nfsd: Fix possible BUG_ON firing in set_change_info

If vfs_getattr in fill_post_wcc returns an error, we don't
set fh_post_change.
For NFSv4, this can result in set_change_info triggering a BUG_ON.
i.e. fh_post_saved being zero isn't really a bug.

So:
 - instead of BUGging when fh_post_saved is zero, just clear ->atomic.
 - if vfs_getattr fails in fill_post_wcc, take a copy of i_ctime anyway.
   This will be used i seg_change_info, but not overly trusted.
 - While we are there, remove the pointless 'if' statements in set_change_info.
   There is no harm setting all the values.

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 2a533a0af2a9..7e84a852cdae 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -260,9 +260,11 @@ void fill_post_wcc(struct svc_fh *fhp)
 	err = vfs_getattr(fhp->fh_export->ex_path.mnt, fhp->fh_dentry,
 			&fhp->fh_post_attr);
 	fhp->fh_post_change = fhp->fh_dentry->d_inode->i_version;
-	if (err)
+	if (err) {
 		fhp->fh_post_saved = 0;
-	else
+		/* Grab the ctime anyway - set_change_info might use it */
+		fhp->fh_post_attr.ctime = fhp->fh_dentry->d_inode->i_ctime;
+	} else
 		fhp->fh_post_saved = 1;
 }