From: SelvaKumar S <redacted>

Repurpose [cqe->res, cqe->flags] into cqe->res64 (signed) to report
64bit written-offset for zone-append. The appending-write which requires
reporting written-location (conveyed by IOCB_ZONE_APPEND flag) is
ensured not to be a short-write; this avoids the need to report
number-of-bytes-copied.
append-offset is returned by lower-layer to io-uring via ret2 of
ki_complete interface. Make changes to collect it and send to user-space
via cqe->res64.

Signed-off-by: SelvaKumar S <redacted>
Signed-off-by: Kanchan Joshi <redacted>
Signed-off-by: Nitesh Shetty <redacted>
Signed-off-by: Javier Gonzalez <redacted>
---
 fs/io_uring.c                 | 49 ++++++++++++++++++++++++++++++++++++-------
 include/uapi/linux/io_uring.h |  9 ++++++--
 2 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7809ab2..6510cf5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c

@@ -1244,8 +1254,15 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
 		req->flags &= ~REQ_F_OVERFLOW;
 		if (cqe) {
 			WRITE_ONCE(cqe->user_data, req->user_data);
-			WRITE_ONCE(cqe->res, req->result);
-			WRITE_ONCE(cqe->flags, req->cflags);
+			if (unlikely(req->flags & REQ_F_ZONE_APPEND)) {
+				if (likely(req->result > 0))
+					WRITE_ONCE(cqe->res64, req->rw.append_offset);
+				else
+					WRITE_ONCE(cqe->res64, req->result);
+			} else {
+				WRITE_ONCE(cqe->res, req->result);
+				WRITE_ONCE(cqe->flags, req->cflags);
+			}
 		} else {
 			WRITE_ONCE(ctx->rings->cq_overflow,
 				atomic_inc_return(&ctx->cached_cq_overflow));

@@ -1284,8 +1301,15 @@ static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags)
 	cqe = io_get_cqring(ctx);
 	if (likely(cqe)) {
 		WRITE_ONCE(cqe->user_data, req->user_data);
-		WRITE_ONCE(cqe->res, res);
-		WRITE_ONCE(cqe->flags, cflags);
+		if (unlikely(req->flags & REQ_F_ZONE_APPEND)) {
+			if (likely(res > 0))
+				WRITE_ONCE(cqe->res64, req->rw.append_offset);

+			else
+				WRITE_ONCE(cqe->res64, res);
+		} else {
+			WRITE_ONCE(cqe->res, res);
+			WRITE_ONCE(cqe->flags, cflags);
+		}
 	} else if (ctx->cq_overflow_flushed) {
 		WRITE_ONCE(ctx->rings->cq_overflow,
 				atomic_inc_return(&ctx->cached_cq_overflow));

@@ -1943,7 +1967,7 @@ static inline void req_set_fail_links(struct io_kiocb *req)
 		req->flags |= REQ_F_FAIL_LINK;
 }