[PATCH RFC 09/10] shmem: Implement shmem_destroy_super()

[Kirill Tkhai <ktkhai@virtuozzo.com>]

Similar to xfs_fs_destroy_super() implement the method
for shmem.

shmem_unused_huge_count() just touches sb->s_fs_info.
After such the later freeing it will be safe for
unregister_shrinker() splitting (which is made in next
patch).

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 mm/shmem.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4829798869b6..35c65afefbc8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3427,6 +3427,12 @@ static void shmem_put_super(struct super_block *sb)
 
 	percpu_counter_destroy(&sbinfo->used_blocks);
 	mpol_put(sbinfo->mpol);
+}
+
+static void shmem_destroy_super(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+
 	kfree(sbinfo);
 	sb->s_fs_info = NULL;
 }
@@ -3504,6 +3510,7 @@ int shmem_fill_super(struct super_block *sb, void *data, size_t data_size,
 
 failed:
 	shmem_put_super(sb);
+	shmem_destroy_super(sb);
 	return err;
 }
 
@@ -3630,6 +3637,7 @@ static const struct super_operations shmem_ops = {
 	.evict_inode	= shmem_evict_inode,
 	.drop_inode	= generic_delete_inode,
 	.put_super	= shmem_put_super,
+	.destroy_super	= shmem_destroy_super,
 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
 	.nr_cached_objects	= shmem_unused_huge_count,
 	.free_cached_objects	= shmem_unused_huge_scan,