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

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 59cbe1b..39672b7 100644 (file)
--- 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 = {