NFS: Fix nfs_set_page_dirty()

Be more careful about testing page->mapping.

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

1 files changed, 11 insertions, 1 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 797558941745..8593965a35ef 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1531,10 +1531,18 @@ int nfs_wb_page(struct inode *inode, struct page* page)
 
 int nfs_set_page_dirty(struct page *page)
 {
-        spinlock_t *req_lock = &NFS_I(page->mapping->host)->req_lock;
+        struct address_space *mapping = page->mapping;
+        struct inode *inode;
+        spinlock_t *req_lock;
         struct nfs_page *req;
         int ret;
 
+        if (!mapping)
+                goto out_raced;
+        inode = mapping->host;
+        if (!inode)
+                goto out_raced;
+        req_lock = &NFS_I(inode)->req_lock;
         spin_lock(req_lock);
         req = nfs_page_find_request_locked(page);
         if (req != NULL) {
@@ -1547,6 +1555,8 @@ int nfs_set_page_dirty(struct page *page)
         ret = __set_page_dirty_nobuffers(page);
         spin_unlock(req_lock);
         return ret;
+out_raced:
+        return !TestSetPageDirty(page);
 }