NFS: Fix a memory leak in nfs_readdir

We need to ensure that the entries in the nfs_cache_array get cleared
when the page is removed from the page cache. To do so, we use the
freepage address_space operation.

Change nfs_readdir_clear_array to use kmap_atomic(), so that the
function can be safely called from all contexts.

Finally, modify the cache_page_release helper to call
nfs_readdir_clear_array directly, when dealing with an anonymous
page from 'uncached_readdir'.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 10 insertions, 9 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index e03537ff9350..d529e0e99efa 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -57,7 +57,7 @@ static int nfs_rename(struct inode *, struct dentry *,
                       struct inode *, struct dentry *);
 static int nfs_fsync_dir(struct file *, int);
 static loff_t nfs_llseek_dir(struct file *, loff_t, int);
-static int nfs_readdir_clear_array(struct page*, gfp_t);
+static void nfs_readdir_clear_array(struct page*);
 
 const struct file_operations nfs_dir_operations = {
         .llseek         = nfs_llseek_dir,
@@ -83,8 +83,8 @@ const struct inode_operations nfs_dir_inode_operations = {
         .setattr        = nfs_setattr,
 };
 
-const struct address_space_operations nfs_dir_addr_space_ops = {
-        .releasepage = nfs_readdir_clear_array,
+const struct address_space_operations nfs_dir_aops = {
+        .freepage = nfs_readdir_clear_array,
 };
 
 #ifdef CONFIG_NFS_V3
@@ -214,17 +214,15 @@ void nfs_readdir_release_array(struct page *page)
  * we are freeing strings created by nfs_add_to_readdir_array()
  */
 static
-int nfs_readdir_clear_array(struct page *page, gfp_t mask)
+void nfs_readdir_clear_array(struct page *page)
 {
-        struct nfs_cache_array *array = nfs_readdir_get_array(page);
+        struct nfs_cache_array *array;
         int i;
 
-        if (IS_ERR(array))
-                return PTR_ERR(array);
+        array = kmap_atomic(page, KM_USER0);
         for (i = 0; i < array->size; i++)
                 kfree(array->array[i].string.name);
-        nfs_readdir_release_array(page);
-        return 0;
+        kunmap_atomic(array, KM_USER0);
 }
 
 /*
@@ -639,6 +637,8 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page* page)
 static
 void cache_page_release(nfs_readdir_descriptor_t *desc)
 {
+        if (!desc->page->mapping)
+                nfs_readdir_clear_array(desc->page);
         page_cache_release(desc->page);
         desc->page = NULL;
 }
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 314f57164602..e67e31c73416 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -289,6 +289,7 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
                 } else if (S_ISDIR(inode->i_mode)) {
                         inode->i_op = NFS_SB(sb)->nfs_client->rpc_ops->dir_inode_ops;
                         inode->i_fop = &nfs_dir_operations;
+                        inode->i_data.a_ops = &nfs_dir_aops;
                         if (nfs_server_capable(inode, NFS_CAP_READDIRPLUS))
                                 set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
                         /* Deal with crossing mountpoints */