make sure that freeing shmem fast symlinks is RCU-delayed

Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index a43f41cb3c430166afc7fda3f09571007fe74acf..4d4780c00d345e9e5fd50f5394b89d93c57c966b 100644 (file)
--- 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 */

diff --git a/mm/shmem.c b/mm/shmem.c
index 38c5e72c7008cbb2e35bcb2998209a8f53cf3333..440e2a7e6c1c2ca706376eb72d719fb8b83af05a 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -701,8 +701,7 @@ static void shmem_evict_inode(struct inode *inode)
                        list_del_init(&info->swaplist);
                        mutex_unlock(&shmem_swaplist_mutex);
                }
-       } else
-               kfree(info->symlink);
+       }
 
        simple_xattrs_free(&info->xattrs);
        WARN_ON(inode->i_blocks);
@@ -2549,13 +2548,12 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
        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 {
                inode_nohighmem(inode);
                error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
@@ -3132,6 +3130,7 @@ static struct inode *shmem_alloc_inode(struct super_block *sb)
 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));
 }