[PATCH 4.4 235/342] make sure that freeing shmem fast symlinks is RCU-delayed

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit 3ed47db34f480df7caf44436e3e63e555351ae9a upstream.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/shmem_fs.h |    5 +----
 mm/shmem.c               |    9 ++++-----
 2 files changed, 5 insertions(+), 9 deletions(-)

--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -15,10 +15,7 @@ struct shmem_inode_info {
 	unsigned int		seals;		/* shmem seals */
 	unsigned long		flags;
 	unsigned long		alloced;	/* data pages alloced to file */
-	union {
-		unsigned long	swapped;	/* subtotal assigned to swap */
-		char		*symlink;	/* unswappable short symlink */
-	};
+	unsigned long		swapped;	/* subtotal assigned to swap */
 	struct shared_policy	policy;		/* NUMA memory alloc policy */
 	struct list_head	swaplist;	/* chain of maybes on swap */
 	struct simple_xattrs	xattrs;		/* list of xattrs */
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -620,8 +620,7 @@ static void shmem_evict_inode(struct ino
 			list_del_init(&info->swaplist);
 			mutex_unlock(&shmem_swaplist_mutex);
 		}
-	} else
-		kfree(info->symlink);
+	}
 
 	simple_xattrs_free(&info->xattrs);
 	WARN_ON(inode->i_blocks);
@@ -2462,13 +2461,12 @@ static int shmem_symlink(struct inode *d
 	info = SHMEM_I(inode);
 	inode->i_size = len-1;
 	if (len <= SHORT_SYMLINK_LEN) {
-		info->symlink = kmemdup(symname, len, GFP_KERNEL);
-		if (!info->symlink) {
+		inode->i_link = kmemdup(symname, len, GFP_KERNEL);
+		if (!inode->i_link) {
 			iput(inode);
 			return -ENOMEM;
 		}
 		inode->i_op = &shmem_short_symlink_operations;
-		inode->i_link = info->symlink;
 	} else {
 		error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
 		if (error) {
@@ -3083,6 +3081,7 @@ static struct inode *shmem_alloc_inode(s
 static void shmem_destroy_callback(struct rcu_head *head)
 {
 	struct inode *inode = container_of(head, struct inode, i_rcu);
+	kfree(inode->i_link);
 	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
 }