linux-kernel - [PATCH 09/12] nfsd: support concurrent renames.

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Message-ID: <165516230201.21248.13160043266041158437.stgit@noble.brown>
Date:   Tue, 14 Jun 2022 09:18:22 +1000
From:   NeilBrown <neilb@...e.de>
To:     Al Viro <viro@...iv.linux.org.uk>, Daire Byrne <daire@...g.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Chuck Lever <chuck.lever@...cle.com>
Cc:     Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 09/12] nfsd: support concurrent renames.

If the filesystem supports it, renames can now be concurrent with other
updates.
We use lock_rename_lookup_one() to do the appropriate locking in the
right order and to look up the names.

Signed-off-by: NeilBrown <neilb@...e.de>
---
 fs/nfsd/vfs.c |   49 +++++++++++++++++++------------------------------
 1 file changed, 19 insertions(+), 30 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 6cdd5e407600..b0df216ab3e4 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1584,6 +1584,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 	__be32		err;
 	int		host_err;
 	bool		close_cached = false;
+	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 
 	err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
 	if (err)
@@ -1611,41 +1612,37 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 
 	/* cannot use fh_lock as we need deadlock protective ordering
 	 * so do it by hand */
-	trap = lock_rename(tdentry, fdentry);
-	ffhp->fh_locked = tfhp->fh_locked = true;
-	fh_fill_pre_attrs(ffhp, true);
-	fh_fill_pre_attrs(tfhp, true);
-
-	odentry = lookup_one_len(fname, fdentry, flen);
-	host_err = PTR_ERR(odentry);
-	if (IS_ERR(odentry))
+	trap = lock_rename_lookup_one(tdentry, fdentry, &ndentry, &odentry,
+				      tname, tlen, fname, flen, 0, 0, &wq);
+	host_err = PTR_ERR(trap);
+	if (IS_ERR(trap))
 		goto out_nfserr;
+	ffhp->fh_locked = tfhp->fh_locked = true;
+	fh_fill_pre_attrs(ffhp, (ndentry->d_flags & DCACHE_PAR_UPDATE) == 0);
+	fh_fill_pre_attrs(tfhp, (ndentry->d_flags & DCACHE_PAR_UPDATE) == 0);
 
 	host_err = -ENOENT;
 	if (d_really_is_negative(odentry))
-		goto out_dput_old;
+		goto out_unlock;
 	host_err = -EINVAL;
 	if (odentry == trap)
-		goto out_dput_old;
+		goto out_unlock;
 
-	ndentry = lookup_one_len(tname, tdentry, tlen);
-	host_err = PTR_ERR(ndentry);
-	if (IS_ERR(ndentry))
-		goto out_dput_old;
 	host_err = -ENOTEMPTY;
 	if (ndentry == trap)
-		goto out_dput_new;
+		goto out_unlock;
 
 	host_err = -EXDEV;
 	if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
-		goto out_dput_new;
+		goto out_unlock;
 	if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
-		goto out_dput_new;
+		goto out_unlock;
 
 	if ((ndentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK) &&
 	    nfsd_has_cached_files(ndentry)) {
 		close_cached = true;
-		goto out_dput_old;
+		dget(ndentry);
+		goto out_unlock;
 	} else {
 		struct renamedata rd = {
 			.old_mnt_userns	= &init_user_ns,
@@ -1662,23 +1659,15 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 				host_err = commit_metadata(ffhp);
 		}
 	}
- out_dput_new:
-	dput(ndentry);
- out_dput_old:
-	dput(odentry);
- out_nfserr:
-	err = nfserrno(host_err);
-	/*
-	 * We cannot rely on fh_unlock on the two filehandles,
-	 * as that would do the wrong thing if the two directories
-	 * were the same, so again we do it by hand.
-	 */
 	if (!close_cached) {
 		fh_fill_post_attrs(ffhp);
 		fh_fill_post_attrs(tfhp);
 	}
-	unlock_rename(tdentry, fdentry);
+ out_unlock:
+	unlock_rename_lookup(tdentry, fdentry, ndentry, odentry);
 	ffhp->fh_locked = tfhp->fh_locked = false;
+ out_nfserr:
+	err = nfserrno(host_err);
 	fh_drop_write(ffhp);
 
 	/*