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From:   "J. Bruce Fields" <bfields@redhat.com>
To:     linux-nfs@vger.kernel.org
Cc:     linux-fsdevel@vger.kernel.org,
        Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <schumakeranna@gmail.com>,
        Chuck Lever <chuck.lever@oracle.com>,
        "J. Bruce Fields" <bfields@redhat.com>
Subject: [PATCH 3/3] nfsd: skip some unnecessary stats in the v4 case
Date:   Tue, 19 Jan 2021 14:24:57 -0500
Message-Id: <1611084297-27352-4-git-send-email-bfields@redhat.com>
In-Reply-To: <1611084297-27352-1-git-send-email-bfields@redhat.com>
References: <1611084297-27352-1-git-send-email-bfields@redhat.com>
Precedence: bulk

From: "J. Bruce Fields" <bfields@redhat.com>

In the typical case of v4 and an i_version-supporting filesystem, we can
skip a stat which is only required to fake up a change attribute from
ctime.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfsd/nfs3xdr.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 821db21ba072..e22d5d209d08 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -260,24 +260,25 @@ void fill_pre_wcc(struct svc_fh *fhp)
 	struct inode    *inode;
 	struct kstat	stat;
 	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
-	__be32 err;
 
 	if (fhp->fh_no_wcc || 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;
+	if (!v4 || !inode->i_sb->s_export_op->fetch_iversion) {
+		__be32 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;
 	}
 	if (v4)
 		fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
 
-	fhp->fh_pre_mtime = stat.mtime;
-	fhp->fh_pre_ctime = stat.ctime;
-	fhp->fh_pre_size  = stat.size;
 	fhp->fh_pre_saved = true;
 }
 
@@ -288,7 +289,6 @@ void fill_post_wcc(struct svc_fh *fhp)
 {
 	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
 	struct inode *inode = d_inode(fhp->fh_dentry);
-	__be32 err;
 
 	if (fhp->fh_no_wcc)
 		return;
@@ -296,12 +296,15 @@ void fill_post_wcc(struct svc_fh *fhp)
 	if (fhp->fh_post_saved)
 		printk("nfsd: inode locked twice during operation.\n");
 
-	err = fh_getattr(fhp, &fhp->fh_post_attr);
-	if (err) {
-		fhp->fh_post_saved = false;
-		fhp->fh_post_attr.ctime = inode->i_ctime;
-	} else
-		fhp->fh_post_saved = true;
+	fhp->fh_post_saved = true;
+
+	if (!v4 || !inode->i_sb->s_export_op->fetch_iversion) {
+		__be32 err = fh_getattr(fhp, &fhp->fh_post_attr);
+		if (err) {
+			fhp->fh_post_saved = false;
+			fhp->fh_post_attr.ctime = inode->i_ctime;
+		}
+	}
 	if (v4)
 		fhp->fh_post_change =
 			nfsd4_change_attribute(&fhp->fh_post_attr, inode);
-- 
2.29.2