* [PATCH] io_uring: do not recycle buffer in READV
@ 2022-07-21 13:13 Dylan Yudaken
2022-07-21 14:31 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Dylan Yudaken @ 2022-07-21 13:13 UTC (permalink / raw)
To: Jens Axboe, Pavel Begunkov, io-uring
Cc: Kernel-team, linux-kernel, Dylan Yudaken, Ammar Faizi
READV cannot recycle buffers as it would lose some of the data required to
reimport that buffer.
Reported-by: Ammar Faizi <[email protected]>
Fixes: b66e65f41426 ("io_uring: never call io_buffer_select() for a buffer re-select")
Signed-off-by: Dylan Yudaken <[email protected]>
---
I think going forward we can probably re-enable recycling for READV, or perhaps stick
it in the opdef to make it a bit more general. However since it is late in the merge
cycle I thought the simplest approach is best.
Worth noting the initial discussed approach of stashing the data in `struct io_rw` would not
have worked as that struct is full already apparently.
Dylan
fs/io_uring.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a01ea49f3017..b0180679584f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1737,6 +1737,14 @@ static void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
(req->flags & REQ_F_PARTIAL_IO))
return;
+ /*
+ * READV uses fields in `struct io_rw` (len/addr) to stash the selected
+ * buffer data. However if that buffer is recycled the original request
+ * data stored in addr is lost. Therefore forbid recycling for now.
+ */
+ if (req->opcode == IORING_OP_READV)
+ return;
+
/*
* We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
* the flag and hence ensure that bl->head doesn't get incremented.
base-commit: ff6992735ade75aae3e35d16b17da1008d753d28
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] io_uring: do not recycle buffer in READV
2022-07-21 13:13 [PATCH] io_uring: do not recycle buffer in READV Dylan Yudaken
@ 2022-07-21 14:31 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2022-07-21 14:31 UTC (permalink / raw)
To: asml.silence, dylany, io-uring; +Cc: linux-kernel, Kernel-team, ammarfaizi2
On Thu, 21 Jul 2022 06:13:25 -0700, Dylan Yudaken wrote:
> READV cannot recycle buffers as it would lose some of the data required to
> reimport that buffer.
>
>
Applied, thanks!
[1/1] io_uring: do not recycle buffer in READV
commit: 934447a603b22d98f45a679115d8402e1efdd0f7
Best regards,
--
Jens Axboe
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