md: introduce mddev_create/destroy_wb_pool for the change of member device

Previously, we called rdev_init_wb to avoid potential data
inconsistency when array is created.

Now, we need to call the function and create mempool if a
device is added or just be flaged as "writemostly". So
mddev_create_wb_pool is introduced and called accordingly.
And for safety reason, we mark implicit GFP_NOIO allocation
scope for create mempool during mddev_suspend/mddev_resume.

And mempool should be removed conversely after remove a
member device or its's "writemostly" flag, which is done
by call mddev_destroy_wb_pool.

Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9a9762c..b43207a 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -37,6 +37,7 @@
 
 */
 
+#include <linux/sched/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/kthread.h>
 #include <linux/blkdev.h>
@@ -137,6 +138,64 @@ static int rdev_init_wb(struct md_rdev *rdev)
        return 1;
 }
 
+/*
+ * Create wb_info_pool if rdev is the first multi-queue device flaged
+ * with writemostly, also write-behind mode is enabled.
+ */
+void mddev_create_wb_pool(struct mddev *mddev, struct md_rdev *rdev,
+                         bool is_suspend)
+{
+       if (mddev->bitmap_info.max_write_behind == 0)
+               return;
+
+       if (!test_bit(WriteMostly, &rdev->flags) || !rdev_init_wb(rdev))
+               return;
+
+       if (mddev->wb_info_pool == NULL) {
+               unsigned int noio_flag;
+
+               if (!is_suspend)
+                       mddev_suspend(mddev);
+               noio_flag = memalloc_noio_save();
+               mddev->wb_info_pool = mempool_create_kmalloc_pool(NR_WB_INFOS,
+                                                       sizeof(struct wb_info));
+               memalloc_noio_restore(noio_flag);
+               if (!mddev->wb_info_pool)
+                       pr_err("can't alloc memory pool for writemostly\n");
+               if (!is_suspend)
+                       mddev_resume(mddev);
+       }
+}
+EXPORT_SYMBOL_GPL(mddev_create_wb_pool);
+
+/*
+ * destroy wb_info_pool if rdev is the last device flaged with WBCollisionCheck.
+ */
+static void mddev_destroy_wb_pool(struct mddev *mddev, struct md_rdev *rdev)
+{
+       if (!test_and_clear_bit(WBCollisionCheck, &rdev->flags))
+               return;
+
+       if (mddev->wb_info_pool) {
+               struct md_rdev *temp;
+               int num = 0;
+
+               /*
+                * Check if other rdevs need wb_info_pool.
+                */
+               rdev_for_each(temp, mddev)
+                       if (temp != rdev &&
+                           test_bit(WBCollisionCheck, &temp->flags))
+                               num++;
+               if (!num) {
+                       mddev_suspend(rdev->mddev);
+                       mempool_destroy(mddev->wb_info_pool);
+                       mddev->wb_info_pool = NULL;
+                       mddev_resume(rdev->mddev);
+               }
+       }
+}
+
 static struct ctl_table_header *raid_table_header;
 
 static struct ctl_table raid_table[] = {
@@ -2223,6 +2282,9 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
        rdev->mddev = mddev;
        pr_debug("md: bind<%s>\n", b);
 
+       if (mddev->raid_disks)
+               mddev_create_wb_pool(mddev, rdev, false);
+
        if ((err = kobject_add(&rdev->kobj, &mddev->kobj, "dev-%s", b)))
                goto fail;
 
@@ -2259,6 +2321,7 @@ static void unbind_rdev_from_array(struct md_rdev *rdev)
        bd_unlink_disk_holder(rdev->bdev, rdev->mddev->gendisk);
        list_del_rcu(&rdev->same_set);
        pr_debug("md: unbind<%s>\n", bdevname(rdev->bdev,b));
+       mddev_destroy_wb_pool(rdev->mddev, rdev);
        rdev->mddev = NULL;
        sysfs_remove_link(&rdev->kobj, "block");
        sysfs_put(rdev->sysfs_state);
@@ -2771,8 +2834,10 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len)
                }
        } else if (cmd_match(buf, "writemostly")) {
                set_bit(WriteMostly, &rdev->flags);
+               mddev_create_wb_pool(rdev->mddev, rdev, false);
                err = 0;
        } else if (cmd_match(buf, "-writemostly")) {
+               mddev_destroy_wb_pool(rdev->mddev, rdev);
                clear_bit(WriteMostly, &rdev->flags);
                err = 0;
        } else if (cmd_match(buf, "blocked")) {

diff --git a/drivers/md/md.h b/drivers/md/md.h
index d449d51..10f9820 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -730,6 +730,8 @@ extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 extern void md_reload_sb(struct mddev *mddev, int raid_disk);
 extern void md_update_sb(struct mddev *mddev, int force);
 extern void md_kick_rdev_from_array(struct md_rdev * rdev);
+extern void mddev_create_wb_pool(struct mddev *mddev, struct md_rdev *rdev,
+                                bool is_suspend);
 struct md_rdev *md_find_rdev_nr_rcu(struct mddev *mddev, int nr);
 struct md_rdev *md_find_rdev_rcu(struct mddev *mddev, dev_t dev);