linux-kernel - Re: Linux 4.10-rc7

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Date:   Mon, 6 Feb 2017 09:19:24 +0100
From:   Christoph Hellwig <hch@....de>
To:     Dave Jones <davej@...emonkey.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: Linux 4.10-rc7

On Mon, Feb 06, 2017 at 01:00:32AM -0500, Dave Jones wrote:
> This one smells funny to me.

Double mnt_want_write, no idea why lockdep isn't reporting that for me.
Fix below:

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ca13236dbb1f..a974368026a1 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -359,11 +359,6 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
 	err = fh_verify(rqstp, fhp, ftype, accmode);
 	if (err)
 		return err;
-	if (get_write_count) {
-		host_err = fh_want_write(fhp);
-		if (host_err)
-			goto out_host_err;
-	}
 
 	dentry = fhp->fh_dentry;
 	inode = d_inode(dentry);
@@ -416,6 +411,12 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
 
 	iap->ia_valid |= ATTR_CTIME;
 
+	if (get_write_count) {
+		host_err = fh_want_write(fhp);
+		if (host_err)
+			goto out_host_err;
+	}
+
 	fh_lock(fhp);
 	host_err = notify_change(dentry, iap, NULL);
 	fh_unlock(fhp);