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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
        steved@redhat.com
Cc:     linux-nfs@vger.kernel.org
Subject: [RFC PATCH] NFSv4.1 support for NFS4_RESULT_PRESERVER_UNLINKED
Date:   Tue, 18 Jan 2022 14:02:51 -0500
Message-Id: <20220118190251.55526-1-olga.kornievskaia@gmail.com>
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From: Olga Kornievskaia <kolga@netapp.com>

In 4.1+, the server is allowed to set a flag
NFS4_RESULT_PRESERVE_UNLINKED in reply to the OPEN, that tells
the client that it does not need to do a silly rename of an
opened file when it's being removed.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
---
 fs/nfs/dir.c              | 6 ++++--
 fs/nfs/nfs4proc.c         | 2 ++
 include/linux/nfs_fs.h    | 1 +
 include/uapi/linux/nfs4.h | 1 +
 4 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 00b222e48d6f..71f72e102b42 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2319,8 +2319,10 @@ int nfs_unlink(struct inode *dir, struct dentry *dentry)
 		spin_unlock(&dentry->d_lock);
 		/* Start asynchronous writeout of the inode */
 		write_inode_now(d_inode(dentry), 0);
-		error = nfs_sillyrename(dir, dentry);
-		goto out;
+		if (!(NFS_I(d_inode(dentry))->flags & NFS_INO_PRESERVE_UNLINKED)) {
+			error = nfs_sillyrename(dir, dentry);
+			goto out;
+		}
 	}
 	if (!d_unhashed(dentry)) {
 		__d_drop(dentry);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2fbe04d12e44..1a9d25f23dcd 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2727,6 +2727,8 @@ static int _nfs4_proc_open(struct nfs4_opendata *data,
 		nfs4_sequence_free_slot(&o_res->seq_res);
 		nfs4_proc_getattr(server, &o_res->fh, o_res->f_attr, NULL);
 	}
+	if (o_res->rflags & NFS4_OPEN_RESULT_PRESERVE_UNLINKED)
+		set_bit(NFS_INO_PRESERVE_UNLINKED, &NFS_I(dir)->flags);
 	return 0;
 }
 
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 7a134e4c03e8..36fcd8d0487c 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -297,6 +297,7 @@ struct nfs4_copy_state {
 #define NFS_INO_LAYOUTCOMMITTING (10)		/* layoutcommit inflight */
 #define NFS_INO_LAYOUTSTATS	(11)		/* layoutstats inflight */
 #define NFS_INO_ODIRECT		(12)		/* I/O setting is O_DIRECT */
+#define NFS_INO_PRESERVE_UNLINKED (13)		/* preserve file if removed while open */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {
diff --git a/include/uapi/linux/nfs4.h b/include/uapi/linux/nfs4.h
index 800bb0ffa6e6..14acfe5300b7 100644
--- a/include/uapi/linux/nfs4.h
+++ b/include/uapi/linux/nfs4.h
@@ -46,6 +46,7 @@
 #define NFS4_OPEN_RESULT_CONFIRM		0x0002
 #define NFS4_OPEN_RESULT_LOCKTYPE_POSIX		0x0004
 #define NFS4_OPEN_RESULT_MAY_NOTIFY_LOCK	0x0020
+#define NFS4_OPEN_RESULT_PRESERVE_UNLINKED	0x0008
 
 #define NFS4_SHARE_ACCESS_MASK	0x000F
 #define NFS4_SHARE_ACCESS_READ	0x0001
-- 
2.27.0