NFS: Don't SIGBUS if nfs_vm_page_mkwrite races with a cache invalidation

In the case where we lock the page, and then find out that the page has
been thrown out of the page cache, we should just return VM_FAULT_NOPAGE.
This is what block_page_mkwrite() does in these situations.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

1 files changed, 8 insertions, 9 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 59cbe1ba0511..39672b731736 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -551,7 +551,7 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
         struct file *filp = vma->vm_file;
         struct dentry *dentry = filp->f_path.dentry;
         unsigned pagelen;
-        int ret = -EINVAL;
+        int ret = VM_FAULT_NOPAGE;
         struct address_space *mapping;
 
         dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%s/%s(%ld), offset %lld)\n",
@@ -567,21 +567,20 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
         if (mapping != dentry->d_inode->i_mapping)
                 goto out_unlock;
 
-        ret = 0;
         pagelen = nfs_page_length(page);
         if (pagelen == 0)
                 goto out_unlock;
 
-        ret = nfs_flush_incompatible(filp, page);
-        if (ret != 0)
-                goto out_unlock;
+        ret = VM_FAULT_LOCKED;
+        if (nfs_flush_incompatible(filp, page) == 0 &&
+            nfs_updatepage(filp, page, 0, pagelen) == 0)
+                goto out;
 
-        ret = nfs_updatepage(filp, page, 0, pagelen);
+        ret = VM_FAULT_SIGBUS;
 out_unlock:
-        if (!ret)
-                return VM_FAULT_LOCKED;
         unlock_page(page);
-        return VM_FAULT_SIGBUS;
+out:
+        return ret;
 }
 
 static const struct vm_operations_struct nfs_file_vm_ops = {