* [PATCH for-6.0] io_uring/rw: fix short rw error handling
@ 2022-09-09 11:11 Pavel Begunkov
2022-09-09 14:59 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Pavel Begunkov @ 2022-09-09 11:11 UTC (permalink / raw)
To: io-uring; +Cc: Jens Axboe, asml.silence
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.
Cc: [email protected]
Signed-off-by: Pavel Begunkov <[email protected]>
---
io_uring/rw.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 1babd77da79c..1e18a44adcf5 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -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;
}
--
2.37.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH for-6.0] io_uring/rw: fix short rw error handling
2022-09-09 11:11 [PATCH for-6.0] io_uring/rw: fix short rw error handling Pavel Begunkov
@ 2022-09-09 14:59 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2022-09-09 14:59 UTC (permalink / raw)
To: Pavel Begunkov, io-uring
On Fri, 9 Sep 2022 12:11:49 +0100, Pavel Begunkov wrote:
> 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.
>
> [...]
Applied, thanks!
[1/1] io_uring/rw: fix short rw error handling
commit: 4d9cb92ca41dd8e905a4569ceba4716c2f39c75a
Best regards,
--
Jens Axboe
^ permalink raw reply [flat|nested] 2+ messages in thread
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