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

Web:        https://git.kernel.org/torvalds/c/39ca1bf624b6b82cc895b0217889eaaf572a7913
Commit:     39ca1bf624b6b82cc895b0217889eaaf572a7913
Parent:     76c479480b9afff4c585a17e19a1efe3457a2d9b
Refname:    refs/heads/master
Author:     Amir Goldstein <[email protected]>
AuthorDate: Wed Jan 3 17:14:35 2018 +0200
Committer:  J. Bruce Fields <[email protected]>
CommitDate: Thu Feb 8 13:40:17 2018 -0500

    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 <[email protected]>
    Signed-off-by: J. Bruce Fields <[email protected]>
---
 fs/nfsd/nfs3xdr.c | 31 ++++++++++++++++++++++++++++++-
 fs/nfsd/nfs4xdr.c |  2 +-
 fs/nfsd/nfsfh.h   | 28 ++++++----------------------
 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
@@ -250,6 +250,34 @@ encode_wcc_data(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp)
 	return encode_post_op_attr(rqstp, p, 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
  */
@@ -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;
-	}
-}