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

commit bc4866b6e0b44f8ea0df22a16e5927714beb4983 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index f036153d9f50eaaa93bd8d8d6bc4da231a9f26d3..e8929eeb9e5a2de8c941bc4467a49a2a841ecc2f 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -560,7 +560,7 @@ 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",
@@ -576,21 +576,20 @@ 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 = {