[PATCH V4 1/2] NFSD: Offer write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE

[Dai Ngo <dai.ngo@xxxxxxxxxx>]

RFC8881, section 9.1.2 says:

  "In the case of READ, the server may perform the corresponding
   check on the access mode, or it may choose to allow READ for
   OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
   implementation may unavoidably do (e.g., due to buffer cache
   constraints)."

and in section 10.4.1:
   "Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/
   OPEN4_SHARE_ACCESS_BOTH and if an OPEN_DELEGATE_WRITE delegation
   is in effect"

This patch offers write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE
only. Also deleted no longer use find_rw_file().

Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
 fs/nfsd/nfs4state.c | 34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 0f97f2c62b3a..b533225e57cf 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -633,18 +633,6 @@ find_readable_file(struct nfs4_file *f)
 	return ret;
 }
 
-static struct nfsd_file *
-find_rw_file(struct nfs4_file *f)
-{
-	struct nfsd_file *ret;
-
-	spin_lock(&f->fi_lock);
-	ret = nfsd_file_get(f->fi_fds[O_RDWR]);
-	spin_unlock(&f->fi_lock);
-
-	return ret;
-}
-
 struct nfsd_file *
 find_any_file(struct nfs4_file *f)
 {
@@ -5382,7 +5370,6 @@ static int nfsd4_cb_recall_done(struct nfsd4_callback *cb,
 	if (dp->dl_stid.sc_status)
 		/* CLOSED or REVOKED */
 		return 1;
-
 	switch (task->tk_status) {
 	case 0:
 		return 1;
@@ -5987,14 +5974,19 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	 *  "An OPEN_DELEGATE_WRITE delegation allows the client to handle,
 	 *   on its own, all opens."
 	 *
-	 * Furthermore the client can use a write delegation for most READ
-	 * operations as well, so we require a O_RDWR file here.
+	 * Furthermore, section 9.1.2 says:
+	 *
+	 *  "In the case of READ, the server may perform the corresponding
+	 *  check on the access mode, or it may choose to allow READ for
+	 *  OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
+	 *  implementation may unavoidably do (e.g., due to buffer cache
+	 *  constraints)."
 	 *
-	 * Offer a write delegation in the case of a BOTH open, and ensure
-	 * we get the O_RDWR descriptor.
+	 *  We choose to offer a write delegation for OPEN with the
+	 *  OPEN4_SHARE_ACCESS_WRITE access mode to accommodate such clients.
 	 */
-	if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) {
-		nf = find_rw_file(fp);
+	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
+		nf = find_writeable_file(fp);
 		dl_type = deleg_ts ? OPEN_DELEGATE_WRITE_ATTRS_DELEG : OPEN_DELEGATE_WRITE;
 	}
 
@@ -6116,7 +6108,7 @@ static bool
 nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
 		     struct kstat *stat)
 {
-	struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);
+	struct nfsd_file *nf = find_writeable_file(dp->dl_stid.sc_file);
 	struct path path;
 	int rc;
 
@@ -7063,7 +7055,7 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
 		return_revoked = true;
 	if (typemask & SC_TYPE_DELEG)
 		/* Always allow REVOKED for DELEG so we can
-		 * retturn the appropriate error.
+		 * return the appropriate error.
 		 */
 		statusmask |= SC_STATUS_REVOKED;
 
-- 
2.43.5