FAILED: patch "[PATCH] io_uring/rw: fix short rw error handling" failed to apply to 5.19-stable tree

The patch below does not apply to the 5.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

4d9cb92ca41d ("io_uring/rw: fix short rw error handling") f2ccb5aed7bc ("io_uring: make io_kiocb_to_cmd() typesafe") 14b146b688ad ("io_uring: notification completion optimisation") 6a9ce66f4d08 ("io_uring/net: make page accounting more consistent") 2e32ba5607ee ("io_uring/net: checks errors of zc mem accounting") 3ff1a0d395c0 ("io_uring: enable managed frags with register buffers") 492dddb4f6e3 ("io_uring: add zc notification flush requests") 4379d5f15b3f ("io_uring: rename IORING_OP_FILES_UPDATE") 63809137ebb5 ("io_uring: flush notifiers after sendzc") 10c7d33ecd51 ("io_uring: sendzc with fixed buffers") e29e3bd4b968 ("io_uring: account locked pages for non-fixed zc") 06a5464be84e ("io_uring: wire send zc request type") bc24d6bd32df ("io_uring: add notification slot registration") 68ef5578efc8 ("io_uring: add rsrc referencing for notifiers") e58d498e81ba ("io_uring: complete notifiers in tw") eb4a299b2f95 ("io_uring: cache struct io_notif") eb42cebb2cf2 ("io_uring: add zc notification infrastructure") e70cb60893ca ("io_uring: export io_put_task()")
72c531f8ef30 ("net: copy from user before calling __get_compat_msghdr") 7fa875b8e53c ("net: copy from user before calling __copy_msghdr")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4d9cb92ca41dd8e905a4569ceba4716c2f39c75a Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Fri, 9 Sep 2022 12:11:49 +0100
Subject: [PATCH] io_uring/rw: fix short rw error handling

We have a couple of problems, first reports of unexpected link breakage for reads when cqe->res indicates that the IO was done in full. The reason here is partial IO with retries.

TL;DR; we compare the result in __io_complete_rw_common() against req->cqe.res, but req->cqe.res doesn't store the full length but rather the length left to be done. So, when we pass the full corrected result via kiocb_done() -> __io_complete_rw_common(), it fails.

The second problem is that we don't try to correct res in io_complete_rw(), which, for instance, might be a problem for O_DIRECT but when a prefix of data was cached in the page cache. We also definitely don't want to pass a corrected result into io_rw_done().

The fix here is to leave __io_complete_rw_common() alone, always pass not corrected result into it and fix it up as the last step just before actually finishing the I/O.

index 1babd77da79c..1e18a44adcf5 100644
@@ -206,6 +206,20 @@ static bool __io_complete_rw_common(struct io_kiocb *req, long res)
 	return false;
 }
 
+static inline unsigned io_fixup_rw_res(struct io_kiocb *req, unsigned res)
+{
+	struct io_async_rw *io = req->async_data;
+
+	/* add previously done IO, if any */
+	if (req_has_async_data(req) && io->bytes_done > 0) {
+		if (res < 0)
+			res = io->bytes_done;
+		else
+			res += io->bytes_done;
+	}
+	return res;
+}
+
 static void io_complete_rw(struct kiocb *kiocb, long res)
 {
 	struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);

@@ -213,7 +227,7 @@ static void io_complete_rw(struct kiocb *kiocb, long res)
 
 	if (__io_complete_rw_common(req, res))
 		return;
-	io_req_set_res(req, res, 0);
+	io_req_set_res(req, io_fixup_rw_res(req, res), 0);
 	req->io_task_work.func = io_req_task_complete;
 	io_req_task_work_add(req);
 }

@@ -240,22 +254,14 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)
 static int kiocb_done(struct io_kiocb *req, ssize_t ret,
 		       unsigned int issue_flags)
 {
-	struct io_async_rw *io = req->async_data;
 	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
-
-	/* add previously done IO, if any */
-	if (req_has_async_data(req) && io->bytes_done > 0) {
-		if (ret < 0)
-			ret = io->bytes_done;
-		else
-			ret += io->bytes_done;
-	}
+	unsigned final_ret = io_fixup_rw_res(req, ret);
 
 	if (req->flags & REQ_F_CUR_POS)
 		req->file->f_pos = rw->kiocb.ki_pos;
 	if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw)) {
 		if (!__io_complete_rw_common(req, ret)) {
-			io_req_set_res(req, req->cqe.res,
+			io_req_set_res(req, final_ret,
 				       io_put_kbuf(req, issue_flags));
 			return IOU_OK;
 		}

@@ -268,7 +274,7 @@ static int kiocb_done(struct io_kiocb *req, ssize_t ret,
 		if (io_resubmit_prep(req))
 			io_req_task_queue_reissue(req);
 		else
-			io_req_task_queue_fail(req, ret);
+			io_req_task_queue_fail(req, final_ret);
 	}
 	return IOU_ISSUE_SKIP_COMPLETE;
 }