fs: icache RCU free inodes

RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

Documentation/filesystems/porting

@@ -346,3 +346,17 @@ look at examples of other filesystems) for guidance.
 for details of what locks to replace dcache_lock with in order to protect
 particular things. Most of the time, a filesystem only needs ->d_lock, which
 protects *all* the dcache state of a given dentry.
+
+--
+[mandatory]
+
+	Filesystems must RCU-free their inodes, if they can have been accessed
+via rcu-walk path walk (basically, if the file can have had a path name in the
+vfs namespace).
+
+	i_dentry and i_rcu share storage in a union, and the vfs expects
+i_dentry to be reinitialized before it is freed, so an:
+
+  INIT_LIST_HEAD(&inode->i_dentry);
+
+must be done in the RCU callback.

arch/powerpc/platforms/cell/spufs/inode.c

@@ -71,12 +71,18 @@ spufs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
-static void
-spufs_destroy_inode(struct inode *inode)
+static void spufs_i_callback(struct rcu_head *head)
 {
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
 	kmem_cache_free(spufs_inode_cache, SPUFS_I(inode));
 }
 
+static void spufs_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, spufs_i_callback);
+}
+
 static void
 spufs_init_once(void *p)
 {

drivers/staging/pohmelfs/inode.c

@@ -826,6 +826,13 @@ const struct address_space_operations pohmelfs_aops = {
 	.set_page_dirty 	= __set_page_dirty_nobuffers,
 };
 
+static void pohmelfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(pohmelfs_inode_cache, POHMELFS_I(inode));
+}
+
 /*
  * ->detroy_inode() callback. Deletes inode from the caches
  *  and frees private data.
@@ -842,8 +849,8 @@ static void pohmelfs_destroy_inode(struct inode *inode)
 
 	dprintk("%s: pi: %p, inode: %p, ino: %llu.\n",
 		__func__, pi, &pi->vfs_inode, pi->ino);
-	kmem_cache_free(pohmelfs_inode_cache, pi);
 	atomic_long_dec(&psb->total_inodes);
+	call_rcu(&inode->i_rcu, pohmelfs_i_callback);
 }
 
 /*

drivers/staging/smbfs/inode.c

@@ -62,9 +62,16 @@ static struct inode *smb_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void smb_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(smb_inode_cachep, SMB_I(inode));
+}
+
 static void smb_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(smb_inode_cachep, SMB_I(inode));
+	call_rcu(&inode->i_rcu, smb_i_callback);
 }
 
 static void init_once(void *foo)

fs/9p/vfs_inode.c

@@ -237,9 +237,16 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
  *
  */
 
+static void v9fs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(vcookie_cache, v9fs_inode2cookie(inode));
+}
+
 void v9fs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(vcookie_cache, v9fs_inode2cookie(inode));
+	call_rcu(&inode->i_rcu, v9fs_i_callback);
 }
 #endif
 

fs/adfs/super.c

@@ -240,9 +240,16 @@ static struct inode *adfs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void adfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(adfs_inode_cachep, ADFS_I(inode));
+}
+
 static void adfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(adfs_inode_cachep, ADFS_I(inode));
+	call_rcu(&inode->i_rcu, adfs_i_callback);
 }
 
 static void init_once(void *foo)

fs/affs/super.c

@@ -95,9 +95,16 @@ static struct inode *affs_alloc_inode(struct super_block *sb)
 	return &i->vfs_inode;
 }
 
+static void affs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(affs_inode_cachep, AFFS_I(inode));
+}
+
 static void affs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(affs_inode_cachep, AFFS_I(inode));
+	call_rcu(&inode->i_rcu, affs_i_callback);
 }
 
 static void init_once(void *foo)

fs/afs/super.c

@@ -498,6 +498,14 @@ static struct inode *afs_alloc_inode(struct super_block *sb)
 	return &vnode->vfs_inode;
 }
 
+static void afs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(afs_inode_cachep, vnode);
+}
+
 /*
  * destroy an AFS inode struct
  */
@@ -511,7 +519,7 @@ static void afs_destroy_inode(struct inode *inode)
 
 	ASSERTCMP(vnode->server, ==, NULL);
 
-	kmem_cache_free(afs_inode_cachep, vnode);
+	call_rcu(&inode->i_rcu, afs_i_callback);
 	atomic_dec(&afs_count_active_inodes);
 }
 

fs/befs/linuxvfs.c

@@ -284,12 +284,18 @@ befs_alloc_inode(struct super_block *sb)
         return &bi->vfs_inode;
 }
 
-static void
-befs_destroy_inode(struct inode *inode)
+static void befs_i_callback(struct rcu_head *head)
 {
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
         kmem_cache_free(befs_inode_cachep, BEFS_I(inode));
 }
 
+static void befs_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, befs_i_callback);
+}
+
 static void init_once(void *foo)
 {
         struct befs_inode_info *bi = (struct befs_inode_info *) foo;

fs/bfs/inode.c

@@ -248,9 +248,16 @@ static struct inode *bfs_alloc_inode(struct super_block *sb)
 	return &bi->vfs_inode;
 }
 
+static void bfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(bfs_inode_cachep, BFS_I(inode));
+}
+
 static void bfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(bfs_inode_cachep, BFS_I(inode));
+	call_rcu(&inode->i_rcu, bfs_i_callback);
 }
 
 static void init_once(void *foo)

fs/block_dev.c

@@ -409,13 +409,20 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
-static void bdev_destroy_inode(struct inode *inode)
+static void bdev_i_callback(struct rcu_head *head)
 {
+	struct inode *inode = container_of(head, struct inode, i_rcu);
 	struct bdev_inode *bdi = BDEV_I(inode);
 
+	INIT_LIST_HEAD(&inode->i_dentry);
 	kmem_cache_free(bdev_cachep, bdi);
 }
 
+static void bdev_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, bdev_i_callback);
+}
+
 static void init_once(void *foo)
 {
 	struct bdev_inode *ei = (struct bdev_inode *) foo;

fs/btrfs/inode.c

@@ -6495,6 +6495,13 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
 	return inode;
 }
 
+static void btrfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
+}
+
 void btrfs_destroy_inode(struct inode *inode)
 {
 	struct btrfs_ordered_extent *ordered;
@@ -6564,7 +6571,7 @@ void btrfs_destroy_inode(struct inode *inode)
 	inode_tree_del(inode);
 	btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
 free:
-	kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
+	call_rcu(&inode->i_rcu, btrfs_i_callback);
 }
 
 int btrfs_drop_inode(struct inode *inode)

fs/ceph/inode.c

@@ -368,6 +368,15 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
 	return &ci->vfs_inode;
 }
 
+static void ceph_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ceph_inode_cachep, ci);
+}
+
 void ceph_destroy_inode(struct inode *inode)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
@@ -407,7 +416,7 @@ void ceph_destroy_inode(struct inode *inode)
 	if (ci->i_xattrs.prealloc_blob)
 		ceph_buffer_put(ci->i_xattrs.prealloc_blob);
 
-	kmem_cache_free(ceph_inode_cachep, ci);
+	call_rcu(&inode->i_rcu, ceph_i_callback);
 }
 
 

fs/cifs/cifsfs.c

@@ -334,10 +334,17 @@ cifs_alloc_inode(struct super_block *sb)
 	return &cifs_inode->vfs_inode;
 }
 
+static void cifs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(cifs_inode_cachep, CIFS_I(inode));
+}
+
 static void
 cifs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(cifs_inode_cachep, CIFS_I(inode));
+	call_rcu(&inode->i_rcu, cifs_i_callback);
 }
 
 static void

fs/coda/inode.c

@@ -56,9 +56,16 @@ static struct inode *coda_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void coda_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(coda_inode_cachep, ITOC(inode));
+}
+
 static void coda_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(coda_inode_cachep, ITOC(inode));
+	call_rcu(&inode->i_rcu, coda_i_callback);
 }
 
 static void init_once(void *foo)

fs/ecryptfs/super.c

@@ -62,6 +62,16 @@ static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
 	return inode;
 }
 
+static void ecryptfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct ecryptfs_inode_info *inode_info;
+	inode_info = ecryptfs_inode_to_private(inode);
+
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
+}
+
 /**
  * ecryptfs_destroy_inode
  * @inode: The ecryptfs inode
@@ -88,7 +98,7 @@ static void ecryptfs_destroy_inode(struct inode *inode)
 		}
 	}
 	ecryptfs_destroy_crypt_stat(&inode_info->crypt_stat);
-	kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
+	call_rcu(&inode->i_rcu, ecryptfs_i_callback);
 }
 
 /**

fs/efs/super.c

@@ -65,9 +65,16 @@ static struct inode *efs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void efs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(efs_inode_cachep, INODE_INFO(inode));
+}
+
 static void efs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(efs_inode_cachep, INODE_INFO(inode));
+	call_rcu(&inode->i_rcu, efs_i_callback);
 }
 
 static void init_once(void *foo)

fs/exofs/super.c

@@ -150,12 +150,19 @@ static struct inode *exofs_alloc_inode(struct super_block *sb)
 	return &oi->vfs_inode;
 }
 
+static void exofs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(exofs_inode_cachep, exofs_i(inode));
+}
+
 /*
  * Remove an inode from the cache
  */
 static void exofs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(exofs_inode_cachep, exofs_i(inode));
+	call_rcu(&inode->i_rcu, exofs_i_callback);
 }
 
 /*

fs/ext2/super.c

@@ -161,9 +161,16 @@ static struct inode *ext2_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void ext2_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ext2_inode_cachep, EXT2_I(inode));
+}
+
 static void ext2_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(ext2_inode_cachep, EXT2_I(inode));
+	call_rcu(&inode->i_rcu, ext2_i_callback);
 }
 
 static void init_once(void *foo)

fs/ext3/super.c

@@ -479,6 +479,13 @@ static struct inode *ext3_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void ext3_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ext3_inode_cachep, EXT3_I(inode));
+}
+
 static void ext3_destroy_inode(struct inode *inode)
 {
 	if (!list_empty(&(EXT3_I(inode)->i_orphan))) {
@@ -489,7 +496,7 @@ static void ext3_destroy_inode(struct inode *inode)
 				false);
 		dump_stack();
 	}
-	kmem_cache_free(ext3_inode_cachep, EXT3_I(inode));
+	call_rcu(&inode->i_rcu, ext3_i_callback);
 }
 
 static void init_once(void *foo)

fs/ext4/super.c

@@ -841,6 +841,13 @@ static int ext4_drop_inode(struct inode *inode)
 	return drop;
 }
 
+static void ext4_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ext4_inode_cachep, EXT4_I(inode));
+}
+
 static void ext4_destroy_inode(struct inode *inode)
 {
 	ext4_ioend_wait(inode);
@@ -853,7 +860,7 @@ static void ext4_destroy_inode(struct inode *inode)
 				true);
 		dump_stack();
 	}
-	kmem_cache_free(ext4_inode_cachep, EXT4_I(inode));
+	call_rcu(&inode->i_rcu, ext4_i_callback);
 }
 
 static void init_once(void *foo)

fs/fat/inode.c

@@ -514,9 +514,16 @@ static struct inode *fat_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void fat_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
+}
+
 static void fat_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
+	call_rcu(&inode->i_rcu, fat_i_callback);
 }
 
 static void init_once(void *foo)

fs/freevxfs/vxfs_inode.c

@@ -337,6 +337,13 @@ vxfs_iget(struct super_block *sbp, ino_t ino)
 	return ip;
 }
 
+static void vxfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(vxfs_inode_cachep, inode->i_private);
+}
+
 /**
  * vxfs_evict_inode - remove inode from main memory
  * @ip:		inode to discard.
@@ -350,5 +357,5 @@ vxfs_evict_inode(struct inode *ip)
 {
 	truncate_inode_pages(&ip->i_data, 0);
 	end_writeback(ip);
-	kmem_cache_free(vxfs_inode_cachep, ip->i_private);
+	call_rcu(&ip->i_rcu, vxfs_i_callback);
 }

fs/fuse/inode.c

@@ -99,6 +99,13 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	return inode;
 }
 
+static void fuse_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(fuse_inode_cachep, inode);
+}
+
 static void fuse_destroy_inode(struct inode *inode)
 {
 	struct fuse_inode *fi = get_fuse_inode(inode);
@@ -106,7 +113,7 @@ static void fuse_destroy_inode(struct inode *inode)
 	BUG_ON(!list_empty(&fi->queued_writes));
 	if (fi->forget_req)
 		fuse_request_free(fi->forget_req);
-	kmem_cache_free(fuse_inode_cachep, inode);
+	call_rcu(&inode->i_rcu, fuse_i_callback);
 }
 
 void fuse_send_forget(struct fuse_conn *fc, struct fuse_req *req,

fs/gfs2/super.c

@@ -1405,9 +1405,16 @@ static struct inode *gfs2_alloc_inode(struct super_block *sb)
 	return &ip->i_inode;
 }
 
+static void gfs2_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(gfs2_inode_cachep, inode);
+}
+
 static void gfs2_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(gfs2_inode_cachep, inode);
+	call_rcu(&inode->i_rcu, gfs2_i_callback);
 }
 
 const struct super_operations gfs2_super_ops = {

fs/hfs/super.c

@@ -167,9 +167,16 @@ static struct inode *hfs_alloc_inode(struct super_block *sb)
 	return i ? &i->vfs_inode : NULL;
 }
 
+static void hfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(hfs_inode_cachep, HFS_I(inode));
+}
+
 static void hfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(hfs_inode_cachep, HFS_I(inode));
+	call_rcu(&inode->i_rcu, hfs_i_callback);
 }
 
 static const struct super_operations hfs_super_operations = {

fs/hfsplus/super.c

@@ -488,9 +488,17 @@ static struct inode *hfsplus_alloc_inode(struct super_block *sb)
 	return i ? &i->vfs_inode : NULL;
 }
 
+static void hfsplus_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(hfsplus_inode_cachep, HFSPLUS_I(inode));
+}
+
 static void hfsplus_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(hfsplus_inode_cachep, HFSPLUS_I(inode));
+	call_rcu(&inode->i_rcu, hfsplus_i_callback);
 }
 
 #define HFSPLUS_INODE_SIZE	sizeof(struct hfsplus_inode_info)

fs/hostfs/hostfs_kern.c

@@ -247,9 +247,16 @@ static void hostfs_evict_inode(struct inode *inode)
 	}
 }
 
+static void hostfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kfree(HOSTFS_I(inode));
+}
+
 static void hostfs_destroy_inode(struct inode *inode)
 {
-	kfree(HOSTFS_I(inode));
+	call_rcu(&inode->i_rcu, hostfs_i_callback);
 }
 
 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)

fs/hpfs/super.c

@@ -177,9 +177,16 @@ static struct inode *hpfs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void hpfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(hpfs_inode_cachep, hpfs_i(inode));
+}
+
 static void hpfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(hpfs_inode_cachep, hpfs_i(inode));
+	call_rcu(&inode->i_rcu, hpfs_i_callback);
 }
 
 static void init_once(void *foo)

fs/hppfs/hppfs.c

@@ -632,9 +632,16 @@ void hppfs_evict_inode(struct inode *ino)
 	mntput(ino->i_sb->s_fs_info);
 }
 
+static void hppfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kfree(HPPFS_I(inode));
+}
+
 static void hppfs_destroy_inode(struct inode *inode)
 {
-	kfree(HPPFS_I(inode));
+	call_rcu(&inode->i_rcu, hppfs_i_callback);
 }
 
 static const struct super_operations hppfs_sbops = {

fs/hugetlbfs/inode.c

@@ -663,11 +663,18 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
 	return &p->vfs_inode;
 }
 
+static void hugetlbfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
+}
+
 static void hugetlbfs_destroy_inode(struct inode *inode)
 {
 	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
 	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
-	kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
+	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
 }
 
 static const struct address_space_operations hugetlbfs_aops = {

fs/inode.c

@@ -272,6 +272,13 @@ void __destroy_inode(struct inode *inode)
 }
 EXPORT_SYMBOL(__destroy_inode);
 
+static void i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(inode_cachep, inode);
+}
+
 static void destroy_inode(struct inode *inode)
 {
 	BUG_ON(!list_empty(&inode->i_lru));
@@ -279,7 +286,7 @@ static void destroy_inode(struct inode *inode)
 	if (inode->i_sb->s_op->destroy_inode)
 		inode->i_sb->s_op->destroy_inode(inode);
 	else
-		kmem_cache_free(inode_cachep, (inode));
+		call_rcu(&inode->i_rcu, i_callback);
 }
 
 /*
@@ -432,6 +439,7 @@ void end_writeback(struct inode *inode)
 	BUG_ON(!(inode->i_state & I_FREEING));
 	BUG_ON(inode->i_state & I_CLEAR);
 	inode_sync_wait(inode);
+	/* don't need i_lock here, no concurrent mods to i_state */
 	inode->i_state = I_FREEING | I_CLEAR;
 }
 EXPORT_SYMBOL(end_writeback);

fs/isofs/inode.c

@@ -81,9 +81,16 @@ static struct inode *isofs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void isofs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(isofs_inode_cachep, ISOFS_I(inode));
+}
+
 static void isofs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(isofs_inode_cachep, ISOFS_I(inode));
+	call_rcu(&inode->i_rcu, isofs_i_callback);
 }
 
 static void init_once(void *foo)

fs/jffs2/super.c

@@ -40,9 +40,16 @@ static struct inode *jffs2_alloc_inode(struct super_block *sb)
 	return &f->vfs_inode;
 }
 
+static void jffs2_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(jffs2_inode_cachep, JFFS2_INODE_INFO(inode));
+}
+
 static void jffs2_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(jffs2_inode_cachep, JFFS2_INODE_INFO(inode));
+	call_rcu(&inode->i_rcu, jffs2_i_callback);
 }
 
 static void jffs2_i_init_once(void *foo)

fs/jfs/super.c

@@ -115,6 +115,14 @@ static struct inode *jfs_alloc_inode(struct super_block *sb)
 	return &jfs_inode->vfs_inode;
 }
 
+static void jfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct jfs_inode_info *ji = JFS_IP(inode);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(jfs_inode_cachep, ji);
+}
+
 static void jfs_destroy_inode(struct inode *inode)
 {
 	struct jfs_inode_info *ji = JFS_IP(inode);
@@ -128,7 +136,7 @@ static void jfs_destroy_inode(struct inode *inode)
 		ji->active_ag = -1;
 	}
 	spin_unlock_irq(&ji->ag_lock);
-	kmem_cache_free(jfs_inode_cachep, ji);
+	call_rcu(&inode->i_rcu, jfs_i_callback);
 }
 
 static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)

fs/logfs/inode.c

@@ -141,13 +141,20 @@ struct inode *logfs_safe_iget(struct super_block *sb, ino_t ino, int *is_cached)
 	return __logfs_iget(sb, ino);
 }
 
+static void logfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(logfs_inode_cache, logfs_inode(inode));
+}
+
 static void __logfs_destroy_inode(struct inode *inode)
 {
 	struct logfs_inode *li = logfs_inode(inode);
 
 	BUG_ON(li->li_block);
 	list_del(&li->li_freeing_list);
-	kmem_cache_free(logfs_inode_cache, li);
+	call_rcu(&inode->i_rcu, logfs_i_callback);
 }
 
 static void logfs_destroy_inode(struct inode *inode)

fs/minix/inode.c

@@ -68,9 +68,16 @@ static struct inode *minix_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void minix_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(minix_inode_cachep, minix_i(inode));
+}
+
 static void minix_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(minix_inode_cachep, minix_i(inode));
+	call_rcu(&inode->i_rcu, minix_i_callback);
 }
 
 static void init_once(void *foo)

fs/ncpfs/inode.c

@@ -58,9 +58,16 @@ static struct inode *ncp_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void ncp_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ncp_inode_cachep, NCP_FINFO(inode));
+}
+
 static void ncp_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(ncp_inode_cachep, NCP_FINFO(inode));
+	call_rcu(&inode->i_rcu, ncp_i_callback);
 }
 
 static void init_once(void *foo)

fs/nfs/inode.c

@@ -1438,9 +1438,16 @@ struct inode *nfs_alloc_inode(struct super_block *sb)
 	return &nfsi->vfs_inode;
 }
 
+static void nfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(nfs_inode_cachep, NFS_I(inode));
+}
+
 void nfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(nfs_inode_cachep, NFS_I(inode));
+	call_rcu(&inode->i_rcu, nfs_i_callback);
 }
 
 static inline void nfs4_init_once(struct nfs_inode *nfsi)

fs/nilfs2/super.c

@@ -162,10 +162,13 @@ struct inode *nilfs_alloc_inode(struct super_block *sb)
 	return &ii->vfs_inode;
 }
 
-void nilfs_destroy_inode(struct inode *inode)
+static void nilfs_i_callback(struct rcu_head *head)
 {
+	struct inode *inode = container_of(head, struct inode, i_rcu);
 	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
 
+	INIT_LIST_HEAD(&inode->i_dentry);
+
 	if (mdi) {
 		kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
 		kfree(mdi);
@@ -173,6 +176,11 @@ void nilfs_destroy_inode(struct inode *inode)
 	kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
 }
 
+void nilfs_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, nilfs_i_callback);
+}
+
 static int nilfs_sync_super(struct nilfs_sb_info *sbi, int flag)
 {
 	struct the_nilfs *nilfs = sbi->s_nilfs;

fs/ntfs/inode.c

@@ -332,6 +332,13 @@ struct inode *ntfs_alloc_big_inode(struct super_block *sb)
 	return NULL;
 }
 
+static void ntfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ntfs_big_inode_cache, NTFS_I(inode));
+}
+
 void ntfs_destroy_big_inode(struct inode *inode)
 {
 	ntfs_inode *ni = NTFS_I(inode);
@@ -340,7 +347,7 @@ void ntfs_destroy_big_inode(struct inode *inode)
 	BUG_ON(ni->page);
 	if (!atomic_dec_and_test(&ni->count))
 		BUG();
-	kmem_cache_free(ntfs_big_inode_cache, NTFS_I(inode));
+	call_rcu(&inode->i_rcu, ntfs_i_callback);
 }
 
 static inline ntfs_inode *ntfs_alloc_extent_inode(void)

fs/ocfs2/dlmfs/dlmfs.c

@@ -351,9 +351,16 @@ static struct inode *dlmfs_alloc_inode(struct super_block *sb)
 	return &ip->ip_vfs_inode;
 }
 
+static void dlmfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(dlmfs_inode_cache, DLMFS_I(inode));
+}
+
 static void dlmfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(dlmfs_inode_cache, DLMFS_I(inode));
+	call_rcu(&inode->i_rcu, dlmfs_i_callback);
 }
 
 static void dlmfs_evict_inode(struct inode *inode)

fs/ocfs2/super.c

@@ -569,9 +569,16 @@ static struct inode *ocfs2_alloc_inode(struct super_block *sb)
 	return &oi->vfs_inode;
 }
 
+static void ocfs2_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ocfs2_inode_cachep, OCFS2_I(inode));
+}
+
 static void ocfs2_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(ocfs2_inode_cachep, OCFS2_I(inode));
+	call_rcu(&inode->i_rcu, ocfs2_i_callback);
 }
 
 static unsigned long long ocfs2_max_file_offset(unsigned int bbits,

fs/openpromfs/inode.c

@@ -343,9 +343,16 @@ static struct inode *openprom_alloc_inode(struct super_block *sb)
 	return &oi->vfs_inode;
 }
 
+static void openprom_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(op_inode_cachep, OP_I(inode));
+}
+
 static void openprom_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(op_inode_cachep, OP_I(inode));
+	call_rcu(&inode->i_rcu, openprom_i_callback);
 }
 
 static struct inode *openprom_iget(struct super_block *sb, ino_t ino)

fs/proc/inode.c

@@ -65,9 +65,16 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
 	return inode;
 }
 
+static void proc_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
+}
+
 static void proc_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
+	call_rcu(&inode->i_rcu, proc_i_callback);
 }
 
 static void init_once(void *foo)

fs/qnx4/inode.c

@@ -425,9 +425,16 @@ static struct inode *qnx4_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void qnx4_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(qnx4_inode_cachep, qnx4_i(inode));
+}
+
 static void qnx4_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(qnx4_inode_cachep, qnx4_i(inode));
+	call_rcu(&inode->i_rcu, qnx4_i_callback);
 }
 
 static void init_once(void *foo)

fs/reiserfs/super.c

@@ -529,9 +529,16 @@ static struct inode *reiserfs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void reiserfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(reiserfs_inode_cachep, REISERFS_I(inode));
+}
+
 static void reiserfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(reiserfs_inode_cachep, REISERFS_I(inode));
+	call_rcu(&inode->i_rcu, reiserfs_i_callback);
 }
 
 static void init_once(void *foo)

fs/romfs/super.c

@@ -400,9 +400,16 @@ static struct inode *romfs_alloc_inode(struct super_block *sb)
 /*
  * return a spent inode to the slab cache
  */
+static void romfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
+}
+
 static void romfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
+	call_rcu(&inode->i_rcu, romfs_i_callback);
 }
 
 /*

fs/squashfs/super.c

@@ -440,9 +440,16 @@ static struct inode *squashfs_alloc_inode(struct super_block *sb)
 }
 
 
+static void squashfs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
+}
+
 static void squashfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
+	call_rcu(&inode->i_rcu, squashfs_i_callback);
 }
 
 

fs/sysv/inode.c

@@ -333,9 +333,16 @@ static struct inode *sysv_alloc_inode(struct super_block *sb)
 	return &si->vfs_inode;
 }
 
+static void sysv_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(sysv_inode_cachep, SYSV_I(inode));
+}
+
 static void sysv_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(sysv_inode_cachep, SYSV_I(inode));
+	call_rcu(&inode->i_rcu, sysv_i_callback);
 }
 
 static void init_once(void *p)

fs/ubifs/super.c

@@ -272,12 +272,20 @@ static struct inode *ubifs_alloc_inode(struct super_block *sb)
 	return &ui->vfs_inode;
 };
 
+static void ubifs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct ubifs_inode *ui = ubifs_inode(inode);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ubifs_inode_slab, ui);
+}
+
 static void ubifs_destroy_inode(struct inode *inode)
 {
 	struct ubifs_inode *ui = ubifs_inode(inode);
 
 	kfree(ui->data);
-	kmem_cache_free(ubifs_inode_slab, inode);
+	call_rcu(&inode->i_rcu, ubifs_i_callback);
 }
 
 /*

fs/udf/super.c

@@ -139,9 +139,16 @@ static struct inode *udf_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void udf_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(udf_inode_cachep, UDF_I(inode));
+}
+
 static void udf_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(udf_inode_cachep, UDF_I(inode));
+	call_rcu(&inode->i_rcu, udf_i_callback);
 }
 
 static void init_once(void *foo)

fs/ufs/super.c

@@ -1412,9 +1412,16 @@ static struct inode *ufs_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void ufs_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(ufs_inode_cachep, UFS_I(inode));
+}
+
 static void ufs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(ufs_inode_cachep, UFS_I(inode));
+	call_rcu(&inode->i_rcu, ufs_i_callback);
 }
 
 static void init_once(void *foo)

fs/xfs/xfs_iget.c

@@ -91,6 +91,17 @@ xfs_inode_alloc(
 	return ip;
 }
 
+STATIC void
+xfs_inode_free_callback(
+	struct rcu_head		*head)
+{
+	struct inode		*inode = container_of(head, struct inode, i_rcu);
+	struct xfs_inode	*ip = XFS_I(inode);
+
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_zone_free(xfs_inode_zone, ip);
+}
+
 void
 xfs_inode_free(
 	struct xfs_inode	*ip)
@@ -134,7 +145,7 @@ xfs_inode_free(
 	ASSERT(!spin_is_locked(&ip->i_flags_lock));
 	ASSERT(completion_done(&ip->i_flush));
 
-	kmem_zone_free(xfs_inode_zone, ip);
+	call_rcu(&ip->i_vnode.i_rcu, xfs_inode_free_callback);
 }
 
 /*

include/linux/fs.h

@@ -737,7 +737,10 @@ struct inode {
 	struct list_head	i_wb_list;	/* backing dev IO list */
 	struct list_head	i_lru;		/* inode LRU list */
 	struct list_head	i_sb_list;
-	struct list_head	i_dentry;
+	union {
+		struct list_head	i_dentry;
+		struct rcu_head		i_rcu;
+	};
 	unsigned long		i_ino;
 	atomic_t		i_count;
 	unsigned int		i_nlink;

include/linux/net.h

@@ -120,7 +120,6 @@ enum sock_shutdown_cmd {
 struct socket_wq {
 	wait_queue_head_t	wait;
 	struct fasync_struct	*fasync_list;
-	struct rcu_head		rcu;
 } ____cacheline_aligned_in_smp;
 
 /**

ipc/mqueue.c

@@ -237,9 +237,16 @@ static struct inode *mqueue_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
+static void mqueue_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
+}
+
 static void mqueue_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
+	call_rcu(&inode->i_rcu, mqueue_i_callback);
 }
 
 static void mqueue_evict_inode(struct inode *inode)

mm/shmem.c

@@ -2415,13 +2415,20 @@ static struct inode *shmem_alloc_inode(struct super_block *sb)
 	return &p->vfs_inode;
 }
 
+static void shmem_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
+}
+
 static void shmem_destroy_inode(struct inode *inode)
 {
 	if ((inode->i_mode & S_IFMT) == S_IFREG) {
 		/* only struct inode is valid if it's an inline symlink */
 		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
 	}
-	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
+	call_rcu(&inode->i_rcu, shmem_i_callback);
 }
 
 static void init_once(void *foo)

net/socket.c

@@ -262,20 +262,20 @@ static struct inode *sock_alloc_inode(struct super_block *sb)
 }
 
 
-static void wq_free_rcu(struct rcu_head *head)
+static void sock_free_rcu(struct rcu_head *head)
 {
-	struct socket_wq *wq = container_of(head, struct socket_wq, rcu);
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct socket_alloc *ei = container_of(inode, struct socket_alloc,
+								vfs_inode);
 
-	kfree(wq);
+	kfree(ei->socket.wq);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(sock_inode_cachep, ei);
 }
 
 static void sock_destroy_inode(struct inode *inode)
 {
-	struct socket_alloc *ei;
-
-	ei = container_of(inode, struct socket_alloc, vfs_inode);
-	call_rcu(&ei->socket.wq->rcu, wq_free_rcu);
-	kmem_cache_free(sock_inode_cachep, ei);
+	call_rcu(&inode->i_rcu, sock_free_rcu);
 }
 
 static void init_once(void *foo)

net/sunrpc/rpc_pipe.c

@@ -161,10 +161,18 @@ rpc_alloc_inode(struct super_block *sb)
 	return &rpci->vfs_inode;
 }
 
+static void
+rpc_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	INIT_LIST_HEAD(&inode->i_dentry);
+	kmem_cache_free(rpc_inode_cachep, RPC_I(inode));
+}
+
 static void
 rpc_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(rpc_inode_cachep, RPC_I(inode));
+	call_rcu(&inode->i_rcu, rpc_i_callback);
 }
 
 static int