ecryptfs: add bdi backing to mount session

This ensures that dirty data gets flushed properly.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/ecryptfs/ecryptfs_kernel.h

@@ -35,6 +35,7 @@
 #include <linux/scatterlist.h>
 #include <linux/hash.h>
 #include <linux/nsproxy.h>
+#include <linux/backing-dev.h>
 
 /* Version verification for shared data structures w/ userspace */
 #define ECRYPTFS_VERSION_MAJOR 0x00
@@ -393,6 +394,7 @@ struct ecryptfs_mount_crypt_stat {
 struct ecryptfs_sb_info {
 	struct super_block *wsi_sb;
 	struct ecryptfs_mount_crypt_stat mount_crypt_stat;
+	struct backing_dev_info bdi;
 };
 
 /* file private data. */

fs/ecryptfs/main.c

@@ -497,17 +497,25 @@ struct kmem_cache *ecryptfs_sb_info_cache;
 static int
 ecryptfs_fill_super(struct super_block *sb, void *raw_data, int silent)
 {
+	struct ecryptfs_sb_info *esi;
 	int rc = 0;
 
 	/* Released in ecryptfs_put_super() */
 	ecryptfs_set_superblock_private(sb,
 					kmem_cache_zalloc(ecryptfs_sb_info_cache,
 							 GFP_KERNEL));
-	if (!ecryptfs_superblock_to_private(sb)) {
+	esi = ecryptfs_superblock_to_private(sb);
+	if (!esi) {
 		ecryptfs_printk(KERN_WARNING, "Out of memory\n");
 		rc = -ENOMEM;
 		goto out;
 	}
+
+	rc = bdi_setup_and_register(&esi->bdi, "ecryptfs", BDI_CAP_MAP_COPY);
+	if (rc)
+		goto out;
+
+	sb->s_bdi = &esi->bdi;
 	sb->s_op = &ecryptfs_sops;
 	/* Released through deactivate_super(sb) from get_sb_nodev */
 	sb->s_root = d_alloc(NULL, &(const struct qstr) {

fs/ecryptfs/super.c

@@ -122,6 +122,7 @@ static void ecryptfs_put_super(struct super_block *sb)
 	lock_kernel();
 
 	ecryptfs_destroy_mount_crypt_stat(&sb_info->mount_crypt_stat);
+	bdi_destroy(&sb_info->bdi);
 	kmem_cache_free(ecryptfs_sb_info_cache, sb_info);
 	ecryptfs_set_superblock_private(sb, NULL);