mtd: Convert to dynamically allocated bdi infrastructure

MTD already allocates backing_dev_info dynamically. Convert it to use
generic infrastructure for this including proper refcounting. We drop
mtd->backing_dev_info as its only use was to pass mtd_bdi pointer from
one file into another and if we wanted to keep that in a clean way, we'd
have to make mtd hold and drop bdi reference as needed which seems
pointless for passing one global pointer...

CC: David Woodhouse <dwmw2@infradead.org>
CC: Brian Norris <computersforpeace@gmail.com>
CC: linux-mtd@lists.infradead.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

3 files changed, 18 insertions, 17 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 66a9dedd1062..23e2e56ca54e 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -46,7 +46,7 @@
 
 #include "mtdcore.h"
 
-static struct backing_dev_info *mtd_bdi;
+struct backing_dev_info *mtd_bdi;
 
 #ifdef CONFIG_PM_SLEEP
 
@@ -496,11 +496,9 @@ int add_mtd_device(struct mtd_info *mtd)
          * mtd_device_parse_register() multiple times on the same master MTD,
          * especially with CONFIG_MTD_PARTITIONED_MASTER=y.
          */
-        if (WARN_ONCE(mtd->backing_dev_info, "MTD already registered\n"))
+        if (WARN_ONCE(mtd->dev.type, "MTD already registered\n"))
                 return -EEXIST;
 
-        mtd->backing_dev_info = mtd_bdi;
-
         BUG_ON(mtd->writesize == 0);
         mutex_lock(&mtd_table_mutex);
 
@@ -1775,13 +1773,18 @@ static struct backing_dev_info * __init mtd_bdi_init(char *name)
         struct backing_dev_info *bdi;
         int ret;
 
-        bdi = kzalloc(sizeof(*bdi), GFP_KERNEL);
+        bdi = bdi_alloc(GFP_KERNEL);
         if (!bdi)
                 return ERR_PTR(-ENOMEM);
 
-        ret = bdi_setup_and_register(bdi, name);
+        bdi->name = name;
+        /*
+         * We put '-0' suffix to the name to get the same name format as we
+         * used to get. Since this is called only once, we get a unique name. 
+         */
+        ret = bdi_register(bdi, NULL, "%.28s-0", name);
         if (ret)
-                kfree(bdi);
+                bdi_put(bdi);
 
         return ret ? ERR_PTR(ret) : bdi;
 }
@@ -1813,8 +1816,7 @@ static int __init init_mtd(void)
 out_procfs:
         if (proc_mtd)
                 remove_proc_entry("mtd", NULL);
-        bdi_destroy(mtd_bdi);
-        kfree(mtd_bdi);
+        bdi_put(mtd_bdi);
 err_bdi:
         class_unregister(&mtd_class);
 err_reg:
@@ -1828,8 +1830,7 @@ static void __exit cleanup_mtd(void)
         if (proc_mtd)
                 remove_proc_entry("mtd", NULL);
         class_unregister(&mtd_class);
-        bdi_destroy(mtd_bdi);
-        kfree(mtd_bdi);
+        bdi_put(mtd_bdi);
         idr_destroy(&mtd_idr);
 }
 
diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
index 20c02a3b7417..e69e7855e31f 100644
--- a/drivers/mtd/mtdsuper.c
+++ b/drivers/mtd/mtdsuper.c
@@ -18,6 +18,7 @@
 #include <linux/ctype.h>
 #include <linux/slab.h>
 #include <linux/major.h>
+#include <linux/backing-dev.h>
 
 /*
  * compare superblocks to see if they're equivalent
@@ -38,6 +39,8 @@ static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
         return 0;
 }
 
+extern struct backing_dev_info *mtd_bdi;
+
 /*
  * mark the superblock by the MTD device it is using
  * - set the device number to be the correct MTD block device for pesuperstence
@@ -49,7 +52,9 @@ static int get_sb_mtd_set(struct super_block *sb, void *_mtd)
 
         sb->s_mtd = mtd;
         sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
-        sb->s_bdi = mtd->backing_dev_info;
+        sb->s_bdi = bdi_get(mtd_bdi);
+        sb->s_iflags |= SB_I_DYNBDI;
+
         return 0;
 }
 
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index eebdc63cf6af..79b176eca04a 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -334,11 +334,6 @@ struct mtd_info {
         int (*_get_device) (struct mtd_info *mtd);
         void (*_put_device) (struct mtd_info *mtd);
 
-        /* Backing device capabilities for this device
-         * - provides mmap capabilities
-         */
-        struct backing_dev_info *backing_dev_info;
-
         struct notifier_block reboot_notifier;  /* default mode before reboot */
 
         /* ECC status information */