fs: Remove SB_I_DYNBDI flag

Now that all bdi structures filesystems use are properly refcounted, we
can remove the SB_I_DYNBDI flag.

Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/mtd/mtdsuper.c

···
 	sb->s_mtd = mtd;
 	sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
 	sb->s_bdi = bdi_get(mtd_bdi);
-	sb->s_iflags |= SB_I_DYNBDI;
 
 	return 0;
 }

fs/gfs2/ops_fstype.c

···
 	s->s_bdev = data;
 	s->s_dev = s->s_bdev->bd_dev;
 	s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
-	s->s_iflags |= SB_I_DYNBDI;
 	return 0;
 }
 

fs/nfs/super.c

···
  	nfs_initialise_sb(sb);
 
 	sb->s_bdi = bdi_get(old_sb->s_bdi);
-	sb->s_iflags |= SB_I_DYNBDI;
 
 	return 0;
 }

fs/nilfs2/super.c

···
 	sb->s_max_links = NILFS_LINK_MAX;
 
 	sb->s_bdi = bdi_get(sb->s_bdev->bd_bdi);
-	sb->s_iflags |= SB_I_DYNBDI;
 
 	err = load_nilfs(nilfs, sb);
 	if (err)

fs/super.c

···
 	hlist_del_init(&sb->s_instances);
 	spin_unlock(&sb_lock);
 	up_write(&sb->s_umount);
-	if (sb->s_iflags & SB_I_DYNBDI) {
+	if (sb->s_bdi != &noop_backing_dev_info) {
 		bdi_put(sb->s_bdi);
 		sb->s_bdi = &noop_backing_dev_info;
-		sb->s_iflags &= ~SB_I_DYNBDI;
 	}
 }
 
···
 	s->s_bdev = data;
 	s->s_dev = s->s_bdev->bd_dev;
 	s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
-	s->s_iflags |= SB_I_DYNBDI;
 
 	return 0;
 }
···
 	}
 	WARN_ON(sb->s_bdi != &noop_backing_dev_info);
 	sb->s_bdi = bdi;
-	sb->s_iflags |= SB_I_DYNBDI;
 
 	return 0;
 }

include/linux/fs.h

···
 /* sb->s_iflags to limit user namespace mounts */
 #define SB_I_USERNS_VISIBLE		0x00000010 /* fstype already mounted */
 
-/* Temporary flag until all filesystems are converted to dynamic bdis */
-#define SB_I_DYNBDI	0x00000100
-
 /* Possible states of 'frozen' field */
 enum {
 	SB_UNFROZEN = 0,		/* FS is unfrozen */