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>

2 files changed, 14 insertions, 13 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;
 }
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 4d476ff08ae6..60fce3dc5cb5 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -484,18 +484,17 @@ static inline bool nfsd4_not_cached(struct nfsd4_compoundres *resp)
 static inline void
 set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
 {
-        BUG_ON(!fhp->fh_pre_saved || !fhp->fh_post_saved);
-        cinfo->atomic = 1;
+        BUG_ON(!fhp->fh_pre_saved);
+        cinfo->atomic = fhp->fh_post_saved;
         cinfo->change_supported = IS_I_VERSION(fhp->fh_dentry->d_inode);
-        if (cinfo->change_supported) {
-                cinfo->before_change = fhp->fh_pre_change;
-                cinfo->after_change = fhp->fh_post_change;
-        } else {
-                cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
-                cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
-                cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
-                cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
-        }
+
+        cinfo->before_change = fhp->fh_pre_change;
+        cinfo->after_change = fhp->fh_post_change;
+        cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
+        cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
+        cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
+        cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
+
 }
 
 int nfs4svc_encode_voidres(struct svc_rqst *, __be32 *, void *);