nfsd: store stat times in fill_pre_wcc() instead of inode times

The time values in stat and inode may differ for overlayfs and stat time
values are the correct ones to use. This is also consistent with the fact
that fill_post_wcc() also stores stat time values.

This means introducing a stat call that could fail, where previously we
were just copying values out of the inode.  To be conservative about
changing behavior, we fall back to copying values out of the inode in
the error case.  It might be better just to clear fh_pre_saved (though
note the BUG_ON in set_change_info).

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 37 insertions, 24 deletions

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 2758480555fa..1a70581e1cb2 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -251,6 +251,34 @@ encode_wcc_data(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp)
 }
 
 /*
+ * Fill in the pre_op attr for the wcc data
+ */
+void fill_pre_wcc(struct svc_fh *fhp)
+{
+	struct inode    *inode;
+	struct kstat	stat;
+	__be32 err;
+
+	if (fhp->fh_pre_saved)
+		return;
+
+	inode = d_inode(fhp->fh_dentry);
+	err = fh_getattr(fhp, &stat);
+	if (err) {
+		/* Grab the times from inode anyway */
+		stat.mtime = inode->i_mtime;
+		stat.ctime = inode->i_ctime;
+		stat.size  = inode->i_size;
+	}
+
+	fhp->fh_pre_mtime = stat.mtime;
+	fhp->fh_pre_ctime = stat.ctime;
+	fhp->fh_pre_size  = stat.size;
+	fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
+	fhp->fh_pre_saved = true;
+}
+
+/*
  * Fill in the post_op attr for the wcc data
  */
 void fill_post_wcc(struct svc_fh *fhp)
@@ -261,7 +289,8 @@ void fill_post_wcc(struct svc_fh *fhp)
 		printk("nfsd: inode locked twice during operation.\n");
 
 	err = fh_getattr(fhp, &fhp->fh_post_attr);
-	fhp->fh_post_change = nfsd4_change_attribute(d_inode(fhp->fh_dentry));
+	fhp->fh_post_change = nfsd4_change_attribute(&fhp->fh_post_attr,
+						     d_inode(fhp->fh_dentry));
 	if (err) {
 		fhp->fh_post_saved = false;
 		/* Grab the ctime anyway - set_change_info might use it */
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 5dcd7cb45b2d..e4395abd0f2b 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1996,7 +1996,7 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
 		*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
 		*p++ = 0;
 	} else if (IS_I_VERSION(inode)) {
-		p = xdr_encode_hyper(p, nfsd4_change_attribute(inode));
+		p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
 	} else {
 		*p++ = cpu_to_be32(stat->ctime.tv_sec);
 		*p++ = cpu_to_be32(stat->ctime.tv_nsec);
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 43f31cf49bae..99be87b50ebe 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -252,36 +252,20 @@ fh_clear_wcc(struct svc_fh *fhp)
  * By using both ctime and the i_version counter we guarantee that as
  * long as time doesn't go backwards we never reuse an old value.
  */
-static inline u64 nfsd4_change_attribute(struct inode *inode)
+static inline u64 nfsd4_change_attribute(struct kstat *stat,
+					 struct inode *inode)
 {
 	u64 chattr;
 
-	chattr =  inode->i_ctime.tv_sec;
+	chattr =  stat->ctime.tv_sec;
 	chattr <<= 30;
-	chattr += inode->i_ctime.tv_nsec;
+	chattr += stat->ctime.tv_nsec;
 	chattr += inode->i_version;
 	return chattr;
 }
 
-/*
- * Fill in the pre_op attr for the wcc data
- */
-static inline void
-fill_pre_wcc(struct svc_fh *fhp)
-{
-	struct inode    *inode;
-
-	inode = d_inode(fhp->fh_dentry);
-	if (!fhp->fh_pre_saved) {
-		fhp->fh_pre_mtime = inode->i_mtime;
-		fhp->fh_pre_ctime = inode->i_ctime;
-		fhp->fh_pre_size  = inode->i_size;
-		fhp->fh_pre_change = nfsd4_change_attribute(inode);
-		fhp->fh_pre_saved = true;
-	}
-}
-
-extern void fill_post_wcc(struct svc_fh *);
+extern void fill_pre_wcc(struct svc_fh *fhp);
+extern void fill_post_wcc(struct svc_fh *fhp);
 #else
 #define fh_clear_wcc(ignored)
 #define fill_pre_wcc(ignored)