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Subject[PATCH v2 3/3] NFS: Fix a memory leak in nfs_readdir
Date
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
releasepage address_space operation (which also requires us to set
the Pg_private flag).

Change nfs_readdir_clear_array to use kmap_atomic(), so that the
function can be safely called from all direct reclaim 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>
---
fs/nfs/dir.c | 22 +++++++++++++++++-----
fs/nfs/inode.c | 1 +
include/linux/nfs_fs.h | 1 +
3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 3ec3f1c..4c6319e 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -58,6 +58,7 @@ static int nfs_rename(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_invalidatepage(struct page*, unsigned long);

const struct file_operations nfs_dir_operations = {
.llseek = nfs_llseek_dir,
@@ -85,6 +86,7 @@ const struct inode_operations nfs_dir_inode_operations = {

const struct address_space_operations nfs_dir_addr_space_ops = {
.releasepage = nfs_readdir_clear_array,
+ .invalidatepage = nfs_readdir_invalidatepage,
};

#ifdef CONFIG_NFS_V3
@@ -216,15 +218,22 @@ void nfs_readdir_release_array(struct page *page)
static
int nfs_readdir_clear_array(struct page *page, gfp_t mask)
{
- 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);
+ ClearPageUptodate(page);
+ ClearPagePrivate(page);
+ return 1;
+}
+
+static
+void nfs_readdir_invalidatepage(struct page *page, unsigned long offset)
+{
+ nfs_readdir_clear_array(page, 0);
}

/*
@@ -624,6 +633,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page* page)
if (ret < 0)
goto error;
SetPageUptodate(page);
+ SetPagePrivate(page);

if (invalidate_inode_pages2_range(inode->i_mapping, page->index + 1, -1) < 0) {
/* Should never happen */
@@ -639,6 +649,8 @@ 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, GFP_KERNEL);
unlock_page(desc->page);
page_cache_release(desc->page);
desc->page = NULL;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 314f571..0018e07 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_addr_space_ops;
if (nfs_server_capable(inode, NFS_CAP_READDIRPLUS))
set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
/* Deal with crossing mountpoints */
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c66fdb7..b5d3ab0 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -401,6 +401,7 @@ extern const struct inode_operations nfs3_file_inode_operations;
#endif /* CONFIG_NFS_V3 */
extern const struct file_operations nfs_file_operations;
extern const struct address_space_operations nfs_file_aops;
+extern const struct address_space_operations nfs_dir_addr_space_ops;

static inline struct nfs_open_context *nfs_file_open_context(struct file *filp)
{
--
1.7.3.2


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