old->group)
+               sysfs_remove_group(&mddev->kobj, old->group);
+
+       mddev->bitmap_ops = (void *)head;
+       if (mddev->bitmap_ops && mddev->bitmap_ops->group &&
+           sysfs_create_group(&mddev->kobj, mddev->bitmap_ops->group))
+               pr_warn("md: cannot register extra bitmap attributes for %s\n",
+                       mdname(mddev));
 }
 
 static void mddev_clear_bitmap_ops(struct mddev *mddev)
 {
+       if (mddev->bitmap_ops && mddev->bitmap_ops->group)
+               sysfs_remove_group(&mddev->kobj, mddev->bitmap_ops->group);
        mddev->bitmap_ops = NULL;
 }
 
 int mddev_init(struct mddev *mddev)
 {
-       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)) {
-               mddev_clear_bitmap_ops(mddev);
+                           PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
                return -ENOMEM;
-       }
 
        if (percpu_ref_init(&mddev->writes_pending, no_op,
                            PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
-               mddev_clear_bitmap_ops(mddev);
                percpu_ref_exit(&mddev->active_io);
                return -ENOMEM;
        }
@@ -714,7 +729,6 @@ EXPORT_SYMBOL_GPL(mddev_init);
 
 void mddev_destroy(struct mddev *mddev)
 {
-       mddev_clear_bitmap_ops(mddev);
        percpu_ref_exit(&mddev->active_io);
        percpu_ref_exit(&mddev->writes_pending);
 }
@@ -6046,11 +6060,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
                return ERR_PTR(error);
        }
 
-       if (md_bitmap_registered(mddev) && mddev->bitmap_ops->group)
-               if (sysfs_create_group(&mddev->kobj, mddev->bitmap_ops->group))
-                       pr_warn("md: cannot register extra bitmap attributes 
for %s\n",
-                               mdname(mddev));
-
        kobject_uevent(&mddev->kobj, KOBJ_ADD);
        mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, 
"array_state");
        mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level");
@@ -6126,6 +6135,25 @@ static void md_safemode_timeout(struct timer_list *t)
 
 static int start_dirty_degraded;
 
+static int md_bitmap_create(struct mddev *mddev)
+{
+       if (!md_bitmap_registered(mddev))
+               mddev_set_bitmap_ops(mddev);
+       if (!mddev->bitmap_ops)
+               return -ENOENT;
+
+       return mddev->bitmap_ops->create(mddev);
+}
+
+static void md_bitmap_destroy(struct mddev *mddev)
+{
+       if (!md_bitmap_registered(mddev))
+               return;
+
+       mddev->bitmap_ops->destroy(mddev);
+       mddev_clear_bitmap_ops(mddev);
+}
+
 int md_run(struct mddev *mddev)
 {
        int err;
@@ -6290,9 +6318,9 @@ int md_run(struct mddev *mddev)
                        (unsigned long long)pers->size(mddev, 0, 0) / 2);
                err = -EINVAL;
        }
-       if (err == 0 && pers->sync_request && md_bitmap_registered(mddev) &&
+       if (err == 0 && pers->sync_request &&
            (mddev->bitmap_info.file || mddev->bitmap_info.offset)) {
-               err = mddev->bitmap_ops->create(mddev);
+               err = md_bitmap_create(mddev);
                if (err)
                        pr_warn("%s: failed to create bitmap (%d)\n",
                                mdname(mddev), err);
@@ -6365,8 +6393,7 @@ int md_run(struct mddev *mddev)
                pers->free(mddev, mddev->private);
        mddev->private = NULL;
        put_pers(pers);
-       if (md_bitmap_registered(mddev))
-               mddev->bitmap_ops->destroy(mddev);
+       md_bitmap_destroy(mddev);
 abort:
        bioset_exit(&mddev->io_clone_set);
 exit_sync_set:
@@ -6389,7 +6416,7 @@ int do_md_run(struct mddev *mddev)
        if (md_bitmap_registered(mddev)) {
                err = mddev->bitmap_ops->load(mddev);
                if (err) {
-                       mddev->bitmap_ops->destroy(mddev);
+                       md_bitmap_destroy(mddev);
                        goto out;
                }
        }
@@ -6580,8 +6607,7 @@ static void __md_stop(struct mddev *mddev)
 {
        struct md_personality *pers = mddev->pers;
 
-       if (md_bitmap_registered(mddev))
-               mddev->bitmap_ops->destroy(mddev);
+       md_bitmap_destroy(mddev);
        mddev_detach(mddev);
        spin_lock(&mddev->lock);
        mddev->pers = NULL;
@@ -7361,16 +7387,16 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
        err = 0;
        if (mddev->pers) {
                if (fd >= 0) {
-                       err = mddev->bitmap_ops->create(mddev);
+                       err = md_bitmap_create(mddev);
                        if (!err)
                                err = mddev->bitmap_ops->load(mddev);
 
                        if (err) {
-                               mddev->bitmap_ops->destroy(mddev);
+                               md_bitmap_destroy(mddev);
                                fd = -1;
                        }
                } else if (fd < 0) {
-                       mddev->bitmap_ops->destroy(mddev);
+                       md_bitmap_destroy(mddev);
                }
        }
 
@@ -7685,12 +7711,12 @@ static int update_array_info(struct mddev *mddev, 
mdu_array_info_t *info)
                                mddev->bitmap_info.default_offset;
                        mddev->bitmap_info.space =
                                mddev->bitmap_info.default_space;
-                       rv = mddev->bitmap_ops->create(mddev);
+                       rv = md_bitmap_create(mddev);
                        if (!rv)
                                rv = mddev->bitmap_ops->load(mddev);
 
                        if (rv)
-                               mddev->bitmap_ops->destroy(mddev);
+                               md_bitmap_destroy(mddev);
                } else {
                        struct md_bitmap_stats stats;
 
@@ -7716,7 +7742,7 @@ static int update_array_info(struct mddev *mddev, 
mdu_array_info_t *info)
                                put_cluster_ops(mddev);
                                mddev->safemode_delay = DEFAULT_SAFEMODE_DELAY;
                        }
-                       mddev->bitmap_ops->destroy(mddev);
+                       md_bitmap_destroy(mddev);
                        mddev->bitmap_info.offset = 0;
                }
        }
-- 
2.39.2


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