Patch "nfsd: skip some unnecessary stats in the v4 case" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nfsd: skip some unnecessary stats in the v4 case

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-skip-some-unnecessary-stats-in-the-v4-case.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 64a8b8f5a32dc8a9c3d7fd24302acc342e272625
Author: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Date:   Fri Jan 29 14:27:01 2021 -0500

    nfsd: skip some unnecessary stats in the v4 case
    
    [ Upstream commit 428a23d2bf0ca8fd4d364a464c3e468f0e81671e ]
    
    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@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 00a96054280a6..9d9a01ce0b270 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -364,6 +364,11 @@ encode_wcc_data(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp)
 	return encode_post_op_attr(rqstp, p, fhp);
 }
 
+static bool fs_supports_change_attribute(struct super_block *sb)
+{
+	return sb->s_flags & SB_I_VERSION || sb->s_export_op->fetch_iversion;
+}
+
 /*
  * Fill in the pre_op attr for the wcc data
  */
@@ -372,24 +377,26 @@ 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 (fs_supports_change_attribute(inode->i_sb) || !v4) {
+		__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;
 }
 
@@ -400,7 +407,6 @@ 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;
@@ -408,12 +414,16 @@ 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 (fs_supports_change_attribute(inode->i_sb) || !v4) {
+		__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);