NFSD: Replace nfsd_write()'s "stable" argument with "iocb_flags"

The current nfsd_write() API is not NFS version-agnostic, as it
relies on callers to pass an NFSv3 stable_how value to determine
the persistence of the requested WRITE. NFSv2 does not use a
stable-how value on the wire, and NFSv4 has its own stable_how4
(though stable_how and stable_how4 happen to share the same
numeric values).

To remove the dependence on NFSv3-specific XDR values from NFSD's
generic VFS APIs, replace nfsd_write()'s stable argument with an
argument that passes a set of IOCB flags instead of an XDR-defined
value.

The NFSv4 WRITE and COPY paths had been borrowing the NFSv3
stable_how constants for their own on-the-wire stable values,
relying on the numeric coincidence noted above. Convert those
sites to the stable_how4 enumerators so the v4 code expresses
its own protocol's values directly, with no change in behavior.

While here, bound-check the decoded NFSv3 WRITE stable value, as
the NFSv4 WRITE decoder already does, and make the nfsd3_writeargs
stable field unsigned to suit.

The larger benefit is one less NFSv4 dependency on nfs3.h.

Link: https://patch.msgid.link/20260723182043.990391-3-cel@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index 1a3981c26b23..41b7cdcc674f 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -263,6 +263,12 @@ enum why_no_delegation4 { /* new to v4.1 */
 	WND4_IS_DIR = 8,
 };
 
+enum stable_how4 {
+	UNSTABLE4	= 0,
+	DATA_SYNC4	= 1,
+	FILE_SYNC4	= 2,
+};
+
 enum lock_type4 {
 	NFS4_UNLOCK_LT = 0,
 	NFS4_READ_LT = 1,